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OCR A level bio > Excretion > Flashcards

Excretion Flashcards

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1
Q

What is excretion

A

Removing metabolic wastes e.g. co2 and nitrogen based byproducts to maintain metabolism

Enables organisms to maintain PH balance and regulate osmotic pressure

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2
Q

Whats the structure of the mammalian liver

A

Liver lobules are connected to:

Hepatic veins which takes deoxygenated blood away from liver and is attached to:

Hepatic portal vein: which contains products of digestion and hepatic artery: supplies oxygenated blood via sinusoid capillaries

and bile duct: transports bile to gall bladder for storage

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3
Q

Outline functions of mammalian liver

A

Site of gluconeogenesis, glycolysis and glycognesis

Stores glycogen

Deaminates excess amino acids, forming ammonia and organic acids- acids can be respired

Detoxifies chemicals

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4
Q

Describe structure of mammalian kidney

A

Fibrous capsule: protects kidney

Cortex: outer region consists of bowmans capsules, convulated tubules and blood vessels

Medulla: inner region consisting of collecting ducts, loops of henle and blood vessels

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5
Q

What are the main excretory products

A

co2, urea, ammonia and bile pigments

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6
Q

Why do we get rid of metabolic waste products

A

They can alter the pH interfering with cell processes so the normal metabolism is affected, they may also inhibit enzymes

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7
Q

Why is excess co2 a problem

A

Mostly transported as hydrogen carbonate ions the formation which releases H ions,
Affects the PH of the cytoplasm of the RBC’s changing the bonds and shape of Hb reducing affinity for o2

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8
Q

Why must we excrete nitrogenous compounds

A

Amino acids cant be stored as they contain a toxic amino group which needs removing

Absorbed by cells and decreases their water potent and they burst

Uric acid may crystallise in joints

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9
Q

Which vessel does blood flow into the liver

A

hepatic artery (oxygenated from the heart

hepatic portal vein (deoxygenated blood from digestive system)

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10
Q

What is the bile duct

A

Duct carries the bile secreted in the liver from the liver to gall bladder

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11
Q

In which vessel does blood from the vein and arteries mix

A

A sinusoid

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12
Q

What is the purpose of blood passing through sinusoids

A

They put the blood in close contact with liver cells that alter the concentrations of substances in it

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13
Q

What do kupfer cells in sinusoids do

A

They recycle and break down RBC producing bilirubin as well

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14
Q

What vessels drain blood from the liver

A

Hepatic vein

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15
Q

What are the metabolic functions of hepatocytes

A

Protein synthesis
Transformation/storage of carbs
Synthesis of cholesterol and detoxification

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16
Q

How do hepatocytes store glycogen

A

In granules in the cytoplasm

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17
Q

How might hepatocytes detoxify substances

A

May oxidise, reduce or combine with another molecule

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18
Q

How is alcohol broken down by detoxification

A

Ethanol broken down by ethanol dehydrogenase to ethanal which is dehydrogenated by ethanal dehydrogenase to ethanoate which combines with coenzyme A to form acetyl coenzyme .

NAD forms reduced NAD from h ions

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19
Q

Why does alcohol make fat build up

A

Because NAD is used to detoxify it and it is used up doing this so cannot break down fatty acid

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20
Q

Which part of amino acids make them toxic

A

Amino group

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21
Q

What is deamination

A

Amine group and H removed from Amino Acid to form ammonia and a keto acid which may be respired or converted to glucose/fat

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22
Q

What is the ornithine cycle

A

Ammonia is toxic so it is converted to urea. Ammonia and co2 combined to urea and water

Urea diffuses through the phospholipid bilayer of the hepatocytes and into kidney

