Bio notesPRACTICAL
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Starch: Add few drops of iodine, +ve result = blue-black color (for plants , first in
darkness for 48 hours , then in sunlight for a few, take leaf and boil in water for two
minutes, warmed in ethanol till leaf have no color left, dipped in water briefly and then
add iodine
Reducing sugars: Add Benedict’s reagent, then mixture is heated in water bath for 2 to 3
minutes.
+ve result (increasing concentration of sugar) = blue → green → yellow → orange → red
-ve result = remains blue
Proteins: Add few drops of Biuret reagent, +ve result = mauve color, -ve result = remains
blue
Fats: Emulsion test; ethanol is added to mixture, and this is poured into a test tube with
an equal amount of distilled water, +ve result = milky-white emulsion
Vitamin C: Decolourisation of DCPIP shows that a vitamin C is probably present.
When designing an experiment Write: 'repeat experiment to get more reliable results
and minimize error’
Chlorophyll, light Is Necessary for Photosynthesis
Sodium bicarbonate produces CO2, Sodium hydroxide absorbs CO2
Investigating what happens when varying the factors affecting photosynthesis- light
intensity, carbon dioxide and temperature
germinate fastest when it has access to water, oxygen and is at a warm temperature
gravitropism In each case the roots will turn to go downwards, and the shoot turns to
grow upwards,
The independent variable is plotted on the x axis
Dependent variable (i.e. the one that changes as a result in a change of the other) is
plotted on the y axis.
Magnification= size of drawing/ size of specimen
Independent variable – the variable that is altered.
Dependent variable – the variable being tested or measured
Controlled variable – a variable that is kept the same
CHARACTERISTICS OF LIVING ORGANISMS-
o Movement: action by an organism or part of an organism causing a change of position
or place
o Respiration: the chemical reactions that break down nutrient molecules in living cells to
release energy
o Sensitivity: ability to detect or sense changes in the environment (stimuli) and to make
responses
o Growth: permanent increase in size and dry mass by an increase in cell number or cell
size or both
o Reproduction: processes that make more of the same kind of organism
o Excretion: removal from organisms of toxic materials, the waste products of metabolism
(chemical reactions in cells including respiration) and substances in excess of
requirements
o Nutrition: taking in of nutrients which are organic substances and mineral ions,
containing raw materials or energy for growth and tissue repair, absorbing and
assimilating them
Binomial system: a system of naming species in which the scientific name of an organism is
made up of two parts showing the genus (starting with a capital letter) and species (starting
with a lower-case letter), written in italics when printed (therefore underlined when written)
e.g. Homo sapiens
REMEMBER
KING PHILIP CAME OVER FOR GOOD SPAGHETTI
KINGDOM, PHYLUM, CLASS, ORDER, FAMILY, GENUS, SPECIES
o DNA is the chemical from which chromosomes are made
o Each DNA molecule is made up of strings of smaller molecules containing four bases
o The sequences of bases in DNA and of amino acids in proteins are used as a more
accurate means of classification (cladistics)
Kingdoms
o Animal: Multi-cellular ingestive heterotrophs (eat living organisms)
o Plant: Multi-cellular photosynthetic autotrophic (make their own food) organism with a
cellulose cell wall.
o Fungi: Single celled or multi cellular heterotrophic organism with cell wall not made of
cellulose, spread by spreading of spores in moist/dark/warm environment, saprotrophs
(feed off dead organisms) or parasites
o Prokaryotes: Single celled organism with no true nucleus
o Protoctista: Single celled organism with a nucleus
Vertebrates
Mammals:
o Fur/hair on skin
o Can live on land and in water
o 4 limbs
o Lungs to breathe
o Give birth to live young
Reptiles:
o Scales on skin
o Usually, 4 legs
o Lungs to breathe
o Hard eggs
Fish:
o Wet scales
o External fertilization and soft eggs
o Gills to breathe
Amphibians:
o Smooth, moist skin
o External fertilization and soft eggs
o Gills/lungs to breathe so can live on land and in water
o 4 legs
Birds:
o Feathers on body and scales on legs
o Have 2 legs and 2 wings
o Lungs to breathe
o Hard eggs
Arthropods (Invertebrates with Legs)
Crustaceans: (e.g., crabs)
o Have an exoskeleton
o 1 pair of compound eyes
o 2 body segment – cephalothorax and abdomen
o More than four pairs of legs
o 2 pairs of antennae sensitive to touch and chemicals
Arachnids: (e.g., spiders)
o 2 body segment – cephalothorax and abdomen
o Four pairs of legs
o Pair of chelicerae to hold prey
o Two pedipalps for reproduction
o Simple eyes
Myriapods: (e.g., centipede)
o Segmented body
o Additional segments formed
o One pair of antennae
o 70+ pairs of legs – 1 or 2 pairs on each segment
o Fused head and thorax and segmented abdomen
o Simple eyes
Insects: (e.g., bees)
o 3 body segments – head, thorax, and abdomen
o 3 pairs of legs
o 1 pair of antennae
o 1 or 2 pairs of wings
o Compound and simple eyes
Classifying Plants
Ferns:
o Do not produce flowers
o They are plants with roots, stems and leaves
o Have leaves called fronds
o Reproduce by spores
Flowering plants:
o They are plants with roots, stems and leaves
o Reproduce sexually by means of flowers and seeds
o Seeds are produced inside the ovary in the flower
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Dichotomous key: uses visible features to classify organisms. It is which gives you a
choice of two features and you follow the one that applies: each choice leads to another
choice until the organism is narrowed down to its genus and finally species
Monocotyledons- one cotyledon, parallel vein, fibrous root, floral parts in 3s
Dicotyledons- two cotyledon, vein netlike, taproot present, floral parts in 4s or 5s
Viruses and Bacteria
Virus- covered by protein coat, no cell membrane, no cytoplasm, DNA or RNA (only a few
genes), non-living unless in host
Bacteria- covered by cell wall, has cell membrane, has cytoplasm, has enough DNA for several
100 genes, living
A IS ALWAYS WITH T AND C IS ALWAYS WITH G. (DNA)
Structure of a DNA:
 Chromosomes are made of a molecule called DNA
 Each chromosome is a very long molecule of tightly coiled DNA
 Two strands coiled together to form a double helix
 Each strand contains chemicals called bases
 Cross-links between strands are formed by pairs of bases
 The bases always pair up in the same way:
 A and T, C and G
ORGANIZATION OF THE ORGANISM
All typical cells have:
o Cell membrane: differentially or partially permeable to allow certain substances to enter
and leave the cell.
o Cytoplasm: where chemical reactions take place
o Nucleus: contains DNA and controls the cell
o Mitochondria: organelle where aerobic respiration happens
o Ribosome: makes protein and can be found floating within the cytoplasm
o A typical animal cell (e.g. the liver cell) has all above
Only plant cells have:
o Vacuole: stores food & water & helps to maintain shape of cell
o Cell wall: rigid to keep shape of cell
o Chloroplasts: contain chlorophyll, which absorbs light energy for photosynthesis
o A typical plant cell (e.g. the palisade cell) has all the above things.
