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WJEC A2 Biology > The Kidney- Unit 3.7 > Flashcards

The Kidney- Unit 3.7 Flashcards

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1
Q

Name the main source of nitrogen containing wastes in animals:

A

Amino acid breakdown

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2
Q

Why do aquatic organisms excrete ammonia directly?

A

The ammonia quickly dilutes in the surrounding water, reducing its toxicity

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3
Q

What is the advantage of having an excretory product that is low toxicity, like urea?

A

It can remain in the body for longer

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4
Q

Explain the advantages that uric acid has over urea. (2)

A

It is virtually non-toxic.
Very little water required so is conserved.

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5
Q

What organism is uric acid excreted by?

A

Birds

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6
Q

What organism is urea excreted by?

A

Mammals

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7
Q

What does the skin excrete? (2)

A

Urea and other salts

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8
Q

What does the liver excrete?

A

Chemical waste in bile

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9
Q

What do the kidneys excrete? (3)

A

Urea, uric acid and ammonium salts

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10
Q

Where does deamination take place?

A

Loop of Henle

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11
Q

Describe deamination.

A

Excess amino acids are converted into ammonia, then into urea in the liver, and carried to the kidney to be filtered and excreted in urine. (amino group is removed)

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12
Q

What is homeostasis?

A

The ability to return to a set point whilst constant changes in body temperature, pH and water potential is occurring, maintaining a dynamic equilibrium. (regulating)

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13
Q

What is negative feedback in homeostasis?

A

Movement away from a set point (due to change in the internal environment) triggers a corrective action, counteracting the change, ensuring the set point is restored.

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14
Q

What does positive feedback do?

A

An effector amplifies the change to continue

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15
Q

Advantage of ammonia being soluble for fish?

A

Diffuses across gills easily

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16
Q

Does excreting ammonia use energy from the fish?

A

No

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17
Q

What are the kidney’s two main functions?

A

Excretion and osmoregulation

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18
Q

Is energy required for a bird to release uric acid?

A

Yes, a large amount

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19
Q

What are the properties of uric acid? (2)

A

Insoluble in water & non-toxic

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20
Q

Why is urea made?

A

Because excess amino acids cannot be stored

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21
Q

Name the three main components of a regulatory control system in the body. (along with input/output)

A
  1. Input
  2. –> receptor
  3. co-ordinator
  4. effector
  5. –> output (repeat)
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22
Q

What is ultrafiltration?

A

Filtering of small molecules out of the blood into the Bowman’s capsule under high pressure.

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23
Q

What 5 substances will be present in the (glomerular) filtrate for ultrafiltration?

A

Urea
Water
Salts
Glucose
Amino acids

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24
Q

Explain the effect on filtration rate during a large loss of blood from the body. (2)

A

If hydrostatic pressure decreases, so will filtration rate.
Less blood is available to move into the filtrate.

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25
Q

Name the part of the nephron which provides the osmotic gradient for reabsorption.

A

Loop of Henle

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26
Q

Which arteriole in the Loop of Henle is wider and which is narrower?

A

Wider- Afferent
Narrower- Efferent

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27
Q

Where does ultrafiltration occur?

A

In the glomerulus in the nephron.

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28
Q

What do the capillaries have in Bowman’s capsule?

A

Fenestrae

29
Q

What is attached to the capillaries?

A

Podocyte with filtration slits

30
Q

Where does the Bowman’s capsule lead into?

A

Proximal Convoluted Tubule

31
Q

What happens in the Proximal Convoluted Tubule?

A

Selective reabsorption

32
Q

What adaptations does the PCT have? (3)

A

Mitochondria (ATP)
Microvilli (SA)
Close association with capillaries (Short diffusion distance)

33
Q

What happens to 50% of urea and amino acids in the PCT?

A

Goes back into the blood via diffusion due to the concentration gradient

34
Q

How does water leave the filtrate?

A

Osmosis

35
Q

Amino acids and glucose, as well as salts, water and urea are non-selectively filtered out of the blood in the Bowman’s capsule. (useful or not) How are amino acids and glucose selectively reabsorbed in PCT?

A

Co-transport with sodium ions

36
Q

What happens in the descending limb of the Loop of Henle? (3)

A

1) Filtrate moves down.
2) Water leaves via osmosis from high water potential to low water potential.
3) As filtrate moves down, it becomes more concentrated due to more ions present.

37
Q

What happens in the ascending limb of the Loop of Henle? (4)

A

1) Filtrate moves up.
2) Sodium actively transported out
3) As filtrate moves up, it contains less ions so water potential increases.
4) Filtrate becomes more dilute.

38
Q

Which limb is permeable to water and slightly permeable to sodium?

A

Descending limb

39
Q

Which limb is impermeable to water and permeable to sodium?

A

Ascending limb

40
Q

What does the counter current multiplier mechanism create in the medulla?

A

A high solute concentration

41
Q

What is travelling through the Loop of Henle?

A

The filtrate

42
Q

Explain how stage 1 kidney disease causes protein to appear in the urine.

A

Kidney basement membrane may become damaged, leaving larger fenestrae so that protein can fit through when it could not originally.

43
Q

What route does ultrafiltration take?

