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BIOC192 2024 > Lecture 33 > Flashcards

Lecture 33 Flashcards

1
Q

What is the fuel mobilisation process for carbohydrates?

A

Glycogenolysis to obtain glucose for glycolysis

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2
Q

What is the fuel mobilisation process for fats?

A

Lipolysis to obtain FAs for beta-oxidation

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3
Q

What is the fuel mobilisation process for proteins?

A

Proteolysis to obtain amino acids for energy

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4
Q

What are fuel mobilisation processes controlled by?

A

Hormones; glucagon and adrenaline

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5
Q

What is glucagon?

A

A peptide hormone secreted by pancreatic alpha-cells

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6
Q

What is proglucagon?

A

A polypeptide precursor that gives rise to glucagon in pancreatic alpha cells and GLP-1 in L-cell and brain

(E.g. of different processing pathways in different cells)

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7
Q

What is glucagon secretion stimulated by?

A

Fasting and starvation, low blood glucose, amino acids, exercise and stress (via adrenaline)

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8
Q

What does glucagon do?

A

Activates processes that increase blood glucose

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9
Q

What is adrenaline?

A

A hormone and neurotransmitter synthesised from tyrosine in the adrenal gland

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10
Q

When is adrenaline released?

A

During physical or psychological stress perceived by the hypothalamus which signals to the adrenal gland

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11
Q

How does the hypothalamus signal to the adrenal gland?

A

Via the sympathetic nervous system

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12
Q

What does adrenaline do?

A

Stimulates liver and muscle to activate processes that increase blood glucose and primes the body for a ‘fight or flight’ response (e.g. increased heart rate, bronchodilation, redirection of blood flow and increased blood sugar)

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13
Q

What do adrenaline and glucagon bind to?

A

G-protein coupled receptors that cause a conformation change, activating the G-protein

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14
Q

What do the activated G-proteins do?

A

Activate adenylyl cyclase enzyme

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15
Q

What does adenylyl cyclase do?

A

Increase cAMP levels which activates protein kinase A (PKA) via allosteric activation

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16
Q

What does PKA do?

A

The activity of PKA can activate (catabolic processes) or inhibit downstream (anabolic processes) enzymes

17
Q

What happens to signalling pathways once they are stimulated?

A

They are reset to respond to future signals

18
Q

Where do ligands diffuse during GPCR signalling down regulation?

A

Away from the receptor

19
Q

When are g-proteins active?

A

When there is a GTP bound

20
Q

When are g-proteins inactive?

A

When there is a GDP bound

21
Q

What are the two mechanisms that can lead to g-protein downregulation?

A

Intrinsic GTPase and PDE

22
Q

How does intrinsic GRPase work?

A

Intrinsic GTPase activity in the ativated Gs subunit of the g-protein converts it back to the inactive state

23
Q

How does PDE work?

A

Phosphodiester enzyme (PDE) metabolises cAMP to prevent PKA activation

24
Q

What inhibits PDE?

A

Caffeine

25
Q

How does lipolysis occur in adipose cells?

A

Through phosphorylation, PKA activates hormone-sensitive lipase which hydrolysis the TAGs in fat droplets to FFAs and then releases them bound to albumin to be transported to the tissues in the blood

26
Q

What do adipocytes also release during lipolysis?

A

Glycerol and FFAs

27
Q

What does the released glycerol from adipocytes do?

A

Is sent to the liver to be used as gluconeogenic precursors which make new glucose

28
Q

What is hormone sensitive lipase?

A

Combination of glucagon and adrenaline

29
Q

Where are fatty acids used?

A

In all aerobic tissues except the brain

30
Q

How does glucagon stimulate beta-oxidation?

A

Through up regulating of transcription of genes required for beta-oxidation and down-regulating DNL (synthesis of new fatty acids)

31
Q

How much protein is stored in the body?

A

10-15kg however there are no specific storage proteins

32
Q

What can loss of too much protein cause?

A

Structural and functional damage, hence it must be as conserved as possible

33
Q

How is ATP generated aerobically in exercising muscle?

A

Glucose from the blood or from glycogen undergoes oxidative metabolism and can enter the CAC

34
Q

How is ATP generated anaerobically in exercising muscle?

A

Glycogen is converted to G6P and anaerobic glycolysis occurs. Phosphocreatine mobilised as well

35
Q

Explain anaerobic glycolysis

A

Muscle glucogen is the source of fuel, O2 is not required, ATP is generated by SLP and pyruvate is reduced to lactate to generate NAD+.

36
Q

What does lactate cause?

A

Muscle pH to drop, thus fatigue

37
Q

What is phosphocreatine?

A

An energy buffer made from gly, arg and met. A high-energy phosphate compound where phosphate can be transferred to ADP to make ATP. 20um per gram of muscle provides ~10s worth of ATP

38
Q

What does exercise do in relation to creatine?

A

Uses phosphocreatine to create creatine

39
Q

What does recovery do in relation to creaine?

A

Uses creatine to create phosphocreatine

BIOC192 2024 (36 decks)

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