Photosynthesis & ATP synthesis
Heterotroph: Organisms which feed on organic matter (mammals)
Autotroph: Organisms which make food using inorganic matter (plants)
Respiration: Process of converting inorganic matter into energy
CO2 diffusion: Stomata ------> Air spaces ------> mesophll ------> chlorophyll
(Contains Chlorophyll)
Leaf necessities:
1. Contain chlorophyll and other pigments arranged to absorb light
2. Be able to absorb CO2 and dispose of oxygen
3. Have decent water supply
4. Be able to transport manufactured carbohydrates to the rest of the plant
Large surface area and thinness allow for maximum light absorption
The upper epidermis has thin flat transparent cells which secrete a waxy
transparent cuticle that prevents water loss.
(The lower epidermis contains more stomata since they don’t directly face the
sun; Upper has less to avoid excess water loss.)
Stomata (pores) regulate diffusion of gases. They are
surrounded by 2 guard cells that regulate the rate of
transpiration by swelling up and spreading out when
turgid and absorbing water, allowing gases to diffuse
through stomata, then, shrinking and closing up when
flaccid as it releases water.
A decrease in water potential is needed for more water to be absorbed; this is achieved by
removing hydrogen ions using energy from ATP and the addition of potassium ions using indirect
active transport.
Palisade cell light adaptation:
1. Long & cylinderal position 90* from epidermis
2. Large vacuole restricts chloroplasts to edges
3. Proteins in cytoplasm can move chloroplasts to
absorb enough light or protect against excessive sun
Palisade cell gaseous exchange adaptation
(Palisade cell)
[Photosynthesis only occues in spongy
mesophll during high light intensities since
1. Long narrow air spaces providing surface area their air spaces provide a large surface area
2. Thin cell walls
containing moist cell walls ]
Chlorophyll structure and function
Also contain ribosomes and dna
Starch grains store carbohydrates
The membrane contains chlorophyll (type a & b) which is a pigment that absorbs
certain wavelengths (colours) of light (unabsorbed colours are reflected and seen)
NB: Chlorophyll A absorbs slightly longer wavelengths than B.
Carotenoids such as carotene and xanthophlls are pigments that absorb shorter
wavelengths but aren’t completely necessary.
Light dependant stage
Location: Thylakoids in chloroplasts
-these thylakoids contain phoyosystems (chlorophyll cluster) which absorb and
transfer light to form ATP
Photophosphorylation: photo (using light) phosphorylation (phosphate addition)
Cyclic photophosphorylation
-Only Ps1 is used
- No NADPH formed
1. Light is absorbed
2. Electron gains energy and moves
across carriers
3. Energy is used to form ATP
4. Electron returns and cycle repeats
ADP: Adenosine diphosphate
ATP: Adenosine triphosphate
680nm : PSII
I700nm : PSI
Non- cyclic photophosphorylation
(Z scheme)
-PSI & PSII
- forms NADPH
1. Cyclic photophosphorylation
2. Electron go to PSI
3. Energy is used to form NADPH
(photolysis)
Background: H2O splits: “O” is disposed, H+ reacts with NADP & E- entered PS
Light Independent stage (dark)
Location: stroma of chloroplasts
- it contains the enzyme Rubisco (Ribulose bisphosphate carboxylase) which catalyzes the
combination reaction between CO2 & RuBP (Ribulose bisphosphate)
ATP & NADPH are used in this process to produce carbohydrates (glucose etc)
1. 6RuBP (5C) + 6CO2= 6C (unstable) which
then splits into (12) 3C GP/ PGA
(6C split into 2- 3Cs)
(phosphosglycerate)
(GP/ PGA)
2. 12 ATP gives a phosphate to 12 GP (3C)
forming 12/TP (3C) and NADPH2 is oxidized.
3. 5/6 of TP rearranges to regenerate RUBP
83%
(Sugar)
by 6 ATP giving phosphates, 1/6 form glucose
Ribulose-5-phosphate
1,3- biphosphoglycerate
Factors affecting rate of photosynthesis
A limiting factor is what limits the rate of reaction during Photosynthesis. If enough
isn't supplied to the plant the rate would increase .
Light intensity
-Light provides energy for the light dependant reaction. (Doesn't affect LIDS)
-increased light = increased rate
-too much light = optimum rate (light saturation)
Carbon dioxide concentration
-Air= 0.04% CO2
-Absorbed through stomata
-The diffusion gradient keeps gases moving in as the [inside] < [
outside]
Temperature
-Mainly affects light independant stage since enzymes are present & denature
exceeding optimum temp (Doesn't affect LDS)
Photorespiration: Rubisco catalyzes a reaction bonding O2 to RuBP instead of
CO2 if the temperature is too high
-Affects kinetic energy, higher temp = more motion & collisions = increased rate
Quanitiy of chlorophll
-More chlorophyll = more absorbtion of light energy
-Lack of nutrients, disease and environmental stress cause damage to
chloroplasts, resulting in decrease in chlorophyll
Light effect on Calvin cycle
- Light isn't needed, but the products (ATP & NaDP) from photophosprylation are
-When light isn't supplied, ATP & NADPH is no longer given to the calvin cyle
-ATP & NADP are used as fuel for the conversion of GP (PGA) to TP
- GP piles up and the process continues till TP is used up
Respiration & ATP synthesis
Active transport: moving substances against concentration gradient (requires energy)
ATP: Adenosine Triphosphate, ADP: Adenosine Diphosphate (energy currency)
Hydrolysis: When ATP loses a phosphate, 30.5kJ of energy is released.
