Biochem

Question 1

Micro nutrients vs macro nutrients

Answer 1

Micro - single molecules

Macro - polymers - carbs, proteins, lipids, nucleotides

Question 2

Essential amino acids

Answer 2

– Phenylalanine, histidine, isoleucine, lysine, leucine, methionine, threonine, valine and tryptophan
– Cysteine, glycine, arginine are also essential for premature babies

Question 3

Examples of important AA as precursors

Answer 3

– His -> histamine
– Trp -> serotonin, melatonin
– Phe -> Tyr -> DOPA -> dopamine -> epinephrine

Question 4

How do potassium, sodium and chlorine move through the body?

Answer 4

between cells and cell compartments, actively pumped rather than passive diffusion

Question 5

Concentrations of potassium and sodium inside and outside cells

Answer 5

Intracellular - K high, Na low

Extracellular - K low, Na High

Question 6

Example of symporter and anti-porter

Answer 6

Symporter - potassium in one direction and chlorine in same direction
Antiporter - sodium in one direction, potassium in other direction

Question 7

How does the kidney maintain Na/K balance in plasma?

Answer 7

– Renin activates angiotensin I, which is converted to angiotensin II (by ACE), causing the secretion of aldosterone which increases reabsorption of Na and vasoconstriction ⇒ Na retained

Question 8

What is hyponatremia and hypokalaemia?

Answer 8

Hyponatremia (low Na+)
– Can result in headaches, seizures and coma.
– Due to low Na diet and diuretic drugs, extreme fluid loss, e.g. diarrhoea.

Hypokalemia (low K+)
– Can result in weakness and muscle cramps, cardiac
arrhythmias or paralysis in extreme cases.
– Due to diuretics, or excessive diarrhoea or vomiting (e.g. bulimia)

Question 9

Consequence of XS liquorice consumption

Answer 9

Hypokalemia it blocks 11beta-hydroxysteroid dehydrogenase

Question 10

How is vitamin D involved in calcium regulation?

Answer 10

• During low calcium intake:
– Parathyroid gland secretes parathyroid hormone PTH
– PTH stimulates 1-hydroxylase
– PTH + calcitriol stimulate osteoclasts to mobilise bone and increase calcium resorption by kidneys

Question 11

Consequences of vitamin D deficiency

Answer 11

• Rickets

- Osteomalacia

Question 12

Vitamin B1, 2, 3 deficiency

Answer 12

Vitamin B1:
Beriberi, abnormal blood sugar, depression, fatigue, vomiting, gastrointestinal disorders.
Vitamin B2:
Light sensitivity, cracks / inflammation of lips, tongue, corners of mouth, dizziness, insomnia
Vitamin B3:
Pellagra (dementia, death), nausea, vomiting, fatigue, dermatitis, loss of appetite, swollen red tongue, Greater risk for some non-melanoma skin cancers.

Question 13

Deficiency and XS B12?

Answer 13

Def: pernicious anaemia
XS: liver disease
– also used to reverse cyanide poisoning