Azwa's Test Review

During aerobic cellular respiration, oxygen gas is consumed at the same rate as carbon dioxide gas is produced. In order to provide accurate volumetric measurements of oxygen gas consumption, the experimental setup should include which of the following?

• A substance that removes carbon dioxide gas

• A plant to produce oxygen

• A glucose reserve

• A valve to release excess water

The chemical reaction for photosynthesis is

6CO₂ + 12H₂O + light energy C₆H₁₂O₆ + 6O₂ + 6H₂O

If the input water is labeled with a radioactive isotope of oxygen, ¹⁸O, then the oxygen gas released as the reaction proceeds is also labeled with ¹⁸O. Which of the following is the most likely explanation?

• During the light reactions of photosynthesis, water is split, the hydrogen atoms combine with the CO₂, and oxygen gas is released.

• During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released.

• During the Calvin cycle, water is split, regenerating NADPH from NADP⁺, and oxygen gas is released.

• During the Calvin cycle, water is split, the hydrogen atoms are added to intermediates of sugar synthesis, and oxygen gas is released.

Which of the following questions is most relevant to understanding the Calvin cycle?

• How does chlorophyll capture light?

• How is ATP used in the formation of 3-carbon carbohydrates?

• How is NADP⁺ reduced to NADPH?

• How is ATP produced in chemiosmosis?

What most likely causes the trends in oxygen concentration shown in the graph above?

• The water becomes colder at night and thus holds more oxygen.

• Respiration in most organisms increases at night.

• More organisms are respiring at night than during the day.

• Photosynthesis produces more oxygen than is consumed by respiration during the day.

A respirometer is a container used to measure the amount of oxygen consumed by an organism. A respirometer was used to determine how environmental temperature affects the uptake of oxygen in one 300-gram rat and one 50-gram mouse. The results of this experiment are shown on the graph below.

Which of the following statements best explains why oxygen is taken up more rapidly at 12°C than at 20°C?

• Oxygen is more soluble in blood at lower temperatures.

• At 12°C a higher rate of oxygen consumption is required to maintain a high body temperature.

• In colder temperatures, more heat is lost at the surface of the skin and the heat is replaced by deeper breathing.

• Oxygen is taken up more rapidly because of the greater expansion of the lungs caused by the loss of heat.

During aerobic cellular respiration, oxygen gas is consumed at the same rate as carbon dioxide gas is produced. In order to provide accurate volumetric measurements of oxygen gas consumption, the experimental setup should include which of the following?

• A substance that removes carbon dioxide gas

• A plant to produce oxygen

• A glucose reserve

• A valve to release excess water

Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide. In fact, it comes from ____.

• water

• glucose

• air

• electrons from NADPH

Why are C₄ plants able to photosynthesize with no apparent photorespiration?

• they do not participate in the Calvin cycle.

• They use PEP carboxylase to initially fix CO₂.

• They conserve water more efficiently.

• They exclude oxygen from their tissues.

CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they ____.

• fix CO₂ into organic acids during the night

• fix CO₂ into sugars in the bundle-sheath cells

• fix CO₂ into pyruvate in the mesophyll cells

• use photosystem I and photosystem II at night

The alternative pathways of photosynthesis using the C₄ or CAM systems are said to be compromises. Why?

• Each one minimizes both water loss and rate of photosynthesis.

• C₄ compromises on water loss and CAM compromises on photorespiration.

• Both minimize photorespiration but expend more ATP during carbon fixation.

• CAM plants allow more water loss, while C₄ plants allow less CO₂ into the plant.