Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Metabolism
molecule ¦ mälə kyoōl¦noun Chemistry
a group of atoms bonded together, representing the smallest fundamental unit of a chemical
compound that can take part in a chemical reaction.
The molecules in cells are constantly interacting: being formed, broken down or exchanged. These
chemical reactions -- in fact, all the chemical processes occurring within an organism -- are called
it’s metabolism. An organism is regulated (regulate: To control or maintain the rate of speed so it
operates properly), and the rate of its chemical activity is maintained by special large protein
molecules called Enzymes.
Enzymes are also used in the digestive system to break down energy from the food we eat - to
compounds - which are then absorbed by the blood to be transported around the body to the cells.
Enzymes
Enzymes bind to one or more specific ligands, called
substrates, and convert them into chemically modified
‘products’.
They work by providing an Active Surface/Site where the
Reactions occur at the active site
reaction takes place. The Substrate binds on to the active site
(Chemical attraction) much like an Jigsaw puzzle. It needs to fit precisely.
Each Enzyme is highly specific, catalyzing only a single type of reaction - and no other.
Every reaction requires a catalyst. Enzymes can react without themselves being changed - they
act as a catalyst for the reaction. Biological catalysts are called Enzymes.
catalyst ¦ katl-ist¦noun
[ Induced Fit Model ]
a substance that increases the rate of a chemical reaction without itself undergoing any permanent
chemical change.
[ Lock & Key Model ]
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
An perfect enzyme - Substrate fit.
Effect of pH
( PRAC 1 - part B )
❖ Generally, all intra-cellular enzymes
(those within a cell) will show a peak
activity of about pH = 7 -- very close to neutrality
❖ Digestive enzymes such as “pepsin”
from the stomach will work best in
much more acidic environments.
❖ CO2 can cause elevation of pH
Practical:
Tested enzyme catalase (potato)
Activity was inhibited at pH 5 & pH 8.5
Was most effective at a relatively neutral pH of 6.5.
Effect of Substrate Concentration
( PRAC 1 - part C )
❖ Initially the rate of reaction increases as the
substrate concentration goes up, just as with any
reaction.
Soon though, the graph flattens out because the
enzyme molecules become “saturated’’with substrate
and cannot work any faster.
Practical :
Tested enzyme catalase (potato)
Concentration of substrate (Hydrogen peroxide)
Optimum at 50% Hydrogen Peroxide 50% Water.
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Effect of Temperature
( PRAC 1 - part A )
❖ Not all enzymes will peak at the same temperature, or
have exactly the same shape graph. In mammals, most
enzymes will peak at around the animal’s normal body
temperature.
❖ Beyond a peak temp, the enzymes 3-D shape begins to
change. The substrate no longer fits the active sit so well
and the reaction slows. If the temperature is changed, the
enzyme may reshape and be successfully restored. But if
it has reached an extreme temperature. there will be a
permanent distortion with which activity can not be
restores. We say the enzyme has become ‘Denatured’
Practical:
Enzyme rennin (stomach enzyme) in solidifying milk. (curdling)
Most effective at 40 °c.
➡ Enzymes have a specific range of operation. Change any of the conditions and the enzyme will
become denatured.
Homeostasis
❖ Enzymes are very sensitive to the conditions around them. It is vital that the “internal
environment” of any organism is kept as constant as possible so that enzymes and
chemistry keep operating normally. Water / Salt balance, Blood sugar levels, Ox and Carbon levels.
❖ The process of “Keeping Everything The Same” is called homeostasis.
Two homeostatic mechanism stages;
1.
Detecting changes from the stable state: Detected by organs called
receptors or sensors. They contain neurons, which detect information
from external (somatic) and internal (Viseral) environments, and send
nerve impulses appropriately.
e.g Thermoreceptors, Photoreceptors, Mechanoreceptors, Baroreceptores (pressure)
2.
