Metabolic homeostasis: anabolic/catabolic state

Question 1

What are the 4 basic metabolic pathways?

Answer 1

Fuel oxidative pathways
Fuel storage and mobilisation
Biosynthetic pathways
Detoxification/waste disposal pathways

Question 2

What is the anabolic pathway?

What is the catabolic pathway?

Answer 2

Synthesise large molecules (biosynthetic and fuel storage)

Breakdown large molecules (fuel oxidation)

Question 3

What balance must be met and what is it called?

Answer 3

Fuel availability vs Tissue needs

Metabolic homeostasis

Question 4

What are the effects if metabolic homeostasis isn’t met? (2)

Answer 4

Significant decreases: hypoglycaemia, limited brain metabolism
Too much: Hyperosmolar effects, coma, neurological effects

Question 5

How is the balance between use, release and storage maintained? (3)

Answer 5

Blood
Hormones
Central Nervous sytem

Question 6

When hormones are released, what are the 3 main parts they effect?

Answer 6

Muscle
Liver
Adipose (fat) tissue

Question 7

What is insulin and where is it produced?

Answer 7

Insulin is an anabolic hormone

Released from Beta cells of islets of langerhans

Question 8

How is insulin stimulated and what is its action? (3)

Answer 8

Stimulated by glucose entering cells

Insulin promotes: Glucose -> fuel, storage as glycogen, inhibited fuel metabolism

Question 9

What is glucagon and where is it produced?

Answer 9

Contra-insular hormone

Released from alpha cells of pancreas

Question 10

How is glucagon stimulated and what does it promote?

Answer 10

Stimulated by insulin and glucose levels falling

Promotes: Glucose production (gluconeogenesis, glycogenolysis)

Question 11

What is the absorptive state and what are the effects of it (3)?

Answer 11

Well-fed state: 2- 4 hrs after eating a meal

• Elevated insulin:glucagon ratio
• Readily available substrates
• Anabolic state

Question 12

What happens to the liver after a meal?

Answer 12

Liver is bathed in blood containing nutrients

-Takes up carbs, lipids and A.A.

Question 13

What happens when carbohydrates are metabolised? (5)

Answer 13

Increased glucose uptake
Increased phosphorylation of glucose
Increased gluconeogenesis
Increased glycolysis
Increased insulin to glucagon, increase in glycolytic enzymes

Question 14

Where is fat metabolised and what is the effect?

Answer 14

Liver

Increased triacylglycerol synthesis

Question 15

How are amino acids metabolised? (2)

Answer 15

Protein synthesis in the liver

Exported to other tissues to be used or degraded

Question 16

What is the fasting state and what are the effects (3)?

Answer 16

If no food is taken in after the end of the absorptive state

• Glucose levels, A.A acids fall
• Insulin decrease, glucagon and epinephrine increase
• Catabolic state

Question 17

What are the 4 things that control flow of intermediates through the metabolic pathway?

Answer 17

Substrate availability
Allosteric regulation of enzymes
Covalent modification of enzymes
Induction-repression of enzyme synthesis

Question 18

What are the 3 enzymes that are active in there absorptive AND fasting state?

Answer 18

Glycogen phosphorylase
Glycogen phosphorylase kinase
Hormone sensitive lipase

Question 19

What are the 3 processes that occur in the fasting stage in the liver, muscle and adipose tissue?

Answer 19

Liver - glycogenolysis (releasing glucose)
Adipose tissue - lipolysis (releasing FA’s & glycerol)
Muscle - proteolysis (realising A.A)

Question 20

What is the main function of the liver in carbohydrate metabolism?

Answer 20

Produce glucose by glcogenolysis and gluconeogenesis

Question 21

What is the major energy source in liver tissue?

Answer 21

Fatty acid oxidation

Question 22

How does a hyper catabolic state occur?

Answer 22

Injury: burns & septic stress

Question 23

What happens in a hyper catabolic state? (3)

Answer 23

• Cortisol is the main mediator of response
• Amino acids are used in a prioritised fashion
• Glutamine efflux from skeletal muscle can provide an energy source