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1
What is the primary function of enzymes in living organisms?
A
To store genetic information for protein synthesis
B
To provide structural support to cell membranes
C
To serve as a source of energy for cellular processes
D
To act as biological catalysts that speed up chemical reactions
2
Which of the following best describes the effect of temperature on enzyme activity?
A
Enzyme activity decreases steadily as temperature increases.
B
Enzyme activity increases indefinitely as temperature rises.
C
Enzyme activity is unaffected by temperature changes.
D
Enzyme activity increases with temperature up to an optimum, then decreases due to denaturation.
3
A student tests the effect of pH on an enzyme found in the human stomach. At which pH would the enzyme most likely show maximum activity?
A
pH 2
B
pH 12
C
pH 9
D
pH 7
4
If the concentration of substrate is increased while enzyme concentration remains constant, what happens to the rate of reaction?
A
The rate decreases because excess substrate inhibits the enzyme.
B
The rate increases continuously without limit.
C
The rate remains constant regardless of substrate concentration.
D
The rate increases until all enzyme active sites are occupied, then levels off.
5
Which statement correctly explains why an enzyme is said to be 'specific'?
A
Each enzyme has a unique active site that fits only specific substrates.
B
Each enzyme can catalyze any reaction in the cell.
C
Enzymes are specific only to temperature and pH conditions.
D
Enzymes are specific because they are made of proteins.