10
14.
Enzymes are used by living organisms to catalyse reactions. Some of these reactions occur in
the cytoplasm of cells. Other reactions take place outside cells, for example the digestion of
foods in the human gut.
(a)
State the name used by biochemists for the chains and cycles of reactions that occur
inside cells.
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(1)
(b)
Enzymes of digestion in humans are secreted by glands. They have a pH optimum which
allows them to work efficiently in the part of the gut into which they are secreted.
(i)
In the table below, identify the missing enzyme, the two glands, and the pH
optimum
Name of
enzyme
Gland secreting
the enzyme
Substrate
Products
pH optimum
amylase
starch
maltose
triglycerides fatty acids and
glycerol
7
(4)
(ii)
Outline the effect of pH values above and below the optimum on enzyme structure.
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(2)