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Medicine year 1 > Metabolism > Flashcards

Metabolism Flashcards

1
Q

Glycogenesis

A

synthesis of glycogen from glucose

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2
Q

Glycogenolysis

A

Breakdown of glycogen to form glucose

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3
Q

Gluconeogenesis

A

synthesis of glucose from metabolic precursors

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4
Q

Are are glucose monomers attached in a glycogen polymer (2)

A

straight chain: α 1-4 glycosidic links
Branches: α 1-6 glycosidic links

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5
Q

Which protein is a glycogen primer bonded to

A

glycogenin

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6
Q

Which enzyme adds glucose molecules in a straight chain

A

glycogen synthase

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7
Q

What does glycogen synthase use to extend the glycogen chain

A

UDP glucose

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8
Q

What enzyme is used to introduce branches in glycogen molecules

A

transglycosylase

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9
Q

What regulates the activity of glycogen synthase (2)

A

insulin - activates glycogen synthase
Glucagon - inhibits glycogen synthase

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10
Q

What are the two types of glycogen

A

Liver
Muscle

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11
Q

Describe liver glycogen (3)

A

broken down between meals
Used to maintain blood glucose
Released to supply energy to tissues

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12
Q

Describe muscle glycogen (2)

A

not available for blood glucose maintenance
Provides energy via cellular respiration

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13
Q

Which is more likely to occur overnight: glycogenolysis or gluconeogenesis

A

gluconeogenesis as hepatic glycogen is depleted

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14
Q

what enzyme is involved in glycogenolysis

A

glycogen phosphorylase

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15
Q

What is glucose-1-phosphate converted to in glycogenolysis

A

Glucose-6-phosphate

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16
Q

What happens to liver glucose-6-phosphate (2)

A

It is de-phosphorylated
Glucose is released into bloodstream

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17
Q

what happens to muscle glucose-6-phosphate (2)

A

it cannot be de-phosphorylated
Used to provide energy via cellular respiration

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18
Q

When must new glucose be synthesised

A

during prolonged starvation

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19
Q

What are the precursors of gluconeogenesis (3)

A

lactate
Amino acids
Glycerol

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20
Q

What converts lactate to glucose

A

the liver

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21
Q

How are amino acids obtained for gluconeogenesis

A

derived from muscle protein by proteolysis

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22
Q

How is glycerol obtained for gluconeogenesis

A

derived from triglycerides by lipolysis

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23
Q

What is the main site of gluconeogenesis

A

the liver

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24
Q

Why is gluconeogenesis not the reverse of glycolysis

A

Energetically unfavourable steps in glycolysis must be overcome

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25
Q

How does gluconeogenesis alter energy distribution

A

Reduces liver energy to distribute glucose to other tissues

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26
Q

How is gluconeogenesis regulated (2)

A

by hormones
Regulation by insulin is dominant

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27
Q

What does increased fat intake without increased energy expenditure lead to (2)

A

Increased number and size of adipocytes

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28
Q

What controls energy storage in adipose tissue (2)

A

Genetic and environmental factors

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29
Q

What is fat required for (3)

A

energy
Essential fatty acids, membranes, and vesicles
Transport of fat-soluble vitamins

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30
Q

What are the types of lipids (3)

A

Simple
Compound
Steroids

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31
Q

What do triglycerides consist of

A

one glycerol unit and three fatty acids

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32
Q

What types of fatty acids exist

A

saturated, unsaturated, or polyunsaturated

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33
Q

Which compound is the main energy storage form in adipose tissue

A

Triglycerides

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34
Q

What is the structure of fatty acids generally like

A

straight chain, aliphatic

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35
Q

How do the states of plant and animal fats compare

A

animal fats are generally solid, plants fats are generally liquid

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36
Q

What must happen to fatty acids before they are oxidised

A

they must be converted to CoA derivatives in the cytoplasm

37
Q

where does further oxidation of fatty acids (after conversion to CoA derivatives) take place

A

Matrix of mitochondria

38
Q

What is the significance of the carnitine shuttle (2)

A

A carrier mechanism that transports molecules into the mitochondrial matrix for further oxidation
Results in acyl-CoA inside the matrix

39
Q

B oxidation (4)

A

Cycle of reactions resulting in oxidation of fatty acids
Occurs in mitochondrial matrix
Requires enzymes
Yields ATP

40
Q

What are the products of β oxidation (4)

A

1 acetyl-CoA
1 FADH2
1 fatty acyl-CoA
1 NADH + H+

41
Q

Where does fat absorption occur

A

Into mucosal cells of the intestine

42
Q

What are the main products of fat absorption (3)

A

glycerol
Fatty acids
Monoglycerides

43
Q

One absorbed by the intestine, where do fatty acids go

A

shorter chain - portal blood
Longer chain (+monoglycerides) - enter lymph then blood stream

44
Q

Once in muscle/adipose tissue, what occurs to chylomicrons

A

The lipids are cleaved by lipoprotein lipases

45
Q

What are free fatty acids used for in muscle

A

oxidation to provide energy

46
Q

What are free fatty acids used for in adipose tissue

A

Re synthesis to triaglycerols

47
Q

How are ketone bodies formed (3)

