protein structure

Question 1

state them and describe what the different levels of protein structure are

Answer 1

primary, sequence of amino acids
secondary, polypeptide backbone
tertiary,3D structure of polypeptide(including side chains)
quarternary, arrangement of protein subunits

Question 2

name the 3 types of secondary structure in proteins

Answer 2

alpha helix, beta sheets, triple helix

Question 3

describe the structure of an alpha helix

Answer 3

rod-like, one polypeptide chain, CO of one amino acid H bonds to NH of nearby amino acid

Question 4

describe the structure of beta sheets

Answer 4

polypeptide backbone almost fully extended, can involve more than 1 chain, can go anti and parallel, turns between strands, repeated zigzag structure

Question 5

describe the structure of a triple helix, found in collagen

Answer 5

3 left-handed chains twisted around each other to form a right handed superhelix, contains inter-chain H bonds as well as covalent inter and intra-molecular bonds

Question 6

describe the functions of collagen

Answer 6

is found in bone and connective tissue, influencing their strength

Question 7

what is the tertiary structure of a protein and what 2 types of protein arise from the tertiary structure

Answer 7

tertiary structure is the arrangement of all atoms of polypeptide in 3D space
can be fibrous proteins or globular

Question 8

describe the structure of fibrous proteins and give 2 examples

Answer 8

polypeptide chains organised roughly parallel, consist of long fibres or large sheets, usually strong, insoluble
examples = keratin (hair), collagen(connective tissue)

Question 9

describe the structure of globular proteins and give 2 examples

Answer 9

protein folded to a more or less spherical shape, usually soluble in water, polar side chains outside facing with hydrophobic in facing, usually have lots of alpha helixes and beta sheets
examples = myoglobin and haemoglobin

Question 10

state the forces that stabilise the tertiary structure of the protein

Answer 10

covalent disulphide bonds, electrostatic interactions(salt bridges), hydrophobic interactions, H bonds

Question 11

describe what the electrostatic bonds in proteins are

Answer 11

the attraction between the positive and negative charges, creates salt bridges

Question 12

describe what hydrophobic interactions in proteins are

Answer 12

the attraction between hydrophobic side-chains (van der Waal’s), weak individually but have strong organising influence when clustered together in centre of globular proteins

Question 13

what types of chemical agents or physical condition can effect the protein structure(cause denaturation)

Answer 13

heat, causes increases vibrations of bonds
extremes of pH, interferes with electrostatic interactions
reducing agents, reduce and disrupt disulphide bonds

Question 14

describe the quaternary structure of a protein and give an example

Answer 14

proteins that have more than one polypeptide chain can create subunits, between 2 and 12, which can be identical or different
for example haemoglobin has 4 subunits