Lecture 4.1: Energy Storage- Carbohydrates and Lipids

Question 1

Types of fuel reserves in body (4)

Answer 1

Triacylglycerol
Liver Glycogen
Muscle Glycogen
Muscle Protein

Question 2

Which tissues have an absolute need for glucose as fuel?

Answer 2

Erythrocytes and leukocytes
Testes
Kidney medulla
Lens and cornea of the eye
Brain

Question 3

Hypoglycaemia (4 glucose levels)

Answer 3

2.8mmol/L : Confusion
1.7mmol/L : Weakness, Nausea
1.1mmol/L : Muscle Cramps
0.6mmol/L : Brain Damage, Death

Question 4

Glucose Utilisation Over Time

Answer 4

2 hrs after meal: Glucose from food
2-8 hrs after: Glycogenolysis (Glycogen)
8-10 hrs after: Gluconeogenesis (Lactate, Glycerol, Amino acids)

Question 5

How is Glycogen Stored?

Answer 5

As granules in muscle and liver cells

Question 6

Glycogen

Answer 6

– Human Starch, stored in liver and skeletal muscle
– α-glucose
– Contains α1,4 and α1,6 glycosidic bonds
– Highly Branched Structure [allows more rapid breakdown from all ends for
energy production]

Question 7

Glycogenesis (Glycogen Synthesis)

Answer 7

Diagram on iPad

Question 8

Regulation of Glycogen Metabolism: Glucagon, Adrenaline

Answer 8

Mechanism is phosphorylation
Glycogen synthase decreased
Glycogen phosphorylase increased

Question 9

Regulation of Glycogen Metabolism: Insulin

Answer 9

Mechanism is de-phosphorylation
Glycogen synthase increased
Glycogen phosphorylase decreased

Question 10

Glycogen Storage Diseases (GSD I-XI)

Answer 10

Arise from deficiency or dysfunction of enzymes involved in glycogen metabolism

Severity depends on enzyme/tissue affected

11 distinct types

Question 11

Why is excess glycogen storage harmful?

Answer 11

Can lead to tissue damage

Question 12

Why is insufficient glycogen degradation harmful?

Answer 12

Can lead to hypoglycaemia (low glucose levels)
Poor exercise tolerance

Question 13

Types of GSDs (4 out of 11)

Answer 13

McArdle Disease (GSD V)
Von Gierke Disease (GSD I)
Cori Disease (GSD III)
Pompe’s Disease (GSD II)

Question 14

McArdle Disease (GSD V)

Answer 14

Muscle glycogen phosphorylase deficiency
Exercise-induced muscle pain and cramps
Fatigue/ Tiredness

Question 15

Von Gierke Disease (GSD I)

Question 16

Cori Disease (GSD III)

Question 17

Pompe’s Disease (GSD II)

Question 18

Gluconeogenesis (de novo glucose synthesis)

Answer 18

Synthesis of glucose from non-hexose precursors

Beyond 8-10 hours of fasting, liver glycogen stores start to deplete and an alternative source of glucose is required

Occurs in liver and to lesser extent in kidney cortex, major precursors include: Lactate, Glycerol, Pyruvate, Glucogenic amino acids (mainly alanine)

Question 19

Key Enzymes In Gluconeogenesis

Answer 19

Phosphoenolpyruvate carboxykinase (PEPCK)
Fructose 1,6-bisphosphatase
Glucose-6-phosphatase

Question 20

Regulation of Gluconeogenesis

Answer 20

Glucagon, Cortisol: Increases PEPCK and Fructose 1,6 bisphosphatase, Stimulates Gluconeogenesis

Insulin: Decreases PEPCK and Fructose 1,6 bisphosphatase, Inhibits Gluconeogenesis

Question 21

Lipid (Triacylglycerol) Storage

Answer 21

Highly efficient energy store
Energy content per gram twice that of carbohydrate or protein
Excess energy is converted to triacylglycerol (TGs) for storage
Stored as anhydrous white adipose tissue
The storage and mobilisation of TGs is under hormonal control