Integration to metabolism

Question 1

• What are the three fuel storages of the heart?

Answer 1

Fatty Acids

Lactate

Ketone Bodies

Question 2

• What percentage of the total body weight is brain and nervous tissue?
• What is adipose tissue?

Answer 2

2%

Long term storage site for fatty acids in the form of triglycerides

Question 3

• What are carbohydrates broken down into?

- What happens to pyruvate before it becomes acetyl CoA?

Answer 3

Simple sugars

It is reduced and decarboxylated

Question 4

• Where in the body can excess G6P be used to generate glycogen?
• What can excess acetyl CoA be used to generate?

Answer 4

Liver and muscle

Fatty acids

Question 5

• What and where are fatty acids stored?

- What is produced during extreme exercise?

Answer 5

They are stored as triglycerides in adipose tissue

Lactic acid

Question 6

• What is the definition of hypoglycaemia?

- List 3 ways the body can avoid hypoglycaemia?

Answer 6

Plasma glucose level falling below 3mM

1. Breakdown of liver glycogen stores occurs to maintain plasma glucose levels
2. Release free FAs from adipose tissue
3. Convert acetyl CoA into ketone bodies via the liver

Question 7

• What is the overall aim of gluconeogenesis?

- What is the Cori cycle?

Answer 7

To generate glucose from pyruvate

When lactate is taken up by the liver and utilised to regenerate pyruvate by Lactate Dehydrogenase

Question 8

• What are the products of triglyceride hydrolysis?

- Which enzymes catalyse the irreversible reactions of glycolysis?

Answer 8

FAs and glycerol

Hexokinase, phosphofructokinase and pyruvate kinase

Question 9

• What is the first reaction of gluconeogenesis catalysed by and where does it occur?
• Where do the remaining reactions take place?

Answer 9

Pyruvate carboxylase
Mitochondria

Cytosol (water-soluble components of cell cytoplasm)

Question 10

• What is the delta G value for gluconeogenesis?
• How many molecules does the deamination of all 20 amino acids give rise to?
• Name all of these molecules?Urea → waste product

Answer 10

-38 kJ/mol which is favourable

7    

pyruvate, acetyl CoA, Acetoacetyl CoA, alpha-ketoglutarate, succinyl CoA, fumerate and oxaloacetate

Question 11

• What gives rise to glucose via gluconeogenesis?

- What do ketogenic amino acids give rise to?

Answer 11

Glucogenic amino acids

Skeletons that can be used to synthesise FAs and ketone bodies.

Question 12

• Can fatty acids be converted into glucose via gluconeogenesis?

Answer 12

No

But they can be converted into ketone bodies and used by tissues such as muscle and brain

Question 13

• List 5 things that occur during exercise (aerobic)?

Answer 13

Contractions increase ATP demand

Contractions increase glucose transport 

Muscle glycolysis increases (adrenaline)

Gluconeogenesis increases (adrenaline)

Fatty acids increase (adrenaline)

Question 14

• What is the problem during anaerobic respiration?

- What is broken down to meet ATP demands during anaerobic respiration?

Answer 14

Demands of contracting the muscle for ATP can’t be met by OP.

Glycogen within the muscle

Question 15

• What happens to pyruvate during anaerobic respiration?

- What happens after a meal when blood glucose levels increase?

Answer 15

It is taken up by the liver and converted into lactate by LD to replenish NAD+ levels and maintain glycolysis

High glucose stimulates insulin release from pancreas
High insulin stimulates glucose uptake from liver and muscle
Overall stimulation of synthetic pathways

Question 16

• What occurs after a meal when blood glucose levels have decreased?

Answer 16

Increased glucagon secretion (and reduced insulin) from islets

Glucose production in liver resulting from glycogen breakdown and gluconeogenesis

Utilisation of fatty acid breakdown as alternative substrate for ATP production

Question 17

• What occurs after prolonged fasting?

Answer 17

Glucagon/insulin ratio increases further

Adipose tissue begins to hydrolyse triglyceride to provide fatty acids for metabolism

TCA cycle intermediates are reduced in amount to provide substrate for gluconeogenesis

Protein breakdown provides amino acid substrates for gluconeogenesis

Ketone bodies are produced from fatty acids and amino acids in liver to substitute partially the brain’s requirement for glucose

Question 18

• What is the Michaelis constant (KM)?
• Where is hexokinase 1 found and what is it’s KM?
• Where is hexokinase 4 found and what is it’s KM?

Answer 18

The concentration of substrate at which an enzyme functions at a half-maximal rate (Vmax).

Muscle, 0.1mM

Liver, 4mM

Question 19

• When is insulin secreted?

- When is glucagon secreted?

Answer 19

When glucose levels rise
Stimulates uptake and use of glucose and storage as glycogen and fat

When glucose levels fall

Question 20

• What are glucocorticoids?
• What causes type 1 diabetes?
• What causes type 2 diabetes?

Answer 20

Steroid hormones which increase synthesis of metabolic enzymes concerned with glucose availability

Beta-cell dysfunction (failure to secrete enough insulin)

Individual fails to respond appropriately to insulin

Question 21

• List complications of diabetes

Answer 21

Hyperglycaemia

Cardiovascular complications 

Ketoacidosis 

Coma as a cause of hypoglycaemia 

Atherosclerosis