6 - Vitamins and minerals 2

Question 1

What are the nutrients with antioxidant properties.

Answer 1

Vitamin E
Vitamin C
Vitamin A (precursor beta-carotene)
Selenium

Question 2

What is an oxygen molecule that becomes a free radical?

Answer 2

A reactive oxygen species

Question 3

What a) metabolic and b) environmental factors cause free radicals?

Answer 3

Metabolic) Immune system fighting reactions
Mitochondrial respiration
Microsomal oxygenases from xenobiotic metabolism

Environmental) Pollution, excess sunlight, toxic substances, radiation, tobacco smoke, asbestos.

Question 4

Oxygen radicals can directly react with nucleotide bases. Give some consequences/examples of

a) Single strand breaks.
b) Mutations of nucleotide bases.

Answer 4

SS breaks - Depletion of intracellular antioxidants, NAD+ depletion, activation of poly-ADP-ribose polymerase

Mutations - Deamination resulting in base pair switching, guanine oxidation can cause mis-pair with adenine

Question 5

In ROS DNA damage, what can guanine be oxidised into, and what is the consequence of this?

Answer 5

Guanine -> 8-hydroxyguanine or 8-oxoguanine
8OHG can mis-pair with adenine during DNA replication.
This is refered to as a G:C to T:A mutation

Question 6

what is the role of MUTYH in terms of DNA damage by ROS

Answer 6

A repair enzyme glycosylase involved in the excision of mis-paired adenine

Question 7

How do antioxidant a)vitamins/b)minerals work?

Answer 7

Vitamins - donate their electrons or hydrogen molecules to free radicals to stabilize them and reduce oxidative damage

Minerals - act as cofactors within enzyme systems that convert free radicals to less damaging substances which can be excreted.

Question 8

What is the role of the following enzymes?

a) Superoxide dismutase
b) Catalase
c) Glutathione peroxidase

Answer 8

SOD - Converts free radicals to less damaging substances e.g. hydrogen peroxide through a dismutation reaction
Catalase - converts hydrogen peroxide to H20+02
GP - Eliminates hydrogen peroxide and nitrogen species

Question 9

Explain the dismutation reaction of superoxide dismutase.

Give some minerals that are part of the SOD complex

Answer 9

Oxidation of a superoxide -> oxygen (loses an electron)
Followed by reduction of another superoxide with hydrogen to form h202

Copper, zinc (found in cytosol) and manganese (found in mitochondria)

Question 10

What is the effect of ROS on cell membranes?

Answer 10

• Produce lipid radicals -> oxidise neighbouring lipids -> chain reaction
• Compromise membrane fluidity and oxidative damage to membrane
• arterial accumulation forming atherosclerotic plaques
  and Toxic aldehyde formation -> carcinogenic

Question 11

What are the benefits of vitamin E consumption on the body?

Answer 11

Incorporated into biological membranes
Protects polyunsaturated fatty acids (PUFAs), fatty cell components, and LDLs from oxidation (lower heart disease risk)
Added to oil-based foods and skincare products to reduce rancidity and spoilage
Normal nerve and muscle development
Enhances immune system
Promotes vitamin A absorption, if low

Question 12

What are the biologically active forms of vitamin E?

Answer 12

Tocopherol compounds are the biologically active forms

Alpha-tocopherol is most active (potent), found in food and supplements

Question 13

What are the biochemical functions of vitamin C?

What is it converted from? and to? in order to donate H+ to free radicals

Answer 13

Conversion of proline to hydroxyproline
Synthesis of collagen (prevents scurvy)
General cellular reductant (anti-oxidant)
Converted from ascorbic acid to dehydroascorbic acid

Question 14

What is the relationship between vitamin C and E?

Answer 14

Vitamin C helps regenerate vitamin E molecules that have scavenged free radicals.

Question 15

What are the role of Plant polyphenols?

Answer 15

Contain several oxidisable -OH groups which can donate electrons to ROS, reducing them to less reactive species
May posses significant antioxidant action in vitro.

Question 16

What are the active forms of vitamin A? (and their benifits e.g. bone health)

Answer 16

Retinol - vision, sexual reprocution, bones, immune
Retinal - Vision, sex, bone, immune
Retinoic acid - Cell differentiation, bone health, imm

Question 17

What is the role of vitamin K in the liver?

Answer 17

Acts as an enzyme cofactor, promoting synthesis of carboxyglutamic acid

Question 18

What are the 3 main vitamins associated with hypervitaminosis? And their effects

Answer 18

Hypervitaminosis A
Birth defects, spontaneous abortion
Hypervitaminosis D
Hypercalcaemia (especially in children)
Hypervitaminosis E
Long-term use of supplements may be associated with hemorrhaging in the brain; hemorrhagic stroke