Revision Exercise 4 Answers/ymt/aoghss
1.
True or false
Decide whether each of the following statements about enzyme is true or false. Correct by
rewriting it if it is false.
(i)
Enzymes can speed up the rate of
biochemical reactions
T
(ii)
Enzymes are secreted by glands
only
F
(iii)
All enzymes leave the cell and exert F
their actions outside the cell.
Some enzymes work inside cells.
(iv)
Catalase is the only enzyme found
in plant and animal tissue cells.
Other enzymes are also found in plant and
animal tissues (e.g. amylase)
(v)
Enzymes are still present at the end T
of the reactions
(vi)
Catalase can be used to produce
oxygen in the tissue cells
(vii) Enzymes are proteins
F
F
Enzymes are produced by all cells.
Catalase is the enzyme produced by cells to
remove hydrogen peroxide inside cells.
T
(viii) Enzymes are specific in their action. T
2.
(ix)
Enzymes can only catalyse a
reaction in one direction only
F
(x)
Enzymes are denatured at high
temperatures
T
Enzymes catalyze reaction in both directions
Answers only:
(i)
(ii)
The gas is oxygen.
It can relight a glowing splint
(1) The one originally at 0℃
(2) In the sample kept at 100℃, the enzyme has been
denatured. In the sample kept at 0℃, the enzyme has
become temporarily inactive only, it resumes its function
again at room temperature.
3.
(iii)
No, enzyme actions are specific
(iv)
amount of hydrogen peroxide (or substrate used), pH
Which of the following is an example of (a) osmosis, (b) diffusion, (c) active transport, (d)
none of the above
(i)
Exchange of gases in the alveoli of the lungs.
b
(ii)
Absorption of water into the root.
a
(iii)
Absorption of digested food in the gut.
(iv)
Uptake of minerals of a foul smell near a polluted river
b, c
b
Revision Exercise 4 Answers/ymt/aoghss
(v)
The detection of a foul smell near a polluted river
b
(vi)
The swelling of a fruit when it is immersed in water.
a
(vii) The movement of carbon dioxide through the stomata during photosynthesis
4.
b
True or false
(i)
Water molecules are smaller than
sugar molecules
T
(ii)
Water molecules can only pass in
but not out of the dialyzing tubing
F
Water molecules can pass in both directions
across the dialysis membrane
(iii)
This experiment can be used to
demonstrate active transport
F
This experiment can be used to demonstrate
osmosis not active transport
(iv)
The water potential inside the
dialysis tubing is higher than that
outside
F
The water potential inside the dialysis tubing
is lower than that outside
(v)
There are only sugar molecules
F
Water molecules are also present
inside the dialysis tubing
(vi)
5.
The dialysis tubing is selectively
permeable
T
(vii) The amount of sugar molecules
increases as water passes into the
tubing
F
(viii) The level of the liquid in the glass
tube rises
T
The amount of sugar molecules remain
unchanged. Only the concentration changes.
Fill in blanks
(i)
Diffusion is the movement of molecules from a region where
they are in ______________ concentration to another region
where they are in a ______________ concentration.
higher
lower
(ii)
In plants _____________ are absorbed from the root hairs by
diffusion.
mineral salts
(iii)
Green plants obtain ___________ carbon dioxide for
carbon dioxide
photosynthesis by diffusion. It enters the leaf through the
stomata.
(iv)
Diffusion also occurs in out lungs. ___________ diffuses from
the lungs into the blood and _____________ diffuses from the
blood into the lungs.
oxygen
carbon dioxide
(v)
Osmosis is the movement of _____________ molecules from a water
region of _____________ water potential to the region of
higher
_____________ water potential through a
lower
Revision Exercise 4 Answers/ymt/aoghss
__________________ membrane.
6.
Answer only
(i)
the potato should be peeled
(ii)
osmosis
(iii)
The liquid level inside the cavity rises. The living cells in the
potato act as selectively permeable membrane. The distilled
water outside has a higher water potential.
(iv)
The liquid level inside falls. The boiled potato becomes freely
permable. The sucrose molecules diffuse out.
selectively permeable