(This is catalyzed by the enzyme ATPases)
Glycolysis (breaking glucose apart)
Location: cytoplasm
1. Phosphorylation (glucose -------> glucose-6-phosphate)
2. Isomerisation (glucose-6-phosphate -------> fructose-6-phosphate)
3. Phosphorylation (fructose-6-phosphate --------> fructose biphosphate)
4. Lysis (fructose biphosphate -------> Dihydroxyacetone phosphate & Glyceradehyde phosphate
5. Oxidation, loss of H (NAD ------> NADH)
6. Phosphorylation (Glyceradehyde phosphate -------> Glyceradehyde biphosphate)
7. Dephosphorylation (Glyceradehyde biphosphate -------> 3-phosphosglycerate
8. Isomerisation ( 3-phosphosglycerate ------> 2-phosphosglycerate)
9. Dephosphorylation (2-phosphosglycerate -------> pyruvate)
Mitochondria
Link reaction: Oxidative Decarbonization
Pyruvate enters mitochondria once O2 is available to continue aerobic respiration
1. Decarbonization & Dehydrogenation of pyruvate: "C" excreted, "H" reduces
(NAD-------> NADH)
2. Combination of Coenzyme A (CoA) forming acetyl CoA
Krebs Cycle
Location: matrix of mitrondria
-Produces ATP, CO2, FADH2 NADH2
1. Carboxylation (oxaloacetate (4C) + acetyl CoA (2C) -------> citrate (6C)
2. Isomerisation (citrate ------> Isocitrate)
3. Oxidatative Decarboxylation (Isocitrate (6C)------> alpha ketoglutarate (5C)
4. Oxidatative Decarboxylation (alpha ketoglutarate (5C) -------> succinate (4C)
5. Oxidation (succinate (4C) ------->fumerate (4C) (2FAD------>FADH2)
6. Isomerisation (fumerate (4C) -------> malate (4C) (in the presence of water)
7. Oxidation (malate (4C) -------> oxaloacetate (4C) (NAD-----> NADH2)
Oxidative decarboxylation forms (2NAD -------> 2NADH2, 2CO2)
(Inorganic phosphates (Pi)
flow freely in the cytoplasm)
2
2
X2
2
Electron transport chain: Oxidative Phosphorylation
Location: Inner membrane (cristae) of Mirochondria
-Contains complex molecule, proteins and cytochromes known as electron carries
- NADH and FADH2 from Krebs cycle are oxidized in this process
- Once oxidized, NAD and FAD return to the Krebs cycle to be reused
- ATP Synathases & Complexes 1, 3 & 4: intrinsic proteins, Complex 2: extrinsic
- Coenzyme Q & cytochrome C: transfer molecules
1. Oxidation: NADH donates electron to EC1 and H+ moves to intermembrane
2. Transportation: Electron goes to CoQ
3. Oxidation: FADH donates electron to EC2 then sends it to CoQ
4. Transportation: Electron moves from CoQ to EC3 & H+ moves to intermembrane
5. Transportation: Electron moves to Cyt C, then EC4 & H+ moves to intermembrane
6. H2O Formation: Electron moves to oxygen which splits to form 2H2O
7. Chemiosomosis: H+ moves down ATP synthase catalyzing formation of ATP
8. Cycle repeats
T
4H= 1 ATP
Oxygen has 6 v.e therefore if you add to that it'll gain a full
she'll and no longer be reactive
Therefore an O ion / 1/2O is used so it wouldn't lose reactivity
Aerobic Respiration (Presence of air)
Glycolysis in cytoplasm
Link reaction in matrix
Matrix
{
{
{
Electron transport chain
Glucose
Pyruvate
Acetyl CoA
Krebs Cycle
NaDPH2 & FADH2 --------> ATP
Structure and function of mitochondria
Shape, size and quantity of mitochondria in a cell depends on cell activity/ purpose
Anaerobic Respiration/ Lactic fermentation
Location: cytoplasm in absence of oxygen
Amount of ATP formed: 2
Pyruvate + NADH ------> lactate + NAD
-Lactate produces in muscle cells during excersise since more O2 is needed, it
diffuses into blood to be carried around the body.
-High lactate concentration affects the brain & causes disorientation & nausea
- Too much lactate stops muscle contraction
- Hepatocytes (liver cells) absorb lactate and convert it to pyruvate.
-Removal of lactate by hepatocytes requires oxygen (why athletes breathe so hard
after excersice to provide extra oxygen to cells)
-Extra oxygen needed: oxygen debt
Lactic fermentation
Fermentation in yeast
Uses of Anaerobic Respiration
-Yeast fermentation: Alcohol, rum (sucrose) , wine (grapes) , beer (starch from
barley grain broken into maltose), yogurt (lactic fermentation of milk)
Respiratory substrate
Substance used to make ATP
-Carbohydrates & proteins: 17kJg of energy
- Lipids 39kJg of energy
-Molecules with more H release more energy since it's stored in the e- of H
-Red blood and brain cells entirely depend on glucose as a substrate
Measuring rate of Aerobic Respiration
-Uses O2 to make CO2
-If a respiring organism is placed in a closed system and CO2 is removed, volume
of gas will reduce as O2 is used up.
