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CELL II > Integration + Metabolism > Flashcards

Integration + Metabolism Flashcards

1
Q

How much glucose does the brain use daily?

A

100-120g glucose daily

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2
Q

What’s the energy used for by the brain?

A

for Na+-K+ transport to maintain membrane potential + synthesis of neurotransmitters

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3
Q

Role of GLUT3?

A

glucose transport in brain

has a low Km – saturated under most conditions

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4
Q

What’s the danger point of brain?

A

when plasma glucose drops to below 2.2mM

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5
Q

How does brain use FA?

A

not for energy but for membrane biosynthesis

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6
Q

How much CO does brain use?

A

Brain is approx. 2% of body mass but takes 20% of the cardiac output

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7
Q

Main source of energy for cardiac muscle?

A
  • FA
  • lactate
  • ketone bodies
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8
Q

What does adipose tissue contain?

A

Reservoir metabolic energy in form of TAG

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9
Q

How much TAG does 70kg man have?

A

15kg of TAG

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10
Q

How’s FA delivered?

A

by chylomicrons

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11
Q

Role of GLUT4?

A

Glucose is transported to adipose tissue
Glucose uptake is insulin sensitive
Glucose transported to striated muscle

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12
Q

Role of kidney?

A
  • Produce urine
  • Plasma filtered up 60 times daily
  • Water soluble material reabsorbed to prevent loss
  • During starvation contributes half of blood glucose via gluconeogenesis
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13
Q

How much energy does kidney consume?

A

only 0.5% body mass but consumes 10% of the energy

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14
Q

Role of liver?

A
  • Plays central role in regulating metabolism: carb, FA, AA

- Provides fuel for brain, muscle, other peripheral organs

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15
Q

Where does liver get energy?

A

takes its energy from α-ketoacids

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16
Q

Role of GLUT2?

A

Transports glucose into hepatocytes (not insulin-sensitive)

Transports glucose out of the cell into blood

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17
Q

Role of glucokinase?

A

phosphorylates glucose

18
Q

Role of glucose-6 phosphatase?

A

converts G6P from glycogen breakdown (or gluconeogenesis) to glucose

19
Q

Describe muscle glucose metabolism

A
  • glucose uptake by GLUT4 is insulin-dependent
  • glucose -> G6P by hexokinase (Km 0.1mM for glucose)
  • low free [glucose] in cell
  • glucose mobilised from glycogen in exercise
  • glycolysis of G6P is rapid source of ATP
20
Q

Role of hexokinase?

A

glucose -> G6P

21
Q

Fuel for a sprint or marathon?

A
  • ATP directly powers myosin
  • Converts chemical energy to movement
  • Muscle ATP stores are small
  • Power + speed dependent on rate of ATP production
22
Q

What does resting muscle use as a major source of energy?

A

FA

23
Q

What’s a sprint powered by?

A

ATP stores
Glycolysis
Glycogen
Creatine phosphate

24
Q

What’s muscle creatine phosphate?

A

small store of ATP

Creatine phosphate + ADP ATP + creatine

25
Q

Role of creatine?

A

via

Creatine phosphate + ADP ATP + creatine

26
Q

Role of kinase?

A

via

creatine + ATP creatine phosphate + ADP

27
Q

What causes a fall in pH?

A

Anaerobic breakdown of glycogen stores gives lactate

28
Q

How’s activity of glycogen phosphorylase enhanced?

A

by phosphorylation

29
Q

What’s a marathon powered by?

A
  • Need 150 moles ATP
  • Body glycogen provides only 103 moles
  • Aerobic respiration more efficient
  • Co-operation between muscle, liver, adipose tissue because ATP required > stored by muscle
  • Complete oxidation slow
  • Fats source of ATP, metabolism slower than glycogen + x10 slower than creatine phosphate
  • Use FA ->ACoA -> TCA
  • ½ glycogen is left at end of marathon
30
Q

Interaction between liver + muscle?

A

During exercise glycolysis exceeds capacity of citric acid cycle, pyruvate -> lactate + transported to liver Cori cycle so lactate -> glucose

31
Q

Pathways during fed state?

A 
Glycolysis ↑.
Glycogen synthesis ↑.
Glycogenolysis ↓ (don’t want to produce glucose when sufficient levels in blood).
Gluconeogenesis ↓ (““).
FA synthesis ↑.
FA degradation ↓.
32
Q

Molecules during fed state?

A
  • Glycogen ↑.
  • Glucose ↓.
  • FA ↑.
  • Ketone bodies ↓
33
Q

What happens when you stop eating?

A
  • 1st priority to maintain glucose levels
  • 2nd priority to preserve protein
  • metabolism shifts from glucose -> FA -> ketone bodies
34
Q

Describe what happens during post absoptive phase

A
  • glucose falls
  • insulin levels fall
  • glucagon levels rise
  • phosphorylase a activity increases in liver
  • glycogen breakdown increases
  • drop in insulin reduces glucose uptake by muscle + adipose tissue
35
Q

Describe what happens during early starvation 24hrs

A
  • glucose released from liver due to gluconeogenesis + glycogenolysis
  • mobilisation of FA from adipose tissue
  • glucose use falls as muscle switches to FA oxidation
  • insulin drops causing GLUT4 expression by muscle to fall reducing glucose uptake
  • 45% of resting energy from FA + 40% from glucose
36
Q

Describe what happens during immediate starvation 3-20 days

A
  • glycogen stores depleted
  • increased lipolysis + ketogenesis
  • increased gluconeogenesis to maintain blood glucose
  • ¾ energy from FA at 60hrs
  • β hydroxybutyrate is raised 50 fold at 8 days
  • kidney take over gluconeogenesis from liver
37
Q

Describe what happens during prolonged starvation 3wks

A
  • β hydroxybutyrate plateaux at 20 days
  • brain uses ketone bodies
  • need for glucose falls from 100g to 40g/day
  • lactate + glycerol used as gluconeogenic precursors
  • lactate recycled by the Cori cycle
  • glycerol + AA oxidized
  • proteins -> AA
38
Q

How’s alanine formed?

A

by transamination of pyruvate

39
Q

How skeletal muscle provides energy source from AA?

A

-alanine released into blood
-taken up by liver
-converted to glucose
because muscle can use AA for C skeleton but can’t form urea so liver removes N + releases pyruvate

40
Q

Summary of starvation?

A
  • protein breakdown in muscle when brain starts to use KB + need for glucose is reduced
  • 2wks muscle use FA from adipocytes + KB from liver
  • prolonged starvation gluconeogenesis by kidney amounts to 50% of total
  • KB in liver releases ACoA allowing beta oxidation

CELL II (9 decks)

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