Lecture 33 - Coordinating Metabolism Fuel Mobilisation

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12 Terms

1
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Under what physiological conditions would the body need to mobilise fuels?

fasting

exercising

stress

2
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Where is glucagon produced and what is its effect on blood glucose levels?

Glucagon is produced in the alpha cells of the pancreas. Its main job is to increase blood glucose levels by stimulating glycogenolysis

3
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What is the main role of adrenaline

Adrenaline is to prepare the body for the fight or flight response during stressful situations.

4
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What are two mechanism that lead to downregulation of signal transduction?

Receptor desensitization

Phosphodiesterase activity

5
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Why is fuel mobilization important?

So the body can rapidly convert stored macronutrients into usable energy.

This is required to meet its energy demands during periods of fasting, stress and activity.


For carbohydrates, the process of glycogenolysis is activated to obtain glucose for glycolysis.


For fats, lipolysis is activated to obtain FAs for beta-oxidation.


For proteins, proteolysis to obtain amino acids for energy

6
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What will secretion of glucagon do?

Fasting and starvation

Low blood glucose

Amino acids

Exercise

Stress via adrenaline.

7
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What is adrenaline?

This is a hormone and neurotransmitter. It is synthesised from tyrosine in adrenal glands.

8
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Explain the process of lipolysis

Stored fats (triglycerides) are broken down into their constituent components, glycerol and free fatty acids, to be used as an energy source.

9
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What is glucagon and adrenaline signalling pathways

Glucagon receptors on liver and adrenaline receptors on muscle have similar effect.

Both hormones bind G protein coupled receptors (GPCR).

Binding induces a conformational change that activates the G-protein.

Activated G protein subunit activates adenylyl cyclase enzyme.

Increases in cAMP levels (secondary messenger).

cAMP activates PKA via allosteric activation.

PKA activity can activate or inhibit downstream enzymes

10
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What happens in aerobic exercises in terms of fuel mobilisation

This requires O2

It is low intensity and prolonged

Glucose from blood undergoes oxidative metabolism as does fatty acids

Blood supplies the fuel and O2

Active Citric acid cycle is present

The electron transport chain and oxidative phosphorylation is present

11
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What happens in anaerobic exercises in terms of fuel mobilisation

This doesn't requires O2.

It is high intensity for short periods

Glycogen to glucose-6-P and anaerobic glycolysis

Phosphocreatine

Muscle glycogen source of fuel

O2 not required.

ATP generated by substrate-level-phosphorylation.

Pyruvate reduced to lactate to regenerate NAD+.

ATP generation very rapid but for short time only.

Lactate can cause muscle pH to drop, thus fatigue

12
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What is phosphocreatine?

Is "on site", "fast fuel", provides energy buffer. It is made from Gly, Arg and Met.

It has a 'high-energy phosphate' compound. Phosphate can be transferred to ADP to make ATP.