Lesson 9.2 - Types of proteins

Question 1

What are the two types of proteins?

Answer 1

Globular and fibrous

Question 2

Features of globular proteins?

Answer 2

• Soluble in water
• Compact
• Spherical shape roughly

Question 3

When are globular proteins formed?

Answer 3

When the protein folds into its tertiary structure.
- Hydrophobic R-groups in amino acids are kept away from the aqueous environment.
- Hydrophilic R-groups in amino acids are on the surface of proteins.

Question 4

Why are globular proteins soluble in water?

Answer 4

Hydrophilic amino acids on the surface of the protein.

Question 5

Why is it important for globular proteins to be soluble in water for their function?

Answer 5

• Chemical reactions
• Immunity
• Contraction

Question 6

Examples of globular proteins?

Answer 6

• Insulin
• Haemoglobin
• Catalase

Question 7

What is insulin?

Answer 7

A globular protein. It is the hormone involved in the regulation of blood glucose concentration.

Question 8

Why is it important that insulin is soluble?

Answer 8

Transported in the bloodstream

Question 9

Structure of insulin?

Answer 9

Have to fit to specific receptors on cell-surface membranes to have effect. Precise shapes.

Question 10

Conjugated proteins?

Answer 10

Type of globular protein. Contains non-protein component called a prosthetic group.

Question 11

Name of proteins without prosthetic groups?

Answer 11

Simple proteins

Question 12

Types of prosthetic groups:

Answer 12

• Lipids can combine with proteins to form lipoproteins
• Carbohydrates can combine with proteins to form glycoproteins
• Metal ions
• Molecules derived from vitamins

Question 13

Examples of globular conjugated proteins that contain haem prosthetic group?

Answer 13

• Haemoglobin
• Catalase

Question 14

What is haemoglobin?

Answer 14

Red, oxygen carrying pigment found in red blood cells.

Question 15

Structure of haemoglobin?

Answer 15

Quaternary protein made from 4 polypeptides (2 alpha and 2 beta subunits).

Each subunit contains a prosthetic haem group.

Question 16

Purpose of prosthetic haem group in haemoglobin?

Answer 16

Iron II (Fe2+) ion found in each haem group. Each can combine reversibly with an O2 molecule.

This enables haemoglobin to transport oxygen around the body.

Question 17

What is catalase?

Answer 17

Enzyme that catalyses (increases the rate of reaction) for the break down of hydrogen peroxide.

Question 18

Structure of catalase?

Answer 18

Quaternary structure containing 4 haem prosthetic groups.

Question 19

Purpose of haem prosthetic groups in catalase?

Answer 19

Iron II ions allows catalase to interact with hydrogen peroxide and speed breakdown.

Question 20

Why should hydrogen peroxide be removed from the body?

Answer 20

Common by-product of metabolism. Damaging to cells and cell components when accumulates.