Cells—>
o Red blood cell- transports oxygen (biconcave shape, no nucleus, flexible, has
hemoglobin)
o Muscle cell- contrasts to get structures closer together (long, many protein fibers in
cytoplasm to shorten cell when energy available)
o Ciliated cell- move and push mucus ( tiny hairs called cilia)
o Root hair cell- absorb minerals and water (elongated shape for more surface area)
o Xylem vessel- transport water and dissolved minerals and support plant (no cytoplasm
so water passes freely, no cross walls so cells connect to form tube, lignin makes it
waterproof and strong) water moves up due to transpiration and osmosis
o Palisade cell- photosynthesis ( regular shape so many can fit in small space, many
chloroplasts)
MOVEMENT IN AND OUT OF CELLS
Diffusion- movement from high concentration region to low concentration region (down the
concentration gradient)
Factors influencing faster diffusion:
 Larger concentration gradient
 Higher temperature
 Larger surface area
Osmosis- movement rom region of high-water potential to low water potential region (
probably through a partially permeable membrane)
Concentration of solute outside cell = concentration inside cell → no change in size
Concentration of solute outside cell > concentration inside cell → cell shrinks (Plasmolysis)
Concentration of solute outside cell < concentration inside cell → cell swells (Turgid)
In animal cell if it swells too much then it can explode (crenation)
Active transport- moment from a region of lower concentration to one of higher concentration
against the concentration gradient
BIOLOGICAL MOLECULES
 Carbohydrates: made from Carbon, Hydrogen and Oxygen (CHO)
 Fats and oils: made from Carbon, Hydrogen and Oxygen (CHO)
 Proteins: made from Carbon, Hydrogen, Oxygen, Nitrogen and sometimes Sulfur
(CHON{S})
SUGAR IS STARCH AND GLYCOGEN
FATTY ACIDS AND GLYCEROL IS FATS AND OILS
AMINO ACIDS IS PROTEINS
ENZYMES
 Catalyst: a substance that speeds up a chemical reaction and is not changed by the
reaction
 Enzymes: proteins that function as biological catalysts
 Enzymes lowers amount of energy needed for reaction to take place
 Enzyme lowers the activation energy needed for reaction to take place
 Enzyme+ substrate = enzyme-substrate complex (lock and key theory)
 Substrate: the molecule(s) before they are made to react
 Product: the molecule(s) that are made in a reaction
 Catabolic reaction: molecules are broken down
 Anabolic reaction: molecules are combined
The effects of temperature on enzymes:
 Enzymes have an optimum temperature: the temperature at which they work best
giving the fastest reaction ≈ 37°C in animals
 When temperature increases, molecules move faster so collide with an enzyme in less
time
 Having more energy makes them more likely to bind to active site.
 If temperature is too high, enzyme molecules vibrate too vigorously, and enzyme is
denatured; it loses its shape and will no longer bind with a substrate.
 When the temperature is too low there is not enough kinetic energy for the reaction, so
it reacts too slowly.
The effects of pH on enzymes:
 Enzymes are sensitive to pH
 Some enzymes work best in an acid and others in an alkaline
 Enzymes work best at their optimum pH
 If the pH is changed then the enzyme will denature and will no longer fit with substrateno reaction takes place
Effect of Temperature
Effect of pH
Enzymes and their uses
o Seeds to germinate: the enzymes turn insoluble food stores to soluble.
o Biological washing powders: enzymes are added to washing powders to help remove
stains for example:
o Lipase for lipids from fatty foods and greasy fingerprints
o Protease for proteins from blood stains
o Food industry:
o Isomerase converts glucose to fructose, which is sweeter, so less is needed to give a
sweet taste
o Pectinase helps break down cell walls in fruit juice production, so it increases yield,
lowers viscosity, and reduces cloudiness
PLANT NURITION
o Photosynthesis: process by which plants manufacture carbohydrates from raw
materials using energy from light.
Carbon Dioxide + Water {light + cholorophyll} Glucose +Oxygen
6CO2 + 6H2O{light + cholorophyll}+C6H12 O6 +6O2
o The carbon dioxide diffuses through the open stomata of the leaf of a plant and water is
taken up through roots.
o Chlorophyll is a dye, which traps light energy and converts it into chemical energy for
the formation of carbohydrates and their subsequent storage.
Chlorophyll Is Necessary for Photosynthesis.
Light Is Necessary for Photosynthesis.
Carbon Dioxide is Necessary for Photosynthesis.
Nitrogen is needed for photosynthesis
Magnesium is needed for chlorophyllsynethesis
Limiting factor: something present in the environment in such short supply that it restricts life
processes.
Glasshouse Systems:
o Optimum temperature: thermostatically controlled heaters make the temperature right
for enzymes to work
o Optimum light: light has a high intensity for more photosynthesis, the correct
wavelengths (red and blue not green) and duration controls production of fruit
Leaf structure:
o Cuticle: waxy layer that prevents water loss from top of the leaf
o Epidermis: transparent cell that allows sunlight to pass through to the palisade cell
o Palisade: found at the top of the cell and contains many chloroplasts which absorbs
sunlight.
o Spongy mesophyll layer: irregularly shaped cells which create air spaces to allow
gaseous exchange to take place; do not contain many chloroplasts
o Vascular Bundle: made up of xylem and phloem
o Xylem: vessel which transports water and dissolved minerals and has lignified walls
made of cellulose
o Phloem: bidirectional vessel which transports nutrients, Contains companion cells which
provide energy for active transport of sugars all over plant.
o Stomata: little holes that opens and closes to allow gaseous exchange to take place. The
stomata close to prevent water loss and open to let gases come in and out. When guard
cells lose water, the stoma close (at night), while the stoma open when guard cells gain
water & swell (during the day).
Phloem
HUMAN NUTRITION
 Balanced Diet: getting all the right nutrients in correct proportions
 Diet related to age/sex/activity:
 Children Below 12: Require more calcium
 Teenagers: Highest calorie Intake
 Adults: Balanced meal with less calories
 Pregnant Women: more iron, calcium and folic acid
Malnutrition
 A condition caused by eating an unbalanced diet. Several forms:
 Overnutrition: balanced diet but eating too much of everything
 Undernutrition: having too little food
 Eating foods in incorrect proportions
Effects of Malnutrition
 Starvation: losing strength & finally dying because of lack of food
 Coronary heart disease: eating too much fats which are rich in saturated fatty
acids and cholesterol, may lead to heart attack
 Constipation: lack of roughages in food causes constipation because roughages
are indigestible and form bulks. Friction between bulks and walls of intestine
stimulate the peristalsis
 Obesity: Eating too much fats and carbohydrates leads to their storage in the
body mainly in the forms of fats and causing an increase in body weight. This can
cause; heart attack, stroke, joint pain, mobility impairment, high blood pressure
Deficiencies
 Vitamin C: Scurvy; loss of teeth, pale skin & sunken eyes
 Vitamin D: Rickets; weak bones and teeth
 Calcium: Rickets; weak bones and teeth, also poor clotting of blood, spasms
 Iron: Anaemia: Fatigue (less iron → less haemoglobin → less oxygen transported
→ less respiration → less energy)
Uses
Carbohydrates- energy
Fats- source of energy, building materials, energy storage, insulation, making hormones
Proteins- energy, building materials, enzymes, hemoglobin, structural material (muscle),
hormones, antibodies
Vitamin C- protect cells from ageing, protection of fibers
Vitamin d- absorption of calcium
Calcium- development and maintenance of strong bones and teeth
Iron- making hemoglobin
Fiber- provides bulk for faces
Water- chemical reactions, solvent for transport
Human alimentary canal:
 Ingestion: taking substances (e.g. food, drink) into the body through the mouth.
