It has long been known that when exposed to light under
suitable conditions of temperature and moisture, the green parts of plants use
carbon dioxide from the atmosphere and release oxygen to it. These exchanges
are the opposite of those that occur in respiration. The process is called
photosynthesis. In photosynthesis, carbohydrates are synthesized from carbon
dioxide and water by the chloroplasts of plant cells in the presence of light.
In most plants, the water used in photosynthesis is absorbed from the soil by
the roots and translocated through the xylem of the root and stem to the
leaves. Except for the usually small percentage used in respiration, the oxygen
released in the process diffuses out of the leaf into the atmosphere through
the stomates. Oxygen is the product of the reaction. For each molecule of
carbon dioxide used, one molecule of oxygen is released. A summary chemical
equation for photosynthesis is:
6C02 + 6Н2О --> С6 H12О6 + 6O2
As a result of this process, radiant energy from the sun is
stored as chemical energy. In turn, the chemical energy is used to decompose
carbon dioxide and water. The products of their decomposition are recombined
into a new compound, which is successively built up into more and more complex
substances. After many intermediate steps, sugar is produced. At the same time,
a balance of gases is preserved in the atmosphere.
1. Which title best expresses the ideas in this passage?
(A) A Chemical Equation
(B) The Process of Photosynthesis
(C) The Parts of Vascular Plants
(D) The Production of Sugar
2. In photosynthesis, water
(A) must be present
(B) is produced in carbohydrates
(C) is stored as chemical energy
(D) interrupts the chemical reaction
3. Which process is the opposite of photosynthesis?
4. The combination of carbon dioxide and water to form sugar
results in an excess of
5. The word "stored" in line 13 is closest in
6. In photosynthesis, energy from the sun is
(A) changed to chemical energy
(B) conducted from the xylem to the leaves of green plants
(C) not necessary to the process
(D) released one to one for each molecule of carbon dioxide
7. The word "their" in line 15 refers to
(A) radiant energy and chemical energy
(B) carbon dioxide and water
(D) complex substances
8. The word "successively" in line 15 is close in
(A) with effort
(B) in a sequence
9. Besides the manufacture of food for plants, what is
another benefit of photosynthesis?
(A) It produces solar energy.
(B) It diffuses additional carbon dioxide into the air.
(C) It maintains a balance of gases in the atmosphere.
(D) It removes harmful gases from the air.
10. Which of the following is NOT true of the oxygen used in
(A) Oxygen is absorbed by the roots.
(B) Oxygen is the product of photosynthesis:
(C) Oxygen is used in respiration.
(D) Oxygen is released into the atmosphere through the