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physiology 3003 > Lecture 17--Starvation > Flashcards

Lecture 17--Starvation Flashcards

1
Q

What are the body energy stores (the form)?

A

(1) Free glucose
(2) Glycogen (liver & muscle)
(3) Triacylglycerol (TG)
(4) Protein

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2
Q

What is the highest energy density energy store?

A

Triglycerides

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3
Q

What is the quantity of free energy contained in each storage form? How long would these stores each last?

A

(1) Free glucose: 12g = 0.2MJ = 30minute supply
(2) Glycogen: 450g =7.7 MJ = 18 hours
=> Muscle = 250g glycogen
=> Liver = 100g glycogen
(3) TG: 15kg = 550 MJ = 55 days
(4) Protein: 12.5kg = 210 MJ = 21 days

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4
Q

________ = largest energy store

A

ADIPOSE TISSUE

TGs are mobilised to non-esterified Fatty Acids (NEFA; aka FFA)

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5
Q

What is GLUCAGON

  • Where is it synthesised?
  • What stimulates secretion?
  • What is it’s function?
A

Function: Prevent/minimise hypoglycaemia

Stimulated by: Decrease [glucose], increase in AAs

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6
Q

What pancreatic hormone is released during FASTING?

A

GLUCAGON = prevents hypoglycaemia

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7
Q

Why are Insulin AND Glucagon both stimulated by Amino Acids?

A

Insulin secretion is stimulated by Amino Acids but you haven’t taken in any new CHO… .: cells take up all the available glucose, leaving you hypoglycaemia (glucagon keeps glucose high to maintain glycemic level)

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8
Q

Plasma glucose during fasting is provided by glycogenolysis in the LIVER not muscle. Why?

A

b/c GLUCOSE-6-PHOSPHATASE (is absent in skeletal muscle) .: glucose cannot be liberated from muscle. & glycogen stores can only be utilised within the muscle itself.

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9
Q

Glycogen stores are gone in _________

A

1 day

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10
Q

What is the order of priority for energy store use

A

Glucose–>glycogen–>fat mobilisation–>protein

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11
Q

What tissues cannot used FFA for energy?

A

(1) Heart
(2) Red blood cells
(3) Renal Cortex

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12
Q

Gluconeogenesis

A

Make glucose from non-CHO sources (usually AAs)

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13
Q

____ carbon substrate is needed to synthesise glucose

A

3 carbon substrate is used as a skeleton for glucose synthesis.

  1. Lactate (byproduct of glycolysis)
  2. Pyruvate
  3. Amino Acids (deaminated and used for carbon skeleton)
  4. Glycerol (break down to FFAs)
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14
Q

KETONE BODIES aka _______

Include: (3)

A

KETONE BODIES aka KETOACIDS:

1) ACETOACETATE
2) B-HYDROXY BUTYRATE
3) ACETONE (minor)

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15
Q

ketone bodies are produced by _____ when ________.

A

Produced by the LIVER from FFA

…when OXALOACETATE stores are completely depleted

FFA–>acetyl CoA =gluconeogenesis=> Ketone bodies

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16
Q

What are blood ketone concentrations during STARVATION?

A

6-8mmol/L

17
Q

What proportion of blood ketones are used by the brain during starvation?

A

2/3rds

18
Q

What is the role of thyroid hormone (T3) in starvation?

A

General decrease in metabolism reduces energy requirements

19
Q

For what reason (to do with physiological response to starvation) might crash diets be ineffective?

A

Because starvation leads to an increase in T3 secretion which can reduce overall metabolic energy requirements by up to 1/2

20
Q

Where is the main target for glucagon?

A

The liver

21
Q

What are the responses to insulin in the liver?

A

Promote glycogenesis
Inhibit glycogenolysis
Glucose stored as glycogen
Promote Lipogenesis

22
Q

What are the responses to glucagon in the liver?

A

Inhibit glycogenesis
Promotes glycogenolysis
Promotes lipolysis & FA oxidation
Inhibits lipogenesis

23
Q

What is the hormone of general metabolism that decreases during starvation?

A

Thyroid hormone (T3). Leptin may also signal to reduce metabolism.

24
Q

What is the average daily energy expenditure?

A

9700kJ/day

25
Q

How long is the supply time of glucose, glycogen, TG & protein?

A

30 minutes, 18 hours, 55 days, 21 days

26
Q

What are the hormonal/chemical responses to short term fasting?

A

Decreased plasma glucose, decreased plasma insulin, increased glucagon

27
Q

What inhibits alpha cell secretion?

A

Increased glucose

28
Q

What stimulates alpha cell secretion?

A

Decreased glucose
Increase in Amino Acids (Insulin also increased by AAs. Protein only meal, insulin goes up but also glucagon so that we have glucose levels high but also energy use).

29
Q

Does skeletal muscle have Glucose-6-phosphatase (enzyme 4)?

A

No

30
Q

What are the sources of energy during long-term fasting?

A

Glycogen stores are used in a day - need to use protein eventually

31
Q

What is the total energy supply of TG’s & proteins

A

550 & 210 MJ

32
Q

What is the product of fat breakdown during starvation?

A

Release of Free Fatty Acids

physiology 3003 (15 decks)

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