Protein Structure & Function

Question 1

What is the Hierarchy of protein structure in the following : A B C D

Answer 1

RIMARY STRUCTURE (A) linear sequence (order) of amino acid residues, joined by peptide bonds

SECONDARY STRUCTURE (B) the localised conformation of the polypeptide backbone e.g. α helix or β sheet

TERTIARY STRUCTURE (C) the 3-dimensional structure of an entire polypeptide, including all its side chains

QUATERNARY STRUCTURE (D) the spatial arrangement of polypeptide chains in a protein with multiple subunits

Question 2

In the Secondary structures arrangemet of polypeptide chains what is the bond and what is the bond between

Answer 2

• It is determined by hydrogen bonds between….

the carbonyl oxygen group of one peptide bond and the amide hydrogen

Question 3

What are the 2 types of proteins with tertiary structures?

Answer 3

FIBROUS PROTEINS e.g. collagen, fibroin, keratin

GLOBULAR PROTEINS e.g. albumin, myoglobin, haemoglobin

Question 4

0What are Quaternary Structure (e.g. Haemoglobin) held together by?

Answer 4

Generally held together by:

Electrostatic interactions

Hydrogen bonds

Hydrophobic interactions

Question 5

What are Haemoglobin properties?

Answer 5

Haemoglobin:

• transports oxygen in the blood
• 4 subunits (tetramer)
• 2α and 2β chains (not to be confused with α helix and β sheet)
• each contains a Haem group
• each subunit can bind one O2

Question 6

What are Examples of physical conditions or chemical agent(s) that can denature protein structure:

Answer 6

• heat
• extremes of pH
• DETERGENTS, UREA, GUANIDINE HYDROCHLORIDE
• THIOL AGENTS, REDUCING AGENTS

Question 7

What are the 7 types of protein modifications?

Answer 7

1. Glycosylation
2. Proteolytic cleavage
3. Formation of disulphide bonds
4. Phosphorylation
5. Addition of fatty acids (acylation)
6. Acetylation
7. Ubiquitination

Question 8

What are the 3 main groups of glycoproteins?

Answer 8

PROTEOGLYCANS –the carbohydrate component is the largest constituent by weight

GLYCOPROTEINS – the protein component is the largest constituent by weight

MUCINS – predominantly carbohydrate

Question 9

What is insulin synthesised by?

Answer 9

Insulin is synthesised and secreted by the pancreatic β cells

Question 10

What is Phosphorylation?

Answer 10

Addition of a PHOSPHATE group to Serine, Threonine, Tyrosine residues

Very important in Cell Signalling events and the Cell Cycle

Question 11

Processes Regulated by Protein Degradation:

Answer 11

Gene Transcription

Cell Cycle Progression

Organ formation

Inflammatory Responses

Tumour Suppression

Cholesterol Metabolism

Antigen Processing