1.4.1: Proteins

Question 1

describe the general structure of an amino acid

Answer 1

amine group, r group, central carbon atom, hydrogen atom, carboxyl group

Question 2

what is the general formula of an amino acid

Answer 2

NH2CH(R)COOH

Question 3

what is the R group in an amino acid

Answer 3

variable group

Question 4

how many different amino acids are there

Answer 4

20

Question 5

what bond forms when there is a condensation reaction between amino acids

Answer 5

peptide bond

Question 6

what type of reaction occurs between amino acids to form a peptide bond

Answer 6

condensation reaction

Question 7

what molecule is removed and from which parts of the amino acids are they removed from a condensation reaction occurs between two amino acids

Answer 7

water is removed - OH from carboxyl group of one amino acid, H atom from amine group of the other amino acid

Question 8

How can you tell where a polypeptide starts and finishes

Answer 8

start = N terminal (amine group)
end = C terminal (carboxyl group)

Question 9

Describe what the primary structure of a polypeptide/protein is

Answer 9

number, type and sequence of amino acids in polypeptide chain

Question 10

what are the bonds in the primary structure of a protein and where are they

Answer 10

peptide bonds between carboxyl group and amine group

Question 11

Describe what the secondary structure of a polypeptide/protein is

Answer 11

twisting of the primary structure into a regular structure: either alpha helix or beta pleated sheet or both

Question 12

what are the bonds in the secondary structure of a protein and where are they

Answer 12

hydrogen bonds between carboxyl group and amine group

Question 13

Describe what the tertiary structure of a polypeptide/protein is

Answer 13

further folding of the secondary structure into a 3D globular shape

Question 14

what are the bonds in the tertiary structure of a protein and where are they

Answer 14

hydrogen bonds between carboxyl group and amine group
ionic bonds or disulphide bridges between R groups

Question 15

Describe what the quaternary structure of a polypeptide/protein is

Answer 15

functional protein composed of more than one polypeptide that may be secondary or tertiary in structure but not both

Question 16

what two types of structure can fibrous proteins have

Answer 16

1 - one secondary polypeptide - functional protein
2 - multiple secondary polypeptides (quaternary structure) - functional protein

Question 17

what are two structural properties of fibrous proteins

Answer 17

high tensile strength
insoluble

Question 18

give 2 examples of fibrous proteins and their functions

Answer 18

Collagen - connective tissue e.g. ligaments
Keratin - hard tissue e.g. nails, hair, hooves

Question 19

what two types of structure can globular proteins have

Answer 19

1- one tertiary polypeptide - functional protein
2 - multiple tertiary polypeptides (quaternary structure) - functional protein

Question 20

what does the function of a globular protein depend on

Answer 20

function depends on specific 3D shape

Question 21

what are 2 properties of globular proteins

Answer 21

1 - soluble in water as their surface is hydrophilic and centre is hydrophobic
2 - hydrophobic R groups face inwards, hydrophilic R groups face outwards

Question 22

What is a conjugated protein and give an example

Answer 22

protein with non polypeptide group e.g. haemoglobin has a haem group

Question 23

what happens if you change the primary structure of an amino acid

Answer 23

a non functioning protein is produced

Question 24

what happens when a protein is denatured

Answer 24

change in shape - bonds breaking

Question 25

what are 2 causes of a protein denaturing and state the bonds that break

Answer 25

high temperature - H bonds break extreme pH - ionic bonds break

Question 26

what is the impact on fibrous proteins if it is denatured

Answer 26

lose structural strength

Question 27

what is the impact on globular proteins if it is denatured

Answer 27

become inactive / insoluble