-CO2 is removed with soda lime / KOH
-Water baths are used to maintain temperature
-gas volumes are sensitive to temp and pressure, ensure to maintain it for
accurate results
-
Energy flow and Nutrient Cycling
Terms
- Ecology: study of interactions of organisms in an environment
- Abiotic: Non-living, Biotic: Living
- Fauna: Animals
- Flora: Plants
- Habitat: Area organisms live
- Species: Organisms capable of interbreeding with one another, have similar
characteristics and have fertile offspring
- Population: Members of same species living in a habitat
- Community: Different species living in a habitat
- Ecosystem: A natural unit of living and non living organisms through which energy
flows in a Nutrient cycle
- Niche: role of an organism in an ecosystem
-Trophic level: Feeding level
- Food chain: linear feeding relationship/ transfer of energy
- Food web: Combined food chain
- Biomass: Total mass of organisms of a species living in an area of the environment
NB: Only 10% of energy is passed up each Trophic level
Types of coral
Light absorption loss
-sunlight not hitting leaves
-sunlight being reflected from leaf surface
-sunlight passing through leaves but missing chlorophyll
-some wavelengths not being absorbed
-energy loss during reactions of photosynthesis
Energy loss
-not all parts of plant consumed
-not all plant material is digested, remaining material is excreted for decomposers
-energy lost through heat
Productivity
-Rate at which plants convert light to chemical potential energy
-Units: kJm-2year-1 (kilojoules of energy transfered per square meter per year)
-Gross primary productivity (GPP): Total energy transfered
-Net primary productivity (NPP): Energy remaining after respiration
-Primary productivity is used only for producers however GPP & NPP is for all
-All energy is recycled in an ecosystem, dead cells are broken down into inorganic
materials by decomposers
Nitrogen cycle
-Nitrogen exists as a triple bonded molecule making it unreactive and unusable.
-It must be converted to ammonia (NH3) or nitrate (NO3) (nitrogen fixation)
Nitrogen fixation (organisms)
-Only prokaryotes and archeans are capable of nitrogen fixation eg. Rhizobium
(This bacteria is found in nodules of plant roots sharing a mutualist relationship. During
germination, lectin (protein) is produced binding to polysaccharides on the surface of
Rhizobium. The bacteria invades and spreads along the root hairs causing cells to separate
forming nodules (lumps) for bacteria to live)
Nitrogenase catalyzes conversion of Nitrogen (N2) to Ammonium ions (NH4+)
-Hydrogen (from NADPH)
-ATP (from metabolism of sucrose during photosynthesis )
- Absence of oxygen (leghaemoglobin protein absorbing oxygen)
-Nitrogen fixation (atmosphere): lightning providing energy to form (NO3) which is
dissolved in rain and carried to the ground
-Nitrogen fixation (Haber process): In the production of fertilizer, ammonia is
produced and often converted to ammonium nitrate for fertilizer (cheaper)
-Use of Nitrogen by plants: Amino acids & proteins
-Digestion of nitrogen by animals: Proteins are broken down to amino acids,
absorbed into the blood and distrubuted to the body then built into proteins again.
Excess amino acids are deaminated in the liver and nitrogen is excreted in urea
Return of nitrate to soil from living organisms
-Decomposers break down proteins from dead animals/plants into amino acids
using protease. Some are used for growth of Decomposers while others are broken
down to release nitrogen as ammonia (Ammonification)
-This ammonia is rapidly converted to nitrite and nitrate ions (NO2- & NO3-) by
nitrifying bacteria (nitrosomonas & nitrobacter) which get energy from nitrification
Denitrification
Denitrifying bacteria get energy by reversing nitrogen fixation by converting nitrate
to nitrogen gas which is returned to the air. Common in sewage treatment plants,
compost heaps and wet soils.
Ecological systems, biodiversity & Conservation
Biotic factors: Living
-Feeding (herbivore eats plants)
-Predation (predator kills prey)
-Parasatism (parasyte harming host) (isopods on fish skin)
-Mutalism ( associated organisms benefiting from each other)
-Commensualism (associated organisms neither harming nor benefiting)
-Competition (organisms fighting over organism in short supply)
Abiotic factors: Non-living
-Temperature (too high cause coral bleaching and oxygen solubility)
-Light intensity
-O2 concentration
-CO2 concentration (too high lowers pH, acidification)
-Water supply
-pH of water & soil
-Availability of inorganic ions (nitrate/potassium)
-Humidity
-Wind speed
-Wave action (coral reefs can be damaged due to harsh winds)
Biodiversity
-Species diversity: Number of different species in an ecosystem, quadrat/ habitat
(Habitats further from the tropics contain less species diversity since the tropics
have higher temperatures allowing for faster metabolism, all regions of the world
contain "Hotspots" where diversity is more prominent)
Plant species diversity is affected by:
⁃ Solar radiation
⁃ Rate of water loss
⁃ Humidity
⁃ Temperature
Limitations of species diversity
⁃ presence / absence of a species does not determine ecological health (does
not describe genetic diversity )
⁃ Low abundance of a species can cause extinction in that area
-Genetic diversity: Inherited species variation
(species with low genetic diversity are less likely to survive in a changing
environment)
-Genetic diversity is proportional with population size
-large population size= more genetic diversity and vice versa.
