selenium and biotrans

Question 1

Mention the RDA of selenium

Answer 1

Requirement: 50-100 μg/day

Question 2

List the dietary sources of selenium

Answer 2

-brazil nuts
- oysters
-sunflower seed
- sardines
-chicken
-eggs
- mushrooms
- cottage cheese
-brown rice

Question 3

List the functions

Answer 3

Present in human proteins as a constituent of amino acid selenocysteine
Seleno-proteins include
A. Glutathione peroxidase B. Thioredoxin reductase
( reduces thioredoxin, a coenzyme of ribonucleotide reductase)
C. Deiodinases (remove iodine from thyroid hormones)

• acts as a nonspecific intracellular antioxidant
• complementary to vitamin E
• Availability of vitamin E reduces selenium requirement
• In selenium deficiency, tissue vitamin E content is
  depleted
• Selenium has synergistic action with vitamin E

Question 4

Mention the deficiency manifestations

Answer 4

Keshan disease:
Selenium deficiency in Keshan province in China
Characterized by:
Multifocal myocardial necrosis Cardiac arrhythmias
Cardiac enlargement
Isolated selenium deficiency in other parts of the world:
* Liver necrosis
* Cirrhosis
* Cardiomyopathy
* Muscular dystrophy

Question 5

Define the term biotransformation

Answer 5

-the process whereby a substance is changed from one chemical form to another by a chemical reaction within the body.
-sometimes produces compounds that are more harmful than its precursor

Question 6

List the examples of compounds undergoing
biotransformation

Answer 6

Compounds accidentally ingested
* Preservatives
* Food additives
* Adulterants
* Drugs taken for therapeutic purposes
Eg: Acetaminophen, acetylsalicylic acid
* Compounds produced in the body which are to be eliminated
Eg: bilirubin
Compounds produced by bacterial metabolism: Amines produced by decarboxylation of amino acids
Histidine …Histamine
Lysine……cadaverine
Ornithine…..Putrescine
Tyrosine…..Tyramine
Tryptophan……Tryptamine

Question 7

Describe the types of reactions (Phase 1 and Phase 2) involved in biotransformation in liver giving examples

Answer 7

Phase one reaction:
Alteration of the foreign molecule to add a functional group, which can be conjugated in Phase 2
There are 3 types of phase 1 reactions:
A. Oxidative reactions
B. Reduction reactions C. Hydrolysis
Phase two reaction:
Conjugation

Question 8

What is the difference between ‘biotransfomation’ and ‘detoxification’?

Answer 8

Detoxification is the process in the body by which toxic xenobiotics and metabolites are converted to
* Less harmful substances than the parent compound
* More water soluble than the parent compound
* Compounds that can be excreted from the body

Question 9

Enzyme system involved in detoxification:

Answer 9

-The cytochrome P450 enzymes
Heme-containing enzymes
* Localized in the ER of the liver
* Use NADPH
Inducible (phenobarbital causes increased activity)

Question 10

conjugation

Answer 10

notes