2.4 Enzymes

Enzyme

A biological catalyst that increases the rate of reaction without being used up or permanently altered

Turnover number

Number of reactions an enzyme can catalyse per second

Whst determines the shape of the active site

Tertiary structure of the protein

Active site

The region on an enzyme where the substrate binds

Whst type of proteins are enzymes

Globular

Factors thst change the shape of active site

Temperature change

pH change

Intracellular enzymes

Enzymes that catalyse reactions inside cells

Name 1 intracellular emzyme

Catalase

What does catalase do

Catalyses breakdown of hydrogen peroxide into water and oxygen

Whst is the turnover number of catalase

6 million

Extracellular enzymes

Enzymes made inside the cell the secreated to where they will act

Name 2 extracellular enzymes

1. Amylase

2. Trypsin

What does trypsin do

Breaks proteins down into smaller polypeptide in the small intestine

What does amylase do

Acts in the mouth and small intestine to digest starch into maltose

Where is amylase made

The salivary glands and pancreas

Cofactors

A non protein molecule that binds to an enzyme and is needed for it to function

3 types of cofactors

1. Coenzyme(organic cofactors)

2. Inorganic cofactors

3. Prosthetic groups

Whst are coenzymes

Organic non protein molecules that temporarily bind to the active site

Where do we get coenzymes from⁷

Water soluble vitamins

What is the cofactor for amylase

Chloride ion

What are inorganic cofactors

Inorganic metal ions gained from the diet as minerals

What are prosthetic groups

Cofactors that are tightly and permanently bound to the enzyme via covalent bonds

Prosthetic group of carbonic anhydrase

Zn²+

Why are enzymes specific to their substate

They have unique tertiary structures that make their active sites complementary to a specific substrate

How do enzymes lower the activation energy

Temporary bonds form between the group in the enzymes active site and the substrate

Hiw does the Induced fit model work

The active site slightly changes shape when the substrate binds, this puts strain on the substrates bonds which lowers the activation energy

How does the lock and key model work

Enzymes have a highly specific active site, which is only complementary to a one enzyme, which allows the substrate to bind and form a enzyme substrate complex

Why do most scientists now accept the Induced fit model

It is supported by evidence and research

Whst happens when an enzyme is denatured

• Bonds within the enzyme break

• This changes the tertiary structure

• Which changes the shape of the active site so substrate can no longer fit

2 factors that can cause enzyme denaturation

1. High temperature

2. Extreme pH

5 factors that affect the rate of enzyme controlled reactions

1. Enzyme concentration

2. Substrate concentration

3. Concentration of inhibitors

4. pH

5. temperature

Whst happens when an enzyme is in a high temperature

Greater vibrations in protein

This breaks the weak binds holding the tertiary structure together

Active site irreversibly changes shape abd can no longer change shape

Why does a higher temperature increase rate of enzyme reactions

Molecules have more kinetic energy so frequency of successful collisions increase. More enzyme substrate complexes form

What is Q10

Temperature coefficient: a measure of how much the reaction rate increases when the temperature increases by 10°C

How to calculate Q10

(Rate at T+10°C) ÷ (rate at T)

What is a buffer

solution that resists changes in pH by accepting or donating H+ ions

What happens when enzymes are in solutions below their optimal pH

H+ ions disrupt and break hydrogen binds and ionic interactions in the tertiary structure and change active site shape

Wgat happens to enzymes when placed in alkaline solutions above their optimal pH

OH- ions disrupt and break hydrogen binds and ionic interactions in the tertiary structure and change active site shape

How to test for amylase

Add biuret solution, if amylase is present solution will turn lilac/purple

Why does amylase turn biuret solution purple

Amylase contains peptide bonds

What is an inhibitor

Substances that reduce or stop the activity of an enzyme