2) Unit 1 - Protein Structure

Question 1

What 2 groups are included in amino acids

Answer 1

amino group

carboxyl group

Question 2

what possible characteristics can amino acids have

Answer 2

amino acids may be:

• negative (acidic)
• positive (basic)
• polar
• non polar

Question 3

How are peptide bonds formed between amino acids

Answer 3

dehydration reaction due to the interaction between the amino group of one amino acids and the carboxyl group of the next

Question 4

List the different types of protein structures

Answer 4

• primary
• secondary
• tertiary
• quaternary

Question 5

describe the primary structure of a protein

Answer 5

the sequence of amino acids to make the polypeptide chain

Question 6

Describe how the secondary structure of a protein is formed

Answer 6

formed when some amino acids along a polypeptide chain interact with each other and form hydrogen bonds

Question 7

Name and describe the 2 types of secondary structures

Answer 7

alpha helix:
spiral with r groups sticking out

beta sheet:
•parts of a chain running along side each other forming a sheet.
•R groups sit above and below.
•Can be parallel or anti-parallel

Question 8

describe parallel and anti parallel beta sheets

Answer 8

Parallel:
chains run in the same direction

Anti parallel:
chain runs in opposite directions

Question 9

Describe the tertiary structure of a protein

Answer 9

• overall folding of the polypeptide.
• It occurs due to different interaction between the R groups of the amino acid
• this causes conformational change of the protein

Question 10

List the different interaction that can occur between R groups to form the tertiary structure

Answer 10

• hydrophobic/hydrophillic
• ionic bonds
• hydrogen bonds
• disulfide bridges
• van der waals

Question 11

describe hydrophobic/hydrophillic interactions

Answer 11

• hydrophobic R groups will cluster to the internal parts of the protein
• hydrophillic R groups will moce to the surface of the protein
• protein may take on a globular structure

Question 12

describe ionic bonds

Answer 12

•atoms are oppositely charged and therefore held by an electrostatic attraction

Question 13

describe hydrogen bonds

Answer 13

• occurs when there is a significant difference in elecronegativity of atoms
• they are held by the attraction between H and an electronegative atom such as N, O, F

Question 14

describe disulphide bridges

Answer 14

•covalent bond between two thiol (SH) groups

Question 15

describe van der waals

Answer 15

• temporary uneven distribution of electrons in atoms causing them to become slightly positive or negative
• may result in attraction or repulsion between atoms, therefore causing conformational change of the protein

Question 16

Give an example when a (non-protein) prosthetic group gave added function to a protein

Answer 16

heme in haemoglobin contains iron, which allows oxygen to bind and be transported around the body.

Question 17

what is a Quaternary structure and give an example of one

Answer 17

when several tertiary are joined together. These subunits are held together by all the same interactions as tertiary structure R groups.

example:
hemoglobin

Question 18

name the 3 types and give an example of Quaternary structures

Answer 18

• globular - hormones
• fibrous - keration
• immunoglobulin - antibodies

Question 19

explain why a change in pH would change the conformation of a protein

Answer 19

• changes in pH affect the H+ and OH- ions in a solution
• this may change the charges on the R groups therefore placing stress on bonds
• positive and negative interactions are particularly susceptible e.g hydrogen, ionic

Question 20

explain why a change in temperature would change the conformation of a protein

Answer 20

• increasing temperature increases the kinetic energy of atoms
• this causes them to move more placing stress on bonds
• the weaker inter-molecular bonds are particularly susceptible e.g. van der waals, hydorgen