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Biology A2 Rafa > 5.2 Excretion as an Example of Homeostatic Control > Flashcards

5.2 Excretion as an Example of Homeostatic Control Flashcards

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1
Q

Define excretion

A

The removal of metabolic waste from the body

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2
Q

Define metabolic waste

A

A substance that is produced in excess by the metabolic processes in cells ; it may become toxic

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3
Q

Define ornithine cycle

A

A series of biochemical reactions that convert ammonia to urea

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4
Q

Define nephron

A

The functional unit of the kidney

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5
Q

Define ultrafiltration

A

Filtration of the blood at a molecular level under pressure

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6
Q

Define ADH

A

A hormone that controls the permeability of the collecting duct walls

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7
Q

Define osmoreceptor

A

A sensory receptor that detects changes in water potential

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8
Q

Define glomerular filtration rate

A

the rate at which fluid enters the nephrons

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9
Q

Define monoclonal antibodies

A

Antibodies made of one type of cell - they are specific to one complementary molecule

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10
Q

Define renal dialysis

A

a mechanism used to artificially regulate the concentrations of solutes in the blood

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11
Q

How does blood flow into the liver?

A

Hepatic artery

hepatic portal vein

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12
Q

What does the hepatic portal vein do?

A

DEOXYGENATED blood from the digestive system enters

rich in the products of digestion

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13
Q

Where is blood from hepatic artery and hepatic portal vein mixed?

A

Sinusoid which is lined with liver cells

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14
Q

What moves about within sinusoids?

A

Macrophages called Kupffer cells
breakdown and recycle of old RBC
one of the products of haemoglobin breakdown is bilrubin

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15
Q

Where is bile made and taken\?

A

Bile is made in liver cells and released into pie caniculi which join to make the bile duct

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16
Q

What type of vessel is the hepatic vein?

A

Intralobular

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17
Q

Which has a bigger lumen- Hepatic artery or portal vein?

A

Portal vein

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18
Q

Functions of liver

A

Control of blood glucose, amino acid and lipid levels
Synthesis of bile, plasma proteins and cholesterol
Synthesis of RBC in foetus
Deoxification of alcohol and drugs
Breakdown of hormones
Destruction of RBC
Storage of vitamins A, D, B12 and glycogen

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19
Q

Which two enzymes are involved in detoxification in the liver?

A

catalase for hydrogen peroxide

cytochrome P450 for drugs such as cocaine

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20
Q

Which enzyme in the liver breaks down alcohol?

A

Ethanol dehydrogenase

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21
Q

Path of detoxification of alcohol

A

(ethanol dehydrogenase)ethanol(2H>NAD>reduced NAD)
(ethanal dehydrogenase)ethanal(2H>NAD>reduced NAD)
ethanoic acid
acetyl coenzyme A
respiration

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22
Q

How does fatty liver happen?

A

Too much alcohol, not enough NAD to deal with fatty acids which are converted back to lipids and stored as fat on hepatocytes

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23
Q

Two processes that are involved in the formation of urea

A

deamination followed by the ornithine cycle

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24
Q

Equation for deamination

A

amino acid+oxygen= keto acid + ammonia

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25
Q

Structure of keto acid

A

CROCOOH

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26
Q

Equation for ornithine cycle

A

ammonia + carbon dioxide = urea + water

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27
Q

Formula of urea

A

CO(NH2)2

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28
Q

1st step ornithine

A

ornithine + ammonia + co2 = h20 + citrulline

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29
Q

2nd step ornithine

A

Citrulline + NH3 = h2o + arginine

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30
Q

3rd step ornithine cycle

A

arginine + water = urea + ornithine

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31
Q

Order of kidney

A

capsule
cortex
medulla
pelvis

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32
Q

How are the three layers of the Bowman’s capsule adapted for ultrafiltration

A
  • Endothelium of the capillary (have pores called fenestrations)
  • The basement membrane (mesh of collagen fibres and glycoproteins, acts as filter)
  • The epithelial cells of the Bowman’s capsule (called podocytes, have a specialised shape, hold cell away from endothelium of capillary and ensure there are gaps between cells
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33
Q

What is selectively reabsorbed in the proximal convoluted tubule?

A

All sugars, most mineral ions, some water, amino acids

34
Q

Features of proximal convoluted tubule?

A

Cells have a highly folded surface producing a brush border

35
Q

What happens in the descending loop of Henle?

A

Na and Cl diffuse in

H2O out by osmosis

36
Q

What happens in the ascending LOH?

A

Na and Cl out(active transport)

37
Q

Which cells are specialised for selective reabsorption?

A

Proximal convoluted tubule
highly folded
the cells surface membrane also has cotransporter proteins that transport glucose or amino acids in association with sodium ions, into the cell from the tubule
Many mitochondria

38
Q

Where does the nephron start?

A

Cortex

39
Q

What does the glomerular filtrate contain?

A 
water
amino acids
glucose 
urea
inorganic mineral ions
40
Q

What is left in the blood after ultrafiltration?

A

larger proteins and rbc

41
Q

Mechanisms of selective reabsorption

A

1) sodium outs pumped out of cell lining tubule into blood
2) This creates a concentration gradient
3) Comes back in using con transporter proteins, from proximal convoluted tubule
4) glucose and amino acids are cotransported in
5) glucose concentration increases in cells
6) glucose diffuses out
7) water follows by osmosis into blood

42
Q

Why is reabsorption regarded as secondary active transport

A

Passive con transport but active pumping of mineral ions

43
Q

What is the aim of the LOH?

