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OCR A A level Biology > Excretion > Flashcards

Excretion Flashcards

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1
Q

What is excretion?

A

The removal of metabolic waste products from the body

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2
Q

What does the hepatic artery do?

A

takes oxygenated blood from the heart to the liver for respiration

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3
Q

What does the hepatic vein do?

A

takes deoxygenated blood away from the liver to the heart

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4
Q

What does the hepatic portal vein do?

A

brings blood from the duodenum and ileum so it’s rich in products of digestion. this means any ingested harmful substances are filtered out and broken down instantly.

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5
Q

What are the duodenum and ileum?

A

Parts of the small intestine

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6
Q

What does the bile duct do?

A

takes bile to the gall bladder for storage

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7
Q

What connects the hepatic artery and vein?

A

Sinusoids

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8
Q

What do hepatocytes do?

A

they break down harmful substances into less harmful substances and make them re-enter the blood

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9
Q

What do Kupffer cells do?

A

they remove bacteria and break down old red blood cells.

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10
Q

What do hepatocytes do with bile they produce?

A

they secrete it into bile canaliculi which are tubes that drain into the bile ducts

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11
Q

What do bile ducts from all the liver lobules do after being filled with bile from the bile canaliculi?

A

they eventually join up and leave the liver

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12
Q

How are excess amino acids damaging?

A

they contain nitrogen and nitrogenous substances can’t be stored. therefore, they must be used up in the body.

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13
Q

Describe deamination

A

The amino groups from amino acids are removed , forming ammonia and organic acids

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14
Q

What happens to the organic acids formed in deamination?

A

they can be respired to give ATP or converted to carbohydrate and stored as glycogen

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15
Q

What happens to ammonia in the ornithine cycle?

A

Since ammonia is too toxic for mammals to excrete directly, it combines with CO2 to create urea and water

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16
Q

What happens to the urea formed from the ornithine cycle?

A

it is released from the liver to the blood. the kidneys filter the blood and remove urea as urine that is then excreted from the body.

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17
Q

Briefly describe what detoxification is

A

this is when the liver breaks down harmful substances like alcohol, drugs and unwanted hormones into less harmful substances that can be secreted from the body

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18
Q

Why is alcohol broken down?

A

it can damage cells. excess alcohol over a long period of time can cause cirrhosis of the liver- when liver cells die and scar tissue blocks blood flow

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19
Q

What is alcohol broken down into?

A

It is broken down into ethanal that is then broken down into acetic acid

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20
Q

Why is paracetamol broken down?

A

excess in the blood can lead to liver and kidney failure

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21
Q

Why is insulin broken down?

A

excess can leads to problems with blood sugar levels

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22
Q

Glycogenesis- the liver

A

the liver converts excess glucose into glycogen

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23
Q

How do kidneys excrete waste products?

A
  • blood enters the kidney through the renal artery and passes through the cortex.
  • as blood passes through the capillaries, ultrafiltration occurs
  • useful substances are reabsorbed back into the blood from the tubules in the medulla and cortex. this is selective reabsorption
  • remains pass along tubules then the ureter to the bladder to be expelled as urine.
  • filtered blood passes out of the kidneys through the renal vein
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24
Q

What are nephrons?

A

long tubules along the bundle of capillaries where the blood is filtered

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25
Q

Describe ultrafiltration

A

1- blood from the renal artery enters smaller arterioles in the cortex. Each arterioles splits into a glomerulus
2- the efferent arteriole forces liquid and small molecules in the blood out of the capillary and into the Bowman’s capsule
3- these substances pass through the capillary endothelium, basement membrane and epithelium of the Bowman’s capsule to get into the Bowman’s capsule and enter the nephron tubule
4- the liquid and small molecules are now called a filtrate and pass through the rest of the nephron

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26
Q

What is a glomerulus?

A

a bundle of capillaries looped inside the Bowman’s capsule.

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27
Q

What is the afferent arteriole?

A

the arteriole that takes blood INTO each glomerulus

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28
Q

What is the efferent arteriole?

A

the arteriole that takes blood AWAY from the glomerulus

29
Q

How does the efferent arteriole force liquid and small molecules out of the capillary?

