Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Nutrition & metabolism > carbohydrate metabolism > Flashcards

carbohydrate metabolism Flashcards

1
Q

what does the pancreas do?

A

secretes hormone insulin into blood in response to an increase in blood glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why do we need to maintan blood glucose levels?

A

as glucose is a primary fuel source of brain cells via glycolysis and neurotransmitter synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how much glucose is consumed in a normal diet per day?

A

300g

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what happens when glucose enters the blood?

A

some taken up by liver via facilitated transport (uptake) stores 80-100g

insulin activates hexokinase/glucokinase to store glucose as glycogen (glycogen synthesis)

liver hexokinase reaction reversible so glucose can leave liver cell to maintain blood glucose (glycogenolysis and gluconeogenesis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

describe most remaining glucose being taken up by skeletal muscle?

A

glucose enters muscle via facilitated transport stores up to 400-700g

hexokinase (glucokinase in liver) phosphorylates glucose using ATP to maintain gradient

glucose-6-phosphate is formed and can’t leave cell so enters glycolysis or glycogen synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is glucose transported via in skeletal muscle intake?

A

GLUT4 (maintained hours after exercise)

which is translocated to plasma membrane from intracellular vesicles in response to insulin, muscle contraction and Ca2+ (main)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what occurs in glycogen synthesis?

4 steps

A

glucose-6-phosphate converted to glucose-1-phosphate (G1P) by phosphoglucomutase

uridine diphosphate (UDP) glucose is synthesised from G1P and uridine triphosphate

UDP glucose binds to pre-existing glycogen molecule or glycogenin &UDP released

glycogen synthase and branching enzymes form proglycogen which grows into macroglycogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is glycogenin?

A

enzyme involved in converting glucose to glycogen

situated at core of glycogen molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what stimulates glycogen synthesis?

A

insulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the purpose of glycogen synthesis?

A

glucose molecules added to chain of glycogen for storage

=glycogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what reduces glycogen synthesis?

A

muscle contraction/exercise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is glycogenolysis and what inhibits it?

A

glycogen breakdown into glucose for utilisation (opposite of glycogenesis)

insulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what stimulates glycogenolysis ?

A

(glycogen breakdown)

muscle contraction/exercise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

which process is preferential during exercise?

A

glycolysis (breaking down glucose into usable ATP in liver and skeletal muscle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the main signals stimulating glycogenolysis?

A

(breaking down of glycogen)

calcium and adrenaline (high rates during high contraction in exercise)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what reduces with exercise?

A

insulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is G6P derived from?

A

glycogenolysis and glucose uptake

18
Q

where ensures blood glucose is maintained during postabsorptive period and during fasting?

A

liver as acts as a reserve

19
Q

what has to happen when glycogen reserve is exhausted in liver?

A

glucose must be made from non-carbohydrate precursors (lactate, amino acids and glycerol) via gluconeogenesis

20
Q

what increases during fasting?

A

circulating fatty acuds and glycerol

21
Q

why can’t fatty acids be used as pre-cursors?

A

pyruvate dehydrogenase and pyruvate kinase reactions are irreversible (acetyl-CoA from fatty acids can’t form glucose)

22
Q

what is gluconeogenesis?

A

conversion of pyruvate (made from non-carbohydrate precursors) to glucose

23
Q

what important role does Acetyl-CoA play?

A

inhibiting pyruvate dehydrogenase and diverting pyruvate to oxaloacetate and malate

24
Q

when is lactate produced at high rates?

A

during exercise in muscle and in red blood cells

25
Q

what is pyruvate kinae inhibited by?

A

alanine (amino acid)

26
Q

what can the liver dephosphorylate?

A

glucose-6-P

27
Q

where is glycerol released from?

A

adipose tissue

28
Q

what rate is the liver and gut releasing glucose at rest?

A

liver - 0.1g/min

gut - 1.5g/

29
Q

what rate is glucose taken up from the blood in the brain?

A

0.1g/min (same rate as released from liver)

30
Q

what is the relationship between exercise intensity and rate of glucose uptake?

A

the heavier the intensity, the higher the rate of glucose uptake by skeletal muscle e.g in leg (1g/min so 10x increase than normal)

31
Q

what happens during heavy exercise to blood glucose release and uptake levels?

how is this resolved?

A

blood glucose levels will fall as release rate slower than uptake rate (needs 2g/min)

so rate of glycogenolysis increases as well as glucose output from liver and stores in skeletal muscles used (as adrenaline inhibits insulin production which normally inhibits glucose output)

32
Q

why does higher exercise intensity lead to increased glycogen broken down?

A

higher rate of exercise, high turnover of ATP = high concentration of AMP = activates glycogen phosporylase = greater rate of glycogen broken down

33
Q

when does carbohydrate oxidation decline and why?

how to solve this?

A

carbohydrate oxidation declines after prolonged period of exercise due to depleted glycogen sources

ingest carbohydrates to increase/maintain blood glucose levels and therefore carbohydrate oxidation

34
Q

how can you delay muscle glycogen use during exercise and therefore prolong exercise and maintain glucose levels?

A

ingest carbohydrate electrolyte solution (any carb)

35
Q

what is the maximum carbohydrate oxidation rate faciliatated through 1 type and several types of CHO ingestion?

A

can’t oxidise more than 1-1.2g/min

unless you ingest different types of CHO together

36
Q

describe glycogen loading?

A

depleting muscle glycogen stores then
glycogen loading straight after, then lack of CHO, then loading a few days before competition can increase overall glycogen levels

due to increase in insulin sensitivity in muscles

37
Q

when is glycogen resynthesis highest?

A

few hours post exercise

38
Q

what is glycogenesis?

A

conversion of glucose to glycogen to be stored in the liver

= glycogen synthesis

39
Q

what effect would an increase in glycogenolysis have on glucose uptake and why?

A

uptake would decrease as large amount of glucose-6-phsophate present from glycogenolysis (breakdown of glycogen to glucose)

increased levels inhibit hexokinase so less glucose uptake in cell

40
Q

what are the effects of the drug antimycin A?

A

inhibitor of cytochrome C

causes ATP synthesis and oxidative phosphorylation to be inhibited

Nutrition & metabolism (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions