Hormonal Regulation of Energy Metabolism

Question 1

What are the 2 main energy reserves in humans?

Answer 1

Glycogen and fat

Question 2

What is a characteristic of FA storgae?

Answer 2

Turned over constantly: replenished by consumption and endogenous synthesis and broken down for energy production

Question 3

How does obesity happen?

Answer 3

Consumption/endogenous synthesis exceeds energy requirements

Question 4

What are 3 reasons that glucose is a good food source?

Answer 4

Yields high amount of energy upon oxidation
efficiently stored in polymeric form
utilized by all cells (crosses BBB)

Question 5

What are 2 sources of glucose?

Answer 5

Diet
Glycogen reserves

Question 6

What are the 4 major pathways of glucose metabolism?

Answer 6

Glycogenesis (making glycogen)
Glycogenolysis (breaking glycogen)
Gluconeogenesis (making glucose)
Glycolysis (breaking glucose)

Question 7

What 2 enzymes are involved in regulating glycogen synthesis and breakdown?

Answer 7

Breakdown - glycogen phosphorylase
Synthesis - glycogen synthase

Question 8

What hormones regulate GP and GS?

Answer 8

Insulin
Glucagon
Epinephrine

Question 9

What is the allosteric regulation of GP and GS?

Answer 9

AMP stimulates and ATP inhibits GP

Question 10

Does phosphorylation of GS activate or inactivate it?

Answer 10

Inactivate

Question 11

Does phosphorylation of GP activate or inactivate it?

Answer 11

activate

Question 12

What enzyme does insulin activate?

Answer 12

Protein phosphatase 1

Question 13

What does protein phosphatase do?

Answer 13

Increase glycogen synthase
Decrease glycogen phosphorylase

Question 14

What is the effect of insulin on glycogen metabolism?

Answer 14

Increases glycogen synthesis
Decreases glycogenolysis

Question 15

What is glycogen?

Answer 15

Storgae form of glucose

Question 16

What does epinephrine signal?

Answer 16

Glucose is urgently low

Question 17

What is the effect of epinephrine?

Answer 17

Activates GP and inhibits GS
Increases glycogenolysis
Decreases glycogenesis

Question 18

Define gluconeogenesis?

Answer 18

Synthesis of ‘new glucose’ from common non-carbohydrate precursors

Question 19

What is gluconeogenesis most active?

Answer 19

In fasting state, during prolonged excercise and conditions of carbohydrate starvation

Question 20

Where does gluconeogensis occur?

Answer 20

Liver and to a lesser extent in kidney

Question 21

What is the common starting point for glucose synthesis?

Answer 21

Pyruvate

Question 22

What tissues are gluconeogensis most active?

Answer 22

Tissues that rely least on glucose for energy (liver)
Tissues that need it most (brain, cardiac and skeletal muscle)

Question 23

Why is gluconeogenesis critically important in the liver?

Answer 23

Maintains blood glucose levels so brain and other energy intensive tissues can extract sufficient glucose

Question 24

What are the raw ingredients for glucose synthesis supplied by?

Answer 24

Muscle and other tissues (RBCs)

Question 25

Why is glucose 6 phosphatase critical?

Answer 25

Allows glucose to leave cell
not found in muscle

Question 26

What is the result of fasting?

Answer 26

Gluconeogenesis favored
Glucagon and cortisol induce gluconeogenesis

Question 27

What is the result of feeding?

Answer 27

Favours glycolysis
Insulin induces glycolysis

Question 28

What are 3 characteristics of Fas?

Answer 28

Highly reduced form of carbon
Consumed in diet or synthesised
Stored as triglycerides

Question 29

What is beta oxidation and where does it occur?

Answer 29

in mitochondria
FA broken down into 2c compounds, acetyl CoA

Question 30

What happens when glucose and FA metabolism are balanced?

Answer 30

Acetyl CoA oxidised in TCA cycle

Question 31

Where does FA synthesis occur?

Answer 31

Cytosol (liver, lactating mammary gland)
2C acetyl CoA units condensed to form C16 Fas

Question 32

What is the rate limiting enzyme in FA synthesis?

Answer 32

Acetyl CoA carboxylase

Question 33

How do hormones regulate ACC?

Answer 33

Controlling activity of protein kinases and phosphatases

Question 34

What happens when glucagon activates PKs?

Answer 34

Phosphorylate (inhibit) ACC
Signals energy is low and lipid metabolism should switch FA synthesis to oxidation

Question 35

What happens when insulin activates protein phosphotases?

Answer 35

Dephosphorylate (activate) ACC
Signals energy is abundant and FA oxidation should switch to synthesis

Question 36

What does epinephrine and glucagon stimulate?in FA metabolism

Answer 36

Lipolysis
activate hormone sensitive lipase - hydrolyses TGs to FAs and glycerol

Question 37

What does insulin do to FA metabolism?

Answer 37

Inhibits hormone sensitive lipases and favours TG synthesis

Question 38

What hormones are a satiety signal and stimulate the anorexigenic pathway?

Answer 38

Insulin and GLP-1

Question 39

What hormone stimulates the orexigenic pathway (appetite)?

Answer 39

Ghrelin

Question 40

Where is leptin made?

Answer 40

Adipocytes

Question 41

What does leptin signal?

Answer 41

satiety signal
matches food intake to energy expenditure

Question 42

What is the first priority in starvation?

Answer 42

Provide sufficient glucose to brain

Question 43

What is the secondary priority in starvation?

Answer 43

Shift from utilization of glucose to FAs/ketone bodies

Question 44

What happens after 3 days of starvation?

Answer 44

Ketone bodies are used as a fuel source by brain and heart