Counteracting changes from the stable state: Detected changes are counteracted using effector
organs. e.g Muscles, Glands (motor reflexes [motor: movement] - Autonomic (involuntary)
- Somatic (voluntary)
This counteracting of the Stimulus (what causes the change from stable state) is called a Negative
Feedback System. Causes a reverse of the direction in which the change occurs enabling balance.
A Positive Feedback System will amplify the stimulus instead of reducing it. E.g adding fuel to
fire. This does NOT result in Homeostasis.
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Dilate : Become larger - more open and wide.
‣ Blood Vessels - sometimes called vasodilation or vasoconstriction
Dilation (Widening); When the body is too hot, blood vessels near the skin dilate and the blood is
shunted toward the surface. This way, more heat is radiated away from the body.
Constriction (Narrowing); When the body is cold, the surface blood vessels constrict keeping
blood in the lower levels reducing the loss of heat and causing body heat to be retained.
‣Sweat Glands; Sweat glands secrete perspiration. The evaporation of this water in the external
environment - has a powerful cooling effect.
‣Muscles: Nerve signals can cause the skeletal muscles to begin “shivering”. This extra muscle
activity generates more heat to warm the body
‣Hormones: The hormone thyroxine (produced by the thyroid gland in the neck) controls the rate
of metabolism. It is under the control of the hypothalamus, via another hormone. Metabolism = heat
The Human Nervous System Is made up of:
❖ Central Nervous System : The brain (hypothalamus: the Homeostasis
control centre) & spinal chord acting as control centre to coordinate all the organisms
responses, receiving information interpreting and indicating a response.
❖ Peripheral Nervous System : nerves branching throughout the body, to and
from receptors and effectors. (act as the communication network)
❖ The nervous system works closely with the Endocrine System. The endocrine
system produces hormones in specific glands.
• In a healthy human the internal “core temperature” is about 37°C and is maintained
within 0.5°C. If temperature goes ± 4°c it is a life threatening situation.
The External Environment - Temperature
Homeostasis allows an organism to maintain its cells at a temperature close to optimum
for its enzymes. This allows metabolism to run efficiently. Though homeostasis has it
limits, No organism can remain active and thriving under a full range of temperatures of
the biosphere of Earth. Different organisms have adapted to survive in extreme cold, or
in extreme heat, but never both. e.g. Thermophilic Bacteria of volcanic springs or
certain algae in very cold temps.
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Ectotherms and endotherms have similar behavioral adaptations to hot or cold conditions, but
endotherms have more structural and physiological adaptions for maintaining a constant internal
body temperature. ~ The responses of ectotherms are usually behavioral ~
Fun Fact: Metabolism produces heat in both Endo & Ectotherms.
Ectotherms just canʼt maintain this heat.
Red Kangaroo - Endotherm
Adaptation or response to temperature regulation
Evaporative Heat Loss (EHL) panting, sweating, licking - evaporates water = cooling
Lick forearms - Kangaroos often lick their forearms in very hot weather. Their forearms
have a good blood supply and very little fur; the moisture evaporates and cools the
forearms, thus cooling the blood.
Vasoconstriction / vasodilation ( vaso means blood vessels)
Concentration of Urine to conserve water and can thus tolerate severe dehydration.
Fur acts as insulate to the body - Endotherms rely heavily on body insulation
Behavioral Response to seek shade.
Behavioral Response to be active during later times, when temperatures are cool.
Large Ears (Structural) with many blood vessels, increases the surface area for heat
loss
Producing your own body heat is expensive. Mammals use 70-90% of the food they eat
just to maintain their body temperature, so of course they have to eat a lot.
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Australian lizards in general (blue tongue / frilled neck) - Ectotherm
Adaptation or response to temperature regulation
- Behavioral Response to seek shade / sun -- dependent upon internal body
temperature.
- ‘Bask’ in the sun, in sites that are sheltered from the wind and exposed not only
to direct sunlight but to the warmth reflected off rocks or logs. If the substrate
has been warmed by the sun they will often flatten themselves against it to
absorb as much heat as they can.
