Proteins and Enzymes

Question 1

What is a protein?

Answer 1

A polymer made up of many amino acids joined by peptide bonds

Question 2

What is an amino acid?

Answer 2

The monomers from which proteins are made

Question 3

What is the generic structure of an amino acid?

Answer 3

1. An amine Group (NH2)
2. A Carboxyl group
3. A Hydrogen
4. An R Group

Question 4

What is primary structure?

Answer 4

The sequence of amino acids in the polypeptide chain

Question 5

What is secondary structure?

Answer 5

The long chains of amino acids fold into regions (within the tertiary structure) with repeating patterns

Question 6

What is tertiary structure?

Answer 6

The final 3d resting shape of the protein

Question 7

What is quaternary structure?

Answer 7

The final 3D resting shape of a protein made from more than one polypeptide chain

Question 8

What is an enzyme?

Answer 8

Biological catalysts that increase the rate of reaction by lowering the activation energy

Question 9

What is an active site?

Answer 9

The region of an enzyme where a complementary substrate can bind to form an enzyme-substrate compex

Question 10

What is a metabolic pathway?

Answer 10

A series of enzyme catalysed reactions where the product of one reaction is the reactant in the next reaction

Question 11

What is the lock and key model?

Answer 11

1. Shape of the active site is fixed to a specific shape
2. Active site is complementary to the substrate before, during and after it forms an enzyme substrate complex

Question 12

What is the induced fit theory?

Answer 12

1. Active site and substrate are not complementary before the enzyme-substrate complex is formed
2. Active site changes shape to fit more closely around the substrate to become complementary
3. Forming an enzyme substrate complex strains the bonds in the substrate causing them to form or break

Question 13

What are some factors that effect enzyme catalysed reactions?

Answer 13

1. Temperature
2. p.H (acidity)
3. Enzyme concentration
4. Substrate Concentration
5. Inhibitors

Question 14

What does denatured mean?

Answer 14

A permanent change to the active site which means no more E-S complexes are formed

Question 15

How does temperature effect enzyme catalysed reactions?

Answer 15

1. As temp increases the molecules vibrate more
   - more collisions
   - higher %change of collisions
   -More E-S complexes formed
2. At the optimum temperature/higher
   - molecules vibrate and break internal bonds (ionic and disulphide bridges)
   - Changes the shape of the active site
   -No E-S complexes formed as enzymes are denatured

Question 16

How does pH affect enzyme activity?

Answer 16

1. The OH- or H+ will interact with the Hydrogen bonds or ionic bonds
2. Changes the shape of the tertiary structure
3. Changes the shape of the active site
4. Fewer/No E-S complexes are formed
5. The enzyme is denatured

Question 17

What happens to enzyme catalysed reactions as enzyme concentration increases?

Answer 17

1. The rate increases in a positive correlation
2. As there are more successful collisions
3. More enzyme-substrate complexes form

Question 18

What happens as substrate concentration increases?

Answer 18

1. The R.o.R increases in a positive correlation
2. More successful collisions between enzyme and substrate
3. More enzyme substrate complexes are formed, until all active sites are occupied
   -the enzyme conc is now the limiting factor

Question 19

How do competitive inhibitors work?

Answer 19

1. Competitive inhibitors are of a similar shape to the substrate
2. They can also bind to the active site which prevents the formation of E-S complexes

Question 20

How do non-competitive inhibitors work?

Answer 20

1. Non-Competitive inhibitors bind to another region of the enzyme other than the active site
2. This changes the shape of the Active SIte
3. No more E-S complexes are formed
4. Changing the concentration of substrate wont make any difference