Enzymes

Question 1

For a reaction to occur, molecules must collide in the right orientation.

The number of successful collisions will increase due to certain environmental factors. Name two of these. (2)

Answer 1

• Higher temperatures (1)
• Higher pressures/lower volumes (1)

Question 2

The amount of energy required to start a reaction is called the ___ energy. (1)

Answer 2

Activation (1)

Question 3

Each enzyme catalyses one biochemical reaction. What is this characteristic of enzymes called? (1)

Answer 3

Specificity (1)

Question 4

There are two different models for the specificity of enzymes. What are these called and what are the differences between them? (4)

Answer 4

• Lock and key (1); the enzyme/lock has an active site that is complementary to a specific substrate/key, allowing them to fit. (1)
• Induced fit hypothesis (1); unlike the lock and key theory, this theory suggests that the active site needs to slightly change shape to accommodate for the shape of the substrate. (1)

Question 5

Describe the process of an enzyme catalysing a reaction. (7)

Answer 5

• A substrate binds to the active site of an enzyme, forming the enzyme-substrate complex. (1)
• Initial interactions between the substrate and active site are weak, but rapidly induce changes in the enzyme’s tertiary structure. (1)
• Binding strengthens (between substrate and R groups), putting strain on the bonds within the substrate. (1)
• The substrate is held in such a way that the right atom groups are close enough to react. (1)
• The activation energy is lowered (1) so the reaction occurs. (1)
• Products are released from the enzyme-product complex. (1)

Question 6

What are intracellular enzymes? (1)

Provide one example of the functions of intracellular enzymes. (1)

Answer 6

• Enzymes that act within cells. (1)
• Catalase breaks down hydrogen peroxide in cells. (1)
• Synthesis of polymers from monomers. (1)

Question 7

What are extracellular enzymes? (1)

What is the main function of extracellular enzymes? (1)

Answer 7

• Enzymes that act outside cells. (1)
• Digestion/supplying cells with nutrients (substrates). (1)

Question 8

Fill in the blanks about how starch is digested (8):

Nutrients are often in the form of polymers (such as p___ and p___) and come from our ___. These large molecules are unable to enter ___ directly. E___ enzymes break down polymers into smaller molecules in ___. These smaller molecules are then absorbed into the ___ where they are carried around the body to be used as ___.

Answer 8

• Polysaccharides (1)
• Proteins (1)
• Diet (1)
• Cells (1)
• Extracellular (1)
• Digestion (1)
• Bloodstream (1)
• Substrates (1)