Enzymes

Question 1

what is activation energy and why is it lowered by enzymes?

Answer 1

• activation energy is the energy needed to get reactants ready to react
• lowering activation energy allows for reaction to occur more readily

Question 2

what are enzymes and how are they denatured?

Answer 2

• biological molecules that speed up chemical reactions without getting used themselves
• can be denatured or altered in shape by heating, pH change, salinity etc

Question 3

what is the difference between exergonic and endergonic reactions?

Answer 3

exergonic reactions release net energy and endergonic reactions require (absorb) net energy

Question 4

what is the active site?

Answer 4

a pocket or grove on the enzyme where catalysis occurs

Question 5

describe the lock and key and induced fit model

Answer 5

• lock and key: the enzyme and substrate(s) fit together like puzzle pieces and their shapes are fixed
• induced fit: enzyme shape changes slightly after the substrate bins or as it nears, brings chemical groups together

Question 6

outline the effects of temperature, pH, and substrate concentration on enzyme activity

Answer 6

• increase in temp = increase in enzyme activity because collisions on active site are more frequent with more energy
• eventually a temp is reached and enzyme denatured, activity drops
• pH is similar, more even up and down
• different amino acids have different properties and change with pH
• substrate concentration increase = plateaus as active site filled up

Question 7

describe competitive and non competitive inhibitors with examples

Answer 7

Competitive:
- shape is similar to substrate shape, fit into active site and block substrate
Ex: cyanide, viagra
Non-competitive
- bind to allosteric site (different site) changing shape of active site
- Ex: strychnine, penecilin

Question 8

what is allosteric regulation?

Answer 8

• occurs when function of a protein at one site (active) is affected by the binding of a molecule at another site (allosteric)
• can be inhibitory or stimulating
• end-product inhibition: occurs when one of the products of a metabolic pathway actually inhibits and earlier enzyme in the pathway, usually binding to allosteric site