A

it has a smaller diameter so the blood in the glomerulus is at high pressure

30
Q

What forces the liquid and small molecules in the blood out of the capillaries and into the Bowman’s capsule?

A

the high pressure of blood in the glomerulus

31
Q

What 3 layers do the liquid and small molecules pass through to get into the Bowman’s capsule and into the nephron tubule?

A

the capillary endothelium, the basement membrane, and the epithelium of the Bowman’s Capsule

32
Q

Where does selective reabsorption take place?

A

along the PCT, through the loop of Henle, and along the DCT. useful substances leave the nephron tubules and enter the capillary network wrapped around them.

33
Q

What makes PCT adapted for selective reabsorption?

A

the epithelium of its walls have microvilli to provide a large surface area

34
Q

By what process are useful solutes like glucose, amino acids, vitamins, and some salts reabsorbed along the PCT?

A

active transport and facilitated diffusion

35
Q

Why does water enter the blood by osmosis?

A

the water potential in the blood is lower than the filtrates.

36
Q

What happens when the water potential of the blood is too low?

A

more water is reabsorbed by osmosis into the blood from the nephron tubules. the urine is more concentrated so less water is lost by excretion

37
Q

What happens when the water potential of the blood is too high?

A

less water is reabsorbed by osmosis into the blood from the nephron tubules. the urine is more dilute so more water is lost during excretion.

38
Q

Which parts of the nephron does water potential regulation occur?

A

the DCT, loop of Henle, and collecting duct

39
Q

What 2 limbs make up the loop of Henle?

A

the descending and ascending limbs

40
Q

Describe the countercurrent multiplier mechanism

A

1- near the top of the asc. limb, Na+ and Cl- ions are actively pumped out into the medulla. the asc. limb is impermeable to water so water stays inside the tubule. this creates a low water potential in the medulla as there’s a high conc of ions.
2- there’s a < WP in the medulla than the desc. limb, water moves out of the desc. limb into the medulla by osmosis. this makes the filtrate > concentrated as the desc. limb is impermeable to ions so ions can’t diffuse out. water in the medulla is reabsorbed into the blood through the capillaries.
3-near the bottom of the asc. limb, the ions diffuse out into the medulla, further lowering the WP inside.
4- the 3 stages massively increase the ion conc in the medulla, lowering the WP. this causes water to move out of the collecting duct by osmosis. water in the medulla is reabsorbed into the blood by capillaries.

41
Q

What does it mean if an animal has a longer loop of Henle?

A

they can reabsorb more water form the filtrate

42
Q

What type of loop of Henle do camels have?

A

longer- to produce small volumes of concentrated urine to conserve water

43
Q

What type of loop of Henle do frogs have?

A

none at all can’t produce concentrated urine and don’t need to conserve water as they live in it

44
Q

What monitors the water potential of the blood?

A

osmoreceptors in the hypothalamus. the hypothalamus then sends impulses to the posterior pituitary gland to release ADH into the blood or not

45
Q

How does ADH regulate the water potential of the blood?

A
  • binds to receptors of the plasma membranes of cells in the DCT and collecting duct
  • protein channels called aquaporins are inserted into the plasma membrane to allow water to pass through via osmosis, making the walls of the DCT and collecting duct more permeable to water
  • more water is reabsorbed into the blood
  • a small amount of concentrated urine is produced
46
Q

ADH- dehydration (blood water content too low)

A
  • water potential drops
  • detected by osmoreceptors in the hypothalamus
  • posterior pituitary gland is stimulated to release more ADH into the blood
  • more ADH= DCT and CT more permeable so more water reabsorbed into the blood by osmosis
  • small amount of highly concentrated blood is produced
47
Q

ADH- hydration (blood water content too high)

A
  • water potential rises
  • osmoreceptors in the hypothalamus detect it
  • posterior pituitary gland releases less ADH into the blood
  • DCT and CT are less permeable so less water is reabsorbed into the blood by osmosis
  • large amount of dilute urine produced
48
Q

How can kidney failure be detected?

A

by measuring the GFR- glomerulus filtration rate. a rate lower than normal shows the kidneys arent working properly.

49
Q

What can cause kidney failure?

