Chapter 3- Enzymes

Question 1

What is an enzyme

Answer 1

These are biological catalysts that speed up chemical reactions that remain chemically unchanged

Question 2

what type of proteins are enzymes

Answer 2

GLOBULAR

Question 3

Intra-cellular VS extra-cellular

Answer 3

Intra- These are enzymes that are secreted in the cell and work in the cell e.g Respiratory cells
Extra- Enzymes are secreted in the cell and catalyse reactions outside the cell e.g Digestive cells

Question 4

Describe the structure of enzymes

Answer 4

-They are globular proteins and have a 3D shape
-Their hydrophilic R groups orients to the outside of the molecule making it soluble
-Their Hydrophobic groups orient inwards which are able to maintain its shape due to hydrophobic interactions
-All enzymes have a cleft known as the active site where a substrate fits

Question 5

Describe enzymes according to their tertiary structure.

Answer 5

> they are specific due to their complementary active site
Active site is determined by both the tertiary and primary structure
if the tertiary structure is altered in any way, then the active site will change and may hinder a substrate binding (enzyme- substrate complex)
The changes can be changed by Ph and Temperature

Question 6

Catabolic VS Anabolic

Answer 6

Catabolic- BREAK DOWN of bonds
Anabolic - JOINING of small units

Question 7

Explain the ‘Lock and key model’

Answer 7

~This occurs when the substrate is able to fit into the enzyme perfectly i.e like a lock and key.
~This occurs due to interaction of the R groups from the enzyme and the atoms of the substrate causing either a catabolic or anabolic reaction
when the reaction is done, the products leave the active site

Question 8

Explain the ‘Induced fit model’

Answer 8

~This occurs when a substrate’s shape does not perfectly match the active site but just slightly
~Once it binds with the enzyme it changes it shape, allowing the enzyme- substrate complex to still be formed

Question 9

What is the activation energy

Answer 9

This is when a certain amount of energy needs to be released before a chemical reaction starts

Question 10

What are the factors affecting the rate of enzyme activity

Answer 10

-Temperature
-Ph
-Substrate concentration
-inhibitors

Question 11

why is it easy to measure the rate of catalase hydrogen peroxide

Answer 11

Because one of its products is a gas

Question 12

what can a colorimeter measure

Answer 12

The intensity of the colour produced

Question 13

What happens when we continue to increase the substrate concentration

Answer 13

When this occurs, the enzyme concentration remains constant, hence can lead to every enzyme having a substrate and can lead to substrate molecules ‘queuing up’ as a result.

Question 14

What is Vmax

Answer 14

This refers to maximum amount of enzyme activity. This is when all enzymes are bonded to a substrate

Question 15

What happens when the temperature is too high

Answer 15

This can lead to hydrogen bonds breaking hence the shape of the active site can change and the complex cannot be formed

Question 16

How does pH affect enzyme activity

Answer 16

It depends on the type of enzyme however most enzymes work at pH 7
pH refers to the concentration of hydrogen ions present.
Hydrogen ions react with the R groups which causes ionisation with the amino acids. This can affect the bonding and hence affects the shape of the active site.

Question 17

How do we investigate pH

Answer 17

Using Buffer solutions. Each buffer solution has a specific pH yet maintain it even during a chemical reaction

Question 18

What is competitive inhabitation

Answer 18

This is when another molecule has a complementary shape to the active site and is able bind to the enzyme, this can lead to inhibiting the enzymes activity.

Question 19

How to reduce competitive inhibition

Answer 19

By increasing the substrate concentration then the binding can occur in the usual way.

Question 20

Non competitive reversible inhabitation

Answer 20

This takes place when another molecule binds to another part of the enzyme rather than the active site. The binding can cause a disarrangement of the hydrophobic and hydrogen bonds in the enzyme, this affects the enzymes active site and hence inhibits its activity

Question 21

How can NC inhabitation be essential

Answer 21

This can be used to control and balance out metabolic reactions. This is to avoid enzymes constantly churning out products all the time.

Question 22

describe the end product inhibition

Answer 22

This is when there’s a chain of end products and usually one of the products are able to bind to one part of the enzyme which hence leads to inhibition of enxyme activity

Question 23

what is the relationship between substrate concentration and Vmax

Answer 23

As Substrate conc. increases, the Vmax increases

Question 24

What is Michaelas Menten constant

Answer 24

This is half the Vmax of substrate conc. -KM

Question 25

what type of relationship does KM and affinity have

Answer 25

Inverse
as KM increases, the affinity decreases

Question 26

mention 2 applications of the VM and KM

Answer 26

-Can help in biochem calculations
-can help understand enzyme efficiency
-enzymes performance can be compared

Question 27

which solution is added to mix with an enzyme to immobilise enzymes

Answer 27

Sodium alginate

Question 28

What is sodium alginate mixture added with

Answer 28

Calcium chloride

Question 29

what does the Sodium alginate and calcium chloride form

Answer 29

A jelly which has each droplet create a small bead. when the enzyme is inside the bead we say it is immobilised

Question 30

How do immobilised enzymes catalyse their substrates

Answer 30

The beads are kept in a column. The substrate are inside a liquid and trickle down onto the column where it runs through the enzymes. The enzyme catalyses the substrate and the remaining liquid (products) emerge from the bottom and are purified

Question 31

List 3 advantages of using immobilised enzyme

Answer 31

• no enzyme inhibition
• enzyme is reused
• product is not contaminated with the enzyme
• enzyme is easily recovered
  -less likely to denature