Chapter 1.6 Biological molecules

Question 1

monomer of protein

Answer 1

amino acids (monomers) combined to form polymer polypeptide, which thn combined w other polypep. to form proteins

Question 2

describe how a dipeptide is formed and the bond name

Answer 2

via a condensation reaction between two amino acids

1. An -OH is taken from one aa’s carboxylic group, and an -H from another aa’s amino group is used. Water is elimininated.

A PEPTIDE BOND IS FORMED

Question 3

how are polypeptides formed

Answer 3

via condensation reaction between many amino acids

Question 4

what is the primary structure protein

Answer 4

the (sequence) of amino a in a polypeptide chain 9a poplypep. chain is a chain which has lots of aa joined together via condensation reaction).

Question 5

secondary structure

Answer 5

1. the sequence of amino acids causes parts of a protein molecule to bend into a helix shapes or fold into b pleated sheets
2. hydrogen bonds, formed between the C=O group of one carboxyl group in one AA and the NH group in 1 amino group of ANOTHER AA. The H is +ve charged and the “o” is -ve charged so therefore they form weak bonds known as hydrogen bonds.
   This causes the long polypep. chain to be twisted into a 3D shape, such as a-helix or b-pleated sheets

These hydrogen bonds (several of them formed) provide the strength to hold the protein in its B-pleated sheet or A-helix

Question 6

tertiary structure

Answer 6

1. further folding of the secondary structure
2. to form a unique 3D shape
3. held in place by ionic, disulfide and hydrogen bonds

Question 7

location of bonds in tertiary structure

Answer 7

1. the ionic and disulfide bonds form between the r groups of different aa
   - Ionic bonsds form between any carboxyl group and amino group that were not involved in the formation of peptide bonds
2. disulfide bonds only occur sometimes, as there must be sulfur in the R groups for this bond to occur (S–S)

Question 8

compare ionic, hydrogen and disulphide bonds

Answer 8

1. ionic bonds are WEAKER than disulfide bonds, and easily broken by chnages in pH
2. disulfide bridges = fairly stromg so not easily broken
3. hydrogen= numerous but EASILY broken

Question 9

quaternary

quaternary

Answer 9

a protein made up of more than 1 poypeptide chain

e.g haemoglobin made up of 4 polypeptide chains

Question 10

test for proteins

Answer 10

BUIRET TEST

1. place sample of sol in tt and add an equal vol of NaOH sol to it at room temp
2. add few drops of VERYY dilute (0.05%) COPPER (ii) Sulfate sol + mix gently
3. Purple = presence of peptide bonds, hence presence of protein
   remains blue=no protein