A

in mitochondria of liver cells
From acetyl-CoA
By β oxidation

48
Q

once produced, where do ketones go (2)

A

blood stream
Peripheral tissues

49
Q

Why are ketones important (2)

A

for energy metabolism of heart muscle and the renal cortex
They can be converted back to acetyl-CoA

50
Q

what does fatty acid oxidation produce under normal circumstances

A

acetyl-CoA

51
Q

In cases of starvation/diabetes, what happens to oxaloacetate

A

Used for gluconeogenesis

52
Q

How can acidosis arise in cases of starvation/diabetes (3)

A

fatty acids are oxidases to acetyl-CoA
Acetyl-CoA is converted to ketone bodies
Ketone bodies accumulate

53
Q

What is a sign of acidosis

A

acetone smell on breath

54
Q

How can acidosis be managed in cases of starvation/diabetes

A

starvation - sugar
Diabetes - insulin

55
Q

lipogenesis

A

synthesis of fatty acids

56
Q

What can lead to fatty acid synthesis (2)

A

excess energy intake
Excess carbohydrate intake

57
Q

What occurs during excess carbohydrate intake (3)

A

Excess carbohydrates are converted to fatty acids and triglycerides
Free fatty acids are bound to albumin and transported in plasma
Triglycerides are transported to adipose tissue for storage

58
Q

What transports triglycerides to adipose tissue for storage

A

VLDL

59
Q

What is required for fatty acid synthesis and why

A

electrons
It is a reductive process

60
Q

Describe transport of acetyl-CoA for lipogenesis (2)

A

acetyl-CoA is synthesised in the mitochondria
Citrate transports acetyl-CoA to the cytoplasm for lipogenesis

61
Q

What is the first step required for lipogenesis (2)

A

activation of acetyl-CoA to malonyl-CoA
Catalysed by acetyl-CoA carboxylate

62
Q

Where is acetyl-CoA carboxylate generally expressed (2)

A

liver
Adipose tissue

63
Q

What catalyses the synthesis of fatty acids from Malonyl-CoA

A

Fatty acid synthase

64
Q

What are the four steps of fatty acids synthesis

A

condensation
Reduction
Dehydration
Reduction and release

65
Q

Unregulated forms of fatty acid synthase is associated with what condition

A

cancer

66
Q

What protein does fatty acid synthase contain (among others)

A

acyl-carrier protein

67
Q

What is the longest fatty acid created by fatty acid synthase

A

palmitic acid
16 carbons

68
Q

What does each cycle of reactions in lipogenesis require and why

A

NADPH as an electron donor

69
Q

In lipogenesis, what is each growing acyl chain attached to

A

ACP

70
Q

When is fatty acid synthesis maximal (2)

A

Abundant carbohydrates and energy
Scarce fatty acids

71
Q

How does insulin affect lipid metabolism

A

by stimulating the storage of fuels and protein synthesis

72
Q

How does citrate affect lipogenesis

A

allosterically stimulates acetyl-CoA carboxylate

73
Q

How does palmitoyl-CoA affect lipogenesis

A

antagonises acetyl-CoA carboxylate when fatty acids are in excess

74
Q

What compound is required for triglyceride synthesis and what is used to produce it

A

Glycerol-3-phosphate is required
Liver uses glycerol to produce it
Adipose tissue uses glucose to produce it

75
Q

When does adipose tissue production of triglycerides occur (2)

A

during a fed state
When insulin stimulates adipose uptake of glucose

76
Q

What type of reaction is involved in triglyceride synthesis

A

esterification

77
Q

What does breakdown of amino acids produce (2)

A

ammonium
Ammonia ions

78
Q

How can nitrogen be excreted

A

Urea
Uris acid
Creatinine
Ammonium ions

79
Q

What are the three steps involved in synthesis of urea

A

transanimation
De-animation
Urea cycle

80
Q

What occurs in the transamination step of urea synthesis

A

aminotransferases move the amino group from α amino acids to α keto acids
Produces glutamate

81
Q

What are the two possible routes after glutamate has been produced (transanimation)

A

Amino group on glutamate is transferred to pyruvate, producing alanine
Or glutamine synthase adds an ammonium ion to glutamate, creating glutamine

82
Q

What is the function of alanine and glutamine

A

to carry nitrogen from the blood to the liver

83
Q

Where does deanimation occur

A

liver

84
Q

What happens during de-animation

A

The amino group of glutamate/alanine is converted to a free ammonium ion

85
Q

What is generated as an end product of urea synthesis

A

fumarate

86
Q

How can carbon be transported back to the mitochondrial matrix after synthesis of urea in the cytoplasm (2)

A

fumarate is converted to malate
Carbon is transported via the malate-aspartame shuttle

87
Q

What can ketogenic amino acids give rise to (3)

A

acetyl-CoA or acetoacetyl-CoA
Ketone bodies
Fatty acids

88
Q

What can glycogenic amino acids be degraded to form

A

pyruvate or TCA cycle intermediates

89
Q
A

Medicine year 1 (10 decks)

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