 Egestion: passing out of food that has not been digested, as faeces, through the anus.
 Digestion: the break-down of large, insoluble food molecules into small, water soluble
molecules using mechanical and chemical processes
 Mouth: contains teeth used for mechanical digestion, area where food is mixed with
salivary amylase & where ingestion takes place
 Salivary glands: produce saliva which contains amylase and helps food slide down
oesophagus
 Oesophagus: tube-shaped organ which uses peristalsis to transport food from mouth to
stomach
 Stomach: has sphincters to control movement into and also has pepsin (a protease) to
break down proteins into peptides, it also kills bacteria with hydrochloric acid. They also
have elastic walls.
 Small intestine: tube shaped organ composed of two parts the:
 Duodenum: fats are emulsified by bile, and digested by pancreatic lipase to form
fatty acids and glycerol. Pancreatic amylase and trypsin (a protease) break down
starch and peptides into maltose and amino acids
 Ileum: Maltase breaks down maltose to glucose. This is where absorption takes
place; adapted by having villi and microvilli.
 Pancreas: produces pancreatic juice which contains amylase, trypsin and lipase and
hydrogencarbonate.
 Liver: produces bile, stores glucose as glycogen, interconverting them to keep glucose
concentration constant. Also carries out interconversion of amino acids
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(transamination), deamination and removal of old red blood cells and storage of their
iron. Also, site of breakdown of alcohol and other toxins.
Gall bladder: stores bile from liver
Bile: produced by liver and stored in gall bladder, its role is to emulsify fats, to increase
surface area for the action of enzymes.
Large intestine: tube shaped organ composed of two parts:
 Colon: organ for absorption of minerals and vitamins, and reabsorbing water
from waste to maintain body’s water levels
 Rectum: where faeces are temporarily stored
Anus: ring of muscle which controls when faeces is released.
Diarrhoea
 Diarrhoea: when not enough water is absorbed from the faeces
 To cure this is to give oral rehydration therapy
 One of these infectious by a bacterium causing the diseases cholera (spreads rapidly)
 The cholera bacterium produces a toxin that causes secretion of chloride ions into the
small intestine, causing osmotic movement of water into the gut, causing diarrhoea,
dehydration and loss of salts from the blood
Teeth:
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Incisor – rectangle shape, for cutting and biting
Canine- pointed sharp for holding and cutting
Premolar- blunt for chewing and crushing
Molar- blunt chewing and crushing , has two roots
Structure of teeth –
 Enamel: the strongest tissue in the body made from calcium salts
 Cement: helps to anchor tooth
 Pulp cavity: contains tooth-producing cells, blood vessels, and nerve endings which
detect pain.
 Dentine: calcium salts deposited on a framework of collagen fibres
 Neck: in between crown and root, it is the gums
Chemical Digestion
 Where enzymes are used to break down large insoluble substances such as proteins into
smaller soluble substances like amino acids so that they can be absorbed.
 Amylase: breaks down starch into maltose, it is produced in the pancreas (but also in
the salivary gland)
 Protease: breaks down proteins to peptides (done by pepsin) then into amino acids
(done by trypsin). Pepsin comes from the stomach and trypsin comes from the
pancreas.
 Lipase: breaks down lipids into fatty acids and glycerol, produced by the pancreas.
 Hydrochloric acid in gastric juice:
 Denaturing enzymes in harmful microorganisms in food
 Giving the optimum pH for pepsin activity
Absorption :
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Movement of digested food molecules through wall of the intestine into the blood or
lymph.
The small intestine is the region for absorption of digested food.
The small intestine is folded into many villi which increase the surface area for
absorption. One villus will have tiny folds on the cells on its outside called microvilli.
More surface area means more absorption can happen
Capillary: transports glucose and amino acids
Vein: delivers absorbed products to liver via hepatic portal vein.
Gland: produces enzymes
Lacteal: absorbs fatty acid and glycerol
Epithelium: only one cell thick for faster transport. The cells of the epithelium are folded
to form microvilli.
Small intestine and colon absorb water
 The small intestine absorbs 5–10 dm3 per day
 The colon absorbs 0.3–0.5 dm3 per day
TRANSPORT IN PLANTS:
 Plants contain two types of transport vessel:
o Xylem vessels – transport water and minerals (pronounced: zi-lem) from the
roots to the stem and leaves
o Function: transport tissue for water and dissolved mineral ions
o Adaptations:
o Cells joined end to end with no cross walls to form a long continuous tube
o Cells are essentially dead, without cell contents, to allow free passage of water
o Outer walls are thickened with a substance called lignin, strengthening the
tubes, which helps support the plant
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Phloem vessels – transport food materials (mainly sucrose and amino acids) made by
the plant from photosynthesising leaves to non-photosynthesising regions in the roots
and stem (pronounced: flow-em)
These vessels are arranged throughout the root, stem and leaves in groups
called vascular bundles
Root Hair Cells
Root hairs are single-celled extensions of epidermis cells in the root
They grow between soil particles and absorb water and minerals from the soil
Water enters the root hair cells by osmosis
This happens because soil water has a higher water potential than the cytoplasm of the
root hair cell
The root hair increases the surface area of the cells significantly
This large surface area is important as it increases the rate of the absorption of water
by osmosis and mineral ions by active transport
Pathway Taken by Water
 Osmosis causes water to pass into the root hair cells, through the root cortex and into
the xylem vessels:
Pathway of water into and across a root
 Once the water gets into the xylem, it is carried up to the leaves where it
enters mesophyll cells
 So the pathway is:
root hair cell → root cortex cells → xylem → leaf mesophyll cells
Investigating Water Movement in Plants
 The pathway can be investigated by placing a plant (like celery) into a beaker of water
that has had a stain added to it (food colouring will work well)
 After a few hours, you can see the leaves of the celery turning the same colour as the
dyed water, proving that water is being taken up by the celery
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If a cross-section of the celery is cut, only certain areas of the stalk is stained the colour
of the water, showing that the water is being carried in specific vessels through the stem
- these are the xylem vessels
Transpiration
 Water travels up xylem from the roots into the leaves of the plant to replace the water
that has been lost due to transpiration
 Transpiration is defined as the loss of water vapour from plant leaves by evaporation
of water at the surfaces of the mesophyll cells followed by diffusion of water vapour
through the stomata
 Xylem is adapted in many ways:
o A substance called lignin is deposited in the cell walls which causes the xylem
cells to die
o These cells then become hollow (as they lose all their organelles and cytoplasm)
and join end-to-end to form a continuous tube for water and mineral ions to
travel through from the roots
o Lignin strengthens the plant to help it withstand the pressure of the water
movement
 Movement in xylem only takes place in one direction - from roots to leaves (unlike
phloem where movement takes place in different directions)
 Transpiration has several functions in plants:
o transporting mineral ions
o providing water to keep cells turgid in order to support the structure of the
plant
o providing water to leaf cells for photosynthesis
o keeping the leaves cool (the conversion of water (liquid) into water vapour (gas)
as it leaves the cells and enters the airspace requires heat energy. The using up
of heat to convert water into water vapour helps to cool the plant down)
Water Vapour Loss: Extended
 Evaporation takes place from the surfaces of spongy mesophyll cells
 The many interconnecting air spaces between these cells and the stomata create
a large surface area
 This means evaporation can happen rapidly when stomata are open
Transpiration Stream: Extended
 Water molecules are attracted to each other by cohesion - creating a continuous
column of water up the plant
 Water moves through the xylem vessels in a continuous transpiration stream from
roots to leaves via the stem
 Transpiration produces a tension or ‘pull’ on the water in the xylem vessels by the
leaves
 As water molecules are held together by cohesive forces (each individual molecule
‘pulls’ on the one below it), so water is pulled up through the plant
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If the rate of transpiration from the leaves increases, water molecules are pulled up the
xylem vessels quicker
Translocation
 The soluble products of photosynthesis are sugars (mainly sucrose) and amino acids
 These are transported around the plant in the phloem tubes which are made of living
cells (as opposed to xylem vessels which are made of dead cells)
 The cells are joined end to end and contain holes in the end cell walls (called sieve
plates) which allow easy flow of substances from one cell to the next
 The transport of sucrose and amino acids in the phloem, from regions of production to
regions of storage or use, is called translocation
 Transport in the phloem goes in many different directions depending on the stage of
development of the plant or the time of year; however dissolved food is always