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23
Q

What is the role of the kidney

Study These Flashcards
A

Remove waste products from blood and produce urine

24
Q

Where is each bowmans capsule

25
Which vessel enters the kidney
Renal artery
26
What is the glomerulus
Bunch of the capillaries that are the result of the renal artery splitting into afferent arterioles
27
What is ultrafiltration
When fluid from the blood is pushed into the bowmans capsule
28
Which three layers act as the filter for ultrafiltration
The endothelium of the capillary, the basement membrane and the epithelial cells of the bowmans capsule
29
What substances are filtered out of the glomerulus
Water, amino acids, glucose, urea and mineral ions
30
What substances are not filtered out of the glomerulus and why
Blood cells and proteins because they are too large
31
What is the basement membrane composed of
Meshwork of collagen and glycoprotein fibres Water and small molecule can pass through Proteins too large and are replled by negative charges on fibres
32
Outline the endothelium of blood capillary in the bowmans capsule
Very thin Perforated with thousands of pores about 10nm diameter Provides barrier to cells but not plasma proteins
33
Outline the epithelium of renal capsule of bowmans capsule
Made of cells modified for filtration
34
Describe podocytes
Each cell has many foot like extensions projecting from its surface Extensions wrap around the capillaries of the glomerulus and interlink with extensions from neighbouring cells Extensions fit together loosely leaving filtrarions slits Filtered fluid passes through slits
35
Why is it important that these substances are/are not filtered out
So that the blood is left with a lower water potent which makes reabsorption of water back into blood possible later
36
What happens in the PCT
Reabsorption of most sugara, mineral ions and some water
37
How is salt conc established in loop of henle
Descending limb is permeable to water but not salts but the ascending limb is permeable to salts not water This means that as the loop descends into the medulla, the interstitial fluid becomes more salty and hypertonic as water leaves the tubule by osmosis
38
Outline the countercurrrent mechanism in the vasa recta as a way of establishing a salt gradient
Vasa recta blood network surrounds the loop of henle flows in the opposite direction (counter current) Means salts are released from the ascending limb are drawn down into the medulla, further establishing a salt gradient
39
What happens in the thin ascending limb of henle
As the fluid in the tubule ascends back up towards the cortex, the water potent becomes higher But can't leave as the wale is impermeable to water. Due to counter current from vasa recta, salts are drawn down into the medulla- establishing a salt gradient
40
What happens in the thick ascending loop of henle
Contains large epithelial cells w specialised transport 1. NA/K ATPase pump im membrane pumps 3NA out of and 2k into cell 2. Low intracellular Na conc drives the electroneutral Na-K-2cl co transporter at the apical membrane 3. K is recycled back into the lumen through k channels in the apical membrane= continued NaCl uptake. Cl leaves through chlorine channels in basolateral membrane.
41
What happens in the distal convulated tubule
Actively transport finely tunes the conc of various salts in the tubule- water and NaCl are releases
42
What happens in the collecting duct
When the fluid reaches the collecting duct it has a high water potent. Collecting duct carries fluid back into medulla which contains a lot of salts ( low water potent) As fluid passes through, water moves by osmosis, from the tubule fluid into surrounding tissue Then enters the blood capillaries by osmosis and carried away
43
How is osmoregulation activated
Osmoreceptors in hypothalamus monitor the water potential of the blood If osmoreceptors detect a decrease in the water potential of the blood.. ADH causes kidneys to reabsorb more water which reduces loss of water in the urine
44
What is the effect of ADH on kidneys
ADH causes the luminal membranes of collecting ducts to become more permeable to water by causing an increase in the number of aquaporins in the luminal membranes of collecting duct cells
45
How does ADH work
ADH molecules bind to receptors which activates a signalling cascade= phosphorylation of the aquaporin molecules Phosphorylated aquaporins drive fusion of vesicles with the luminal membranes of the collecting duct cells Water molecules move from the collecting duct through the aquaporins, and into the tissue fluid and blood plasma in the medulla
46
What is the counter current multiplier mechanism
Divided into three segments: descending, thin ascending and thick ascending Increases the conc of solute and ions within the interstitium of the medulla Allows the nephron to reabsorb more water in the same time frame using as little energy as possible
47
Whats osmoregulation
Loop of henle establishes a salt gradient in medulla Anti diuretic hormone regulates the level of water reabsorption in the collecting duct
48
Describe the mechanism of reabsorption in the PCT
Sodium ions pumped out cells lining the tubule, creating a conc gradient of sodium ions towards the cell cytoplasm Sodium ions diffuse into cell via cotransport proteins carrying glucose or amino acid with them The glucose and amino acids diffuse into the blood on the other side of the PCT. A water potent gradient is created in the process so that the water moves into the cell via osmosis
49
Describe changes in glucose conc throughout the tubule
In the PCT glucose is selectively reabsorbed so the conc of it present is removed
50
Describe the changes in Na and K ions conc throughout the tubule
Na ions diffuse into the descending limb of the loop of henle, in the desc limb they are pumped out K ions actively transported into the tubule and when water removed from tubule their conc also increases
51
Describe the changes in urea conc throughout the tubule
As water is withdrawn from the tubule the conc rises Actively moved into the tubule
52
What is osmoregulation
Controlling the water potential throughout the body
53
How do kidneys alter the volume of urine produced
They alter the permeability of the collecting duct
54
What is filtered out of the blood into the nephron during ultrafiltration
Water AA Glucose Urea Inorganic ions
55

OCR A level bio (10 decks)

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