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Biochem Exam 4 > Feed-Fast Cycle > Flashcards

Feed-Fast Cycle Flashcards

1
Q

When is absorptive/well-fed state?

A

First bite of food -> 2-4 hr after ingestion of meal

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2
Q

When is fasting state?

A

4 hours after meal

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3
Q

What is increased in fed state?

A
  • Plasma glucose, AAs and TAG

- Pancreas: insulin (decreased glucagon)

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4
Q

Why is fed state an anabolic period?

A

Increased TAG/gylcogen, replenish fuel stores, enhanced protein synthesis

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5
Q

Who uses glucose as fuel?

A

All tissues

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6
Q

What changes happen in enzymes during fed state?

A

1) Substrate availability (very quick)
2) Allosteric changes (very quick)
3) Kinases addition, phosphatases removal of phosphate groups (minutes -> hours)
4) Gene level - induction/repression enzyme synthesis (takes hours -> days)

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7
Q

In your liver during fed, what is the first thing that will happen?

A

Glycogenesis

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8
Q

How does glucose enter the liver? Is it insulin dependent/independent?

A

GLUT-2 (insulin-INDEPENDENT)

-Just reacts to the fact that blood [glucose] increased because you just ate

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9
Q

What happens to the excess glucose?

A

AAs from gut -> liver -> fat (VLDLs)

  • AAs also make proteins
  • some AAs make acetyl CoA -> TCA cycle
  • some made pyruvate -> glycogenesis
  • excess will make urea
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10
Q

2 key outcomes of liver in fed state?

A

Glycogen and fat

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11
Q

What plays a central role in sugar metabolism?

A

G6P

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12
Q

Upregulation by GLUT-4 mediated by insulin occurs only where?

A

Muscle and adipose only

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13
Q

Upregulation by GLUT-4 mediated by glucagon occurs only where?

A

No where

-Glucagon will never regulate uptake of glucose

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14
Q

Making of ketone bodies, most significance portion of gluconeogenesis during fasting, breaking down glycogen to maintain normal blood [glucose], manage making urea when AA is being broken down.. occurs where?

A

Liver only

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15
Q

I activate HSL during fasting.

A

Adipose only

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16
Q

If I don’t uptake glucose, I will die.

A

RBCs only

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17
Q

When I break down glycogen I use that glucose in TCA cycle.

A

Liver only

18
Q

What happens in adipose tissue during fed?

A

1) Glucose comes in via GLUT-4
2) Glucose -> G6P -> pyruvate -> acetyl CoA -> TCA cycle
3) Making of TAG from glycerol + FAs (released from chylomicrons and VLDLS)

19
Q

When insulin goes down at 3 am what will happen in your muscle cells?

A

Breakdown of protein (especially alanine)

20
Q

In fed state what happens in resting skeletal muscle?

A

1) Glucose comes in via GLUT-4
2) Glycogenesis
3) TCA cycle
4) AAs -> Protein

21
Q

What happens in the brain in fed?

A

Same as in fasting because loves glucose so much:

1) Glucose comes in via GLUT-1 (insulin insensitive) -> TCA cycle

22
Q

When does brain stop using glucose?

A

After 3 days of starvation

23
Q

What happens to plasma levels in fasting?

A

Gluocse, AAs and TAG decrease

-Insulin secretion decreases, glucagon/ephinephrine increases

24
Q

Why happens in catabolic (fasting) period?

A

1) Glycogen degradation in liver
2) TAG degradation (fat cells activate HSL -> FAs -> liver, muscle + glycerol -> only liver for gluconeogenesis)
3) Protein degradation

25
Q

What are 2 priorities during fasting?

A

1) Maintain adequate glucose (for RBCs + brain)

2) Mobilize FAs from adipose (liver use them for energy + make KBs)

26
Q

What supplies the great majority of energy stores?

A

TAG

-Glycogen is very minimal compared to what you get from FAs

27
Q

What happens 1st to the liver during fasting?

A

Glycogenolysis

28
Q

What happens 2nd to the liver during fasting?

A

Gluconeogenesis

-Takes longer and more energy

29
Q

At 3 day mark (starvation) what is shut down?

A

Gluconeogenesis

-B/c comes tremendously from muscle protein

30
Q

What is the enzyme present in the liver that will break down G-6-P to free glucose?

A

Glucose 6-phosphatase

31
Q

In fasting, where are the free FAs coming from in the liver?

A

Adipose carried on albumin

-Not TAG/chylomicrons/VLDLs (like in fed)

32
Q

During fasting, what is used by the liver for ketogenesis?

A

AAs, lactate + glycerol (from muscle and adipose) -> beta-oxidation

33
Q

What is the liver not able to do with the KBs?

A

Use them

-lacks thiophorase enzyme

34
Q

What favors gluconeogenesis in the liver?

A

Pyruvate -> activation of fructose 2,6-bisphosphatase

35
Q

Can the brain use KBs?

A

Yes when concentrations are really high

-after 3 days 3-hydroxybutyrate (KB) extremely increases

36
Q

What is the 1st enzyme/process in adipose tissue during fasting?

A

Lipolysis by HSL

37
Q

What is the 2nd process in adipose tissue during fasting?

A

Release of 3 FAs + glycerol into blood

38
Q

How does the muscle know that you are fasting?

A

Very sensitive to low insulin

-Does not know there is high glucagon (no glucagon receptors)

39
Q

What does the muscle 1st do during fasting?

A

Break down its protein -> AAs -> gluconeogenic precursors (glutamine + alanine -> liver)

40
Q

What does the muscle use during fasting to meet energy needs?

A

FAs and KBs

41
Q

After 3 days of starvation what does muscle stop using?

A

KBs

-Brain needs them

Biochem Exam 4 (7 decks)

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