Here are my notes for the final topic in the january exam.

Hope they help and let me know what you have thought of them all

Thanks Jordan

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Excretion is the removal of metabolic wastes from the body.
Any waste products from metabolic reactions are lost via excretion e.g. CO2 urea and H2O2.
DEFAECATION is not excretion it is egestion. This is because it is the removal of undigested bulk
(fibre) from the body. Faeces have not been in the body's cells and so are not classed as excretion.
Products from cells are excreted because they exist in excess or they are reaching poisonous levels
or are interfering with metabolic processes. For example Respiratory acidosis is when there is too
much CO2 which makes the blood acidic.
Inefficient CO2 leads to...
The formation of Carbonic Acid.
H+ forming lowering the pH. If the pH falls below 7.35 the sufferer will show the following
Slowed breathing
If we eat too much amino acids (protein) the surplus amino acids will be secreted as urea.
De-animation is where the toxic amine group is removed from the amino acid and forms ammonia.
This ammonia is then converted into the less soluble and less toxic urea. The by-product Keto acid can
be used as a respiratory substrate if serine is the amino acid and pyruvate is the acid.
In the presence of CO2 the ammonia is then converted into urea and water. It then passes from the
liver into the bloodstream. Once at the kidneys it is filtrated and ends up in urine.

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The arrangement of liver cells in a lobule:
The liver is a dense organ with closely packed cells with multiple jobs. Its functions are:
To process nutrients from the digestive system.
To store glucose as glycogen.
To breakdown hormones.
To produce bile.
To excrete bile pigments.
To store vitamins and minerals.
To break down excess amino acids. (as explained earlier)
Kupffer cells are found in the sinusoids. They are macrophages as they are phagocytes that ingest
other cells.…read more

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Kidney nephron
In the glomerulus the blood plasma is put under pressure and filtrated through gaps in the squamous
endothelium called fenestrations or "little windows." This fluid then passes through the basement
membrane which is a collagen mesh. It then passes through podocytes which are slit like cell. These
stages prevent proteins and blood cells passing through into the Bowmann's Capsule.
After Bowmann's capsule it is the proximal convoluted tubule, this is where 85% of the filtered
water and ions are reabsorbed.…read more

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This selective re-absorption of ions, amino acids and glucose etc lowers the water potential in the
cells and increases the water potential and so water carries out osmosis and leaves the tubule. Any
unfiltrated proteins are reabsorbed by endocytosis.
Protein bound toxins are not filtered at the glomerulus and so they are actively transported into the
PCT from the surrounding capillary.
The loop of henle descends into the medulla and fine tunes the ionic and water content of the blood.…read more

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Once i the urine their presence can be tested using gas
Gas chromatography works by vaporising the urine sample by dissolving it in another gas. It will then
be passed through a tube with an absorbant lining. The different substances will come out of the
urine at a particular time (at the end of their retention time). The retention time for each molecule is
unique. The lining of the tube is then analysed to make a chromatogram.…read more

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Damage due to Obstruction of ureters,
obstruction of ureter, bladder or kidney.
bladder or urethra
Diabetes mellitus
reduces blood supply
to kidney
Symptoms/leads to Nephrons are progressively Little of no urine
destroyed leading to; produced
Reduced quantity of Accumulation of
urine nitrogenous waste in
Dilute urine blood
Dehydration Salt imbalance
Salt imbalance Pain
Severe high blood
pressure Is often reversible if treated
Coma and convulsions quickly.…read more

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Kidney transplants
The number of transplants is limited by the availiability of donors and the availability of good
tissue matches with the patient.
Tissue rejection is prevented with the use of drugs such as cyclosporine A which will damp the
immune response. They are also referred to as immunosuppressants. As you only need one
kidney, close relatives can act as donors to reduce risk of rejection.…read more


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