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13 biochemistry > L14 - glucose metabolism > Flashcards

L14 - glucose metabolism Flashcards

1
Q

why is glycogens branched structure an advantage?

A

allows quick breakdown due to having many end residues

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2
Q

describe glycogen structure

A

protein core

many branches

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3
Q

what controls glycogen breakdown in liver

A

blood [glucose]

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4
Q

what controls glycogen breakdown in muscles

A 
local control 
Ca2+ 
AMP 
ATP
adrenaline
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5
Q

what key enzyme is involved in glycogen synthesis (glycogenesis)

A

glycogen synthase

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6
Q

what key enzyme is involved in glycogen breakdown (glycogenolysis)

A

glycogen phosphorylase

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7
Q

what is the final product of glycogenolysis in liver

A

glucose

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8
Q

what is the final product of glycogenolysis in muscle

A

glucose - 6 - phos

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9
Q

what is the main energy source in glycogenesis

A

ATP

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10
Q

what is the main energy source in glycogenolysis

A

Pi

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11
Q

what enzyme converts glucose to glucose 6 phosphate in glycogenesis
in liver
in muscle

A

hexokinase (muscle)

glucokinase (liver

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12
Q

what reactions are reversible in glycogenesis

A
  1. glucose 6 phos ——- glucose 1 phos
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13
Q

what is the ‘activated’ form of glucose in glycogenesis

A

UDP glucose

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14
Q

function of glycogen synthase?

A

attaches UDP glucose to existing glycogen (straight chain)

a 1-4 linkage

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15
Q

how are a 1-6 linkages formed during glycogenesis

A

by a branching enzyme

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16
Q

how are a 1-6 bonds broken during glycogenolysis

A

debranching enzyme

17
Q

function of glycogen phosphorylase

A

adds Pi to glycogen chain forming glucose 1 phosphate

18
Q

how is the phosphate of glucose-1-phos removed forming glucose in glycogenolysis

A

glucose-6-phosphatase hydrolyses using h2o

19
Q

where does glycolysis occur

A

cytosol of all tissues

20
Q

what does glycolysis form

A

2x pyruvate (C3)

21
Q

how does hexokinase/glucokinase facilitate uptake of glucose

A
  1. converting glucose to G6P gives it a -ve charge so it cant cross the membrane
  2. maintains glucose conc
22
Q

what are the irreversible reactions in glycolysis

A

(1) glucose —- G6P
(3) F6P —– fructose 1,6 bisphosphate
(10) phosphoenol pyruvate —- pyruvate

23
Q

what reactions use ATP in glycolysis

A

(1) glucose —- G6P

24
Q

what reactions produce ATP in glycolysis

A

(7) 1,3 biphosphoglycerate —- 3 phosphoglycerate

(10) phosphoenol pyruvate —- pyruvate

25
Q

equation for anaerobic pyruvate reaction

A

pyruvate + NADH + H+ NAD+ + lactate

26
Q

why does NADH + H+ need to be deoxidised?

A

to reproduce NAD+ which is essential for reaction 6 in glycolysis

27
Q

what catalyses the reaction pyruvate lactate

A

lactate dehydrogenase

28
Q

where does the pyruvate lactate reaction occur

A

muscles

29
Q

where does lactate get converted back to pyruvate

A

liver

30
Q

in what ways is glycogen metabolism regulated

A

allosteric & hormonal (adrenaline/glucagon)

31
Q

how is glycogen metabolism regulated by hormones

A

hormones activate protein kinase

phosphorylation switches glycogen synthase off
phosphorylation switches glycogen phosphorylase on

32
Q

how is glycolysis regulated by allosteric activity

A

allosteric regulation of phosphofructokinase

citrate &ATP - allosteric inhibitors
AMP - allosteric activator

33
Q

name the allosteric inhibitors acting on phosphofructokinase to regulate glycolysis

A

citrate

ATP

34
Q

name the allosteric activator acting on phosphofructokinase to regulate glycolysis

A

AMP

35
Q

why are ATP and citrate inhibitors of glycolysis ?

A

high ATP indicates the tissue has enough energy
high citrate indicates TCA cycle is increased

tell us that glycolysis isnt needed

36
Q

what are specialised functions for glycolysis in
muscle
RBCs
brain

A

muscle - ATP production during intensive exercise (anaerobic)

RBCs - only source of ATP (no mitochondria)

brain - major source of ATP (cant use fats as fuel)

37
Q

when is a metabolic compound considered high energy?

A

when its hydrolysis could power ATP synthesis

13 biochemistry (16 decks)

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