Proteins

Question 1

What elements make up proteins

Answer 1

Carbon hydrogen oxygen nitrogen and sometimes sulphur H

Question 2

How many different naturally occurring amino acids are there

Answer 2

20

Question 3

Protein examples P

Answer 3

Haemoglobins enzymes hormones antibodies

Question 4

Describe general formula for amino acids / backbone for every protein

Answer 4

R group is different for every protein, amine group → NH 2
Carboxylic acid group → Coo H

Question 5

What happens when 2 amino acids undergo-condensation reaction

Answer 5

Polymerisation → dipeptide formed with peptide bond between H of amine group and OH of carboxylic acid group

Question 6

.are amino acids polar

Answer 6

Originally no but h+ ion from hydroxide ion moves to amine group making it polar

Question 7

Primary structure

Answer 7

Order of amino acids in polypeptide chain joined by peptide bonds → type, number + sequence of amino acids linked by peptide chains by condensation reaction

Question 8

Secondary structure

Answer 8

Folding of the primary structure / polypeptide chain to form alpha helix or beta pleated sheet held together by multiple weak hydrogen bonds between peptide bonds of polypeptide chain

Question 9

Tertiary structure → shown by globular protein

Answer 9

Further folding of polypeptide chain to form very specific 3D complex shapes → bonds between R groups, ionic bonds between. - and negative r groups, hydrogen bonds between non-polar groups, hydrophobic interactions between non-polar r groups clustering in middle and disulphide bonds between S in cysteine amino acids in R group (covalent) → in tertiary structure, projecting from amino acid helix are r groups which may interact to form bonds helping maintain tertiary structure

Question 10

Quaternary structure

Answer 10

2 or more polypeptide chains in tertiary form joined together with same bonds as tertiary → only few proteins

Question 11

Note:

Answer 11

In alpha helix (tertiary) r groups project from it and may interact to form bondsto maintain the 3d shape

Question 12

How is a protein’s function determined

Answer 12

By its structure

Question 13

Globular protein examples

Answer 13

Enzymes antibodies hormones haemoglobin

Question 14

Fibrous protein examples

Answer 14

Keratin + collagen → alpha helices linked into strands keratin has secondary and quatemary structure whereas collagen is only quaternary

Question 15

Properties of globular proteins

Answer 15

Soluble, prosthetic group, metabolic role spherical+ compact

Question 16

Properties of fibrous proteins

Answer 16

Insoluble, structural roles, no prosthetic group and forms fibres

Question 17

Describe structure of haemoglobin

Answer 17

4 polypeptide chains,2 alpha and 2 beta, 4 haem groups I each one binds o2 → haem group contains mineral ion

Question 18

Describe. structure of collagen → ,skin bone ligament

Answer 18

3 identical polypeptide chain wound around each other as triple alpha-helix and the polypeptides within the triple helix are bound by hydrogen bands + disulphide covalent bonds hold separate molecules together → chains very close together and every 3rd amino acid is glycene → polypeptides are very close together because glycine is smallest amino acid. And triple helices line up in parallel and crosslink with covalent bonds forming very strong fibres so collagen= very strong

Question 19

Prosthetic groups

Answer 19

Non protein bits that some proteins have in quaternary structure

Question 20

Why could insertion of wrong amino and during protein synthesis lead to an enzyme which doesn’t function

Answer 20

Wrong amino acids → diff primary → diff secondary → diff tertiary → wrong amino acid leads to changes in bonding in tertiary structure so it folds differently and forms different shaped molecule with different shaped active site

Question 20

What happens when enzyme heated to too high temperature

Answer 20

Bonds in tertiary structure break so different parts of protein not held together so active site shape altered so substrates no longer complementary and can’t bind to it so no longer functions

Question 21

How do carrier molecules / proteins specifically recognise the molecule they are supposed to carry

Answer 21

Transport proteins are specific to the thing they transport due to their shape

Question 22

Functional examples at each stage

Answer 22

① primary → none because not functional
② secondary
③tertiary → carrier proteins, enzymes plasma proteins, channel proteins antibodies, lysozymes
④ haemoglobin, keratin, collagen

Question 23

What direction does hydrophobic and hydrophilic interactions face

Answer 23

Hydrophobic interactions → point inwards centre of molecule
Hydrophilic → points outwards

Question 24

Two functions ofproteins

Answer 24

Growth and repair

Question 25

How do R groups interact to determine tertiary structure of protein

Answer 25

Ionic bonds form between oppositely charged r groups,. Hydrophobic r groups in centre of molecule and hydrophilic r groups on outside so in contact with water molecules, hydrogen bonds and disulphide bonds between sulfur or cystine → bonds between r groups determine tertiary structure due to folding

Question 26

What is polymerisation

Answer 26

Process where small molecules called monomers join together to form large molecules called polymers