- Orientating themselves in sunlight to modify exposure. E.g. side on for most, or
straight and direct for less.
Temperature Control in Plants - (Not too important)
- They cannot run away or seek shade - they need structural or physiological adaptations
- Some plants may be deciduous - they loose leaves in cold weather & grow again.
- in hot weather w/ lots of water available (Tropical jungle) plants cool themselves by
allowing maximum evaporative cooling. Stomates open and transpiration occurs.
- in hot and DRY weather = small, hard leaves reduce the surface area being hit by
sun. Also leaves are orientated so as to absorb sun at the coolest part of day. (most
eucalyptus leaves hang vertically). Plants in hot dry climates, usually conserve
water by reducing transpiration in the hottest part of the day.
Internal Transport ; The Human Circulatory System
‣ Composition of the Blood
‣ The solvent is made up of about 90% water
‣ Function is to transport ;
- Waste materials such as Urea & Carbon Dioxide.
- Products of digestion such as salts, amino acids,
fats (lipids) & sugars
- Certain hormones
‣ WBC’s Larger than RBC yet, less numerous.
‣ There are several types & are used to fight infection.
‣ Has a nucleus
‣ Platelets are used to clot the blood when necessary
‣ Donut shaped, Their function is to carry respiratory gases,
particularly oxygen (carried as oxyhaemoglobin). When the
blood reaches the body tissue the high concentration of
dissolved CO2 lowers pH of the blood slightly. This causes
the haemoglobin proteins to change shape slightly and release
oxygen molecules. The haemoglobin then picks up some of
carbon and takes it to the lungs.
‣ Oxygen has difficulty dissolving in water. Hemoglobin
molecules contain iron that easily pick up oxygen. (MUCH
better than plasma)
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Respiration
Oxygen + glucose (oxygen and glucose must react) -> CO2 + H2O (waste products ) + Energy
[Fun Fact]: The flow of blood distributes heat around the body.
~ 1 Micrometre (um) = 0.001 mm
Red Blood Cell 7
um
[ 6-8 ]
White Blood Cell 11um
[ 10-12 ]
Two important types of white blood cell:es.
1. Phagocytes can actively move about by flowing their cytoplasm and
can move from the blood into the tissue fluid. They surround and ingest
bacteria, foreign bodies and dead cells, and collect at areas of infection or
injury.
2. Lymphocytes act specifically against foreign
material. They make antibodies which help the bodyʼs defence against
disease.
As the blood circulates around the body, it’s chemical composition undergoes a series of changes.
‣ Factors effecting the Blood ; CO2
& the importance of removing
Side note: An acid has a low pH, a neutral solution has a pH of 7 and an alkaline solution has a high pH
Carbon Dioxide doesn’t just dissolve in water, it reacts! forming a weak acid.
The level of carbon dioxide critically affects the pH of cells. Remember, enzymes are very sensitive to pH changes. If the carbon dioxide is not removed by the blood it will dissolve into the cells forming carbonic acid. To avoid this problem, CO2 is carried away in the blood as rapidly as it is produced in the cells. The concentration of oxygen and carbon dioxide is of much interest to doctors. The most important measurement is “Percentage Oxygen Saturation” (%SpO2). A reading of 95% -­‐ 100% is indicative of good health. Nutrients & Nitrogenous Wastes
Pulse Oximeter
• Measures %SpO2 (Percentage Oxygen Saturation)
in arterial blood (blood being pumped from the heart)
• Works by emitting light from two diodes; one visible red
light and the other infrared. These are directed through the
tissue of the finger, and the absorption of the light into the
haemoglobin is measured. This gives a direct measurement of the
%SpO2 because haemoglobin with or without absorbs these light
beams differently.
• Non - invasive technique, useful for rapid, continuous monitoring of
blood.
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Arterial Blood Gas (ABG) Analysis
• Measures %SpO2 (Percentage Oxygen Saturation) as well as,
concentration of carbon dioxide and pH
• Process is invasive (sample of blood must be taken) and there can be
a delay between sampling and availability of results.
