enzymes

Question 1

What are enzymes?

Answer 1

Globular proteins that have a tertiary structure.
They are synthesized by living cells and can act inside the cell (intercellular) or be secreted by cells (extracellular)
Biological catalyst

Question 2

What is an active site?

Answer 2

The site that is created by the 3D shape of the enzyme where only a specific substrate molecule fits and binds to.

Question 3

What is the active site determined by?

Answer 3

The sequence of amino acids in the polypeptide: is the sequence changes so does the active site and the substrate will not bind to the active site bc they are no longer complementary

Question 4

How do enzymes work?

Answer 4

1. Substrate and enzyme will collide successfully. Substrate will fit and bind to active site by interactions with R groups/polar atoms of the amino acids that make up active site to form ENZYME - SUBSTRATE COMPLEX
2. Ability of R groups and substrate form bonds affected by temp and pH
3. Bonds in substrate are distorted - puts strain on bonds that are going to be broken and increase chance they will break
4. Breaking bonds brings new atoms in substrate closer together and new bonds form
5. Energy is needed for reaction to take place called ACTIVATION ENERGY
6. Enzyme substrate reaction forms - activation energy needed for reaction is reduced - reaction takes place faster - enzyme acts as biological catalyst

Question 5

Describe the lock and key hypothesis

Answer 5

The active site in the enzyme is a lock into which only one substrate molecule can fit like a key.
Substrate must be complementary
- active site is a fixed shape = substrate must collide in correct orientation to form bonds
- when substrate binds enzyme chemical changes take place + substrate molecules are either digested or combined to form new products
- ENZYME IS NOT AFFECTED BY REACTION AND CAN BE REUSED

Question 6

Define anabolism

Answer 6

2 substrate molecules are combined to form a single product molecule

Question 7

Define catabolism

Answer 7

Breaking down complex substrate molecules into 2 or more product molecules

Question 8

Describe the induced fit theory

Answer 8

• as substrate molecule enters active site, forces of attraction between substance + R groups of the amino acids are formed
• this causes shape of active site to change and stronger bonds are formed with substrate
• this weakens bonds in substrate which lowers activation energy of reaction
• when products are released from substrate the active site returns to original shape
  ENZYME IS NOT AFFECT BY REACTION AND CAN BE REUSED

Question 9

What are similarities and differences between the 2 enzyme theories?

Answer 9

Differences
1. induced fit - active site can change shape to improve the bonding to substrate
lock and key - active site is a fixed shape
Similarities
1. substrates bond to the enzyme

Question 10

How does changes in pH affect bonds?

Answer 10

Amino acids both contain basic and acidic groups.
changes in pH can change the bonding between these groups therefore causing changes to secondary and tertiary structure of a protein

Question 11

How does the enzyme denature?

Answer 11

if bonds are not formed then the enzyme may not be able to lower activation energy and denatures

Question 12

How does temperature affect enzymes?

Answer 12

as Temp increases particles gain kinetic energy.
enzyme and substrate will have more kinetic energy so there are more successful collisions therefore more enzyme - substrate complexes formed and rate of reaction increases

Question 13

How does an INCREASE in temperature change enzymes?

Answer 13

Increased heat gives more energy to particles.
Bonds in enzymes begin to vibrate and break - weak hydrogen bonds are broken first
Loss in secondary and tertiary structure means shape of active site changes and active site no longer forms bonds with substrate
- enzyme has fully denatured