A

Reduce the volume of urine without changing its concentration

44
Q

What does the LOH use?

A

Hairpin countercurrent multiplier system

45
Q

Steps of mechanism of loop of henle

A

1) Na and Cl are actively pumped out of the thick ascending into the medulla
2) water doesn’t follow because the ascending limb is impermeable to water
3) water moves out of thin descending limb through osmosis
4) At the base, na and cl start to diffuse out (passive as more and more salty)
5) water is lost in collecting duct

46
Q

Where is most salty in the medulla

A

Base of loop of Henle

47
Q

How does the body maintain how much water is lost?

A

Changing permeability of collecting duct to water

48
Q

What does the distal convoluted tubule do?

A

Uses hormones to adjust concentrations of mineral ions in an active process

49
Q

Where are osmoreceptors?

A

Hypothalamus, they shrink when there is a fall in water potential

50
Q

What happens when osmorecpeotrs detect a change?

A

Cause neurosecretory cells in the hypothalamus to release ADH

51
Q

Where is ADH stored?

A

Posterior pituitary gland in vesicles and released by exocytosis

52
Q

What does ADH do?

A

Prevents the production of dilute urine

53
Q

How does ADH work?

A

attached to receptor on plasma membrane
vesicles with aquaporins fuse with the membrane
this allows water to respond to the solute concentration in the medulla,
water moves back into the blood

54
Q

ADH half life

A

20 mins

55
Q

Normal reading of GFR

A

90-120cm3min-1

56
Q

Diagnosis of chronic kidney disease and failure

A

<60 chronic kidney disease

<15 kidney failure + immediate medical attention

57
Q

Why do kidneys fail?

A

Diabetes
Heart disease
Infection
Hypertension

58
Q

Treatment of kidney failure

A

Renal dialysis

Kidney transplant

59
Q

Two types of renal dialysis

A

Haemodialysis and peritoneal dialysis

60
Q

Explain haemodialysis

A

Blood goes into machine which is shaped to form many artificial capillaries
Heparin is added
Countercurrent
2-3 times per week
Air trap/air detector to get rid of bubbles

61
Q

Explain peritoneal dialysis

A

Tube permanently implanted into abdomen
Fluid fills peritoneal cavity and is taken out
Can walk around

62
Q

Good things about kidney transplant

A

Freedom from dialysis
Feel physically fitter
Quality of life
Self image

63
Q

Bad things about kidney transplants

A
  • Need immunosuppresant drugs
  • Side effects (fluid retention, high blood pressure, infections)
  • Need regular checks
  • Major surgery under general anaesthetic
64
Q

What hormone is tested for in pregnancy testing?

A

Human chorionic gonadotrophin (hCG)

65
Q

What organs are involved in excretion?

A

Lungs- CO2
Kidney - Urea removed from blood
Liver - Bilirubin
Skin - Salts, H2O, urea, uric acid, ammonia

66
Q

What are the main excretory products?

A
  • CO2
  • Nitrogen containing compounds, such as urea
  • Other compounds, such as bile pigments
67
Q

Which organ stores urea?

A

The bladder stores it as urine

68
Q

Which organ produces urea?

A

The liver

69
Q

Which organ filters urea?

A

The kidneys

70
Q

How could you explain somebody having a higher concentration of urea in their body?

A

Eating more protein - amino acids which cant be stored

71
Q

What is bilirubin?

A

Product of the breakdown of haemoglobin, a bile pigment

72
Q

Explain why toxins should not simply be excreted

A

They could contain energy that could be used for respiration

They should therefore be processed before excreted

73
Q

What are pores in the endothelium of the capillary in the kidney called?

A

Fenestrations

74
Q

What is left in the blood after it has filtered through the glomerulus?

A
  • red blood cells

- large proteins (>69,000D)

75
Q

Why is it important that blood has a low water potential after being filtered through the glomerulus?

A

So that some fluid is retained in the capillaries

76
Q

Why are the proximal and distil tubules convoluted?

A

Increases surface area of tube interior that is exposed to the blood
Maximal reabsorption

77
Q

Where does selective reabsorption take place?

A

Proximal convoluted tubule

78
Q

How is the proximal convoluted tubule specialised for selective reabsorption?

A
  • the cell surface membrane is folded into microvilli
  • the cell surface membrane has special cotransporter proteins that can transport glucose/amino acids (with NA+) from tubule
  • many mitochondria
79
Q

What is reabsorbed in selective rebsorption?

A
  • all sugars
  • amino acids
  • some ions
  • some water
80
Q

How does the body regulate how much H2O is reabsorbed?

A

By adjusting the permeability of collecting duct walls to water

81
Q

Two differences between cells lining the descending limb and the thick ascending limb

A
  • Thick ascending limb cells have protein pumps for removing Na+ and Cl-
  • Thick ascending limb cell surface membranes lack channels for the efficient diffusion of water
82
Q

What can be detected in blood if not reabsorbed?

A
  • excess glucose (diabetes)
  • alcohol
  • many recreational drugs
  • anabolic steroids
  • human chorionic gonadotrophin (hCG)

Biology A2 Rafa (14 decks)

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