-Ecosystem diversity: Number of ecosystems
(more ecosystems give rise to more species diversity)
Ecosystem stability
Ecosystems with complex food webs with high biodiversity are more stable.
Endemic species: Found in only 1 county eg.tasmanian devil in Australia
Importance of diversity maintenance:
-maintain stability of ecosystem (can prevent climate change
-Species that can be used for medicinal purposes can be lost (over 7000 drugs
are derived from plants)
-Ecotourism: tourists observe biodiversity of a country
Conservation:
Protection of species, habitats and ecosystems to maintain biodiversity
-Situ conservation: in habitat (protection from erosion, deforestation, desertification,
sea acidification, pollution, farming etc.)
-Ex Situ conservation: out habitat ( parks, wildlife/ nature reserves, zoos, botanic
gardens, seed/embryo banks etc.)
Loss of rainforests
Deforestation is used to create plantations of rubber or oil palm, charcoal production
and subsistence farming. This leads to soil erosion leading to the land becoming
permanently degraded. When habitats are lost it may be hard for organisms to find
a new one exactly the same since they all differ in some way. In poorer areas, slash
and burn is used where an area is cleared and burned to release nutrients, if done
excessively can cause permemant damage.
Rainforests retains water in soil and when it's cleared the water runs off into rivers and streams which makes rainforests
viable for drinking water. The pressure for short-term financial gain is what pushes deforestation to continue, meaning the
government should place policies to permit this in order to conserve.
Transport in plants
Requirements: CO2, Oxygen, Organic nutrients, Inorganic ions and water
Uptake of ions:
Inorganic ions are absorbed from between soil particles through root hairs then
transported to the xylem to be carried to parts of the plant.
Facilitated diffusion: Higher concentration of ions in the soil than in the root hair cell
Active transport: Lower concentration of ions in the soil than in the root hair cell
(energy required)
Osomosis
Movement of water through a selectively permeable membrane from high to low
concentration/potential (less negative to more negative)
Water Transport in Xylem
1. The thin layer of water covering each soil particle is absorbed by root hairs.
2. Water passively travels from the epidermis, to the cortex then to the stele
Routes:
Aploplast: Cell wall to Cell wall
Symplast: Cytoplasm through plasmodesmata
Vacuolar: Vacuole using cytoplasm and plasmodesmata
(A band of waterproof suberin that forces water through
the selectively permeable membrane to the cytoplasm)
(Vacuolar)
3. Water is actively transported through the endodermis, pericycle then xylem
Xylem vessels are made up of stacked xylem
"element". Patterns are formed by lignin
(waterproof ) which eventually kills the element as it
ages. Water is moved through the spaces/ pits of
the lignin. (Lignin keeps water within and supports
the cell)
Mechanisms of mass flow:
Capillarity: Cohesion & Adhesion
-Cohesion: Hydrogen bonds connect H2O
-Adhesion: H2O sticking to xylem vessels for
Transpiration
Water leaves xylem through a "pit" then moves to cell wall and is evaporated forming
water vapour which diffuses into the air spaces in spongy mesophyll. When the water
potential is lower in the atmosphere, a gradient forms causing vapour to the diffuse
out the leaf through the stomata.
As water evaporates from the cell walls, it's replaced by osomosis forming a
transpiration pull using Cohesion and Adhesion. (Continuous water movement is
known as the transpiration stream).
(Root pressure is osmotic/hydrostatic pressure that builds up in roots due to water
potential gradient to send water up the xylem)
Factors affecting transpiration:
-Humidity: Low atmospheric humidity = High transpiration rate
-Temperature: Increase in temp = Increase in evaporation & transpiration
-Light intensity: Stomata close at night (small aperture) reducing transpiration
-Air movements: Winds push humid air, increasing transpiration
-Plant structure & leaf anatomy: larger leaf= larger surface area
Translocation: Food Transport in Phloem
Assimilates: Substances being transported which are made by the plant (sucrose)
Symport: different substances moving in the same direction
Antiport: different substances moving in different directions
1. H+ diffuses into the mesophyll from the companion cell then back to the
companion cell with sucrose ([H+] < in companion cell while [sucrose] is = in both
which is why H+ is needed in order to pass sucrose since there is no gradient )
2. Sucrose and H+ diffuse into the sieve element through the plasmodesmata by
from the companion cell
3. Sucrose then diffuses out the phloem into the "sink" (eg. Roots)
4. Sucrose is converted to glucose/ fructose by "invertase" and used for
respiration or stored as starch.
5. Water returns to the xylem once the food reaches the sink since it's just a
carrier and the water potential gets less negative as the food is diffused to the sink
The Circulatory System
Blood:
The body & blood contains:
-approximately 5dm3 of blood weighing 5kg
-Plasma & plasma proteins
-Erythrocytes: red blood cells (2.5 x 1013)
-Leucosytes: white blood cells (5 x 1011)
-Platelets (6 x 1012)
Erythrocytes (Red blood cells)
- Pigment: Haemoglobin (Hb): Globular protein
- Function: transporting O2 & CO2 between lungs and respiratory tissue
-Very small (7um): close to membrane allowing easy exchange
- Diconcave disc allowing larger surface area to volume ratio & fast diffusion
- No nucleus, mitochondria or reticulum, leaving more space for haemoglobin
Role of Haemoglobin
- Each Haemoglobin can bind to 8 oxygen atoms forming oxyhaemoglobin.
