Unit 1: Protein From Achieve

Question 1

Describe the formation and function of proteins

Answer 1

mRNA carries a complimentary copy of DNA from the nucleus into the ribosome within the cytoplasm where proteins are made, because mRNA carries a complimentary copy of DNA it is therefore made in the nucleus.

Question 2

Describe a catalyst, naming a biological catalyst

Answer 2

A catalyst will:

Speed up a chemical reaction
Remain chemically unchanged after the reaction
Lower the activation energy needed for the reaction to occur.
All living cells produce biological catalysts to speed up cellular reactions.

A biological catalyst is called an ENZYME.

Question 3

Describe and explain key terms associated with enzyme action

Answer 3

During a chemical reaction the reactant that an enzyme will work on is known as the SUBSTRATE.

The substance formed is known as the PRODUCT.

Enzyme action can be summarised using the following equation:
Enzyme
Substrate———————>product
(The enzyme is always placed above the arrow of the chemical reaction being catalysed.)

The substrate molecule fits into a special site on the enzyme called the ACTIVE SITE. An enzyme substrate complex forms, facilitating the reaction.

Substrate+enzyme—>enzyme-substrate complex—>enzyme-product—> enzyme+product(s)

The active site and the substrate are described as being complementary in shape. This allows the substrate to fit into the enzyme.

An enzyme will catalyse only one specific reaction. Just like a key will only work on a specific lock.

In summary:
Enzymes are specific and complementary in shape to the substrate.

Question 4

Use examples to describe a degradation reaction and synthesis reactions

Answer 4

A degradation reaction is the breakdown of a large molecule into a small molecule(s).

Example
Amylase
Starch——————-> maltose
Example
Catalase
Hydrogen peroxide——————>oxygen+water
A synthesis reaction is when small molecules are built up to form a larger molecule.

Example
Phosphorylase
Glucose+phosphate———————>starch

Question 5

Describe conditions which affect enzyme activity

Answer 5

An enzyme is most active given certain conditions. These conditions are known as the optimum conditions.

Enzymes and other proteins are affected by temperature and pH.

The optimum temperature for enzymes within the human body is 37oC.

In certain conditions an enzyme can become denatured. This is where the shape of the active site changes and will no longer allow the substrate to bind to it. This lowers the rate of reaction.