Lecture 33 - Coordinating Metabolism: Fuel Mobilisation

Question 1

What is the fuel mobilisation process for carbohydrates?

Answer 1

Glycogenolysis to obtain glucose for glycolysis

Question 2

What is the fuel mobilisation process for fats?

Answer 2

Lipolysis to obtain FAs for beta-oxidation

Question 3

What is the fuel mobilisation process for proteins?

Answer 3

Proteolysis to obtain amino acids for energy

Question 4

What are the fuel mobilisation processes controlled by?

Answer 4

Hormones - Glucagon and Adrenaline

Question 5

What is proglucagon?

Answer 5

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)

Question 6

What is glucagon?

Answer 6

A peptide hormone secreted by pancreatic alpha-cells

Question 7

What is glucagon secretion stimulated by?

Answer 7

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

Question 8

What does glucagon do?

Answer 8

Stimulates liver to activate processes that increase blood glucose

Make glucose from non-carboyhrate sources e.g glycerol and amino acids (gluconeogenesis)

Breakdown of glycogen in the liver to glucose (glycogenolysis)

Question 9

What is adrenaline?

Answer 9

A hormone and neurotransmitter synthesised from tyrosine in the adrenal gland

Question 10

When is adrenaline released?

Answer 10

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

Question 11

How does the hypothalamus signal to the adrenal gland?

Answer 11

Via the sympathetic nervous system

Question 12

What does adrenaline do?

Answer 12

Stimulates liver and muscle to activate processes that increase blood glucose

Question 13

What do adrenaline and glucagon bind to?

Answer 13

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

Question 14

What do the activated G-proteins do?

Answer 14

Activate adenylyl cyclase enzyme

Question 15

What does adenylyl cyclase do?

Answer 15

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

Question 16

What does PKA do?

Answer 16

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

Question 17

When are g-proteins active?

Answer 17

When there is a GTP bound

Question 18

When are g-proteins inactive?

Answer 18

When there is a GDP bound

Question 19

What is the name of glycogen mobilisation?

Answer 19

Glycogenolysis

Question 20

What is glycogen converted to via glycogen phosphorylase?

Answer 20

Glucose-1-Phosphate via hydolysis

Question 21

What is Glucose-1-Phosphate converted to via mutase?

Answer 21

Glucose-6-Phosphate

Question 22

What is missing in muscle cells?

Answer 22

Glucose-6-Phosphatase

Question 23

What cells have Glucose-6-Phosphatase

Answer 23

Liver cells

Question 24

What is Glucose-6-Phosphate used for in muscle cells?

Answer 24

Glycolysis only, as missing glucose-6-phosphotase

Question 25

What is Glucose-6-Phosphate used for in liver cells?

Answer 25

Glucose via glucose-6-phosphatase

Question 26

Signaling pathways once stimulated have be...?

Answer 26

reset to respond to future signals.

Question 27

Ligands diffuse ____ from receptor

Answer 27

Away (down-regulates GPCR signalling)

Question 28

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

Answer 28

Intrinsic GTPase and PDE

Question 29

How does intrinsic GTPase work?

Answer 29

Intrinsic GTPase activity in the activated Gs subunit of the g-protein converts it back to the inactive state (GDP-bound)

Question 30

What is cAMP secondary messenger metabolized by?

Answer 30

Phosphodiester enzyme (PDE). 

Question 31

PDE is inhibited by?

Answer 31

Caffeine

Question 32

What do phosphatases do?

Answer 32

remove phosphate groups on phosphorylated proteins

Question 33

How does lipolysis occur in adipose cells?

Answer 33

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

Question 34

What do adipocytes also release during lipolysis?

Answer 34

Glycerol and FFAs

Question 35

What does the released glycerol from adipocytes do?

Answer 35

Is sent to the liver to be used to make new glucose

Question 36

How does glucagon stimulate beta-oxidation?

Answer 36

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

Question 37

What can loss of too much protein cause?

Answer 37

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

Question 38

How is ATP generated aerobically in exercising muscle?

Answer 38

Glucose from the blood or from glycogen (as G-6-P) undergoes oxidative metabolism and can enter the CAC

Question 39

How is ATP generated anaerobically in exercising muscle?

Answer 39

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

Question 40

What happens in anaerobic glycolysis?

Answer 40

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

Question 41

What does lactate cause?

Answer 41

Muscle pH to drop, thus fatigue

Question 42

What is phosphocreatine?

Answer 42

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

Question 43

What does exercise do in relation to creatine?

Answer 43

Uses phosphocreatine to create creatine

Question 44

What does recovery do in relation to creaine?

Answer 44

Uses creatine to create phosphocreatine