Proteins

Question 1

What are proteins made of ?

Answer 1

They are made of the monomers called amino acids which join together to form/the polymer protein

Question 2

Describe the structure of an amino acid

Answer 2

It has a central carbon that is bonded with 4 groups being
A carboxyl group on the right hand side-COOH
A amino group on the left hand side - H2N
A variable group below the central carbon - R
A hydrogen above the central carbon - H

Question 3

How is a dipeptide formed?

Answer 3

Amino acids are joined together through a condensation reaction between the hydrogen and the OH group eliminating water . This forms a peptide bond between the 2 amino acids

Question 4

What happens at the primary structural level?

Answer 4

Amino acids are in a polypeptide chain

Question 5

What happens at the secondary structural level?

Answer 5

The polypeptide chain twists/coils to form an alpha helix in one section , in another section is folds to form a beta pleated sheet. These are held in place by hydrogen bonds

Question 6

What happens at the tertiary structural level?

Answer 6

Further folding of the protein forming in a 3D structure with a unique shape . Held in place by different bonds ( hydrogen , ionic , disulphide ,hydrophobic/Phillic bonds)

Question 7

What happens at the quaternary structural level?

Answer 7

Polypeptide chains bond together forming things like haemoglobin

Question 8

Describe Hydrophobic and hydrophilic interactions

Answer 8

weak interactions between polar and non polar r groups . Proteins are in an aq environment of the cytoplasm so the way they fold depends on heir properties , hydrophilic will be on the outside of the protein and hydrophobic will be on the inside shielded

Question 9

Strength of hydrogen bonds

Answer 9

Weak bonds that can be broken by temperature of ph

Question 10

Ionic bonds

Answer 10

Stronger than hydrogen bonds and form between oppositely charged r groups

Question 11

Disulphide bonds/ bridges

Answer 11

There are covenant bonds formed between an r group with 2 sulphur atoms meaning they are the strongest bonds

Question 12

What are the 2 types of proteins?

Answer 12

Globular portions and fibrous proteins

Question 13

Describe the structure of a globular protein

Answer 13

These are proteins whose molecules curl up into a ball/ spherical shape.
• They curl up so that their non-polar (hydrophobic) groups are in the centre while the hydrophilic groups are on the outside. This always them to be soluble in water

Question 14

Example of a globular protein

Answer 14

Insulin which is involved in the regulation of blood glucose concentration

Question 15

An example of a quaternary protein

Answer 15

Haemoglobin is a red oxygen carrying pigment found in red blood cells made of 4 polypeptide chains

Question 16

Describe the structure of fibrous proteins

Answer 16

Their molecules do not curl into a ball shape. ( no 3D structure )
. Instead they form long strands
• They are not soluble in water
• Their role is mostly structural

Question 17

3 examples of fibrous proteins

Answer 17

Keratin
Elastin
Collagen

Question 18

What is keratins properties

Answer 18

They are present in hair, skin and nails.
Strong disulphide bonds forming strong inflexible and insoluble materials

Question 19

Properties of elastin

Answer 19

Found in elastic fibres present in the walls of blood vessels and alveoli . They give flexibility to expand when needed

Question 20

Properties of collagen

Answer 20

Connective tissue found in skin and ligaments which has some flexibility

Question 21

What happens when a protein denatures

Answer 21

The bonds that hold the tertiary structure in place break , losing their unique shape going back to its secondary structure

Question 22

What is the importance of the primary level

Answer 22

If the aminos acids sequence are different it will cause one of the 4 bonds to bond in a different place resulting in a different 3D shape which changes it active site