- When O2 is in [high], Haemoglobin combines then releases it in places with [low]
Oxygen-Haemoglobin dissolution curve
- Partial pressure: availability/ concentration of O2
- Saturation: amount of oxygen bound to blood
- Greater partial pressure = greater saturation
Neutrophil & Monkcyte: Phagocytic
Basophill: Heparin & Histamine
Esonophil: Antihistamine
Lymphocyte: Antibodies
Allosteric Effect: An empty Haemoglobin is tense, hence
why it is harder for the first oxygen to bind. However, Hb
begins to relax as more O2 is added, increasing affinity.
In the lungs where partial pressure is high, most Hb
molecules are fully saturated, however in respiring tissue
where partial pressure is low, Hb loses O2. (The last O2 is
only given in high demand )
Arteries: Away from heart (oxygenenated)
- Blood doesn't move slowly, but in surges (pulse) which correspond to heart beat
-As the heart's ventricles relax and blood pressure decreases, arteries recoil
inwards to give blood a little "push"
- When the ventricles contract, Arteries widen to lower blood pressure
Veins: To heart (deoxygenated)
- For blood to move to the heart, valves prevent backflow
Capillaries:
- Form networks (beds) around every tissue (except cornea & cartilage)
-Their size and thin walls allow rapid transfer of substances and allows blood to
get as close as possible to cells
Carbon dioxide transport
When CO2 diffuses into plasma:
- 5% remains as CO2 molecules in plasma
- 85% diffuses into erythrocytes where the enzyme carbonic anhydrase
catalyzes the reaction between CO2 & H2O. The HCO3 ions diffuse out of
erythrocyte, into plasma then carried to lungs while The H+ from reacts with
Haemoglobin to form Haemoglobinic acid (HHb). This causes Haemoglobin to
release and oxygen
Goes to lungs
- 10% combines with Haemoglobin to form carbaminohaemoglobin. causes
Haemoglobin to release oxygen. When blood reaches the lungs, HbCO2 gives up
CO2 into the alveoli, making room for Hb to accept oxygen once again.
Bohr shift (Christian Bohr: 1904)
- Bohr effect: High CO2 concentration causes Haemoglobin to release O2 more
readily. High [CO2] is found in respiring tissues that need oxygen.
- Dissociation curves with higher [CO2] lie to the right & below "standard" [CO2].
As seen in red, when more oxygen is needed/ when
less oxygen is available, saturation decreases.
The Heart
Oxygenated blood: Pulmonary vein -------> Aorta Deoxygenated blood: Vena Cava -------> Pulmonary artery
Aorta
Vena cava
Pulmonary artery
Pulmonary vein
(Left)
(Right)
Pulmonary vein
Vena Cava
Aorta
The Cardiac Cycle
Atrial diastole: Oxygenated blood from pulmonary veins enter left atrium
.
Deoxygenated blood from vena cava enter right atrium
Atrial systole: Atria contract, cupid valves open and blood enters ventricles
Ventricular systole: Ventricles contract & semilunar valves open (1st heart sound: lub)
Oxygenated blood from left ventricle flows into the aorta
Deoxy-blood from right ventricle flows into pulmonary artery
Ventricular diastole: Semi-lunar valves close, atria refills and ventricles relax
2nd heart sound dub
Controlling Heart Beat
Heart muscles are myogenic (automatically contracts and relaxes in unison)
- Sino-atrial node (SAN): Coordinating system responsible for rhythm of cardiac
muscles, located in right atrium.
- SAN's rhythm is slightly faster and set a wave of electric activity when it
contracts causing atrial walls to contract simultaneously and blood to fill ventricles
- Atrio-ventricale node (AVN): A small patch of conducting fibres located between
atria & ventricles which pick up electric waves, delays it for 0.1s then passes it
unto Purkyne tissue/Bundle of His
-The electric wave is spread rapidly from the B.O.H, down the septum then spreads
up and outwards through the ventricle walls making it contract and squeeze blood
into arteries.
Regulation of Cardiac Output
(Cardiac output: The amount of blood pumped by the heart per minute)
High volume of blood to heart: Heart pumps faster and harder to push out blood
- Increased blood stretches cardiac muscles thus stimulating SAN to have slightly
faster action potentials causing harder contractions and increased stroke volume.
NB: rate is increased during excersice because of lack of O2 in the blood (as you
excersise it gets hard to breathe so insufficient oxygen is supplied to lungs) The drop of O2
stimulates blood vessels to release "NO" causing vasodilation (widening/ relaxation of
blood vessels) of arterioles supplying blood to excersing muscles, increasing rate.
Higher rate (more blood) = more O2 being transported to muscles
Nerves running to the heart carry impulses from cardiovascular centre in medulla
- Vagus (parasympathetic nerve): Brain to SAN & AVN (decrease heart rate)
- Sympathetic nerve: Brain to areas in cardiac muscle (increase heart rate)
- Before excersice the brain sends impulses to the "SPN" to increase heart beat before blood comes
- High pressure: baroreceptors stretch artery walls sending impulses to the brain then to the vagus
to slow down heart rate
- Low pressure: Impulses are not sent to the brain, the cardiovascular centre sends impulses to the
"SPN" to increase cardiac output and arterioles to narrow walls (vasodilation)
Homeostasis: maintenance of internal environment
- Cell signaling: When nerves / hormones send information from a cell to another
- Positive feedback: intensifies disturbance in order to combat issue
eg. During menstruation, hormones increase to stimulate ovulation
& during childbirth contracts and hormones help with delivery
- Negative feedback: Has a "set point" that must be maintained
Eg. When blood pressure is high, baroreceptors stretch to send impulses to the
Types of hormones:Catecholamines, insoluble in lipids (e.g. adrenaline.)
