Nucleic acids and proteins

Question 1

Define a protein

Answer 1

Proteins are biomacromolecules built of amino acid subunits and linked by peptide bonds to form a polypeptide chain.

Question 2

Define a polymer

Answer 2

Large molecules made of identical or similar single units

Question 3

Define a monomer

Answer 3

Small sub-units of the large unit of cells (polymer)

Question 4

What is the main function of proteins?

Answer 4

Controls metabolic processes in the cell.

Question 5

What are the main elements that proteins contain?

Answer 5

1. Nitrogen
2. Oxygen
3. Carbon
4. Sulfur (smaller quantities)
5. Phosphurous (small quantities)

Question 6

What is an amino acid?

Answer 6

Monomer of proteins

Question 7

How many amino acids do we have in our bodies?

Answer 7

20 different amino acids

Question 8

Draw the general formula of an amino acid

Answer 8

R
            |
NH2 - C - COOH 
            |
           H

Question 9

What is the name given to the NH2 group and R group respectively?

Answer 9

Amine group and R group

Question 10

What is the importance of the R group?

Answer 10

The R group is variable, so different amino acids have different R groups. Thus, the R group is important as it produces variation within amino acids and thus different functioning etc. (remember all other parts, excluding the R group is identical)

Question 11

What should you look for when determining an amino acid?

Answer 11

R group and Nitrogen element

Question 12

When two amino acids join, what does it form? What about three?

Answer 12

Dipeptide and a tripeptide

Question 13

What joins amino acids

Answer 13

peptide bonds

Question 14

Why is the structure of a protein important?

Answer 14

Allows it to perform its particular role and function.

Question 15

How many levels of organisation do proteins have?

Answer 15

4

Question 16

Why is the structure/shape of a protein important?

Answer 16

Allows it to perform its particular role and function. If a protein’s shape is changed, it can no longer function. If the shape is permanently it is

Question 17

SECONDARY STRUCTURE

1. Define
2. Describe the structure

Answer 17

1. Hydrogen bonds between neighbouring peptide groups result in the localised coiling and folding of segments of the polypeptide chain to help stabilise a 3D shape.
2. Have 3 distinct structures
   ALPHA HELIX: protein chain is loosely coiled and is held by h-bonds
   BETA PLEATED SHEETS: chains are folded so they lie alongside each other, where folded chains are again held by h-bonds.
   RANDOM COILING: proteins do not conform to either an ALPHA HELIX or BETA PLEATED STRUCTURE.

Question 18

TERTIARY STRUCTURE

1. Define
2. Describe the structure

Answer 18

1. Total irregular folding held together by ionic or h-bonds to form a complex shape.
2. 3D structure due to global coiling and folding which becomes critical for the protein’s functioning.
   Bonds important:
3. Ionic bonds
   2.Covalent disulfide bonds
   3.H-bonds
   4.Hydrophobic interactions.

Question 19

QUATERNARY STRUCTURE

1. Define
2. Describe the structure

Answer 19

1/2. occurs in proteins with multiple polypeptide chains which are joined by the same 4 interactions in the tertiary stage to form the final protein.

• associate with non-proteic groups
• either globular or fibrous

Question 20

Define denaturation

Answer 20

the loss of the 3D structure and usually also the biological function of a protein, which is often but not always permanent.

Question 21

Factors affecting denaturation

Answer 21

1. Heavy metals: disrupt ionic bonds, reduce protein charge
2. Strong acids and alkalies: disrupt ionic bonds
3. Heat and radiation: disrupt bonds in proteins through increased energy provided to the atoms
4. Detergents and solvents: form bonds with non-polar groups in the protein, disrupting h-bonds
5. pH