Enzymes 🥀

#becausebreadtastesbetterthankey

What are enzymes?

Enzymes are biological catalysts that speed up the rate of a chemical reaction by reducing the activation energy. The enzyme remains chemically unchanged at the end of the reaction

What is a …

• substrate ?

• Product ?

• a substrate is the starting material / reactant of a reaction (substrate that starts a chemical reaction)

• a product is the end product of a reaction

Explain the lock and key hypothesis

1. An enzyme has a specific 3D shape. It has a depression called the active site

2. Only the substrate with a 3D shape complementary to that of the active site can fit into the enzyme. This results in the formation of an enzyme-substrate complex. The enzyme is just like a lock and the substrate is key. The substrate fits into the enzyme just like a key fits into a lock. This is called the “lock and key hypothesis”

3. 3. While the substrate is attached to the active site, a chemical reaction occurs. The substrate is converted to the products.

4. Later, the products leave the active site. The enzyme remains unchanged. It can catalyse another reaction

What is the mode of action of enzymes

An enzyme helps to catalyse a chemical reaction by lowering its activation energy.

An enzyme has an active site (a depression or 'pocket' on the surface of an enzyme molecule in which the substrate can fit) that has a specific 3D shape.

An enzyme is specific in its action. Only a substrate (the 'key') with a 3D shape complementary to the active site can bind to the enzyme (the 'lock') to form an enzyme-substrate complex.

Chemical reactions will then occur and the substrate is converted into products.

The products are then released from the active site. The enzyme remains unchanged at the end of the reaction. The enzyme's active site is now free for another substrate to bind.

What is enzyme denaturation

• The change in 3D shape of an enzyme or any protein is known as denaturation

• Denaturation can be caused by:

  a) heat

  b) chemicals such as acids and alkalis (change in pH)

• When an enzyme is denatured, there is a loss of the active site 3D shape. Substrate can no longer fit and bind into the enzyme’s active site and no reaction can take place.

Enzymes are affected by ____________ and ___?

Temperature and pH

How do enzymes get affected by temperature?

Low temp, enzymes inactive, KE of enzyme and substrate is low

As the temp increases, enzyme activity increases. Increasing temp means increasing KE

Optimum temp = most active (enzyme activity)

Nyong optimum temp, enzyme activity decreases as the high temp causes the 3D shape of the active site of enzyme to change and is no longer complementary to the shape of the substrate. Enzyme is denatured.

How do enzymes get affected by pH

Changes in pH changes the 3D shape of the enzyme's active site. The enzyme is said to be denatured.

Each enzyme requires a specific pH (a narrow range) where it is most active. This is the optimum pH of the enzyme.

Some enzymes work best in slightly acidic solutions eg. Pepsin in stomach (pH2), others require slightly alkaline solutions eg. Trypsin (pH8) in small intestine.

Amylase in saliva work best in neutral pH 7.

Therefore, each enzyme has a specific optimum pH value.

Extreme changes away from the optimum pH of the solutions denature the enzymes.