transported from the source (where it’s made) to sink (where it’s stored or used):
 During winter, when many plants have no leaves, the phloem tubes may transport
dissolved sucrose and amino acids from the storage organs to other parts of the plant so
that respiration can continue
 During a growth period (eg during the spring), the storage organs (eg roots) would be
the source and the many growing areas of the plant would be the sinks
 After the plant has grown (usually during the summer), the leaves are
photosynthesizing and producing large quantities of sugars; so they become the source
and the roots become the sinks – storing sucrose as starch until it is needed again
xylem- moves minerals and water ions-transpiration stream- flows one way from roots to
leaves -cells dead
phloem-moves sucrose and amino acids- translocation- flows in all directions- living
TRANSPORT IN HUMANS
 The circulatory system is a system of blood vessels with a pump and valves to
ensure one-way flow of blood
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Fish have a two-chambered heart and a single circulation
This means that for every one circuit of the body, the blood passes through the heart
once
Circulatory systems in Mammals
 Mammals have a four-chambered heart and a double circulation
 This means that for every one circuit of the body, the blood passes through the heart
twice
 The right side of the heart receives deoxygenated blood from the body and pumps it to
the lungs (the pulmonary circulation)
 The left side of the heart receives oxygenated blood from the lungs and pumps it to the
body (the systemic circulation)
Advantages of Double Circulation: Extended
 Blood travelling through the small capillaries in the lungs loses a lot of pressure that
was given to it by the pumping of the heart, meaning it cannot travel as fast
 By returning the blood to the heart after going through the lungs its pressure can be
raised again before sending it to the body, meaning cells can be supplied with
the oxygen and glucose they need for respiration faster and more frequently
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The right side of the heart receives deoxygenated blood from the body and pumps it to
the lungs
The left side of the heart receives oxygenated blood from the lungs and pumps it to the
body
Blood is pumped towards the heart in veins and away from the heart in arteries
The two sides of the heart are separated by a muscle wall called the septum
The heart is made of muscle tissue which are supplied with blood by the coronary arteries
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Heart activity can be monitored by using an ECG, measuring pulse rate or listening to
the sounds of valves closing using a stethoscope
Heart rate (and pulse rate) is measured in beats per minute (bpm)
To investigate the effects of exercise on heart rate, record the pulse rate at rest for a
minute
Immediately after they do some exercise, record the pulse rate every minute until it
returns to the resting rate
This experiment will show that during exercise the heart rate increases and may take
several minutes to return to normal
The coronary arteries
 The heart is made of muscle cells that need their own supply of blood to deliver oxygen,
glucose and other nutrients and remove carbon dioxide and other waste products
 The blood is supplied by the coronary arteries
 If a coronary artery becomes partially or completely blocked by fatty deposits called
‘plaques’ (mainly formed from cholesterol), the arteries are not as elastic as they
should be and therefore cannot stretch to accommodate the blood which is being
forced through them - leading to coronary heart disease
 Partial blockage of the coronary arteries creates a restricted blood flow to the cardiac
muscle cells and results in severe chest pains called angina
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Complete blockage means cells in that area of the heart will not be able to respire and
can no longer contract, leading to a heart attack
Reducing the risks of developing coronary heart disease
 Quit smoking
 Diet - reduce animal fats and eat more fruits and vegetables - this will reduce
cholesterol levels in the blood and help with weight loss if overweight
 Exercise regularly - again, this will help with weight loss, decrease blood pressure and
cholesterol levels and help reduce stress
Identifying Structures in the Heart: Extended
 The ventricles have thicker muscle walls than the atria as they are pumping blood out of
the heart and so need to generate a higher pressure
 The left ventricle has a thicker muscle wall than the right ventricle as it has to pump
blood at high pressure around the entire body, whereas the right ventricle is pumping
blood at lower pressure to the lungs
 The septum separates the two sides of the heart and so prevents mixing of oxygenated
and deoxygenated blood
The function of valves
 The basic function of all valves is to prevent blood from flowing backwards
 There are two sets of valves in the heart:
o The atrioventricular valves separate the atria from the ventricles
o The valve in the right side of the heart is called the TRICUSPID and the valve in
the left side is called the BICUSPID
o These valves are pushed open when the atria contract but when the ventricles
contract they are pushed shut to prevent blood flowing back into the atria
o The semilunar valves are found in the two blood arteries that come out of the
top of the heart
o They are unusual in that they are the only two arteries in the body that contain
valves
o These valves open when the ventricles contract so blood squeezes past them
out of the heart, but then shut to avoid blood flowing back into the hear
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Deoxygenated blood coming from the body flows into the right atrium via the vena
cava
Once the right atrium has filled with blood the heart gives a little beat and the blood is
pushed through the tricuspid (atrioventricular) valve into the right ventricle
The walls of the ventricle contract and the blood is pushed into the pulmonary
artery through the semilunar valve which prevents blood flowing backwards into the
heart
The blood travels to the lungs and moves through the capillaries past the alveoli where
gas exchange takes place (this is why there has to be low pressure on this side of the
heart – blood is going directly to capillaries which would burst under higher pressure)
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Oxygen-rich blood returns to the left atrium via the pulmonary vein
It passes through the bicuspid (atrioventricular) valve into the left ventricle
The thicker muscle walls of the ventricle contract strongly to push the blood forcefully
into the aorta and all the way around the body
 The semilunar valve in the aorta prevents the blood flowing back down into the heart
 So that sufficient blood is taken to the working muscles to provide them with
enough nutrients and oxygen for increased respiration
 An increase in heart rate also allows for waste products to be removed at a faster rate
 Following exercise, the heart continues to beat faster for a while to ensure that all
excess waste products are removed from muscle cells
 It is also likely that muscle cells have been respiring anaerobically during exercise and so
have built up an oxygen debt
 This needs to be ‘repaid’ following exercise and so the heart continues to beat faster to
ensure that extra oxygen is still being delivered to muscle cells
 The extra oxygen is used to break down the lactic acid that has been built up in cells as a
result of anaerobic respiration
Arteries
 Carry blood at high pressure away from the heart
 Carry oxygenated blood (other than the pulmonary artery)
 Have thick muscular walls containing elastic fibres
 Have a narrow lumen
 Speed of flow is fast
Veins
 Carry blood at low pressure towards the heart
 Carry deoxygenated blood (other than the pulmonary vein)
 Have thin walls
 Have a large lumen
 Contain valves
 Speed of flow is slow
Capillaries
 Carry blood at low pressure within tissues
 Carry both oxygenated and deoxygenated blood
 Have walls that are one cell thick
 Have ‘leaky’ walls
 Speed of flow is slow
Arterioles and venules
 As arteries divide more as they get further away from the heart, they get narrower
 The narrow vessels that connect arteries to capillaries are called arterioles
 Veins also get narrower the further away they are from the heart
 The narrow vessels that connect capillaries to veins are called venules
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You must be able to identify the main blood vessels to and from the liver
o The hepatic artery brings oxygenated blood from the heart to the liver
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The hepatic vein brings deoxygenated blood from the liver back to the heart
The hepatic portal vein transports deoxygenated blood from the gut to the liver
You need to be able to identify red and white blood cells in photomicrographs and
diagrams
o Red blood cells have a concave disc shape with no nucleus
o White blood cells are usually round in shape with a nucleus
Plasma is important for the transport of carbon dioxide, digested food (nutrients), urea,
mineral ions, hormones and heat energy
Red blood cells transport oxygen around the body from the lungs to cells which require
it for aerobic respiration
o They carry the oxygen in the form of oxyhaemoglobin
White blood cells defend the body against infection by pathogens by carrying
out phagocytosis and antibody production
Platelets are involved in helping the blood to clot
Blood clotting
 Platelets are fragments of cells which are involved in blood clotting and forming scabs
where skin has been cut or punctured
 Blood clotting prevents continued / significant blood loss from wounds