There is also a separate network, responsible for the transport of lymph & bodily/interstitial fluid. (/)
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
The heart consists of four chambers: the right and left atria (Singular: atrium) and the right
& left ventricles.
pulmonary
of or relating to the lungs
The blood moves like this:
All types of blood cells come from
haematopoietic stem cell found in the marrow
of all the major bones in the body.
Body - heart - lungs - heart - body
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Products of Blood Donation
The blood donated from blood donors is often broken apart into components, so each donation can
treat many patients. Whole blood is only kept for emergency situations.
Artificial BlooOooOod
Reasons why research is needed:
• Fresh blood cannot be stored for long, and many parts of the world lack the necessary storage
facilities.
• Blood products can set off immune-responses in patients, even after correct blood typing (similar
to “rejection” of a transplanted organ)
• Donated blood can carry viruses such as hepatitis or HIV
Difficulties
• Artificial products must be totally sterile, disease free and most importantly
able to be accepted and adopted by a patient.
‣ Transport Systems in Plants
Organic = Containing carbon
The Xylem transports water & inorganic minerals
(Mineral Ions) upward only - from the roots (which absorb h20 and minerals)
‣ Xylem tubes are dead, hollow cells that form from root to leaf. Coated with lignin - strength.
‣ TRANSPIRATION ; Is the evaporation of water from the leaves. When the stomates are
open, water can constantly evaporate, creating a tension or “pull”.
‣ COHESION ; aka. capillarity is the tendency of water molecules to strongly cling together.
So, when evaporation from the leaves creates the pull force, each water molecule pulls the one
behind it because of cohesion. The flow that is created is called a “transpiration stream”
‣ ADHESION : Water molecules are not only attracted to each other as in Cohesion, but also to
other substances such as glass or an xylem tube. So they creep up forming a meniscus.
physical properties
of water
[ Passive Transport ]
XYLEM
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
[ Active Transport ]
PHLOEM
The Phloem transports Organic Nutrients (FOOD) esp. Sugars
in either direction.
‣ Food, mainly sugar, is made by photosynthesis in the leaves. This must then be
transported out of the leaves to supply other parts of the plants through the phloem. This
movement is called translocation.
‣ The structure of phloem tubes is made up of two parts; called sieve tubes and companion
cells. The sieve tubes are responsible for the actual transport. They are alive and filled with
a thin cytoplasm that carries sugars through each cell. Alongside the sieve tubes are
companion cells that have many mitochondria that provide ATP to the phloem cells.
in between sieve tubes are sieve plates, that are perforated so each cell is open into the next
- thus forming an continuos tube.
‣ The flow of nutrients through the phloem is caused by pressure difference between the
“source” tissues and the “destination”. The pressure difference is osmotic pressure.
Note: Phloem
on the outside
CAMBIUM ; Consists of cells which can divide to produce
more cells - forming extra phloem and xylem cells.
Stem Cross Section
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
H
O
‣Water is the Solvent of Life
H
Life cannot exist without water. All the chemical reactions of metabolism take place in
water solution. Water is also a reactant or product of many metabolic reactions e.g
Respiration. Also, the transport of materials in the cytoplasm, blood or phloem takes place
mainly in water solution.
Water regulates temperature with it’s high specific heat capacity. This means it can absorb
(or loose) relatively large quantities of energy with minimal temperature change, which helps
stabilize temperature.
‣ Homeostasis of Water & Salts
Water’s concentration and the concentration of the substances dissolved in it, such as
salts, must be kept at the correct levels. If the balance is broken then osmosis may cause
problems. Cells could lose water and dehydrate, or gain to much water and be damaged.
Isotonic environment - one in which the solute concentration is the same
both inside and outside the cell.
‣ The Importance of Removing Metabolic Wastes
As a result of all the metabolic processes that occur in cells, waste products
particularly nitrogenous wastes are constantly being formed. If allowed to
accumulate in the body, they would slow down metabolism (pH can change enzymes) and poison cells. The excretory system is responsible for
maintaining a constant blood composition and therefore maintaing a constant
internal environment.
