Proteins: Biochemistry of Nutrition

Question 1

What are macronutrients?

Answer 1

Proteins, carbohydrates and fats they supply energy blocks for anabolic reactions, excess intake leads to gain in weight.

Question 2

What are micronutrients?

Answer 2

Vitamins and minerals.
Vitamins are organic compounds required for normal metabolic function, which cannot be synthesised in the body and deficiency results in disease.
Minerals: inorganic elements which have a physiological function.

Question 3

What does the reference nutrient intake (RNI) for a micronutrient mean?

Answer 3

It is the amount required to meet the requirements of 97.5 % of the population.

Question 4

What does vitamin B1 (Thiamin) deficiency cause?

Answer 4

Beri-beri: muscle weakness due to nerve damage, the heart can be affected.
In developed countries thiamin deficiency is mostly seen in alcoholics.

Question 5

What is vitamin B2?

Answer 5

Riboflavin: a constituent of the flavin coenzymes FAD and FMN.

Question 6

What does vitamin B3 (Niacin) deficiency cause?

Answer 6

Pellagra: dermatitis, diarrhoea, depressive psychosis and death.

Question 7

What can vitamin B3 do in pharmalogical doses?

Answer 7

Nicotinamide: range of properties, used to treat skin and neurological disorders. Prolonged high dosage can cause liver dosage.
Niacin: lowers LDL-cholesterol and triglycerides. But raises HDL-cholesterol.

Question 8

What is vitamin B7?

Answer 8

Biotin

Question 9

What is biotin used in?

Answer 9

A prosthetic group for carboxylase, a carbon dioxide carrier, biotinylation in Histones, in the biotin cycle and deficiency is linked to birth defects in mice.

Question 10

What is B6?

Answer 10

Pyridoxine, required for many aspects of metabolism. Severe deficiency is uncommon but inadequate intake may be common.

Question 11

What is B12?

Answer 11

The largest B vitamin and contains a cobalt ion. Required for two enzymatic reactions in humans: methionine synthase and L-methylmalonyl-CoA mutase.

Question 12

What can deficiency in B13 cause?

Answer 12

Untreated causes death. Pernicious and microcytic anaemia (inability to absorb) causes neurological symptoms, limb weakness, poor coordination and altered gait.

Question 13

What is Folic acid key to?

Answer 13

One-carbon transfers in synthesis of serine, methionine, glycine, choline, purine nucleotides and dTMP.

Question 14

What does deficiency of folate acid cause?

Answer 14

Megoblastic anaemia, similar to B13 deficiency but no neurological problems in adults.

Question 15

What is vitamin C required for?

Answer 15

A coenzyme for prolyl hydroxylase and lysyl hydroxylase during collagen synthesis. Also involved in bile acid and adrenalin synthesis. May have antioxidant roles.

Question 16

What does deficiency in vitamin C cause?

Answer 16

Scurvy which is abnormally weak collagen causes fatigue, joint pain, muscle weakness, poor healing, skin haemorrhages, gum disease etc. Untreated is fatal as damage and bleeding occurs in heart muscle.

Question 17

What does vitamin E do?

Answer 17

Protects from free radicals and it’s main role is to protect against lipid oxidation in membranes.

Question 18

What are the roles of vitamin A?

Answer 18

Possible antioxidant protection from CVD and cancer, helps vision in dim light.

Excess in pregnancy can cause foetal malformations.

Question 19

Describe vitamin K?

Answer 19

Required for coagulation, found in two forms phylloquinone from plants and menaquinone synthesised from intestinal bacteria.

Question 20

What is a precursor of vitamin D synthesis?

Answer 20

Cholesterol.

Question 21

What does vitamin D do?

Answer 21

Acts as a transitional regulator for synthesis of a range of proteins involved in calcium homeostasis and bone growth/maintenance: binds to receptors in the nucleus, increases calcium and phosphate absorption from the intestine and can mobilise calcium ions from bones if in short dietary supply. Controls over 200 genes.

Question 22

What are vitamin D deficiencies?

Answer 22

Osteomalacia (in adults)/ rickets (in children), may be implicated in cancer, insufficiency in type one diabetes, rheumatoid arthritis, systemic lupus erythematosis, multiple sclerosis and Crohn’s disease.

Question 23

What mineral deficiencies are the greatest global concern?

Answer 23

Iron and Iodine.

Estimated that 2 billion people suffer from iron deficiency anaemia and 740 million from iodine deficiency.

Question 24

What are the roles of iron?

Answer 24

Components of electron carriers (eg. cytochromes) which are key to many processes including the ETC. Component of haem (myoglobin, haemoglobin and haem -containing enzymes).

Question 25

What are the symptoms of iron deficiency?

Answer 25

Anaemia: red blood cells are microcytic (smaller) and hypochromic (paler).

Question 26

What are the roles of calcium?

Answer 26

Cell signalling, blood coagulation, neural transmission, secretion, muscle function, biominerilisation, membrane and cytoskeletal functions.

Question 27

What is hypocalcaemia?

Answer 27

Calcium deficiency, it leads to muscle cramps and spasms (tetany).

Question 28

What controls the levels of plasma calcium?

Answer 28

Vitamin D and parathyroid hormone.
Vitamin D increases the absorption of calcium from the intestines and regulates parathyroid hormone release.
Parathyroid hormone is secreted in response to a drop in plasma calcium levels and releases calcium from bones, stimulates activation of vitamin D in the kidneys and increases calcium reabsorption in the kidneys.

Question 29

What is iodine vital for?

Answer 29

Synthesis of thyroid hormones which determine metabolic basal rate and are essential for normal growth.

Question 30

What does iodine deficiency cause?

Answer 30

During development leads to stunted growth and mental retardation (cretinism). In adults thyroid enlargement (goitre) is seen.

Question 31

What does an excess of iron cause?

Answer 31

Poisoning in children.

Question 32

What does excess vitamin D cause?

Answer 32

Hypercalcaemia.

Question 33

What is excess vitamin A?

Answer 33

Teratogenic and toxic.

Question 34

What can excess vitamin C cause?

Answer 34

Kidney stones.

Question 35

What is Pantothenic acid?

Answer 35

Vitamin B5, a component of CoA.