 Scab formation seals the wound with an insoluble patch that prevents entry of
microorganisms that could cause infection
 It remains in place until new skin has grown underneath it, sealing the skin again
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White blood cells are part of the body’s immune system, defending against infection by
pathogenic microorganisms
 There are two main types, phagocytes and lymphocytes
Phagocytes
 Carry out phagocytosis by engulfing and digesting pathogens
Phagocytosis
 Phagocytes have a sensitive cell surface membrane that can detect chemicals produced
by pathogenic cells
 Once they encounter the pathogenic cell, they will engulf it and release digestive
enzymes to digest it
 They can be easily recognised under the microscope by their multi-lobed nucleus and
their granular cytoplasm
Lymphocytes
 Produce antibodies to destroy pathogenic cells and antitoxins to neutralise toxins
released by pathogens
 They can easily be recognised under the microscope by their large round nucleus which
takes up nearly the whole cell and their clear, non-granular cytoplasm
Conversion of Fibrinogen: Extended
 Platelets are fragments of cells which are involved in blood clotting and forming scabs
where skin has been cut or punctured
 Blood clotting prevents continued / significant blood loss from wounds
 Scab formation seals the wound with an insoluble patch that prevents entry of
microorganisms that could cause infection
 It remains in place until new skin has grown underneath it, sealing the skin again
How the blood clots
 When the skin is broken (i.e. there is a wound) platelets arrive to stop the bleeding
 A series of reactions occur within the blood plasma
 Platelets release chemicals that cause soluble fibrinogen proteins to convert
into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood
cells and therefore forming a clot
 The clot eventually dries and develops into a scab to protect the wound from bacteria
entering
DISEASES AND IMMUNITY
There are 3 main ways in which the body defends itself against disease:
1)
Mechanical barriers – structures that make it difficult for pathogens to get past them and into
the body
a) Skin - covers almost all parts of your body to prevent infection from pathogens. If it is cut or
grazed, it immediately begins to heal itself, often by forming a scab
b) Hairs in the nose - these make it difficult for pathogens to get past them further up the nose
so they are not inhaled into the lungs
2)Chemical barriers – substances produced by the body cells that trap / kill pathogens before
they can get further into the body and cause disease
a) Mucus - made in various places in the body, pathogens get trapped in the mucus and can
then be removed from the body (by coughing, blowing the nose, swallowing etc)
b) Stomach acid - contains hydrochloric acid which is strong enough to kill any pathogens that
have been caught in mucus in the airways and then swallowed or have been consumed in food
or water
3)Cells - different types of white blood cell work to prevent pathogens reaching areas of the
body they can replicate in
a) By phagocytosis - engulfing and digesting pathogenic cells
b) By producing antibodies - which clump pathogenic cells together so they can’t move as easily
(known as agglutination) and releasing chemicals that signal to other cells that they must be
destroyed
 Making antibodies and developing memory cells for future response to infection is
known as active immunity
 There are two ways in which this active immune response happens:
o The body has become infected with a pathogen and so the lymphocytes go
through the process of making antibodies specific to that pathogen
o Vaccination
 Active immunity is slow acting and provides long-lasting immunity
 All cells have proteins and other substances projecting from their cell membrane
 These are known as antigens and are specific to that type of cell
 Lymphocytes have the ability to ‘read’ the antigens on the surfaces of cells and
recognise any that are foreign
 They then make antibodies which are a complementary shape to the antigens on the
surface of the pathogenic cel
 The antibodies attach to the antigens and cause agglutination (clumping together)
 This means the pathogenic cells cannot move very easily
 At the same time, chemicals are released that signal to phagocytes that there are cells
present that need to be destroyed
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The initial response of a lymphocyte encountering a pathogen for the first time and
making specific antibodies for its antigens can take a few days, during which time an
individual may get sick
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Lymphocytes that have made antibodies for a specific pathogen for the first time will
then make ‘memory cells’ that retain the instructions for making those specific
antibodies for that type of pathogen
This means that, in the case of reinfection by the same type of pathogen, antibodies can
very quickly be made in greater quantities and the pathogens destroyed before they are
able to multiply and cause illness
This is how people can become immune to certain diseases after only having them once
It does not work with all disease-causing microorganisms as some of them mutate fairly
quickly and change the antigens on their cell surfaces
Therefore, if they invade the body for a second time, the memory cells made in the first
infection will not recall them as they now have slightly different antigens on their
surfaces (e.g. the cold virus)
Vaccinations give protection against specific diseases and boost the body’s defence
against infection from pathogens without the need to be exposed to dangerous
diseases that can lead to death
The level of protection in a population depends on the proportion of people vaccinated
Vaccines allow a dead or altered form of the disease-causing pathogen, which contains
specific antigens, to be introduced into the body
In this weakened state, the pathogen cannot cause illness but can provoke an immune
response
Lymphocytes produce complementary antibodies for the antigens
The antibodies target the antigen and attach themselves to it in order to create memory
cells
The memory cells remain in the blood and will quickly respond to the antigen if it is
encountered again in an infection by a ‘live’ pathogen
As memory cells have been produced, this immunity is long-lasting
If a large enough percentage of the population is vaccinated, it provides protection for
the entire population because there are very few places for the pathogen to breed - it
can only do so if it enters the body of an unvaccinated person
This is known as herd immunity
If the number of people vaccinated against a specific disease drops in a population, it
leaves the rest of the population at risk of mass infection, as they are more likely to
come across people who are infected and contagious This increases the number of
infections, as well as the number of people who could die from a specific infectious
disease
Herd immunity prevents epidemics and pandemics from occurring in populations
This is the reason that many vaccinations are given to children, as they are regularly
seen by medical practitioners and can be vaccinated early to ensure the entire
vaccinated population remains at a high level
In certain instances, vaccination programmes are run with the aim of eradicating certain
dangerous diseases, as opposed to controlling them at low levels
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An example of a disease which has been eradicated as a result of a successful
vaccination programme is smallpox, which was officially eradicated in 1980 after a
vaccination programme run by the World Health Organisation since the mid-1950s
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Passive immunity is a fast-acting, short-term defence against a pathogen by antibodies
acquired from another individual
Antibodies pass from mother to infant via breast milk - this is important as it helps the
very young to fight off infections until they are older and stronger and their immune
system is more responsive
The body does not make its own antibodies or memory cells in passive immunity,
hence the name
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Cholera causes diarrhoea
 Diarrhoea is the loss of watery faeces from the anus
 If it is severe and continues for a long time, it can lead to death
 Severe diarrhoea can cause the loss of significant amounts of water and ions from the
body, causing the tissues and organs to stop working properly
 It can be effectively treated by oral rehydration therapy
 This is a drink with a small amount of salt and sugar dissolved in it
 There are many causes of diarrhoea, one of which is infection with Vibrio cholerae
bacteria, which causes the disease ch
How cholera leads to diarrhoea
 Ingested via infected water or food, if it enters the small intestine it can cause illness in
the following way:
1. Bacteria attach to the wall of the small intestine
2. They produce a toxin
3. The toxin stimulates the cells lining the intestine to release chloride ions from inside the
cells into the lumen of the intestine
4. The chloride ions accumulate in the lumen of the small intestine and lower the water
potential there
5. Once the water potential is lower than that of the cells lining the intestine, water starts
to move out of the cells into the intestine (by osmosis)
6. Large quantities of water are lost from the body in watery faeces
7. The blood contains too little chloride ions and water
GAS EXCHANGE IN HUMANS
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The surfaces where gas exchange occurs in an organism are very different and different
organisms have evolved different mechanisms for getting the gases to the gas exchange
surface depending on size, where they live etc.