Steroids, soluble in lipids (e.g. testosterone.)
Peptides and proteins (e.g. insulin)
.
Fatty acids (e.g. prostaglandins)
Factors in environment affecting cell activity
- Temperature: Too low slows reactions, too high denatures enzymes & proteins
- Water: Too little in tissue causes water to draw out cells, too much in tissue
causes water to move into cells, making them swell and potentially burst
- [Glucose]: Too little slows down respiration, too much in tissue cause water to
draw out cells
Endocrine System
- Endocrine glands: secrete hormones that travel through blood to target tissues
Endocrine glands
The pancreas: (Endocrine & Exocrine)
- Endocrine: pancreatic juice flows through ducts into duodenum in small intestine
Enzymes involved include: lipase (lipids to fatty acids), amylase (starch to maltose),
trysin (proteins to polypeptides)
- Exocrine: Secretion of hormones by cells in the Islets of Langerhans
Alpha cells: Insulin, Beta Cells: Glucagon
Control of blood glucose (80-120 mg per 100cm3 of blood)
High [glucose]:
Beta Cells start producing insulin which causes:
- Increased absorption of glucose: GLUT4 (glucose transporters) moves into membrane
and forms channels that allow glucose to pass through (Brain & Liver always has this)
- Increased glycogen: glucokinase catalyzes the phosphorylation of glucose,
trapping it in the cell & making it incapable of passing through transporters.
(Phosphofructokinase & glycogen synthase catalyzes conversion to glycogen)
Low [Glucose]
Alpha Cells start producing glucagon which causes:
- Increased break down of glycogen: glucagon binds to receptors in liver activating
enzymes that catalyze: glycogen to glucose allowing it to diffuse out the liver
- Gluconeogenisis: production of glucose from amino acids/ lipids
Control of Insulin Secretion
Beta Cells contain channels in their membrane that allow (K+ & Ca2+) ions to
pass through. K+ channels are usually open, allowing K+ ions to freely pass out
and keep a slightly positive charge outside of the membrane.
High glucose: Glucose is phosphorylated then metabolosed to form ATP. K+
channels close when ATP increases (membrane potential difference decreases)
which causes Ca2+ channels to open allowing ions in. Vesicles containing insulin
move towards the membrane where they fuse and secrete insulin outside the cell.
Risk of Diabetes:
- Being overweight (BMI >27)
- Being 45+
- Being physically inactive
- Being Asian/ Black
Type 1: Not enough insulin produced
Type 2: No insulin produced
Plant Growth Regulators (Hormones)
-Auxin: Control growth (responses to light and gravity)
-Gibberellin: Control stem elongation & seed germination
-Abscicic acid: Control responses to stress (eg. Stomata close when water supply is low)
-Ethene: Control Fruit Ripening
Fruit Ripening
Fruits are needed to disperse seeds along different areas. Their bright colours,
sweet smell & taste attract animals which eat then discrete seeds.
Colour change: Chlorophyll is responsible for the green pigment in unripe fruits,
chloroplasts convert to chromoplasts & chlorophyll breaks down into various
carotenoid pigments as fruits ripen.
Texture: Cell walls break down as the middle lamella becomes partially hydrolysed
and hydrated during ripening making the fruit softer and juicer.
Aroma: Chemical substances responsible for flavor and smell increase as fruit
ripens. Flavor compounds convert to gas and spread in the air around the fruit
which draw animals towards it.
Sweetness: Starch converts to sugar which dissolves in water inside cells and
decreases water potential which causes water to start flowing in them, making the
fruit juicier
Control of fruit Ripening
Fruit Ripening attracts animals. Ethene is a small lipid-soluble gas which diffuses
from fruit to fruit and stimulates ripening (in climacteric fruits) along with a rise in
rate of respiration. Ethene is synthesised from methionine and when produced, it
increases enzyme activity causing more to be synthesised.
Things ethene do:
Restricts stem growth, Breaks bud dormancy, Increases respiration, increases ripening
(Ethene does the samething as a hormone but isn't considered one because it's
function is carried out/ target cell is in the same place it's made)
NB: Climacteric fruits have a spike of ethene production during Ripening, thus
respond better to ethene when applied.
Commercially ethane can be used to control ripening. Fruits are harvested when
mature but still green so they can be transported without damage and reach their
destination before they are too ripe to be sold. They are stored in 02 poor
environments to reduce respiration. Just before their sale they are treated with
ethene which stimulates ripening.
T
Kidney, Excretion & Osmoregulation
Excretion: removal of toxic substances from the body (CO2, urea, salts & H2O
and regulation of ions, water & pH.
Urea: produced in liver and formed from excess amino acids. Blood transports urea
to the kidneys where it is excreted and dissolved in water as urine.
Deamination (liver): Ammonia is formed from Amino Acids while the Amino group is
converted to keto acids which can be stored as fat/ released as energy
nephron
Ultrafiltration:
Blood from renal artery enters glomerlus (bunch of capillaries) from afferent artieriole
and is forcefully filtered through basement membrane and podocytes of bowmans
capsule (efferent artieriole is smaller, increasing hydrostatic pressure.)
