Integrating Metabolism

Question 1

Define “energy coupling”

Answer 1

Energy produced by one action or system being used to drive another reaction.

Question 2

What is an exergonic reaction?

Answer 2

A reaction which releases energy (negative ∆G).

Question 3

What is an endergonic reaction?

Answer 3

A reaction which absorbs energy (positive ∆G).

Question 4

What is anabolism?

Answer 4

A reductive reaction.
Energy requiring reaction.
Produce larger complexes from smaller ones.
Uses the energy from catabolism.

Question 5

What is catabolism?

Answer 5

An oxidative reaction.
Energy releasing.
Breakdown of complex molecules to form simpler ones.

Question 6

What mechanism converts glycogen to glucose-6-phosphate?

Answer 6

Glycogenolysis (via glycogen phosphorylase).

Question 7

Where in the body is glucose-6-phosphate (G6P) primarily used?

Answer 7

Muscles:
Important source of energy during high intensity, shorter exercise.
Liver:
G6P converts to glucose and enters bloodstream.

Question 8

What mechanism converts Glucose-1-phosphate (G1P) to glycogen?

Answer 8

Glycogenesis (via glycogen synthase).

Question 9

Define gluconeogenesis?

Answer 9

The synthesis of glucose from non-carbohydrates (i.e. lactate, glycerol, AAs).

Question 10

Define the Cori cycle.

Answer 10

Lactate produced by muscular glycolysis.
Transported to liver.
Converted to glucose.
Returns to muscles for re-use.

Question 11

What is the term used to describe the sacrifice of muscle protein to produce glucose for the brain?

Answer 11

Starvation

Question 12

Describe what happens during fatty acid oxidation in mitochondria?

Answer 12

Short and medium chain fatty acids enter directly.
Long chains shuttle in using carnitine carriers.
Fatty acids broken down to generate Acetyl-CoA molecules.
Beta oxidation occurs.

Question 13

Describe the beta oxidation of fatty acids?

Answer 13

The breaking down of fatty acids to acetyl-coa to either:
Feed into the TCA cycle
OR
Generate ketone bodies.

Each turn generates:
Acetyl-CoA.
A reducing equivalent for electron transport chain.

Question 14

How is Acetyl-CoA used post-beta oxidation?

Answer 14

Acetyl CoA either generates ketone bodies or feeds into tricarboxylic acid cycle.

Question 15

How is your body supplied with essential and non-essential amino acids?

Answer 15

Essential - from diet.
Non-essential - derived from transamination.

Question 16

What happens in a scenario where there is excess amino acids?

Answer 16

The excess are catabolised to urea via deamination.
The deaminated carbon skeletons are oxidised via the tricarboxylic acid cycle.

Question 17

Where does catabolism of amino acids mainly occur?

Answer 17

In the liver.

Question 18

What occurs during catabolism of amino acids?

Answer 18

Amino group is removed from amino acids (enters urea cycle for excretion).
Carbon skeleton either: Oxidised to CO2 + H20.
Used for gluconeogenesis.
Used for ketogenesis.

Question 19

How is nitrogen metabolised?

Answer 19

Amino nitrogen enters urea cycle for excretion.

Question 20

What is the meaning of the term “amphibolic”?

Answer 20

A cycle which serves as both catatonic and anabolic.

Question 21

What is anaplerosis?

Answer 21

The replenishment of tricarboxylic acid cycle (TCAC) intermediates.

Question 22

What are tricarboxylic acid intermediates? What are their uses?

Answer 22

Metabolites which are not used up in the oxidation of acetyl CoA.
Are used in the synthesis of pyrimidines, porphyrins, lipids etc.

Question 23

In anaplerosis, What does pyruvate carboxylase yield?

Answer 23

Oxaloacetate.

Question 24

In anaplerosis, what does glutamate dehydrogenase yield?

Answer 24

Oxaloacetate.

Question 25

In anaplerosis, what does beta-oxidation of odd-chain fatty acids yield?

Answer 25

Succinyl CoA.

Question 26

Briefly describe the meaning of fed -> fasted.

Answer 26

Contribution of dietary glucose is replaced firstly at the expense of liver glycogen.
Next is the expense of muscle protein by gluconeogenesis.
Key roles in:
Insulin.
Glucagon.
Cortisol.

Question 27

How does your body deal with carbohydrates in a “fed state” of metabolism?

Answer 27

Processes the carbohydrates through:
Glycolysis.
Glycogenesis.
Lipogenesis.

Question 28

How does your body utilise free fatty acids in a “fed state” of metabolism?

Answer 28

Triglycerides are synthesised from free fatty acids (FFA).
For storage in adipose tissue

Question 29

How does your body react to a “fed state” of metabolism in terms of amino acids and proteins?

Answer 29

Amino acid synthesis occurs.
Protein metabolism occurs.

Question 30

What is the key signal for a “fed” metabolic state?

Answer 30

Insulin.

Question 31

In a “fasted state” of metabolism, which mechanisms supply your body with glucose?

Answer 31

Glycogenolysis and gluconeogenesis.

Question 32

During a “fasted state” of metabolism, how is adipose tissue utilised?

Answer 32

Lipolysis of adipose tissue releases free fatty acids and glycerol.
Glycerol converted to glucose via gluconeogenesis.

Question 33

Why does the body begin oxidating free fatty acids and ketones in the fasted state? How does this affect the body?

Answer 33

Oxidation creates a supply of energy, sparing glucose.
Causes ketosis.

Question 34

How does the body utilise proteins and amino acids when in a “fasted state”?

Answer 34

Protein catabolism occurs.
Amino acids converted to glucose through gluconeogenesis.

Question 35

How are pancreatic hormones affected by a “fasted state”?

Answer 35

Glucagon active.
Insulin suppressed.