 All gas exchange surfaces have features in common
 These features allow the maximum amount of gases to be exchanged across the surface
in the smallest amount of time
 They include:
o Large surface area to allow faster diffusion of gases across the surface
o Thin walls to ensure diffusion distances remain short
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Good ventilation with air so that diffusion gradients can be maintained
Good blood supply to maintain a high concentration gradient so diffusion occurs
faster
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Air that is breathed in and air that is breathed out has different amounts of gases in it
due to exchanges that take place in the alveoli
Atmospheric air contains around 20 – 21% oxygen, of which we only absorb around 4 –
5%, breathing out air containing around 16% oxygen
Normal carbon dioxide content of air is around 0.04% and, as carbon dioxide diffuses
into the alveoli from the blood, we breathe out air containing around 4% carbon dioxide
The air we breathe out contains more water vapour than when we breathe it in, and
the temperature of exhaled air is higher than inhaled air
Muscles are only able to pull on bones, not push on them
This means that there must be two sets of intercostal muscles; one to pull the rib cage
up and another set to pull it down
One set of intercostal muscles is found on the outside of the ribcage
(the external intercostal muscles)
The other set is found on the inside of the rib cage (the internal intercostal muscles)
Function of Cartilage in the Trachea: Extended
 Rings of cartilage surround the trachea (and bronchi)
 The function of the cartilage is to support the airways and keep them open during
breathing
 If they were not present then the sides could collapse inwards when the air pressure
inside the tubes drops
 The diaphragm is a thin sheet of muscle that separates the chest cavity from the
abdomen; it is ultimately responsible for controlling ventilation in the lungs
o When the diaphragm contracts it flattens and this increases the volume of the
chest cavity (thorax), which consequently leads to a decrease in air
pressure inside the lungs relative to outside the body, drawing air in.
When the diaphragm relaxes it moves upwards back into its domed shape and
this decreases the volume of the chest cavity (thorax), which consequently leads
to an increase in air pressure inside the lungs relative to outside the
body, forcing air out
The external and internal intercostal muscles work as antagonistic pairs (meaning they
work in different directions to each other)
During inhalation the external set of intercostal muscles contract to pull the ribs up
and out:
o This also increases the volume of the chest cavity (thorax), decreasing air
pressure, drawing air in
During exhalation, the external set of intercostal muscles relax so the ribs drop down
and in:
o This decreases the volume of the chest cavity (thorax) increasing air pressure,
forcing air out
When we need to increase the rate of gas exchange (for example during strenuous
activity) the internal intercostal muscles will also work to pull the ribs down and in to
decrease the volume of the thorax more, forcing air out more forcefully and quickly –
this is called forced exhalation
o There is actually a greater need to rid the body of increased levels of carbon
dioxide produced during strenuous activity!
This allows a greater volume of gases to be exchanged
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Breathing in-external intercostal muscles contract, ribcage moves up and out, diaphragm
contracts and flattens, volume of thorax increases, air is drawn in
Breathing out- external intercostal muscles relax, ribcage moves down and in, diaphragm
relaxes and becomes shaped, volume of thorax decreases, air is forced out
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The passages down to the lungs are lined with ciliated epithelial cells
Cilia comes from the Latin for eyelash, so unsurprisingly these cells have tiny hairs on
the end of them that beat and push mucus up the passages towards the nose and
throat where it can be removed
 The mucus is made by special mucus-producing cells called goblet cells because they are
shaped like a goblet, or cup
 The mucus traps particles, pathogens like bacteria or viruses, and dust and prevents
them getting into the lungs and damaging the cells there
Mucus traps particles, dust and pathogens and cilia beat and push it up and away from the
lungs
RESPIRATION
 Respiration is a chemical process that involves the breakdown of nutrient molecules
(specifically glucose) in order to release the energy stored within the bonds of these
molecules
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Respiration can take place with oxygen (aerobically) or without oxygen (anaerobically).
