Enzymes

Question 1

Roles of enzymes in reactions

Answer 1

Catalyse anabolic reactions (growth)
Catalyse catabolic reactions (breaking down)

Question 2

Mechanism of enzyme action

Answer 2

Need to collide in right direction and specific to one substrate/biochemical reaction
-Lock and key hypothesis = active site is complementary to substrate molecule
-Induced fit hypothesis

Question 3

Induced fit hypothesis

Answer 3

Initial interaction between substrate and enzyme is weak - these change active site of enzymes tertiary structure
Strengthens binding and puts strain on substrate molecule weakening bonds lowering Ea

Question 4

Intracellular enzymes

Answer 4

Enzymes act within cells
Eg catalase breaks down hydrogen peroxide in the cell

Question 5

Extracellular digestion

Answer 5

Large molecules are required to be broken into smaller molecules to enter the cells
Fungi enzymes work outside the body
Eat food and digestive system produce these enzymes to be small enough to enter blood stream

Question 6

Digestion of starch

Answer 6

Begins in the mouth and then onto small intestines
Starch partially broken into maltose - amylase produced in pancreas and saliv. glands
Maltose then broken into glucose uses Maltase in small intestine

Question 7

Digestion of proteins

Answer 7

Trypsin is a protease produced in pancreas and acts in the small intestine forming AA which are absorbed by endothelial cells of digestive system then into blood

Question 8

Factors affecting activity

Answer 8

•Temp- increase collisions more frequent denature after certain point
•pH- when change more significant enzyme denature H+ ions interact w R groups

Question 9

Conc of substrate once effect on activity

Answer 9

Higher collision rate incr rate of reaction

Question 10

Conc of enzymes once effect on activity

Answer 10

Incr No of active sites present form complexes faster
Rate increases up to its maximum all active sites are occupied only way to incr add more enzyme or incr temp

Question 11

Control of metabolic activity

Answer 11

Enzymes activated w cofactors
Enzymes inactivated w inhibitors - competitive/ non competitive

Question 12

Competitive inhibition

Answer 12

Inhibitor has a similar shape to the substrates so blocks from entering active site and enzyme cannot function
Usually effect is temp
Reduces rate of reaction but not lower the V max

Question 13

Non competitive inhibition

Answer 13

Inhibitor bunds to location on enzyme not active site- allosteric site
Causes tertiary structure to change no longer complementary
Examples insecticides irreversibly inhibit acetyl cholinesterase in nervous transmission

Question 14

End product inhibition

Answer 14

When product of reaction acts as an inhibitor to enzyme that produced it -ve feedback
Non competitive reversible inhibition
Eg PFK if atp levels high prevent breakdown of glucose if low less inhibitory and can add 2nd phosphate group

Question 15

Cofactors

Answer 15

A helper component to help enzyme carry out function
Eg catalase requires Cl- ion to form correct active site

Question 16

Prosthetic groups

Answer 16

Are cofactors required by many enzymes in order to carry out function tightly bound permanent factor

Question 17

Precursor activation

Answer 17

Enzymes are produced inactive especially if can cause damage
Need to undergo tertiary structure change to be activated by adding cofactor

Question 18

Apoenzyme

Answer 18

Before cofactor added to enzyme

Question 19

Holoenzyme

Answer 19

When enzyme activated after cofactor added

Question 20

Zymogens/proenzymes

Answer 20

When a change in conditions causes change in tertiary structure and activates precursor enzyme