Selective reabsorption:
- Glomerular filtrate moves through bowmans capsule to the proximal convoluted
tubule where needed substances (glucose, amino acids Na+ & Cl-), are reabsorbed
into the blood capillaries through active transport. Water potential increases in the
tubule causing osomosis into the capillaries.
- Glomerular Filtrate moves down the descending loop of henle where water is
moves out, this increases solute potential. As filtrate moves up the ascending loop of
henle, Na+ moves into the interstitial space. (DLH: impermeable to salt, ALH: imperiable
to H2O). Selective reabsorption occurs again in distal convoluted tubule
Osmoregulation
The hypothalamus detects water potential in blood and produces the hormone ADH.
It moves along axons and is secreted by the pituitary gland if psi is low. This
stimulates aquaporins to bind to the collecting duct making it more permiable to
water, thus absorbing more and creating more concentrated urine.
Nervous Coordination
Central nervous system: brain & spinal cord
Peripheral nervous system: Nerve cells / neurons (Autonomic & Somatic)
Nerves detect changes in the environment and aid in responding to stimuli by
receiving action potentials/ impulses
Movement of impulses / info:
Recieve info
Sensory: receptors to CNS
Detect changes/ stimuli
(Made of Schwann cells)
Protects & insulates axon
Processes info
Relay: CNS to CNS
Transports info
Motor: CNS to effector
Speed up delivery
Transmits info to next cell
Sensory
The flame sends impulses along the
Dorsal root of spinal nerve
Motor
(Reflex action)
Reflex Arc:
Sensory neuron
sensory neurons in the hand which
are transferred to the intermediate
Motor
neuron in the spinal cord which then
sends this impulse to the motor
neurons returning back to the hand
(sensory neuron on detects stimulus)
(effector). The hand then rapidly
responds by moving away.
Resting Potential
Potential difference of a neurons at rest: -70mV in (inside is 70mV > outside)
Sodium potassium pump: 3Na+ moves out and ATP binds to the channel closing
it, 2K+ ions move in, ATP leaves and the channel returns to the original shape
The /membrane is 20x more permiable to K+
Action potential
Membrane potential from -70mV (at rest) to +40mV ( when stimulated)
- Graded potential: if the voltage doesn't pass -55mV depolarization doesn't occur
- Depolarization: Membrane potential reaches the threshold (-55mV), voltage gated
Na+ channels open allowing Na+ to come into the cell (makes inside more postive)
- Repolarization: Voltage gated K+ channels open to rebalance charges by allowing
K+ to go outside the cell (make inside less negative)
- Hyperpolarization: K+ channels stay open too long bringing the potential down to
Transmission of Action Potential
Action potentials trigger a chain reaction along the axon.
Depolarization forms an electric field inducing Na+ channels
to open ahead which leads to action potentials. Action
potentials are only transmitted ahead because the region
behind is still recovering from the last one. This makes them
incaple of generating another action potential. (Refractory
How information is carried
All or nothing law: All Action potentials have the same size but vary in frequency.
Higher frequency = stronger stimulus= more neurons activated. The brain uses the
location that detected the stimulus and frequency to interpret information.
Eg. If a sensory neuron is sending impulses from the retina the brain will interpret it as light.
Speed of conduction
Wider axons and myelin = faster conductions
Saltatory Conduction: unmyelinated structures
Continuous Conduction: Myelin sheath allows
impulses to jump from node to node increasing
speed of conduction.
Synapse
Neurons do not touch but have a gap between them (synaptic cleft). A synapse is
composed of the terminal of the presynaptic neuron, dendrites of the post
synaptic neuron along with the synaptic cleft between them.
Crossing of impulses
1. Action potentials reach the presynaptic neuron’s terminal, stimulating the
calcium channels to open near the terminal and Ca+ to enter the neuron.
2. Vesicles bind to the membrane and release neurotransmitters (acetylcholine)
into the cleft.
3. Neurotransmitters bind to receptors in the postsynaptic neuron which
stimulates Na+ channels to open which creates an action potential
4. Neurotransmitters are broken down by enzymes and taken back to the
presynaptic neuron to be regenerated. (Acetyl CoA + Cl -----> Acetylcholine) If this
doesn't occur the NT would be wasted & action potentials would fire continuously
NB: Cholinergic synapse: synapse which use acetylcholine as their NT
NB: Neuromuscular junction: synapse between motor neurone (pre) and a muscle
(post). Action potentials make muscles contract
Function of synapse
Ensuring one-way transmittion, connecting nerve pathways, memory & learning
Effects of drugs on synapse
Nicotine/ tabacoo has a similar shape to acetylcholine making it capable if binding
to receptors in the postsynaptic neurone. These substance do no break down as
Health and Disease
- Healthy: A state of complete mental, physical and social well-being. allowing you to
live an active and enjoyable life as well as being mentally sound.
- Disease: Anything that impairs the normal functioning of your body
Types of Diseases
- Physical: Damage/ malfunction to your body
- Chronic: Long term diseases (eg. Bronchitis due to smoking)
- Infectious: Caused by pathogens which enter and reproduce in the body (eg. Flu)
- Degenerative: Caused by gradual loss of function in a body part (eg. Alzheimer’s)
- Inherited: Caused by alleles that are genetically inherited (eg. AIDs)
- Deficiency: Lack of nutrients (eg. Anaemia due to lack of iron)
- Mental: Disorders which affect your mind and are sometimes caused by changes
in the structure/ function of parts of the brain eg. (Alzheimer’s is caused by the
deterioration of brain tissue causing memory loss and inability to think logically.)