Much less energy is released for each glucose molecule broken down anaerobically
compared to the energy released when it is broken down aerobically
Respiration occurs in all living cells. Most of the chemical reactions in aerobic respiration
take place in the mitochondria
Humans need this energy to do the following things:
o Contract muscle
o Synthesise proteins
o Cell division (to make new cells)
o Grow
o Enable active transport to take place
o Allow nerve impulses to be generated
o Maintain a constant internal body temperature
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Aerobic respiration requires oxygen and is defined as the chemical reactions in cells
that use oxygen to break down nutrient molecules to release energy
 It is the complete breakdown of glucose to release a relatively large amount of
energy for use in cell processes
 It produces carbon dioxide and water as well as releasing useful cellular energy
Aerobic respirationGlucose+ oxygen carbon dioxide+ water
C6H12O6+6O2  6CO2 +6H2O
Anaerobic Respiration - Respiration Without Oxygen
 Anaerobic respiration does not require oxygen and is defined as the chemical reactions
in cells that break down nutrient molecules to release energy without using oxygen
 It is the incomplete breakdown of glucose and releases a relatively small amount of
energy (compared to aerobic respiration) for use in cell processes
 It produces different breakdown products depending on the type of organism it is taking
place in
 You need to know the equations for anaerobic respiration in humans (animals) and the
microorganism yeast
Anaerobic Respiration in Animals
 Anaerobic respiration mainly takes place in muscle cells during vigorous exercise
 When we exercise vigorously, our muscles have a higher demand for energy than when
we are resting or exercising normally. Our bodies can only deliver so much oxygen to
our muscle cells for aerobic respiration
 In this instance, as much glucose as possible is broken down with oxygen, and some
glucose is broken down without it, producing lactic acid instead
 There is still energy stored within the bonds of lactic acid molecules that the cell could
use; for this reason, less energy is released when glucose is broken down anaerobically
Glucose lactic acid (humans)
Glucosealcohol+ carbon dioxide. (yeast)
C6H12O6 2C2 H5O2H+2CO2
Anaerobic Respiration & Oxygen Debt: Extended
 Lactic acid builds up in muscle cells and lowers the pH of the cells (making them more
acidic)
 This could denature the enzymes in cells so it needs to be removed
 Cells excrete lactic acid into the blood. When blood passes through the liver, lactic acid
is taken up into liver cells where it is oxidised, producing carbon dioxide and water
(Lactic acid reacts with oxygen - this is actually aerobic respiration with lactic acid as the
nutrient molecule instead of glucose)
 So the waste products of lactic acid oxidation are carbon dioxide and water
 This is the reason we continue to breath heavily and our heart rate remains high even
after finishing exercise - we need to transport the lactic acid from our muscles to the
liver, and continue getting larger amounts of oxygen into the blood to oxidise the lactic
acid
 This is known as ‘repaying the oxygen debt
EXCRETION
 Lungs- excrete carbon dioxide during respiration
 Kidneys- excrete, excess water, salts and urea, by producing urine
 Excretion is the removal of the waste substances of metabolic reactions, toxic
materials and substances in excess of requirements
 Carbon dioxide must be excreted as it dissolves in water easily to form an acidic
solution which can lower the pH of cells
 This can reduce the activity of enzymes in the body which are essential for controlling
the rate of metabolic reactions
 For this reason, too much carbon dioxide in the body is toxic
 Urea is also toxic to the body in higher concentrations and so must be excreted
Kidneys They regulate the water content of the blood (vital for maintaining blood pressure)
 They excrete the toxic waste products of metabolism (such as urea) and substances in
excess of requirements (such as salts)
The Nephron
 Each kidney contains around a million tiny structures called nephrons, also known
as kidney tubules or renal tubules
 The nephrons start in the cortex of the kidney, loop down into the medulla and back up
to the cortex
 The contents of the nephrons drain into the innermost part of the kidney and the urine
collects there before it flows into the ureter to be carried to the bladder for storage
Water is reabsorbed at the loop of Henle and collecting duct, salts are reabsorbed a the loop of
Henle, glucose are reabsorbed at the proximal(first) convoluted, and urea isn’t reabsorbed
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Arterioles branch off the renal artery and lead to each nephron, where they form a knot
of capillaries (the glomerulus) sitting inside the cup-shaped Bowman’s capsule
The capillaries get narrower as they get further into the glomerulus which increases the
pressure on the blood moving through them (which is already at high pressure because
it is coming directly from the renal artery which is connected to the aorta)
This eventually causes the smaller molecules being carried in the blood to be forced out
of the capillaries and into the Bowman’s capsule, where they form what is known as
the filtrate
This process is known as ultrafiltration
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The substances forced out of the capillaries are: glucose, water, urea, salts
Some of these are useful and will be reabsorbed back into the blood further down the
nephron
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After the glomerular filtrate enters the Bowman’s Capsule, glucose is the first substance
to be reabsorbed at the proximal (first) convoluted tubule
This takes place by active transport
The nephron is adapted for this by having many mitochondria to provide energy for the
active transport of glucose molecules
Reabsorption of glucose cannot take place anywhere else in the nephron as the gates
that facilitate the active transport of glucose are only found in the proximal convoluted
tubule
In a person with a normal blood glucose level, there are enough gates present to
remove all of the glucose from the filtrate back into the blood
People with diabetes cannot control their blood glucose levels and they are often very
high, meaning that not all of the glucose filtered out can be reabsorbed into the blood in
the proximal convoluted tubule
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As there is nowhere else for the glucose to be reabsorbed, it continues in the filtrate
and ends up in urine
 This is why one of the first tests a doctor may do to check if someone is diabetic is to
test their urine for the presence of glucose
Reabsorption of Water & Salts
 As the filtrate drips through the Loop of Henle necessary salts are reabsorbed back into
the blood by diffusion
 As salts are reabsorbed back into the blood, water follows by osmosis
 Water is also reabsorbed from the collecting duct in different amounts depending on
how much water the body needs at that time
Excretion by Deamination of Amino Acids: Extended
 Many digested food molecules absorbed into the blood in the small intestine are carried
to the liver for assimilation (when food molecules are converted to other molecules
that the body needs)
 These include amino acids, which are used to build proteins such as fibrinogen, a
protein found in blood plasma that is important in blood clotting
 Excess amino acids absorbed in the blood that are not needed to make proteins cannot
be stored, so they are broken down in a process called deamination
o The amino group of all amino acids - NH2 (which contains the nitrogen atoms) is
removed, hence the term de-amin(o)-ation
 Enzymes in the liver split up the amino acid molecules
 The part of the molecule which contains carbon is turned into glycogen and stored
 The other part, which contains nitrogen, is turned into ammonia, which is highly toxic,
and so is immediately converted into urea, which is less toxic
 The urea dissolves in the blood and is taken to the kidney to be excreted
 A small amount is also excreted in sweat
 In deamination, the nitrogen-containing amino group is removed and converted into
ammonia and then urea to be excreted
 The toxic consequences of high urea levels, if it is not excreted effectively, are very
serious:
o Cell death
o Reduced response to insulin, leading to diabetes
o Deposits inside blood vessel
COORDINATION AND RESPONSE:
Nervous Control in Humans
 The nervous system consists of two parts:
 Central nervous system (CNS) consisting of the brain and spinal cord, which are
the areas of coordination
 Peripheral nervous system (PNS) made up of nerves and neurones, which
coordinate and regulate bodily functions.
 Involuntary actions: not under conscious control e.g. reflex action
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Voluntary actions: are done if we decide to carry them out
Types of Neurons
 Nerve impulse: an electrical signal that passes along nerve cells called neurones
Motor neurone-
Sensory neurone-
Relay neuroneReflex arc
 A reflex action is an involuntary, quick action to respond to a stimulus, in order to
protect the body from danger
 E.g. quickly removing your hand from hot metal surface
 They involve three neurones: a sensory neurone, relay neurone and motor neurone.
 The gap between neurones is called a synapse.
 How the reflex arc works:
 A stimulus affects a receptor (cell or organ that converts a stimulus into an
electrical impulse)
 A sensory neurone carries impulse from the receptor to the CNS
 Connector/relay neurone carries impulse slowly (because it has no myelin
sheath) across the spinal chord
 Motor neurone carries impulse from the CNS to the effector
 Effector (either a muscle or a gland) carries out the response
Synapses
 Synapse: a junction between two neurones, consisting of a gap across which impulses
pass by diffusion of a neurotransmitter
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Synaptic cleft: small gap between each pair of neurones
Inside the neurones axon, there are 100s of tiny vacuoles (vessicles each contain a
chemical called neurotransmitter)
 When an impulse arrives, the vessicles move to the cell membrane and empty their
content into the synaptic cleft
 The neurotransmitter quickly diffuses across the tiny gap and attaches to receptor
molecules in the cell membrane of the relay neurone
 This can happen because the shape of the neurotransmitter molecules is complimentary
to the shape of the receptor molecule
 Many drugs e.g. heroin act upon synapses
Antagonistic Muscle
 A muscle that opposes the action of another; e.g. biceps and triceps are antagonistic
muscles or circular and radial muscles in the eye
 Agonist: a muscle that contracts while another relaxes; e.g. when bending the elbow,
the biceps are the agonist
 Antagonist: a muscle that relaxes while another contracts; e.g. when bending the elbow,
the triceps are the antagonist
 Sense organ: groups of receptor cells responding to specific stimuli: light, sound, touch,
temperature and chemicals.
