Energy Production: Carbs 1+2

Question 1

What occurs in stage 1 of metabolism?

Answer 1

Occurs extracellularly (GI tract), complex molecules are broken down to smaller molecules. Breakage of C-N and C-O bonds, and no energy is produced.

Question 2

What occurs in stage 2 of metabolism?

Answer 2

Occurs intracellularly (cystolic and mitochondrial). Has many pathways, C-C bonds are broken and some energy is produced.

Question 3

What occurs in stage 3 of metabolism

Answer 3

Occurs in mitochondria, a single pathway (TCA cycle), is oxidative and some energy is produced. Acetyl CoA is converted to 2CO2.

Question 4

What occurs in stage 4 of metabolism?

Answer 4

Occurs in mitochondria. Electron transport and ATP synthesis. NADH and FAD2H re-oxidised and large amounts of energy carrier (ATP) generated.

Question 5

What’s the general formula for carbohydrates?

Answer 5

(CH2O)n, may contain aldehyde (H-C=O) or keto (-C=O) group

Question 6

Examples of dietary carbohydrates?

Answer 6

Sucrose (Glucose-Fructose disaccharide), Lactose (Glucose-Galactose disaccharide), Maltose (Glucose-glucose disaccharide)

Question 7

Which tissues have an absolute requirement for glucose?

Answer 7

Red blood cells, neutrophils, innermost cells of kidney medulla, lens of eye

Question 8

Describe primary lactase deficiency

Answer 8

Inability to digest lactose products due to an absence of lactase persistence allele. Only occurs in adults.

Question 9

What causes secondary lactase deficiency?

Answer 9

Caused by injury to small intestine, e.g. gastroenteritis, coeliac disease, Crohn’s disease. Occurs in both infants/adults and is generally reversible.

Question 10

Describe congenital lactase deficiency

Answer 10

An autosomal recessive defect in the lactase gene, meaning breast milk can’t be digested.

Question 11

What does allosteric mean?

Answer 11

An activator or inhibitor that binds at ‘another’ site.

Question 12

What are key features of glycolysis?

Answer 12

Oxidation of glucose, NADH production (2 per glucose), synthesis of ATP from ADP with a net gain of 2 ATP.

Question 13

What are the allosteric and hormonal regulators of phosphofructokinase?

Answer 13

Allosteric: inhibited by high ATP and high citrate, stimulated by high AMP and high F2, 6BP. Hormonal: Stimulated by insulin, inhibited by glucagon.

Question 14

When is pyruvate reduced to lactate?

Answer 14

When there is an inability to use NADH for oxidative phosphorylation

Question 15

What’s the equation for lactate production

Answer 15

NADH + H+ + pyruvate <—> NAD+ + lactate
(Lactate dehydrogenase)

Question 16

What is lactic acidosis

Answer 16

Occurs when plasma lactate concentration is above 5mM, above renal threshold and blood pH is lowered.

Question 17

Diseases associated with fructose metabolism.

Answer 17

Essential fructosuria- where fructokinase is missing (fructose in urine). Fructose intolerance- aldolase missing so F1P accumulates in liver causing damage and possible death. Managed by removing fructose and sucrose from diet.

Question 18

What enzymes are involved in galactose metabolism

Answer 18

Galactokinase, Galactose-1-P uridyl transferase, UDP-galactose 4’-epimerase.

Question 19

Describe galactosaemia

Answer 19

Body unable to utilise galactose due to enzyme deficiencies. Problem here is that galactose enters other pathways. Accumulation of galactose-1-P affects liver, kidney and brain. Treatment- no lactose in diet.