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AQA A-level biology > 3B - more exchange and transport systems > Flashcards

3B - more exchange and transport systems Flashcards

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1
Q

why can’t large biological molecules be absorbed from the gut into the blood?

A

because they’re too big to cross the membrane.

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2
Q

what happens to large molecules during digestion?

A

they’re broken down into smaller molecules (e.g. glucose and amino acids) which can move across the cell membranes.

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3
Q

which reaction breaks down the large molecules?

A

hydrolysis reaction.

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4
Q

what are carbohydrates broken down into?

A

disaccharides.

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5
Q

what are fats broken down into?

A

fatty acids and monoglycerides.

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6
Q

what are proteins broken down into?

A

amino acids.

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7
Q

what are enzymes used for?

A

to break down biological molecules in food.

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8
Q

what enzyme catalyses the breakdown of starch?

A

amylase.

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9
Q

what is starch a mixture of?

A

two polysaccharides.

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10
Q

how does amylase work?

A

by catalysing a hydrolysis reaction that breaks the glycosidic bonds in starch to produce maltose (a disaccharide).

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11
Q

where is amylase produced?

A

salivary glands (releases amylase in the mouth) and the pancreas (releases amylase in the small intestine).

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12
Q

what are membrane-bound disaccharidases?

A

enzymes that are attached to the cell membranes of epithelial cells lining the ileum.

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13
Q

what is the ileum?

A

the final part of the small intestine.

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14
Q

what do membrane-bound disaccharidases break down?

A

disaccharides (into monosaccharides).

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15
Q

name three disaccharides.

A

maltose, lactose and sucrose.

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16
Q

how can monosaccharides be transported across the epithelial cell membranes in the ileum?

A

via transporter proteins.

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17
Q

which enzyme catalyses the breakdown of lipids?

A

lipase enzymes.

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18
Q

what do lipids break down into?

A

fatty acids and monoglycerides.

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19
Q

which bonds are broken in lipids?

A

ester bonds.

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20
Q

where are lipases made?

A

mainly in the pancreas (secretes into the small intestine).

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21
Q

what are bile salts produced by?

A

the liver.

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22
Q

what do bile salts do?

A

they emulsify lipids.

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23
Q

what does it mean when lipids are emulsified?

A

they form small droplets.

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24
Q

why is it better that lipids break down into small droplets?

A

several small lipid droplets means that the surface area is larger which means there’s more surface area of lipid for lipases to work on.

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25
Q

what happens to the fatty acids and monoglycerides?

A

they stick with the bile salts to form tiny structures called micelles.

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26
Q

what do micelles do?

A

they help the products of lipid digestion to be absorbed.

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27
Q

what enzymes break down proteins?

A

peptidases.

28
Q

what do proteins break down into?

A

amino acids.

29
Q

which bonds join amino acids together?

A

peptide bonds.

30
Q

what are the three types of peptidases?

A

endopeptidases, exopeptidases and dipepridases.

31
Q

what do endopeptidases do?

A

they act to hydrolyse peptide bonds within a protein.

32
Q

what do exopeptidases do?

A

they act to hydrolyse peptide bonds at the ends of protein molecules. they remove single amino acids from proteins.

33
Q

give three examples of endopeptidases.

A

pepsin, trypsin and chymotrypsin.

34
Q

what are dipeptidases?

A

they’re exopeptidases that work specifically on dipeptides.

35
Q

what do dipeptisases do?

A

they separate the two amino acids that make up a dipeptide by hydrolysing the peptide bond between them

36
Q

where are dipeptidases often located?

A

in the cell-surface membrane of epithelial cells in the small intestines.

37
Q

where are the products of digestion absorbed?

A

across the ileum epithelium into the bloodstream.

38
Q

how is glucose absorbed?

A

by active transport via a co-transporter protein.

39
Q

how is galactose absorbed?

A

active transport via a co-transporter protein.

40
Q

how is fructose absorbed?

A

via facilitated diffusion through a different transporter protein to glucose and galactose.

41
Q

where do micelles help to move fatty acids and monoglycerides to?

A

the epithelium.

42
Q

why can micelles ‘release’ the monoglycerides and fatty acids?

A

because they constantly break up and reform.

43
Q

are whole micelles taken up across the epithelium?

A

no.

44
Q

why can monoglycerides and fatty acids diffuse directly across the epithelial cell membrane?

A

because they’re lipid-solvable.

45
Q

how are amino acids absorbed?

A

sodium ions are actively transported out of the epithelial cells into the ileum. they then diffuse back into the cells through sodium-dependent transporter proteins in the epithelial cell membranes, carrying the amino acids with them.

46
Q

where is haemoglobin found?

A

in the red blood cells.

47
Q

what is the role of haemoblobin?

A

to carry oxygen around the body.

48
Q

what is haemoglobin?

A

a large protein with a quaternary structure.

49
Q

what is haemoglobin quaternary structure made up of?

A

four polypeptide chains, each chain having a haem group which contains an iron ion (gives haemoglobin its red colour).

50
Q

how many molecules of oxygen can each molecule of human haemoglobin carry?

A

4.

51
Q

where does oxygen join to haemoglobin?

A

in the lungs.

52
Q

what is formed when oxygen joins to haemoglobin?

A

oxyhaemoglobin.

53
Q

where does oxyhaemoglobin turn back to haemoglobin?

A

near body cells that need oxygen.

54
Q

what is it called when an oxygen molecule joins to haemoglobin?

A

association or loading.

55
Q

what is it called when oxygen leaves oxyhaemoglobin?

A

dissociation or unloading.

56
Q

what is affinity for oxygen?

A

the tendency a molecule has to bond with oxygen.

57
Q

what does haemoglobin a affinity for oxygen depend on?

A

the conditions it’s in.

58
Q

what’s a condition that affects the affinity for oxygen?

A

partial pressure of oxygen (pO2)

59
Q

what is partial pressure of oxygen?

A

the measure of oxygen concentration.

60
Q

does oxygen load onto haemoglobin to form oxyhaemoglobin where there’s a high or low pO2?

A

high.

61
Q

where does oxygen enter blood capillaries?

A

at the alveoli in the lungs.

62
Q

do alveoli have a high or low pO2?

A

high.

63
Q

when happens in cells to reduce the pO2?

A

respiration.

64
Q

where do red blood cells deliver oxyhaemoglobin to?

A

respiring tissues.

65
Q

what are some factors of the alveoli in the lungs?

A
  • HIGH oxygen concentration
  • HIGH pO2
  • HIGH affinity
  • oxygen LOADS
66
Q

what are some factors of respiring tissues?

A
  • LOW oxygen concentration
  • LOW pO2
  • LOW affinity
  • oxygen UNLOADS
67
Q

what does an oxygen dissociation curve show?

A

how saturated the haemoglobin is with oxygen and any given partial pressure.

AQA A-level biology (10 decks)

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