Enzymes

Question 1

What are enzymes?

Answer 1

Biological catalysts that speed up the rate of reactions in the body

Question 2

Why are enzymes needed in the body?

Answer 2

To speed up the rates of chemical reactions in the cells
To ensure that life as we know it can continue
For digestion to occur quickly so that nutrients can be made available to our cells on demand

Question 3

Example of important enzyme catalyzed reactions (1)

Answer 3

The conversion of hydrogen peroxide produced in cells, to water and oxygen
The enzyme catalase is found in blood, liver, potatoes, beans, and yeast

Question 4

Example of important enzyme catalyzed reactions (2)

Answer 4

Digestive enzymes speed up the hydrolysis of:
Proteins —(pepsin)—> peptides
starch —-(amylase)—> maltose
maltose—(maltase)—-> glucose
lipids—-(lipase)—> fatty acids + glycerol
Digestive enzymes are found in our digestive tract and also in plants

Question 5

List some characteristics of enzymes

Answer 5

-they have a specific shape with an active site on the surface
- The substrate on which the enzyme has an effect has a complementary shape that that of the active site
- The active site of each enzyme is unique and so each enzyme will act on one type of substrate only, eg. catalase enzyme will only break down hydrogen peroxide and amylase enzyme will only digest starch

Question 6

What is the active site

Answer 6

A region or groove on the surface of the enzyme which has a specific shape

Question 7

How enzymes work?

Answer 7

1) Substrate enters active site of enzyme
2) Forms enzyme/substrate complex
3) Forms enzyme/ product complex
4)Products leaving active site of enzyme

Question 8

What happens when enzyme and substrate molecules are mixed tgt?

Answer 8

They collide with each other as they bump into each other due to their kinetic energy

Question 9

The enzyme functions as the

Answer 9

Lock

Question 10

The substrate functions as the

Answer 10

Key. The specific molecule (key) fits into the active site of the enzyme (lock)

Question 11

The molecules of the substrate undergo..

Answer 11

Rearrangement

Question 12

Once products are formed..

Answer 12

They no longer fit into the active site of the enzyme and they move away from the active site.

Question 13

What is the optimum temp for enzymes?

Answer 13

37 degrees Celcius. Once the temp. exceeds this, the enzyme structure starts to break down and the enzyme becomes denatured (cause structure and shape of enzyme to change irreversibly and it can no longer function as a catalyst)

Question 14

Pepsin (in stomach) works best at the pH of

Answer 14

2.0

Question 15

amylase (in mouth) works best at the pH of

Answer 15

under a pH of 7.0

Question 15

amylase (in mouth) works best at the pH of

Answer 15

under a pH of 7.0

Question 16

Inhibitors

Answer 16

Enzymes are affected by the presence of substances called inhibitors. Son inhibitors include mercury, lead, and cyanide. They cause the enzyme to become denatured

Question 17

Cofactors

Answer 17

Enzyme activity can also be sped up by the presence of certain substances called cofactors eg. vitamins/minerals

Question 18

Substrate concentration

Answer 18

The conc. of substrate present can also affect enzyme activity.
low subst. conc. = low rxn. rate
higher subst. conc. = higher rxn. rate
When the graph starts to plateau, the rate of the reaction starts to become constant, this is because there are only a certain fixed number of enzyme active sites available, and the substrate molecules are in excess.

Question 19

Enzyme concentration

Answer 19

As enzyme concentration increases= rxn rate increases
As enzyme concentration decreases= rxn rate decreases