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MB1: Gastrointestinal > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

what is glycogenesis

A

synthesis of glycogen from glucose

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2
Q

what is glycogenolysis

A

breakdown of glycogen to form glucose

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3
Q

what is gluconeogenesis

A

synthesis of glucose from metabolic precursors

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4
Q

when would gluconeogenesis be raised?

A

overnight

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5
Q

when would glycogenolysis be raised

A

in between meals

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6
Q

what is glycogen

A

storage form of glucose

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7
Q

function of liver glycogen

A

maintaining blood glucose

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8
Q

function of skeletal muscle glycogen

A

bursts of energy, not blood glucose

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9
Q

what links keep glucose residues together in glycogen

A

alpha 1-4 glycosidic links

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10
Q

what links keep glycogen branches together

A

1-6 glycosidic links

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11
Q

what breaks gucose down into glucose-6-phosphate

A

hexokinase

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12
Q

what is the primer for glycogen

A

glycogenin, covalently attached to 4 glucose residues

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13
Q

what enzyme converts glucose 6-phosphate to glucose-1-phosphate

A

phosphoglucomutase

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14
Q

Addition of UTP to G-1-P is catalysed by _____

A

UDP-glucose pyrophosphorylase

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15
Q

what enzyme adds glucose residues to glycogen

A

glycogen synthase

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16
Q

can glycogen synthase create new glycogen molecules

A

no, it can only add glucose to existing ones

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17
Q

what enzyme is needed to add glucose to a branch of glycogen

A

transglycolase

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18
Q

what enzyme catalyses glycogenolysis

A

glycogen phosphorylase

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19
Q

true/false - in the liver G-6-P can be dephosphorylated to go back to glucose

A

true

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20
Q

true/false - in skeletal muscle G-6-P can be dephosphorylated to go back to glucose

A

false - it must be broken down via glycolysis and TCA

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21
Q

where does gluconeogenesis occur in the body

A

liver

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22
Q

is gluconeogenesis the reverse of glycolysis

A

no!

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23
Q

what enzyme catalyses synthesis of oxaloacetate from metabolites in gluconeogenesis

A

pyruvate carboxylase

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24
Q

what enzyme bypasses pyruvate kinase

A

PEP carboxylkinase

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25
Q

what enzyme bypasses phosphofructokinase

A

fructose-1,6-bisphosphatase

26
Q

what enzyme bypasses hexokinase to synthesise glucose in gluconeogenesis

A

glucose-6-phosphatase

27
Q

how much energy does gluconeogenesis use

A

4ATP

2GTP

28
Q

where do amino acids participate for use in gluconeogenesis

A

enter TCA to be converted to oxaloacetate

29
Q

what is the cori cycle

A

recovery of lactate to pyruvate, to glucose via gluconeogenesis

30
Q

true/false - insulin promotes glycogenesis and glycolysis

A

true

31
Q

glucagon increases gluconeogenesis by inhibiting ____ and promotoing ____

A

phosphofructokinase

fructose-1,6-biphosphatase

32
Q

what are TAGs made of and where are they stored

A

glycerol and 3 fatty acid chains

adipose

33
Q

true/false - fatty acids are usually in trans configuration

A

false - usually in cis

34
Q

what causes the kink in fatty acid chains

A

the double bond

35
Q

in order for fats to be absorbed into intestinal mucosa cells, they are broken down into ____, ____ or ____

A

glycerol
fatty acids
monoglycerides

36
Q

what is lipolysis and what is it catalysed by

A

breakdown of lipids, catalysed by hormone sensitive lipases

37
Q

before a fatty acid can be oxidised what must it be converted to?

A

CoA derivative

38
Q

is fatty acid oxidation a passive process?

A

no, it requires energy

39
Q

what is the carnitine shuttle

A

carnitine is acylated by acyl-CoA and travels across mitochondria to acylate another CoA to ‘shuttle’ across mitochondria

40
Q

products of beta oxidation

A

1FADH
1NADH+H
1 acyl CoA, 2 carbons shorter
1 Acetyl CoA

41
Q

describe the breakdown of glycerol

A

glycerol kinase converts it to glycerol-3-phosphate

dehydrogenated to dihydroxyacetone phosphate

42
Q

where are ketone bodies formed

A

liver mitochondria

43
Q

when may ketones be dangerous

A

in diabetics as they may develop diabetic ketoacidosis due to the inability to produce insulin

44
Q

where does fatty acid synthesis occur

A

liver, kidney, adipose, brain

45
Q

excess carbohydrate intake causes it to be….

A

converted to TAGs and fatty acids

46
Q

what is required for triglyceride synthesis

A

Glucose 3 phosphate, yielded from glycerol or glucose in the fed state

47
Q

what stimulates triglyceride synthesis

A

insulin in the fed state

48
Q

the first step of fatty acid synthesis requires acetyl CoA. what produces it

A

pyruvate dehydrogenase

49
Q

how does Acetyl-CoA enter the cytoplasm from the mitochondria

A

condenses with oxaloacetate to form citrate to transport to cytoplasm

50
Q

acetyl-CoA carboxylase converts…

A

acetyl-CoA to manonyl-CoA

51
Q

structure and function of fatty acid synthase

A

7 functions and an acyl carrier protein

catalyses synthesis f saturated long chain fatty acids from manonyl-CoA, Acetyl-CoA and NADPH

52
Q

how many carbons are added to the growing fatty acid chain by fatty acid synthase per cycle

A

2

53
Q

what stimulates fatty acid synthesis

A

insulin

citrate

54
Q

what opposes fatty acid storage

A

glucagon

adrenaline

55
Q

main site for amino acid degradation

A

liver

56
Q

what is protein turnover

A

removal of damaged proteins

57
Q

describe amino acid absorption

A

proteolytic enzymes yield amino acids, absorbed by enterocytes that are released into the blood

58
Q

what toxic chemicals are released by amino acids and how are they safely excreted

A

ammonia/ammonium

excretion by urea, uric acid and creatinine

59
Q

aminotransferases turn amino acids to ____

A

glutamic acid

60
Q

why does glutamic acid get de-aminated

A

to yield ammonium

61
Q

describe the ornithine cycle

A

carbamoyl phosphate combines with ornithine and aspartic acid added. coverted to urea and ornithine is reused

62
Q

what happens to the de-aminated carbon skeletons after the ornithine cycle

A

ketogenic bodies may become ketone bodies or fatty acids

glucogenic bodies may used to produce glucose

MB1: Gastrointestinal (19 decks)

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