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Biology > Module 5.2 > Flashcards

Module 5.2 Flashcards

excretion

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1
Q

What is excretion

A

The removal of metabolic waste from the body

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2
Q

Why is excretion important

A

almost all products that are formed in excess by chemical processes must be removed so they do not build up and become toxic or inhibit enzyme activity

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3
Q

why must carbon dioxide be excreted

A

if it builds up in the blood it makes the blood acidic which denatures enzymes
excreted through the lungs

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4
Q

Why must nitrogenous wate be excreted

A

excess amino acids cannot be stored but as they contain a lot of energy the whole molecule should not be excreted
the amino group is removed and excreted as it is toxic while the rest is used for energy

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5
Q

how is the liver supplied with blood

A

hepatic artery
hepatic portal vein

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6
Q

role of the hepatic artery

A

oxygenated blood from the heart supplies oxygen to the very active liver cells for aerobic respiration

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7
Q

role of the hepatic portal vein

A

deoxygenated blood from the digestive system
rich in products of digestion at uncontrolled concentrations go to liver to be controlled

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8
Q

how blood leaves the liver

A

hepatic vein

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9
Q

role of the bile duct

A

carries bile which is a secretion from the liver which has functions in digestion and excretion
from the bile duct it is stored in the gallbladder

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10
Q

how is the liver divided

A

lobes which are further divided into lobules
to ensure the greatest possible contact between the blood and the liver cells

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11
Q

what happens to the blood as it enters the liver

A

as the hepatic artery and hepatic portal vein run into the liver they split into smaller vessels and run between and parallel to the lobules.
The blood from the 2 vessels mixes and pass along a sinusoid

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12
Q

role of the sinusoid

A

lined with liver cells so as blood flows along it it is in close contact with liver cells and the cells can remove substances from the blood and return other substances to the blood

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13
Q

what are kupffer cells

A

move about within sinusoids to break down and recycle old blood cells

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14
Q

what is one of the products of haemoglobin breakdown

A

bilirubin

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15
Q

where is bile released in the liver

A

into the bile canaliculi which join together to form the bile duct

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16
Q

what do the sinusoids empty into

A

branches of the hepatic vein at the centre of each lobule

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17
Q

inter-lobular vessels

A

hepatic artery
hepatic portal vein

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18
Q

intra-lobular vessel

A

hepatic vein

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19
Q

what are liver cells called

A

hepatocytes

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20
Q

specialisation of hepatocytes

A

many micro villi on the surface
dense cytoplasm for the many metabolic functions
many mitochondria

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21
Q

roles of the liver

A

storage of glycogen
detoxification
formation of urea

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22
Q

how the liver stores glycogen

A

glycogen forms granules in the cytoplasm of hepatocytes
able to store 100-120g of glycogen
glycogen can be broken down to release glucose as required

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23
Q

why does alcohol need to be detoxified

A

depresses nerve activity and contains chemical potential energy which can be used for respiration

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24
Q

first step of alcohol break down

A

ethanol dehydrogenase breaks ethanol into ethanal releasing hydrogen which combines with NAD to form reduced NAD

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25
Q

second step of alcohol break down

A

ethanal dehydrogenase breaks ethanal into ethanoic acids releasing hydrogen which combines with NAD to form reduced NAD

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26
Q

final product of alcohol break down

A

acetyl coenzyme a which is used in respiration

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27
Q

why is the liver detoxifying too much alcohol bad

A

NAD is required to break down fatty acids for use in respiration
If too much alcohol is detoxified the stores of NAD are used up and cannot be used for fatty acids
the fatty acids are then stored as fat in the hepatocytes making the liver enlarged

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28
Q

process of deamination

A

removes the amino group from the amino acid producing ammonia and keto acid

29
Q

the ornithine cycle

A

ammonia is soluble and toxic so must be converted to a less toxic form quickly
ammonia is reacted with carbon dioxide to produce urea
urea is less soluble and less toxic

30
Q

functions of the kidney

A

remove waste products from the blood and produce urine

31
Q

how are the kidneys supplied with blood

A

renal artery

32
Q

regions of the kidney from outside to inside

A

pelvis
medulla
cortex
capsule

33
Q

what makes up the kidney

A

nephrons

34
Q

structure of nephrons

A

bowman’s capsule
proximal convoluted tubule
loop of Henle
distal convoluted tubule
collecting duct

35
Q

how does blood supply the nephrons

A

the renal artery splits into many arterioles
afferent arterioles lead into the glomerulus and efferent arterioles lead away from the glomerulus

36
Q

what is the glomerulus

A

a knot of capillaries inside the Bowman’s capsule

37
Q

what is ultrafiltration

A

filtration of the blood at a molecular level under pressure

38
Q

where does ultrafiltration occur

A

the glomerulus and Bowman’s capsule

39
Q

what are the different barriers in ultrafiltration

A

endothelium of the capillary
basement membrane
epithelial cells of the Bowman’s capsule

40
Q

how the endothelium of the capillary enables ultrafiltration

A

gaps between the endothelial cells
the cells contain pores (fenestrations)
allows plasma and the substances dissolved in it to pass out of the capillary

