Energy Storage

Question 1

How is glycogen stored

How many grams in muscle and liver

Answer 1

As granules

Muscle-300g
Liver- 100g

Question 2

Describe the structure of glycogen

Answer 2

Alpha 1-6 and alpha 1-4 glycosidic bonds

Glycogenin protein at core

Alpha 1-6, causes branching

Question 3

Explain Glycogenesis in 4 steps

Answer 3

• Glucose+ATP——>Glucose-6-phosphate+ ADP by Hexokinase
• Glucose-6 to Glucose-1 phosphate by Phosphoglucomutase
• G-1-P + UTP + Water—> UDP-Glucose + 2Pi by G1P Uridyltransferase
• Glycogen(n residues) + UDP-Glucose—> Glycogen( n+1 residues) + UDP by Glycogen Synthase OR Branching enzyme

Question 4

Explain Glycogenolysis

Answer 4

• Glycogen(n residues) + Pi—> Glucose-1-Phopshate + Glycogen(n-1) residues by Glycogen Phosphorylase OR De-branching enzyme
• Glucose-1-P is converted to Glucose-6-Phosphate by Phosphoglucomutase

Question 5

Compare the functions of glycogen stores in Muscle and Liver

Which enzyme is not present in muscles

Answer 5

Liver: Glucose-6-P converted to Glucose and exported to blood. Glycogen acts a blood glucose level buffer

Muscle: G6P enters glycolysis for energy production. Glucose-6-Phosphatase

Question 6

What kind of diseases are Glycogen Storage

How do they arise

Answer 6

Inherited

Deficiency/ dysfunction of enzymes

Question 7

Compare the effects of excess glycogen storage and Diminshed glycogen stores

Answer 7

Excess: Tissue damage
Diminshed: Hypoglycaemia and poor exercise tolerance

Question 8

Compare the causes of von Gierke’s and McArdle disease

Answer 8

McArdle: G-6-Phosphatase deficiency

von Gierke’s disease: Muscle glycogen phosphorylase deficiency

Question 9

Where does Gluconeogenesis occur

Answer 9

Mainly in liver

Less in kidney cortex

Question 10

What are 3 major precursors for Gluconeogenesis

Answer 10

Lactate: From anaerobic glycolysis

Glycerol: From adipose tissue

Amino acids: Mainly alanine

Question 11

Name 3 key enzymes in Gluconeogenesis and what they do

What are the main 2 control steps of the pathway

Answer 11

1. PEPCK: Pyruvate tto phosphoeonolpyruvate
2. Fructose 1,6-bisphosphatase : Fructose 1,6-bisphosphate to Fructose-6-phosphate
3. Glucose-6-phosphatase: G-6-P to Glucose

1 and 2

Question 12

Where does lipogenesis occur mainly

What is the major source of carbon

Answer 12

In liver, dietary glucose

Question 13

Describe Lipogenesis in 5 steps

What 2 substances are needed for this

Answer 13

1. In cytoplasm, Glucose-> Pyruvate
2. In mitochondria, Pyruvate forms Acetyl-CoA and OAA, which combine-> Citrate
3. In cytoplasm, citrate cleaved to re-form OAA and Acetyl-CoA
4. Acetyl-CoA carboxylase forms Malonyl-CoA
5. Fatty acid synthase complex makes fatty acids by adding 2Carbon units from Malonyl-CoA

NADPH and ATP

Question 14

Name 4 Fuel stores in a 70kg man

Answer 14

Triaglycerol
Liver Glycogen
Muscle Glycogen
Muscle protein

Question 15

Compare Fatty Acid Oxidation/ Synthesis in terms of;

Location 
Enzymes 
ATP needed
Intermediated being linked to what
Regulation

Answer 15

Oxidation:

• In mitochondria
• Separate enzymes
• Intermediates linked to CoA
• Little ATP needed (to activate fatty acid)
• Regulated indirectly fatty acid mitochondria

Synthesis:

• In cytoplasm
• Multi enzyme complex
• Intermediates linked to Fatty Acid Synthase complex
• Large amount of ATP needed
• Regulated directly by Acetyl-CoA Carboxylase

Question 16

What is the normal blood glucose concentration

Answer 16

5mM