The eye:
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Cornea: refracts light
Iris: controls how much light enters pupil
Lens: focuses light onto retina
Retina: contains light receptors, some sensitive to light of different colours
Optic nerve: carries impulses to the brain
Accommodation:
Near object- ciliary muscles contract, ligaments relax, lens become short and fat
Distant object- ciliary muscles relax, ligaments are tight, lens becomes long and thin
Low light- radial muscles contract and become shorter making the pupil wider
High light- circular muscles contract and become shorter
Rods- provide low detail, black and white image, packed mostly tightly around edge of retina
Cones-provide detailed, colored images, packed mostly tightly around edge of retina
Fovea:
 Part of the retina where the receptor cells are pushed most closley together
 Where light is focused when you look straight at an object
Hormones
 A chemical substance, produced by a gland, carried by the blood, which alters the
activity of one or more specific target organs and is then destroyed by the liver.
Adrenaline
 A hormone secreted by the adrenal gland.
 It increases pulse rate, makes the glycogen in muscles is converted to glucose and
released into blood, makes you breathe deeper and more rapidly, airways become
wider, and makes skin become pale as blood is diverted away.
 Increases blood glucose concentration for respiration.
Adrenal gland- adrenaline- prepares body for vigorous action
Pancreas-insulin- reduces concentration of glucose in blood
Testis-testosterone- cause development of male sexual characteristics
Ovary- oestrogen- causes development of female sexual characteristics
Glucoregulation
 Blood glucose levels are monitored and controlled by the pancreas
 The pancreas produces and releases different hormones depending on the blood
glucose level
 Insulin is released when blood glucose levels are high – the liver stores excess glucose as
glycogen
 Glucagon is released when blood glucose levels are low – the liver converts stored
glycogen into glucose and releases it into the blood
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When the control of blood glucose does not work, a person is said to have diabetes
Type 1 diabetes is caused by the death of the cells that secrete insulin
 Symptom: hyperglycaemia (feel unwell, dry mouth, blurred vision and feel
thirsty) or hypoglycaemia (tired, show confusion and irrational behaviour)
 Treatment: eating little and often and avoiding large amount of carbohydrates,
injecting insulin to reduce blood glucose concentratio
Thermoregulation
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Constant body temperature is maintained by:
Insulation: provided by fatty tissue retains heat. Hairs become erect to trap warm air by
contracting erector muscles and vice versa.
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Vasodilatation: when it is hot, arterioles, which supply blood to the skin-surface
capillaries, dilate (become wider) to allow more blood near to skin surface to increase
heat loss (face redder)
Vasoconstriction: when it is cold, arterioles, which supply blood to the skin-surface
capillaries, constrict (become smaller) to allow less blood near to skin surface to
decrease heat loss
Sweating: the water evaporates giving a cooling effect
Skin receptors: sense heat and sensory neurons send impulses to the hypothalamus
Shivering: muscular activity generates heat
Thermoregulatory centre: in the hypothalamus, it controls the use of corrective
mechanisms (e.g. sweating and shivering).
Homeostatic Organs
Cells: change composition of blood as they remove nutrients and O2 and add wastes
and CO2
Heart: keeps blood pressure constant to deliver oxygen and nutrients around body
Skin: to maintain heat exchange with external environment
Kidneys: regulate water and salt levels (osmoregulation) and the removal of wastes like
urea (excretion)
Lungs: regulate gas exchange
Intestines: supply soluble nutrients and water to blood
Liver: regulates blood solutes and removes toxins
Tropic Responses
Auxin:
 Plant hormones or growth substances
 Controls tropisms
 It is produced by cells at the tip of roots and shoots of plants
Gravitropism: a response in which a plant grows towards (positive) or away (negative)
from gravity.
Auxins’ role in gravitropism:
 Tend to settle at the bottom end of the root.
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However, this does not make the cells of the tip of the root grow longer; auxins
prevent cells at bottom tip of root from growing, making cells at top of root grow
faster.
 When cells of top of the root grow faster, they push root deeper into soil and
root gets longer.
 The root grows in direction of the gravitational pull.
Phototropism: a response in which a plant grows towards (positive) or away (negative)
from the direction from which light is coming.
Auxins’ role in phototropism:
 If sun shines on right side of a plant’s shoot, auxins will accumulate on dark
opposite left side.
 Auxins accumulating makes cells on left side grow faster than cells on right side.
 When left side of shoot starts growing faster than right side, shoot will start to
bend to right side towards sunlight.
Hormones can be used as weed killers: spraying with high concentrations of hormone
(2,4-D) upsets normal growth patterns. It affects different species differently so might
only kill one species not the other (this is good).
DRUGS:
 Drugs: Any substance taken into the body that modifies or affects chemical reactions in
the body.
Antibiotics
 Antibiotics work by stopping a metabolic practice performed by the bacteria you are
trying to get rid of, but not performed by human cells.
 Some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics
 Development of resistant bacteria such as MRSA can be minimised by limiting use of
antibiotics only when essential and ensuring treatment is completed
 Antibiotics don’t work on viruses because they are not really living and they make the
host cell perform the tasks for them.
REPRODUCTION IN PLANTS :
Asexual Reproduction
 The process resulting in the production of genetically identical offspring from one
parent.
 Bacteria:
 Reproduce by binary fission, each bacterium divides into two.
 The generation time is the time taken for a cell to divide into 2.
 Fungi:
 Single-celled yeast reproduces by binary fission.
 All other fungi produce via spores.
 When the sporangium bursts it spreads the spores.
 Spores land and grow mycelium (roots) for example mushrooms
 Potatoes:
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The shoot from a potato goes back underground and the stem swells to form a
new genetically identical potato.
 The swollen stem acts as a storage organ.
Advantages- no need to find mate, good characteristics are kept
Disadvantages- no variation, harmful genes transferred, overcrowding
Functions of plant parts
 Sepal: protect the flower bud.
 Petal: brightly coloured and scented and may have nectarines which are all used to
attract insects, petals in wind pollinated flowers are tiny, and used for pushing the
bracts (leaf-like structures) apart to expose stamens and stigma
 Anther: has pollen sacs with pollen grains which contain the male nucleus (male
gamete).
 Stigma: platform on which pollen grains land
 Ovary: hollow chamber, ovules grow from the walls.
Pollination
 Pollination: transfer of pollen grains from the male part of the plant (anther of stamen)
to the female part of the plant (stigma).
 Agents of pollination: insects, birds, mammals, water and wind
Insect pollination- colorful petals , nectarines, moderate amount of pollen, pollen spikey/sticky,
anther, and stigma inside flower, stick sigma
Wind pollination- dull petals, no scent, no nectarines, huge amounts of pollen, pollen round and
smooth, anther and stigma hang out, stigma hairy
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Pollen tube: pollen grain lands on stigma and creates a tunnel down the style, through
the micropyle, to the ovules.
Structure of non-endospermic seed:
Formation of a seed: the zygote divides many times by mitosis to form and embryo. The
cotyledon is the food store. The testa stops drying out of embryo.
Wind and animal dispersal are used by plants to colonise new areas; done because new
areas have less competition for light, space and nutrients, so seeds are more likely to
develop.