What are the factors affecting Enzyme

Activity?

Recap

What are enzymes?• Biological catalysts made up of proteins

Function of Enzymes• Enzymes speed up the rate of chemical

reactions in the body; both breaking down (e.g.: starch into maltose) and building up reactions. (e.g: amino acids into proteins).

• Enzymes lower the activation energy

required to start a chemical reaction

Characteristics of Enzymes• Enzymes are highly specific

in action. • Enzymes remain chemically

unchanged at the end of the reaction.

• Enzymes are required in minute amounts.

I. Name that Enzyme !!!I. Name that Enzyme !!!

Proteinase Substrate Name +

-ase

Carbohydratease

I. Name that Enzyme !!!

Mode of Action

Substrate fits in the enzyme active site,just like a key fits into a lock.

An enzyme-substrate complex is formed.

Chemical reactions occur at the active site and products are formed.

What are the factors affecting Enzyme

Activity?

Hydrogen peroxide water and oxygencatalase

What affects enzyme activity?

Petri Dish 1 2 3 4 5

Condition of potato pieces

Raw Cooked Frozen Soaked in Acid

Soaked in Alkali

Observations

0°C• Low temperatures low Kinetic Energy

of enzymes and substrates.

• No/Very few enzyme-substrate complexes are formed.

• Enzymes are inactivated.

20°C (increasing temperature) • Increasing the temperature will lead to the increase in

kinetic energy of enzyme and substrate molecules.

• Enzyme and substrate molecules move with increasing speed and collide more frequently with each other.

• This increases the rate of enzyme-substrate complex formation This increases the rate of enzyme-substrate complex formation and product formation.

Rate of reaction increases

37°C • As the temperature continues to

increase, the rate of enzyme activity also increases until the optimal temperature is reached.

• Optimal temperature is the temperature at which the enzyme works best. Rate of product formation is highest!

Beyond Optimal Temperatures• At high temperatures (>60°C), weak bonds

within the enzyme molecule are broken• Enzyme loses its shape and its active site.• Loss of shape leads to a loss of function.

Enzyme is said to have denatured • Denaturation is the change in 3D structure of

an enzyme or any other protein caused by heat or chemicals such as acids or alkali, causing it to lose its function.

Denaturation

Different enzymes denature at different temperatures. Most enzymes denature at temperatures higher than 60°C. However, there are some enzymes that stay active even

at high temperatures like 80°C (Enzymes in the bacteria Thermus aquaticus)

Effect of pH on enzyme activity

• Enzyme works best within a narrow pH range

• Each enzyme works best at particular pH, known as its optimum pH level.

• At extreme pH levels, enzymes lose their shape and function and become denatured.

Effect of pH on enzyme activity

Effect of Substrate on Enzyme Activity