Atom -> Molecule or Compound -> Organelle -> CELL -> Tissue -> Organ System -> Organism
‣ The Kidney
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
The kidney plays a central role in homeostasis, forming and excreting urine while
regulating water & salt concentrations in the blood. It maintains the precise
balance between waste disposal and the animals needs for water and salts.
The kidney has dual functions of excretion, and the regulation of proper
water and salt concentrations in the body (osmoregulation)
note :There is correlation between the type of wastes produced and the animals
environment.
FISH
A fish kidneys are used not so much for excretion, but for maintaining their water
balance. Fish excrete ammonia. Ammonia is toxic, but can be released continuously and
is highly soluble.
Freshwater Fish
Maintain a higher concentration of solutes in their
body than environment ( hypotonic) Because of this,
water diffuses into the body by osmosis. They must
continually get rid of this excess water - their
kidneyʼs producing copious amounts of dilute urine in
almost a continuos stream! They also absorb salts
to prevent loss.
Saltwater Fish
Have the opposite problem. Their internal
body concentration is lower than their
surroundings (hypertonic).They must drink
salt water to replace any water loss, and
actively excrete the salts.
~ Tend to loose water, & gain salts ~
~ Tend to loose salts, & gain water ~
MAMMALS
On land, however, terrestrial animals need to conserve water. By converting waste into
the less toxic form of urea, mammals can hold wastes in the body and excrete it
periodically. It is highly soluble, much less toxic than ammonia, & can be stored in a
more concentrated solution and so requires less water to remove than ammonia.
Unlike fish, the simple processes of diffusion and osmosis are not adequate to
remove nitrogenous wastes - as they do not occur fast enough to maintain the
required solute concentrations in cells.
I. Diffusion is too slow, requires copious amounts of water to be excreted (which
terrestrial animal cannot afford to do esp. desert), and is non-selective process.
II. Osmosis only deals with water. Water would exit the body and nitrogenous waste
would stay.
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Passive & Active Transport
Diffusion and osmosis are passive processes because there is no expenditure of energy. When
removing nitrogenous wastes, some substances must be REabsorbed against a concentration
gradient (e.g. sugar, amino acids, salts). This requires energy and is called Active transport.
Osmosis then occurs, which causes water to flow from the tubules back into the blood.
(Passive transport - Salt moving out of the tubules will change concentration gradient for water)
The Nephron
FILTRATION
REABSORPTION
SECRETION
The nephron is the smallest functional unit of the kidney. The nephron is a regulatory unit; it
selectively reabsorbs materials required to maintain homeostasis. Approx. 1 mill in human
kidney. The nephrons are arranged in the outer cortex and central medulla & are a complicated
tangle of blood vessels and renal tubules (tubules=Small tubes).
‣ Filtration
Filtration is a non-selective process. The blood pressure
is so high in the glomerulus that liquid from the blood is
forced through the walls of the capillaries into the
bowman's capsule. The liquid produced is called
glomerular filtrate, consisting of blood plasma but no
blood cells or large proteins (they are to large to pass)
‣ Reabsorption
Along the tubule, the composition of the filtrate is
carefully adjusted. Surrounding each nephron tubule is a
large capillary network, to which materials are selectively
re-absorbed (all amino acids, all glucose, all vitamins
(kidneys don’t regulate these) some water, some salt) until
the tubule only carries unwanted substances (urine)
then via
ureter to
bladder
‣ Secretion
Deposits substances that were not removed in filtration
into the proximal and distal tubules (e.g. H+, K+, poisons)
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
*
* Refer to previous notes ʻforms substances are carried in bloodʼ
+
CO2 + H2O -> H 2CO3 -> H + HCO 3
cortex
Carbonic Acid
Bicarbonate ions
The amount of H+ in a
are reabsorbed
solution determines itʼs pH.