A

Glomerulus–> Bowman’s capsule–> PCT–> Loop of Henle–> DCT–> Collecting duct

44
Q

What is osmoregulation? (3)

A

Osmoreceptors (in hypothalamus) detect change in water potential of blood.
Osmoreceptors will stimulate the posterior lobe of the pituitary gland to release ADH into the blood when water potential is low. (hormone)
Water then reabsorbed by osmosis in collecting duct and distal convoluted tubule. (or less reabsorbed)
(It is the control of water potential of plasma, tissue fluid, lymph by regulating water content)

45
Q

What is the process of aquaporins? (4)

A

ADH binds to membrane receptors.
Vesicles containing aquaporins in cytoplasm move to fuse with cell membrane for aquaporins to incorporate.
Water molecules pass through pores into cell, down a water potential gradient.
When levels of cyclic AMP fall in cell, aquaporins are removed from the membrane and accumulated in the vesicles.

46
Q

What is heamodialysis?

A

Removal of waste products, urea and excess salts, from the blood via a dialysis machine.

47
Q

What happens in the DCT and collecting duct?

A

Sodium ions actively transported out of filtrate.
pH regulation (hydrogen carbonate ions raise pH of blood)
ADH affects DCT and collecting duct’s permeability of the walls, regulating water absorption.

48
Q

What are 3 examples of negative feedback?

A

-Glucose concentration in plasma
-Regulation of temperature
-Menstrual cycle

49
Q

What are 2 examples of positive feedback?

A

-Stimulation of uterus to contract, causing labour.
-Clot formation

50
Q

What is excretion?

A

Removal of (nitrogenous) waste from body made during metabolism in cells

51
Q

What is the renal capsule’s function?

A

-Is a layer of tissue surrounding each kidney
-Keep kidney’s in place and protect from damage

52
Q

What is the function of the cortex?

A

Filtration occurs here (via the nephrons)
Receives blood from renal artery due to the dense capillary network the cortex has

53
Q

The renal pyramids project into the pelvis, what is it’s function?

A

Urine passes out before entering the ureter

54
Q

What does the renal artery do?

A

Brings blood TO the kidney (away from heart), branching into arterioles

55
Q

How are Bowman’s capsules supplied with blood? What is formed?

A

-Afferent arteriole
-Knot of capillaries called glomerulus

56
Q

What is the efferent arteriole and how is it formed?

A

The capillaries join up (glomerulus) to form the efferent arteriole and takes blood away from Bowman’s capsule

57
Q

What is the renal threshold?

A

Basement membrane preventing large molecules like proteins, blood cells & platelets from passing through after entering through fenestrae & Bowman’s capsule.

58
Q

Why does blood flowing from glomerulus into the efferent arteriole have a low water potential?

A

As water has been lost & protein concentration is high

59
Q

What molecules are selectively reabsorbed by epithelial cells in PCT?

A

-Glucose
-Amino acids
-Vitamins
-Sodium ions
-Chloride ions
(water absorbed & urea diffused)

60
Q

What cells make up the DCT? What is their function?

A

Similar to the PCT but with microvilli and many mitochondria. These cells actively transport sodium ions into the blood from nephron.
pH of the blood is raised as the DCT can control the base balance of the blood.

61
Q

How is the amount of water reabsorbed regulated in the medulla regulated?

A

Hormones affect the permeability of the walls of the DCT & collecting duct. As a result, the concentration of urine will be affected.

62
Q

What are some adaptations that plants have? (amino acids & nitrogen) (3)

A

-Only synthesise proteins/amino acids they need to avoid excreting nitrogen containing molecules.
-Take up nitrogen/ammonium through roots in soil.
-Legumes uptake nitrogenous compounds through root nodules. (NFB)

63
Q

What are some adaptations that animals have? (2)

A

-Consume protein & synthesise molecules required from the amino acids.
-Excess amino acids cannot be stored so are deaminated/converted/excreted.

64
Q

What can cause water potential in blood to drop?

A

-Reduced water intake
-Sweating
-Large intake of salt

65
Q

Describe the main components of negative feedback specifically for osmoregulation when water potential is LOW.

A

Receptor: Osmoreceptors in hypothalamus monitor solute potential of blood.
Coordinator: Hypothalamus signals posterior lobe of pituitary gland.
Effector: gland releases ADH
Walls of DCT & collecting duct more permeable for reabsorption and set point is resumed.

66
Q

Describe the main components of negative feedback specifically for osmoregulation when water potential is HIGH. (fluid intake high)

A

Receptor: Osmoreceptors in hypothalamus monitor solute potential of blood.
Coordinator: Hypothalamus signals posterior lobe of pituitary gland.
Effector: ADH mechanism inhibited.
Walls of DCT & collecting duct less permeable for less reabsorption.

67
Q

What happens when the kidneys fail?

A

-Urea not removed, can rise to toxic levels
-Excess water not removed so body fluid levels increase & is dilute, affecting metabolic reactions

68
Q

Explain some causes of kidney failure:

A

-Diabetes
-High blood pressure: damages capillaries in glomerulus, preventing ultrafiltration.
-Infection
-Autoimmune diseases
-Severe injury/trauma

WJEC A2 Biology (12 decks)

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