A2 Biology OCR unit 1 notes

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  • Created on: 01-08-14 13:37
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Liver functions
1. monitoring amino acid levels, blood glucose levels, lipid levels
2. detoxification of toxins via oxidation, reduction, methylation, combination with coenzymes with a
high turnover number
3. detoxification of alcohol, drugs
4. destructing of RBCs
5. breakdown of hormones
6. synthesis of bile, RBCs in the fetus, cholesterol and plasma proteins
7. storage of vitamins, minerals and glycogen
liver produces waste it cannot itself excrete, it return it to the blood where the kidney can excrete them.
The kidney excretes:
· excess water
· excess salt
· nitrogenous waste such as urea
· breakdown products of hormones
The presence of hormone substances in the urine can suggest pregnancy or drug use
the waste products produced by the body is mostly
· CO2 from cellular respiration
CO2 travels via hydrogencarbonate ions to the lung where it is exhaled
· nitrogenous compounds such urea produced from breaking down excess amino acids
urea travels via blood plasma to the kidneys where it becomes part of the urine. This urine is stored in
bladder and passed through urethra.
Why are these substances removed?
· Excess CO2 is toxic in 3 ways:
1. because CO2 is carries in hydrogencarbonate ions, the hydrogen ions coproduced causes more
competition with oxygen for association to haemoglobin.
2. The increased hydrogen ions means a more acid blood PH. On a small scale proteins in the blood
act as a buffer, PH change is detected by brain which instructs to increase breathing rate to remove
excess CO2. However if the blood becomes too acidic it increases heart rate, and blood pressure
causing respiratory acidosis which results in fatigue. Many process or disease can be the cause of
low blood PH especially in the lungs, respiratory acidosis.
3. CO2 itself combines with haemoglobin to produce carbaminohaemoglobin, which has less affinity
for oxygen then normal haemoglobin.

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Nitrogenous compounds, the body cannot store proteins or amino acids, although amino acids
contain as much energy as carbohydrates, which mean to excrete them would be wasteful, instead
these are transported to the liver where deamination occurs and the resulting ketoacid is used as
an energy source for respiration, or it may be converted into a carb to be an energy store.…read more

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This hairpin countercurrent multiplier system ensures a buildup of salts in the surrounding tissue
fluid and makes the salt exchange between the limbs more efficient by being close to each other but
running fluid in opposite directions.
· as the descending limb moves down the medulla, medulla has a high concentration of salts, thus
there is diffusion of salts into the limb and osmosis from the limb into the medulla, this gives the limb
a lower WP.…read more

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· take paper length in mm
· multiply by a million
· divide by magnification given, if muim, divide by 1000
· glucose decreases blood WP so enzymes cannot function,
· poor blood circulation may cause gangrene
· glucose crystallises in eye lens, causing it to denature and damaging retina capillaries, causing
Adrenaline mechanism
· adrenaline is a peptide hormone so cannot pass through target cell membrane
· there is a receptor for adrenaline on the outer surface of the membrane which is…read more

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Link matrix
1. Pyruvate dehydrogenase dehydrogenates pyruvate and NAD+ is reduced to NADH, enters OP
2. Pyruvate decarboxylase removes COOH group from pyruvate and makes CO2 and coenzyme A
3. CoA combines with acetate to make acetyl CoA and carries it to krebs cycle in the mitochondrial
1. acetate offloaded from coenzyme A and joins oxaloacetate to form citrate
2. citrate is decarboxylated (producing CO2) and dehydrogenated to form a 5 carbon compound,
H+ reduces NAD+
3.…read more

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The nodes of Ranvier are the places where the myelin sheath skips and the neuronal membrane is exposed.
This is so that the impulse can jump from node to node, greatly increasing the speed of conduction than if
the entire neuronal membrane had to be depolarized. The synapse is a space between two neurons don't
confuse the concept of a 'space' with the nodes.…read more

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If the pressure is too high: the cardioinhibitory centre is stimulated, impulses are sent down the vagus nerve,
the heart rate is slowed and the pressure will fall.
If the pressure is too low: the cardioacceleratory centre is stimulated, impulses are sent down the
accelerator nerve, the heart rate is increased and the pressure will rise.
Endocrine gland: hormones released directly into blood E.G. thyroid gland, Thymus
Exocrine Gland: hormones released through duct. E.…read more

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NaHCo3 allows to neutralise stomach acid
endocrine: beta cells release insulin and alpha cell glucagon into near blood supply
normal BG= 90mg per 100cm3 of blood
BG high
beta cell secrete insulin
insulin target cells are hepatic/muscle/brain cells with receptors
actives adenyl cyclase=> creates glucose channels in membrane
concentrated glucose undergoes glycogenesis => glycogen
some glucose converted to fats or used in respiration
BG low
alpha cells secrete glucagon
glucagon target cells are hepatic cells
gluconeogensis glycogen=> glucose
amino acids+fat=>glucose
Higher BG
Message Converged
useful…read more

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Spatial: when generator potentials in neurones converge to summate to a high concentration of
neurotransmitter to allow diffusion to postsynaptic neurone
Where the synapse is fatigued and vesicles of neurotransmitters for action potential run out. Good to
prevent overstimulation and allow you to become accustom to sounds etc.
Specific pathways
Allow us to memorise and associate certain thoughts in the brain and because receptors have specificity to
their brain receptors, it enables us to sense locations of pain or pressure.…read more

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Once the signal passes to the next nerve, an enzyme called choline esterase destroys the
acetlycholine. Organophosphorus compounds block this enzyme, thus preventing the breakdown of
acetylcholine. Thus acetlycholine acts for an excessively long time causing symptoms like twitches and
increased secretions. After some time, the muscles gets fatigued leading to paralysis.
toxin & muscle relaxant that blocks the , nicotinic acetylcholine receptor one of the two types of
acetylcholine (ACh) receptors, at the neuromuscular junction.…read more


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