- Social: Associated with the social setting someone spends their life in such as
poor housing / sanitation (eg.Cancer alley in loisiana lined with petrochemical industries)
- Self-inflicted: Caused by a person’s choices/ lifestyle (Bronchitis due to smoking)
Epidemiology: The study of pattern of distribution of diseases & the factors which
influence how common it is in an area.
Data used in epidemology:
- Incidence: Number of new cases in a population in a period of time
- Prevalence: Number of people with the disease in a population in a certain time
Acquired immune deficiency syndrome (AIDS)
Caused by human immunodefiency virus (HIV) (a small retrovirus containing protein,
1. Transmission: HIV is carried from someone’s fluid to another
2. Infection: HIV binds to CD4 receptors & CCR5 coreceptors (using GP120
protein) and enters the T-cell, releasing RNA
3. Reverse transcription: A DNA version of RNA is made using reverse
transcriptase.
4. Integration: The DNA is inserted and merged into the chromosomes of the
nucleus in the host cell using an integrase enzyme
5. Replication: The modified DNA synthesises HIV mRNA which then moves out the
nucleus into the cytoplasm where (viral) precursor proteins are made using
ribosomes.
6. Assembly: Precursor proteins are cut by protease, gather together then become
surrounded by the viral matrix
7. Budding: The immature & noninfectious virus leaves the host cell with CD4 then
Ways HIV is passed on (can only survive in blood)
- Sexual intercourse
- Infected needles
- Blood transfusions
HIV- positive: the virus remains in the T-lymphocyte and continues replicating
which can last from 2 weeks- 20 years (Incubation period) ( the person can begin
developing flu-like symptoms.)
AIDS: HIV becomes active and begins destroying cells after budding. A person is
said to have AIDS if they are HIV positve and have less than 14% 0f CD4 cells.
T-lymphocytes are needed to protect against diseases, as more are destroyed by
HIV the body’s immune system is weaker and more prone to death by sickness.
Symptoms of AIDS
Weight loss, night sweats, blurred vision, diarrhea, white spots on tongue, swollen
glands, persistent fever & tiredness
Reasons for high rates HIV/AIDS
- Unprotected sexual intercourse, Multiple partners, Embarrrassment to get
Cancer
The normal control of cell division functions incorrectly due to alteration of genes
leading to uncontrollable growth of cells leading to tumors.
- Cancer: Tumors which spread around the body (harmful)
- Metastasis: “Malignant” tumors which break away and multiply
- Benign: Tumors which stay in one place and don’t overgrow (aren’t harmful)
(Cancer detected earlier has a higher chance of being cured since tumors can start of
benign then become malignant.)
Causes of Cancer:
- Age
- Mutation of repressor genes/ proto-oncogenes to oncogenes causing
uncontrollable cell division
- Exposure to ionising radiation eg. X-rays
- UV light eg. phone screens
- Chemicals (carcinogens) eg. mustard gas
- Infection by viruses which cause damage to DNA, changing structure of proteins
- Weakened immune system
Immunology
Pathogen: A parasite that causes infectious diseases (eg. HIV, flu, e.coli.)
Parasite: A microorganism which harms it’s host, Microorganisms: Virus, bacteria, fungi, protozoa
- Innate immunity: present at birth and uses non-specific cells which cannot
distinguish different pathogens and react to all the same way very quickly.
- Acquired immunity: developed through exposure to pathogens which are
distinguished and remembered by receptors to have a specfic response to each.
Non-specific immunity
First line of defence:
1. The skin is a waterproof protective layer that prevents the entrance of pathogens
and secretes lysozyme to digest foreign organisms.
2. Mucous contains antibodies for recognition and traps foreign organisms to be
engulfed by phagocytes
3. Tears contain lysozyme and it’s function is to wash away particles in the eyes
Second line of defense
Immune response: How white blood cells respond to pathogens. When they enter
the body ,glycoproteins in the membrane recognize them as non-self.
Phagocytes: Neutrophils & macrophages
These are white blood cells which bind to and engulf foreign molecules
- Neutrophil: engulfs, digests and produces chemicals to kill foreign cells. They
actively move out the blood where pathogens are found and often die after killing
bacteria, so are constantly produced in bone marrow.
- Monocytes: form macrophages & mast cells which are in large numbers in the
liver where they are called Kupffer cells. They live relatively long even after killing
bacteria and display broken pathogen molecules on their outer membrane to help
other cells identify invaders (antigen-presenting cells)
- Mast cells: Found near vessels and nerves, their cytoplasm is packed with
granules filled with cytokines as well as histamine & heparin (responsible for
allergic reactions and autoimmune diseases (misdirected attack on own tissue)
Mast cells can be activated in 3 main ways:
1. Injury (physical / chemical eg. Alcohol)
2. Their receptors binding to the antibody IgE (often happens due to harmless
antigens know as allergens (eg. Proteins on the surface of pollen/ peanut)
3. Activated complement proteins
When activated, contents in granules are released causing dilated vessels, rashes,
swelling of tissue and contracted smooth muscles in airways (allergic reactions)