Globular and fibrous proteins

Question 1

what is a fibrous protein

Answer 1

Long ,thin, Regular and repetitive sequence of amino acids, usually insoluble in water

Question 2

what is a globular protein

Answer 2

tend to roll up into a spherical shape, usually soluble in water.

Question 3

what role does fibrous proteins usually have in organisms and why

Answer 3

Structural role- repetitive structure of amino acids.
Insoluble in water
Long and thin

Question 4

How does the solubility of globular proteins ensure their role in an organism

Answer 4

Globular proteins have a Metabolic role in organisms due them being soluble in water

the hydrophobic R group is turned inwards whilst the hydrophilic parts of the amino acid are on the outside

The solubility allows them to be easily transported around organisms

Question 5

How is the shape of a fibrous protein different to a globular protein

Answer 5

Fibrous- Long and Thin
Globular- Spherically shaped

Question 6

What is the function of Collagen.
Give an example

Answer 6

Function- to provide mechanical strength
E.G- In artery walls to prevent bursting
E.G- Bones
E.G- Cartilage

Question 7

what are three examples of Fibrous proteins

Answer 7

Keratin
Collagen
Elastin

Question 8

The function of Keratin is to make molecules hard and strong to provide Protection, what features of Keratin allow it to perform its role

Answer 8

Keratin has lots of cysteine which means it has disulphide bridges and Hydrogen bonding in its polypeptide chains.

Question 9

How does Keratin provide protection from infection

Answer 9

Keratin is also waterproof, creates an impermeable barrier to water-borne pollutants or pathogens

Question 10

What is the function of Elastin

Answer 10

Allows stretch and recoil or adaptations of shapes

Question 11

How does elastin allow things to stretch

Answer 11

Due to cross linking and coiling allows Elastin to be extensible

Question 12

What parts of our body have Elastin

Answer 12

Lungs- allow inflation and deflation
Skin- stretches around bones

Question 13

What 4 polypeptide chains make up the quaternary structure of haemoglobin

Answer 13

2X a-globin chains
2X b-globin chains
Each of these chains have their own tertiary structure providing a very specific shape.

Question 14

What is the prosthetic group used in haemoglobin

Answer 14

A Haem group- containing an iron ion.

-oxygen binds to the iron ion in haemoglobin

Question 15

What is the name given to a protein with a prosthetic group

Answer 15

Conjugated protein
E.G Haemoglobin (Globular protein)

Question 16

Insulin is a Globular protein, it consists of two polypeptide chains.
Describe these 2 polypeptide chains

Answer 16

• Polypeptide chain A: Begins with a section of alpha-helix
  has 21 amino acid residues

-Polypeptide chain B: ends with a section of Beta-pleated sheet
has 30 amino acids

Question 17

Are haemoglobin and Insulin soluble in water

Answer 17

yes they are, due to hydrophilic R groups on the outside of the molecule .

Question 18

Pepsin is a globular protein. How many polypeptide chains make up Pepsin

Answer 18

One
Pepsin consists of one singular polypeptide chain which folds into a tertiary structure

Question 19

Relating to R groups, how is pepsin so stable in acidic environments

Answer 19

Pepsin has a lot more acidic R groups than basic R groups which will accept H+ ions.

Question 20

What bonds are used in a pepsin enzymes

Answer 20

Peptide
Hydrogen
Disulfide bridges

Question 21

Ab initio protein modelling and Comparative protein modelling are both ways scientists can predict protein shape.
What are the differences between the two

Answer 21

Ab initio protein modelling-
model based off electrical properties in atoms in each amino acid.

Comparative protein modelling-
Protein threading, scans the amino acid sequence and gives possible models which match the sequence