5. Proteins and enzymes

Question 1

What is the reverse of a condensation reaction?

Answer 1

A hydrolysis reaction which result in the breakdown of polymers into their component monomers

Question 2

What are some examples of the function of proteins?

Answer 2

• Enzymes (direct reactions)
• Structure and movement (cytoskeleton and connective tissues)
• Regulation (hormones)
• Defence

Question 3

What is the structure of an amino acid?

Answer 3

Each amino acid has both a carboxyl function group and an amino functional group attached to the same carbon atom called the alpha carbon.
Also attached to the alpha carbon atom are a hydrogen atom and a side chain or R group

Question 4

What are the special properties given by R groups?

Answer 4

• Some are polar but uncharged (hydrophilic)
• Some are charged (hydrophilic)
• Some are non-polar (hydrophobic)
• Some form rings
• Some have special properties (forming disulphide bonds)

Question 5

What is the primary structure?

Answer 5

The precise sequence of amino acids in a polypeptide chain held together by peptide bonds.

Question 6

What is the secondary structure of a protein?

Answer 6

The conformation changes in primary structures due to the formation of electrostatic and hydrogen bonds between nearby amino acids.

Question 7

What is the tertiary structure of a protein?

Answer 7

The ultimate configuration that a polypeptide chain takes in reaching the configuration of minimal free energy

Question 8

What are some of the interactions seen in the tertiary structure?

Answer 8

• Covalent disulphide bridges between specific cysteine side chains
• Hydrogen bonds between side chains
• Hydrophobic side chains aggregate together in the interior of the protein had together by dispersion forces
• Ionic attractions between positively and negatively charged side chains forming salt bridges

Question 9

What is the quaternary structure of a protein?

Answer 9

Association of the individual polypeptide chains in proteins composed of multiple polypeptides

Question 10

What is denaturation?

Answer 10

When the tertiary and secondary structure of a protein is disrupted and the biological functions of the protein are destroyed

Question 11

What is renaturation?

Answer 11

Reassembly into a functional protein

Question 12

What are anabolic reactions?

Answer 12

Reactions that link simple molecules to form more complex molecules. They require an input on energy

Question 13

What are catabolic reactions?

Answer 13

These break down complex molecules into simpler ones and release the energy stored in the chemical bonds.

Question 14

What are the 5 different types of regulation?

Answer 14

Inhibitors (competitive)
Inhibitors (non competitive)
Allosteric inhibitors (negative modulators)
Allosteric cooperatively (positive modulators)
Feedback loops

Question 15

What is a competitive inhibitor?

Answer 15

• have similar shape to the usual substrate for the enzyme and compete with the substrate for the active site. Competitors bind temporarily with the the active site
• the complex does not react further to form products
• it can be reversed by increasing substrate concentration so the substrate can outcompete the inhibitor

Question 16

What is a non-competitive inhibitor?

Answer 16

It binds to an enzyme at a site distinct from the active site. This binding causes a change in the shape of the enzyme that alters its activity. This is reversible.

Question 17

What is allosteric regulation?

Answer 17

This occurs when an effector molecule binds to a site other than the active site of an enzyme inducing the enzyme to change its shape.