Biochemistry - Carbohydrates

Phosphofructokinase 1 is negatively regulated by?

Citrate and ATP

Which of the glycolytic enzymes requires ATP as a source of energy?

Hexokinase

During prolonged fasting, which molecular event occurs specifically in the liver but not in skeletal muscle?

Inactivation of glycogen phosphorylase by glucose

Which allosteric effector activates glycogen phosphorylase only in muscles but has no activating effect in liver?

AMP - (activates muscle glycogen phosphorylase b during exercise)

Why can’t muscles glycogen directly maintain blood glucose levels?

Lacks enzyme glucose-6-phosphatase

The synthesis of glucose from pyruvate by gluconeogensis:

Requires participation of biotin

In the glycogen reaction, what is the substrate?

UDP glucose

Rapidly dividing cells have a high need for nucleotide precursors which are provided by:

Pentose phosphate pathway

What compound to lactase break down?

Lactose into glucose and galactose

How is glucose and galactose transported from intestine to the blood?

Active transport (SGLT1) - Na dependent

How is fructose transported from the digestive tract to the blood?

Passive transport (GLUT5)

Which glucose transporters transport glucose non-stop?

GLUT 1 and GLUT 3

What is constant glucose concentration in the blood?

70-100mg/100ml

What is the role of glycolysis?

Degradation of glucose for ATP synthesis

What is the function of triosephosphate isomerise in glycolysis?

Catalyses the reversible reaction between DHAP and Glyceraldehyde-3-P

Which 2 enzymes catalyse the isomerisation reactions in glycolysis?

1. Glucose-6-P isomerase (aldose into ketose)

2. Triosephosphate isomerase (ketose into aldose)

What are the 3 irreversible control enzymes of glycolysis?

1. Hexokinase

2. PFK-1 (regulatory enzyme)

3. Pyruvate kinase

Why is PFK-1 considered the rate-limiting enzyme of glycolysis?

Is regulated by the largest number of allosteric effectors

Which glycolytic enzyme is unique in being regulated by covalent phosphorylation in the liver but not in muscle?

Pyruvate kinase

Which shuttle transfers cytosolic NADH electrons to mitochondria with no loss of ATP yield?

Malate-Asparate shuttle (tranfers electrons to the mitochondrial NAD+)

Which compound is a direct substrate of glycogen synthase?

UDP-glucose

During aerobic glycolysis, electrons and hydrogen from NADH + H+?

Are transported to electron transport chain

During anaerobic glycolysis, electrons and hydrogen from NADH+H are passed onto:

Lactate

The transport of glucose from blood to adipose tissue depends on:

Insulin dependent (GLUT 4)