Enzymes

Question 0

Properties of enzymes

Answer 0

• Biological catalysts that speed up reactions by lowering energy required
• made of proteins
• specific
• not used up during reaction
• require optimum conditions at which they work best

Question 1

Enzymes control what?

Answer 1

Almost every metabolic reaction in living organisms

Question 2

Metabolism

Answer 2

Sum of all chemical reactions that occur in a cell

Question 3

Reactants

Answer 3

Substances that participate in a reaction

Question 4

Substrates

Answer 4

Reactants that bind to an enzyme

Question 5

Products

Answer 5

Form as a result of a reaction

Question 6

Metabolic pathways

Answer 6

Consist of chains of complex chemical reactions assisted by enzymes

Question 7

Energy of activation

Answer 7

• Amount of energy needed to cause a reaction

- enzymes allow reactions to happen at much lower EA

Question 8

Enzyme substrate complex

Answer 8

1. Substances attach to active site
2. Enzyme & substrate fit together like a LOCK & KEY
3. Enzyme holds substances at proper angle for them to react
4. Enzymes can be reused after

Question 9

Degradation (hydrolysis)

Answer 9

1 substrate becomes 2 products

Question 10

Synthesis (condensation)

Answer 10

2 substrates become 1 product

Question 11

Induced-fit model

Answer 11

• bit different from lock & key
• enzyme active site undergoes small change in shape to fit substrate to help reactions occur
• after rxn, active site returns to original shape

Question 12

Cofactors

Answer 12

Must bind to enzyme before the substrate can bind to enzyme

- enzymes that require cofactors are inactive without them

Question 13

Coenzymes

Answer 13

Organic molecules that function as cofactors

- ex. vitamins

Question 14

Temperature effects on rate of reaction

Answer 14

• low: molecules move slowly, few hit enzyme or have enough energy to react - slows reaction rate
• optimal: substrate meters enzyme & has enough energy to react
• high: enzyme denatures and active site can’t accept substrate - slows rxn

Question 15

pH effects on rate of reaction

Answer 15

• low or high: affects bonds within enzyme, change structure & active site, no binding - slow
• optimal: enzymes have specific pH where their bonds aren’t affected

Question 16

Increased Substrate concentration

Answer 16

• more collision with enzymes, active sites fill up -> more products = fast rxn rate
• max rate of rxn reached once enzyme sites are occupied continuously with substrate

Question 17

Enzyme concentration

Answer 17

• Cells regulate rxn rate by regulating enzyme concentration -> high concentration = high rxn rate
• genes turned on & off to regulate enzyme concentration

Question 18

Phosphorylation

Answer 18

When enzymes require a phosphate group to be activated

Question 19

Inhibition

Answer 19

Enzyme is prevented from binding to substrate

Question 20

Competitive inhibition

Answer 20

• competitor molecule shaped similar to substrate
• binds to active site but can’t react & doesn’t leave
• May permanently disable enzymes
• ex poisons …cyanide

Question 21

Non-competitive inhibition

Answer 21

• binds at a site other than active site -> denatures enzyme

- often heavy metals… Lead, mercury, cadmium, etc