Unit 1, Topic 3 Cellular energy, gas exchange and plant physiology

Question 1

What is the Order of the Hierarchical Organisation in Multicellular Organisms

Answer 1

Cells: The basic unit of life.
Tissues: Groups of similar cells working together to perform a specific function.
Organs: Structures composed of different tissues that work together to perform a particular function.
Organ Systems: Groups of organs that work together to carry out complex functions.

Question 2

What is catabolism, and what does it involve?

Answer 2

Catabolism involves the breakdown of complex molecules into simpler ones, releasing energy in the process. This energy is used to power various cellular activities and is stored in the form of ATP.

Question 3

What are some examples of catabolic processes?

Answer 3

The breakdown of glucose during respiration and the digestion of food.

Question 4

What is anabolism, and what does it involve?

Answer 4

Anabolism is the synthesis of complex molecules from simpler ones, such as the formation of proteins from amino acids or DNA synthesis. It requires energy supplied by ATP.

Question 5

What role does ATP play in linking catabolic and anabolic reactions?

Answer 5

ATP serves as the energy currency of the cell, capturing energy released from catabolic reactions and using it to drive anabolic reactions by transferring a phosphate group and releasing energy.

Question 6

What is aerobic respiration?

Answer 6

Aerobic respiration is a catabolic process that breaks down glucose in the presence of oxygen to produce ATP, carbon dioxide, and water.

Question 7

What are the three main stages of aerobic respiration?

Answer 7

Glycolysis, the Krebs cycle, and the electron transport chain.

Question 8

Where does glycolysis occur, and what are its main outputs?

Answer 8

Glycolysis occurs in the cytoplasm and produces 2 pyruvate, 4 ATP (net gain of 2 ATP), and 2 NADH.

Question 9

Where does the Krebs cycle take place, and what are its main outputs?

Answer 9

The Krebs cycle takes place in the mitochondrial matrix and generates NADH, FADH₂, and 2 ATP per glucose molecule.

Question 10

Where does the electron transport chain occur, and what are its main outputs?

Answer 10

The electron transport chain occurs in the inner mitochondrial membrane and produces approximately 32–34 ATP, water, and uses oxygen to accept electrons.

Question 11

How does aerobic respiration compare to anaerobic respiration in terms of oxygen requirement and ATP production?

Answer 11

Aerobic respiration requires oxygen and produces approximately 36–38 ATP per glucose molecule, while anaerobic respiration does not require oxygen and produces only 2 ATP per glucose molecule.

Question 12

What are the primary by-products of anaerobic respiration in animals and yeast/plants?

Answer 12

In animals, the by-product is lactic acid. In yeast and plants, the by-products are ethanol and carbon dioxide.

Question 13

How does the efficiency of aerobic respiration compare to anaerobic respiration?

Answer 13

Aerobic respiration is highly efficient (complete oxidation of glucose), while anaerobic respiration is less efficient (incomplete oxidation of glucose).

Question 14

When is anaerobic respiration typically used?

Answer 14

Anaerobic respiration is used during intense exercise or in oxygen-limited conditions.

Question 15

What are light-dependent reactions, where do they take place?

Answer 15

The light-dependent reactions occur in the thylakoid membranes of the chloroplasts. These reactions require light energy, which is absorbed by chlorophyll and other pigments. The key inputs for these reactions are light, water and ADP and NADP+ molecules.

Question 16

What are light-independent reactions, where do they take place?

Answer 16

The light-independent reactions, also known as the Calvin cycle, take place in the stroma of the chloroplasts. These reactions do not directly require light but use the ATP and NADPH produced during the light-dependent reactions.

Question 17

What are the key structures involved in gas exchange in mammals?

Answer 17

The alveoli in the lungs and the capillaries that surround them and permeate tissues.

Question 18

What are the structural adaptations of alveoli for efficient gas exchange?

Answer 18

Large Surface Area: Millions of alveoli provide a vast surface area for gas exchange.

Thin Walls: One cell thick, reducing the diffusion distance for gases.

Moist Surface: Coated with a thin layer of moisture to aid gas diffusion.

Rich Capillary Network: Surrounded by a dense network of capillaries to maintain a concentration gradient.

Question 19

How do alveoli and capillaries facilitate the exchange of gases?

Answer 19

The exchange is driven by differences in partial pressures of gases. Oxygen diffuses from alveoli (higher partial pressure) into capillaries (lower partial pressure), and carbon dioxide diffuses in the opposite direction.

Question 20

What is the role of partial pressures in gas exchange between alveoli and capillaries?

Answer 20

Oxygen moves from alveoli (higher partial pressure) to blood in capillaries (lower partial pressure), while carbon dioxide moves from blood (higher partial pressure) to alveoli (lower partial pressure).

Question 21

How is gas exchange between capillaries and muscle tissue driven?

Answer 21

Oxygen: Diffuses from capillaries (higher partial pressure) into muscle cells (lower partial pressure).
Carbon Dioxide: Diffuses from muscle cells (higher partial pressure) into capillaries (lower partial pressure).

Question 22

What maintains the efficiency of gas exchange in alveoli?

Answer 22

Continuous breathing and blood flow ensure that oxygen is supplied and carbon dioxide is removed effectively.

Question 23

What are the differences in gas exchange between alveoli and capillaries versus capillaries and muscle tissue?

Answer 23

Alveoli and Capillaries: Oxygen diffuses into the blood, and carbon dioxide diffuses into the alveoli.
Capillaries and Muscle Tissue: Oxygen diffuses into muscle cells, and carbon dioxide diffuses into capillaries.

Question 24

What are the two main types of vascular tissue in plants, and what are their functions?

Answer 24

Xylem: Transports water and minerals from the roots to other parts of the plant and provides structural support.
Phloem: Distributes the products of photosynthesis (e.g., sugars) from the leaves to other parts of the plant.

Question 25

What are the key structural features of xylem?

Answer 25

Hollow, Tube-like Structures: Made of dead cells, such as tracheids and vessel elements.
Lignified Walls: Provide structural support and facilitate efficient transport of water and minerals.

Question 26

How does phloem differ from xylem in terms of structure and function?

Answer 26

Phloem: Composed of living cells (e.g., sieve tube elements and companion cells) with thinner, non-lignified walls. It transports organic nutrients and has a bidirectional flow.
Xylem: Composed of dead cells with thick, lignified walls, providing unidirectional transport of water and structural support.

Question 27

What is the role of stomata in plants?

Answer 27

Stomata are small pores that regulate gas exchange, allowing carbon dioxide to enter for photosynthesis and oxygen to exit. They also enable transpiration, the loss of water vapor.

Question 28

How do guard cells regulate the opening and closing of stomata?

Answer 28

Guard cells become turgid and curve outward when there is sufficient water, opening the stomata. When water is scarce or temperatures are high, they become flaccid, closing the stomata to reduce water loss.

Question 29

What factors affect the rate of transpiration in plants?

Answer 29

Light Intensity: Higher light increases photosynthesis and stomatal opening, raising transpiration rates.
Temperature: Elevated temperatures increase evaporation rates, accelerating transpiration.
Humidity: Lower humidity increases the water vapor gradient, enhancing transpiration, while high humidity reduces it.
Wind: Increased air movement removes water vapor from the leaf surface, increasing transpiration.
Soil Moisture: Adequate soil moisture maintains turgor pressure in guard cells; low moisture reduces transpiration by closing stomata.
Plant Type: Structural adaptations vary among plant species, affecting transpiration rates (e.g., xerophytes have adaptations to minimize water loss).