Week 6: Enzymes

Question 1

What are enzymes?

Answer 1

Protein molecules which act as biological catalysts.

Question 2

Enzymes have a specific region on their surface, called?

Answer 2

an active site

Question 3

The active site has a shape that is complementary to the shape of the?

Answer 3

Reactants/substrates that the enzyme catalyses

Question 4

Enzymes are not consumed in their reaction, therefore…

Answer 4

they can be used over and over again.

Question 5

Most enzymes work inside cells. Why?

Answer 5

This is the site of cell metabolism

Question 6

All reactions involve the breaking of bonds, as well as?

Answer 6

The reforming of bonds

Question 7

Enzymes aid in the breaking/reforming of bonds by…

Answer 7

lowering the amount of energy needed for the reaction

Question 8

How do enzymes lower activation energy?

Answer 8

The substrate binds to the active site of the enzyme by weak bonds, forming an enzyme-substrate complex

• Active site changes slightly to form an exact fit
• Bonds are subjected to pressure which reduces energy and increases likelyhood of reaction
• The product forms and breaks away from the enzyme

Question 9

The specificity of an enzyme is caused by?

Answer 9

The complementary fit between enzyme and substrate

Question 10

What is the induced fit?

Answer 10

The change in the enzyme caused by the substrate binds to the active site of the enzyme

Question 11

Factors that affect enzyme activity:

Answer 11

• Temperature
• pH
• Inhibitors

Question 12

Most human enzymes operate effectively at:

Answer 12

Body temp (35-40*)

Question 13

A higher temperature is generally a good way to speed up reactions. Why?

Answer 13

As temperature increases the substrate molecules will collide more frequently, thus are more likely to interact with the active site

Question 14

What happens if the temperature exceeds the ideal temp?

Answer 14

The enzyme denatures: Active site changes shape so substrates can no longer bind

Question 15

At lower temperatures, the rate of reaction…?

Answer 15

slows down - fewer collisions happen between substrate and enzymes

Question 16

The optimum pH for human enzymes:

Answer 16

6-8

Question 17

Changing pH can alter binding at the active site, therefore:

Answer 17

enzyme denatures

Question 18

Extreme temperature or pH causes reduced enzyme activity due to…

Answer 18

enzyme denaturing

Question 19

Extreme conditions do what to the enzyme bonds?

Answer 19

Break bonds and change the structure of the protein, and alter the shape of the active site

Question 20

What are inhibitors?

Answer 20

Inhibitors are chemicals that reduce the action of enzymes.`

Question 21

Competitive inhibitors:

Answer 21

• Inhibitors block the substrate entering the active site by binding to the active site. They mimic the shape of the substrate (complementary to the shape of some of the active site)
• EG: Cyanide

Question 22

Non-competitive inhibitors:

Answer 22

• Inhibitors bind elsewhere on the enzyme and this changes the shape of the enzyme and thus reduces enzyme-substrate binding.
• EG: Lead, mercury

Question 23

Increasing the concentration of the substrate therefore increases:

Answer 23

the chance of colliding with the enzyme, therefore increasing the reaction rate

Question 24

What is a metabolic pathway?

Answer 24

• Biological reactions usually occur as a series of small regulated steps called a metabolic pathway
• EG: aerobic respiration

Question 25

Metabolic pathways provide:

Answer 25

• A controlled release of small packets of energy that can be trapped to form ATP

Question 26

The controlled release of energy is ideal because:

Answer 26

cells can operate under normal temperatures for living systems (large steps produce unfavourable conditions - eg: high temp and acidity)

Question 27

Each step is catalysed by a different enzyme, therefore,

Answer 27

the reaction can be sped up or slowed down

Question 28

Smaller steps create ____________ which are __________________

Answer 28

Small steps create intermediate compounds that are essential biological molecules required by cells

Question 29

Metabolism

Answer 29

Describes all chemical reactions occurring inside a cell

Question 30

Anabolism

Answer 30

Synthetic reactions, small molecules are used to build bigger molecules (eg: photosynthesis)

Question 31

Catabolism

Answer 31

Large molecules are broken down to form smaller molecules, releasing free energy to form ATP (eg: aerobic respiration)