Chapter 5 Metabolism and Enzymes

Question 1

What is metabolism?

Answer 1

Chemical reactions that occur in a living organism which involve the conversion of food into energy in the form of ATP and the formation of carbohydrate, protein, lipid and nucleic acid

Question 2

What are the types of metabolism in a cell?

Answer 2

Catabolism
Anabolism

Question 3

What is catabolism?

Answer 3

Process of breaking down complex substances into simple substances.
This process releases energy

Question 4

Examples of catabolism

Answer 4

Breakdown of glucose during cellular respiration to generate energy

Question 5

What is anabolism

Answer 5

Process of synthesising complex molecules from simple molecules
This reaction uses or absorbs energy

Question 6

Examples of anabolism

Answer 6

Formation of glucose during photosynthesis

Question 7

What is enzyme

Answer 7

Organic catalyst that is mostly made up of proteins and is produced by living cell organisms

Question 8

Enzymes bind with substrate in a site known as the active site to form what?

Answer 8

Enzyme-substrate complex

Question 9

What are some general characteristics of enzymes?

Answer 9

• Act rapidly
• Only required in small quantities and are reusable
• Structure of enzymes remain unchanged and are not destroyed after a reaction
• Speed up biochemical reactions
• Need cofactors to work efficiently ( vitamin B )

Question 10

What are intracellular and extracellular enzymes

Answer 10

Intracellular enzymes are enzymes synthesised in a cell for its own use
Extracellular enzymes are enzymes secreted outside the cell

Question 11

What is activation energy?

Answer 11

energy needed to break the bond in the substrate molecule before reactions can occur

Enzymes function by reducing the activation energy which speeds up biochemical reaction

Question 12

What are factors that affect the mechanism of enzyme action

Answer 12

Temperature
pH levels
Enzyme concentration
Substrate concentration

Question 13

How does temperature affect the mechanism of enzyme action

Answer 13

• At a low temp, the rate of reaction catalysed by enzymes is low
• When temp rises, the kinetic energy of substrate molecules and enzymes also increase which increase the frequency of effective collision between enzymes and substrate molecules and increases the rate of reaction between enzymes and substrate molecules
• With every rise in temp of 10 C, the rate of reaction controlled by enzymes double until it reaches the optimal temperature which is around 37 C

Question 14

How does pH value of the surrounding solution affect the enzyme activity?

Answer 14

• Most enzymes are most active in the range between pH6 and 8
• Change in pH value will change the charge of the active site of the enzyme molecule and substrate surface. Thus enzyme-substrate complex cannot be formed
• When pH value of the environment returns to the optimum level, charge on the active site is restored and enzyme will return to function as normal
• Extreme change in pH value will break the structural chemical bond and change the active site of enzymes

Question 15

How does the substrate concentration effect enzyme activity?

Answer 15

• If concentration of enzyme is fixed while concentration of substrate increases, reaction rate controlled by enzymes will also increase, leading to an increase in products created
• When substrate concentration increases, opportunity for effective collision between substrate and enzyme molecules also increase
• Reaction rate continues to increase until it reaches maximum level till rate of reaction is constant
• At maximum level, concentration of enzymes become a limiting factor and only an increase of the concentration of enzyme can increase the reaction rate
• After reaching maximum level all active sties of enzymes are saturated with substrate and are involved in catalytic reaction