A

high blood pressure and kidney infections

50
Q

How do kidney infections cause kidney failure?

A
  • cause inflammation of the kidneys which can damage the cells
  • this interferes with filtering in the Bowman’s capsules and reabsorption in other parts of the nephrons
51
Q

How does high blood pressure cause kidney failure?

A
  • can damage the glomeruli
  • the capillaries can be damaged if the blood pressure is too high as the pressure is already high in the glomerulus
  • this means larger molecules like proteins can get through the capillary walls and into the urine
52
Q

What problems arise from kidney failure?

A
  • waste products build up e.g. urea, can cause weight loss and vomiting
  • fluid accumulates in the tissues as kidneys can’t remove excess water. causes parts of the body to swell.
  • electrolyte imbalance e.g. blood can be too acidic, imbalance of calcium and phosphate can cause brittle bones.
  • long term kidney failure can cause anaemia
53
Q

Two main treatments for kidney failure

A

renal dialysis or a kidney transplant

54
Q

What are the 2 types of renal dialysis?

A

haemodialysis and peritoneal dialysis

55
Q

How does haemodialysis work?

A
  • patient’s blood is passed through the machine
  • blood flows on one side of a partially permeable membrane and dialysis fluid on the other, in opposite directions to maintain a steep conc. gradient for diffusion
  • waste products diffuse across the membrane to dialysis fluid.
  • blood cells and larger molecules stay in the blood
56
Q

What are the problems with hemodialysis?

A
  • a person can feel increasingly unwell between sessions. waste products build up in their blood.
  • each session takes 3-4 hrs, and they need 2-3 sessions a week which is expensive and inconvenient for the patient
57
Q

How does peritoneal dialysis work?

A
  • operation is done beforehand to insert a tube into their abdominal cavity
  • the abdominal cavity is lined with a membrane called the peritoneum
  • dialysis fluid is put through the tube to the abdominal cavity
  • waste products from the blood diffuse out of capillaries and across the peritoneum into the dialysis fluid
  • after several hrs, the dialysis fluid is changed
  • this is done at some around 4 times a day or overnight
58
Q

What are the problems with peritoneal dialysis?

A
  • risk of infection around the tube

- no dialysis-free days

59
Q

What are the requirements of a kidney transplant?

A

must be from someone of the same tissue and blood type

60
Q

Advantages of a kidney transplant

A
  • cheaper than dialysis over a long time
  • more convenient than dialysis sessions
  • no feelings of unwellness in between sessions
61
Q

Disadvantages of a kidney transplant

A
  • risk of operation

- risk of the immune system rejecting it (needs to take immunosuppressant drugs)

62
Q

Why are urine tests used?

A

urine is made by filtering blood so you can see what’s in one’s blood by looking at their urine

63
Q

What are urine tests used for?

A

to test for pregnancy and drugs

64
Q

What is hCG?

A

a hormone found in the urine of pregnant women

65
Q

How to test for pregnancy:

A

1- a stick is used with an application area that contains monoclonal antibodies for hCG bound to a coloured bead (blue)
2-when urine is applied, any hCG binds to the antibody on the beads
3-urine moves up the strip, carrying beads with it
4- the test strip has immobilised antibodies to hCG
5- if any hCG is present, strip turns blue as the immobilised antibodies bind to any hCG attached to the blue beads
-if there’s no hCG, they pass through without binding to anything

66
Q

What are anabolic steroids? Give examples.

A

drugs that build up muscle tissue e.g. testosterone, nandrolone.

67
Q

Methods to test for steroids

A

-use gas chromatography/mass spectrometry

68
Q

Gas chromatography/mass spectrometry for steroids

A

1) -urine sample is vapourised and passed through a column containing a polymer
- diff substances move through the column at diff speeds, so substances in the sample separate out
2) a mass spectrometer converts them into ions, then separates the ions based on their M/Z charge. the results are analyzed by a computer and compared with the results of known substances.

69
Q

Test for recreational drugs:

A
  • urine sample is applied to a test strip
  • if a certain amount of the drug is present, a colour change will occur indicating a positive result
  • if the first test is positive, a sample is usually sent for further testing to confirm which drugs had been used. this test uses GM/MS.

OCR A A level Biology (6 decks)

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