41
Q

How the basement membrane enables ultrafiltration

A

Membrane consists of a fine mesh of collagen fibres and glycoprotein
molecules with relative molecular mass over 69000 cannot pass through the mesh (most proteins and blood cells)

42
Q

How the epithelial cells of the Bowman’s capsule enable ultrafiltration

A

the cells (podocytes) have finger-like projections that hold the cells away from the endothelium of the capillary so the fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowman’s capsule

43
Q

how is the high pressure created in ultrafiltration

A

the afferent arteriole is wider than the efferent arteriole

44
Q

what is filtered out of the blood in ultrafiltration

A

water
amino acids
glucose
urea
inorganic ion (sodium chloride, potassium)

45
Q

where does selective reabsorption happen

A

proximal convoluted tubule

46
Q

how selective reabsorption occurs

A

sodium ions are actively pumped out of the cells lining the PCT
cell cytoplasm sodium ion concentration decreases
sodium ions diffuse into cell in cotransporter protein carrying glucose or an amino acid at the same time
water moves into cells by osmosis
glucose and amino acids diffuse into blood and water follows by osmosis

47
Q

descending limb of the loop of henle

A

diffusion of sodium and chloride ions into the descending limb
water moves out of the limb by osmosis and enters capillaries

48
Q

ascending limb of the loop of henle

A

active removal of sodium and chloride ions
as the

49
Q

function of the loop of henle

A

Increase the concentration of mineral ions in the tubule fluid of the descending limb and decrease the mineral ion concentration in the ascending limb
creates water potential gradient in the medulla which gets steeper as it goes towards the pelvis so water can move out of the collecting duct

50
Q

role of adh

A

adh binds to membrane bound receptors in the plasma membrane of collecting duct cells
this causes a chain of enzyme controlled reactions resulting in vesicles containing water permeable channels (aquaporins) to fuse with the cell surface membrane making the collecting duct walls more permeable to water

51
Q

what happens when there is a lot of adh in the blood

A

more water-permeable channels are inserted so more water can be reabsorbed into the blood
less urine is produced and the urine has a lower water potential

52
Q

what happens when adh levels fall

A

the cell surface membrane folds in on itself to create a new vesicles that removes the water-permeable channels from the membrane make the walls less permeable so less water is reabsorbed into the blood
more urine is formed that has a higher water potential

53
Q

role of osmoreceptors in the hypothalamus

A

monitor the water potential of the blood

54
Q

what do osmoreceptors do when blood water potential is low

A

osmoreceptor cells loose water and shrink which stimulates neurosecretory cells in the hypothalamus to release ADH

55
Q

how neurosecretory cells work

A

ADH is manufactured in the cells body in the hypothalamus
adh moves down the axon to the terminal bulb in the posterior pituitary gland where it is stored in vesicles
when stimulated the action potential is carried down the axon and adh is released by exocytosis

56
Q

how does adh enter the blood

A

enters the capillaries running through the posterior pituitary gland

57
Q

causes of kidney failure

A

diabetes
heart disease
hypertension
infection

58
Q

what is glomerular filtration rate

A

measure of how much fluid passes into the nephrons each minutes

59
Q

effect of kidney failure

A

unable to regulate the levels of water and electrolytes in the body
unable to remove waste products from the blood
lower glomerular filtration rate

60
Q

what treatments are there for kidney failure

A

renal dialysis (haemodialysis)
transplant

61
Q

what is dialysis fluid

A

contains the correct concentrations of mineral ions urea water and other substances found in the blood plasma

62
Q

how does dialysis work

A

blood is passed over a partially permeable dialysis membrane that allows the exchange of substances between the blood and dialysis fluid
substances in excess in the blood pass into the dialysis fluid and substances too low in the blood pass into the blood from the dialysis fluid

63
Q

how haemodialysis works

A

blood from an artery or vein is passed into a machine with a dialysis membrane shaped with many capillaries to increase surface area
heparin is used to prevent clotting
dialysis fluid flows in the opposite direction to the blood

64
Q

what happens in a kidney transplant

A

new kidney is implanted into the lower abdomen and attached to the blood supply and the bladder

65
Q

advantages of transplant

A

dialysis is time consuming
feel physically fitter
improved quality of life (can travel)

66
Q

disadvantages of transplant

A

immunosuppressant drugs
major surgery under anaesthetic
regular checks for rejection
side effects of immunosuppressants

67
Q

how urine analysis is used in diagnostics

A

any metabolic product with a relative molecular mass under 69000 can enter the nephron and if not reabsorbed can be detected in the urine e.g. glucose for diabetes, alcohol and drugs, hCG in pregnancy

68
Q

how pregnancy testing works

A

hCG is a hormone that can be found in urine as early as 6 days after conception
relative molecular mass less than 69000 so is found in urine
monoclonal antibodies bind to hCG in urine in pregnancy test kits

69
Q

how are anabolic steroids tested for

A

they are relatively small molecules and can enter the nephron
urine samples are analysed using ga chromatography

Biology (18 decks)

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