Lecture 2

Question 1

Describe the general structures and functions of carbohydrates and function of carbohydrates and how they are digested and absorbed.

Answer 1

(CH2O)n - and aldehyde (aldo-) or ketone group (keto-) may be present.

Carbohydrates are broken down into monosaccharides to pyruvate (lactate) to make CO2 and Acetyl CoA this then enters the Kerb’s cycle.

Question 2

Explain the biochemical basis of lactose intolerance.

Answer 2

Primary lactase deficiency:
- Absence of lactase persistence allele.

Secondary lactase deficiency:
- Caused by injury to the small intestine.

Congenital lactase deficiency
- Extremely rare, autosomal
recessive defect in lactase
gene. Cannot digest breast
milk.

People with lactose intolerance to not have the enzyme lactase this results in a build up of lactose in the bowel.

Question 3

Explain why cellulose is not digested in the human gastrointestinal tract.

Answer 3

Humans do not have the necessary enzymes to break down the cellulose.

Question 4

Describe the glucose-dependency of some tissues.

Answer 4

All tissues can metabolise glucose some have an absolute requirement:
- Red blood cells.
- Neutrophils.
- Innermost cells of kidney medulla.
- Lens of the eye

The CNS prefers glucose as fuel.

The glucose is required for ATP synthesis.

Question 5

Describe the key features and functions of glycolysis.

Answer 5

The functions are:
- Oxidation of glucose
- NADH production (2 per glucose)
- Synthesis of ATP from ADP net 2 ATP per glucose.
- Provides biosynthetic precursors.

The features:
- Central pathway of carbohydrates catabolism.
- Occurs in all tissues(cytosolic).
- Exergonic, oxidative.
- C6 -> 2C3 no loss of CO2.
- irreversible pathway
- With one additional enzyme (LDH), is the only pathway that can operate anaerobically.