Chap 4, Enzymes

Question 1

Explain enzyme reaction in terms of the “lock and key” hypothesis

Answer 1

Enzyme reactions depend on the presence of active sites. Pockets/grooves(depressions) on the surface of an enzyme molecule into which the substrate molecules with matching/complementary shape can fit, to form an enzyme substrate complex.

Question 2

Investigate and explain the effects of temperature on the rate of enzyme-catalysed reactions.

Answer 2

1) as temperature increases, rate of enzyme reaction increases, until optimum temperature.
-increased temp = increased kinetic energy of molecules
-rate of effective collision increases
-rate of enzyme substrate complex formation increases.
(Opposite for low temp)

2) enzymes are most active at its optimum temperature.
-humans(37*C)

3) temperature above optimum causes rapid decline in the rate of enzyme reaction.
-active site begins to lose its original shape & is no longer complementary.

4) at 60*C, all enzyme molecules have been denatured

Question 3

Investigate and explain the effects of pH on the rate of enzyme-catalysed reactions.

Answer 3

When enzymes are placed in pH conditions that vary from the optimum, they start to denature.

Amylase:
Digests starch to maltose
-salivary amylase (pH7)
-pancreatic amylase (pH8)
Maltase:
Digests maltose to starch
Protease:
-digests proteins to polypeptides to amino acids
-Stomach protease (pH2)
-duodenum protease (pH8)
Lipase:
-Digests fats to fatty acids & glycerol
-pancreatic lipase & intestinal lipase (pH8)

Question 4

Why do food molecules need to be digested?

Answer 4

So nutrients can diffuse through cell membrane & become soluble in water