proteins

Question 1

what atoms are proteins composed of

Answer 1

carbon, hydrogen, oxygen, nitrogen (sulphur) atoms

Question 2

basic unit of proteins

Answer 2

amino acids

Question 3

how many amino acids are required for the synthesis of human proteins

Answer 3

20

Question 4

how many essential amino acids are there

Answer 4

8, they cannot be made by the body and must be obtained from our diet

Question 5

word equation for dipeptide

Answer 5

amino acid + amino acid => dipeptide + water

Question 6

structural components of amino acid

Answer 6

amino group, carboxyl group, side chain

Question 7

how is a dipeptide formed

Answer 7

when the amino group of an amino acid reacts with the carboxyl group of another amino acid in condensation to form a peptide bond (w/ a water molecule removed in the reaction)

Question 8

how is a polypeptide formed

Answer 8

formed by further condensation of 3 or more amino acids

Question 9

how are proteins formed

Answer 9

1. a polypeptide is formed by joining many amino acids
2. the polypeptide coils and folds in a specific way into a 3d conformation with the help of attraction forces formed between side chains of different amino acids of the same polypeptide
3. the polypeptide chains may combine with other polypeptides to form a protein

Question 10

what determines the final shape of a protein

Answer 10

the amino acid sequence of a polypeptide

Question 11

what happens with excess amino acids in the body

Answer 11

as excess amino acids cannot be stored, the amino group will be removed and broken down by the liver through deamination into ammonia then urea, which is excreted from the body through urine
carboxyl group + side chain are converted into carbs / lipids for respiration (release of energy for muscle contraction) or storage (glycogen stored in liver / muscles)

Question 12

functions of proteins

Answer 12

• acts as raw material for building up body tissue for growth / repair (production of new body cells / replacement of dead cells lost through injury)
• acts as an important component of cell membranes
• for providing energy when carbs and lipids are used up (as a last resort)
• for producing enzymes / antibodies / haemoglobin and some hormones

Question 13

deficiency disease for lack of protein + symptoms

Answer 13

kwashiorkor
swollen abdomen + weak muscles + slim limbs (common among children in developing countries)

Question 14

cons about plant based sources of proteins

Answer 14

they usually lack one or more types of essential amino acids