Gas exchange in plants and animals : Practice Questions

Which primary structure facilitates gas exchange in the leaves of most plants?

The human lungs contain millions of tiny air sacs known as alveoli. What is the main advantage of having such numerous and small structures for gas exchange?

During strenuous exercise, the body's demand for oxygen significantly increases. Which physiological adjustment directly enhances the rate of oxygen diffusion from the alveoli into the blood capillaries to meet this demand?

Where are stomata, the primary structures for gas exchange in plants, most commonly found?

When humans exhale, which component of the air increases significantly in concentration compared to inhaled air, primarily due to the moist surfaces of the respiratory system?

Smoking can significantly impair the human respiratory system. State one direct way in which smoking adversely affects the efficiency of gas exchange in the lungs.

Describe the main changes in the percentage composition of oxygen (\( \text{O}_2 \)) and carbon dioxide (\( \text{CO}_2 \)) when air is exhaled compared to when it is inhaled by humans. Explain the biological reason for these changes.

A variegated leaf, possessing a green center and white edges, is kept in a sealed transparent container under bright light. Explain the difference in net gas exchange between these two regions and the resulting impact on the container's total \(\text{CO}_2\) level.

Living organisms continuously perform gas exchange to sustain life. This process differs between plants and animals and also varies based on environmental conditions.

(a) Explain how gas exchange occurs in a plant leaf during:

• (i) daytime (when there is sunlight)
• (ii) nighttime (in the absence of light)

(b) Name the small pores on plant leaves through which gas exchange occurs.

(c) Humans, like other animals, also perform gas exchange. Describe the main difference in the concentration of carbon dioxide between inhaled air and exhaled air in humans.

A student investigates gas exchange in a terrestrial plant. She places a single green leaf in a sealed boiling tube containing a small amount of hydrogencarbonate indicator solution and exposes it to bright light for two hours. Hydrogencarbonate indicator changes color based on \( \text{CO}_2 \) concentration: yellow (high), red (normal), and purple (low).

(a) Predict the final color of the indicator and explain your answer by referring to the relative rates of the plant's metabolic processes.
(b) The student then covers the tube with black paper and waits for another two hours. Describe and explain the expected change in the indicator's color.
(c) Through which specific structures on the leaf surface does this gas exchange primarily occur?