There is some secretion of H +
There is a buffer system here that
helps maintain a constant pH
* Nutrients like amino acids, glucose
medulla
- Potassium, Sodium and chloride are
all electrolytes
renal
of or relating to the kidneys
(hypertonic)
Renal Dialysis
You cannot live without you kidneys. Individuals suffering from kidney failure rely on dialysis to
work for them.
Similarities
• Like the nephrons, dialysis selectively removes urea, and other wastes from the blood.
• Both rely on movement of substances through semi-permeable membranes.
Differences
• The kidney is a highly complex organ. it uses both active and passive transport, dialysis only = diffusion.
• Dialysis is much slower and less efficient.
• Does not correct hormone producing functions of the kidney (e.g erythropoietin - that promotes growth of
RBC’s in the bone marrow)
Hormonal Regulation of Salt & Water levels
The amount of water and salts lost by the kidneys is controlled by hormones.
Aldosterone
Is produced by the adrenal glands, which are situated above both kidneys. It
regulates the transfer of sodium. When salt levels are low, more aldosterone is
produced to encourage more reabsorption of sodium ions. Chloride ions follow
passively, & so more salt is absorbed. (note also, it has effect on water due to
osmosis)
ADH (Anti-Diuretic Hormone or Vasopressin)
Reabsorption of water is controlled by ADH. Made by the hypothalamus but
stored and released from the pituitary gland in the brain. If the body lacks
hydration, ADH increases the permeability of the collecting ducts to water. (note:
Collecting ducts pass through medulla which is purposely very salty)
Side Note: Addisonʼs Disease occurs when a person cannot produce Aldosterone. This
leads to osmotic imbalance. Can be treated with “Hormone Replacement Therapy (HRT)”
Maintaining A Balance - HSC Biology 2012 Notes
Peter Richardson
Note: The length of the nephron tubules (esp. Loop of Henle) can be elongated in an animals kidneys ; An adaption
allowing greater reabsorption of water.
Insects:
• All insects are small, and most are adapted for flight. This means they cannot afford to carry
large amounts of water in their bodies just for the purpose of excreting urine. They excrete
uric acid, which precipitates as a solid. It is thousands of times less soluble than ammonia or
urea and has low toxicity, which means that little water is expended to remove it.
Enantiostasis
Enantiostasis does not maintain a constant internal environment like
homeostasis. Enantiostasis means the organism fluctuates with the
environment (hence saving energy). Although there are mechanisms
which still allow metabolic and physiological functions to continue.
• It is particularly important for organisms living in estuarine environment (a point where the
river meets the sea) where salinity varies greatly (due to factors such as tides and rainfall).
• Fish can swim away to evade the salt, and certain crabs can dig below into the mud - but
plant’s are stuck where they are. They must find ways to cope with the salinity daily.
• Plant’s cannot cope with high levels of salt. It is toxic to the plant, accumulating in their leaves.
Also, salt breaks a concentration gradient in the soil; preventing less water from entering the
plant by osmosis.
The Grey Mangrove ~ Avicennia Marina
Salt Excluders: Prevent the entry of salt into their root system, by passive filtration.
Salt Excreters: Special salt glands (usually in the leaves), salt is concentrated here
and then actively secreted from the plant.
Salt Accumulators: Salt is accumulated in part of the plant, such as old bark or
leaves and then shed.
Minimising water loss in Australian Plants
Adaptations of Australian xerophytes (plants adapted to dry conditions) include:
• Thick, waxy, or even reflective cuticles
• Small & narrow leaves that reduce surface area. even needle
like foliage (spinifex grasses)
• Hairy Leaves that reduce airflow across the leaf. (Wind increases
evaporation rates) (grevila alpina)
• Hang vertically, and are oriented to avoid the heat of midday.
• Open / Closed stomates Plants must negotiate a balance
between co2 intake and h20 loss. An adaptive advantage is to
have stomates on the under side of a leaf, away from the
evaporative heat.
Grevillea Alpina
Spinifex Grass
Eucalyptus