1. What is respiration in plants mainly meant for?
ⓐ. Releasing stored energy from food in a usable form
ⓑ. Producing chlorophyll for light absorption in leaves
ⓒ. Absorbing mineral salts from the soil solution
ⓓ. Sending water upward through xylem vessels
Correct Answer: Releasing stored energy from food in a usable form
Explanation: Respiration in plants is the process by which the energy present in food molecules is released in a controlled manner and made available to the cell. Plants prepare food mainly through photosynthesis, but that food must be broken down to obtain usable energy. This released energy supports many life processes such as growth, repair, transport, and synthesis. The process occurs continuously in living cells and is essential for survival. It is not mainly concerned with pigment formation or water transport. Its central role is energy liberation from organic compounds.
2. Which statement best describes cellular respiration?
ⓐ. It is the movement of gases only through stomata
ⓑ. It is the synthesis of glucose using light energy
ⓒ. It is the breakdown of food inside cells to release energy
ⓓ. It is the loss of water vapour from plant surfaces
Correct Answer: It is the breakdown of food inside cells to release energy
Explanation: Cellular respiration refers to the set of reactions in which food substances are broken down within living cells to release energy. The word “cellular” highlights that this is a biochemical process occurring inside the cell, not merely an external exchange of gases. The released energy is then trapped in a usable form for cellular work. This makes it different from photosynthesis, which builds food, and transpiration, which involves water loss. Cellular respiration is therefore a metabolic process directly linked with energy supply. It is a basic requirement for all living plant cells.
3. In plant cells, the immediate energy currency made available through respiration is:
ⓐ. ADP
ⓑ. ATP
ⓒ. DNA
ⓓ. NADP
Correct Answer: ATP
Explanation: ATP is called the energy currency of the cell because it stores energy in a form that can be used immediately for biological work. During respiration, the energy released from food is not left free in the cell; instead, much of it is captured in ATP molecules. These molecules then provide energy for processes such as active transport, biosynthesis, and cell maintenance. ATP is useful because it can be broken down quickly whenever energy is needed. This makes it the main link between energy release and energy use. Hence respiration is closely associated with ATP formation.
4. Why do plant cells need to release energy from food molecules?
ⓐ. To increase the green colour of leaves permanently
ⓑ. To convert stomata into storage structures
ⓒ. To make external growth occur without cell activity
ⓓ. To perform vital activities such as growth and transport
Correct Answer: To perform vital activities such as growth and transport
Explanation: Plant cells need energy because life processes cannot continue without an internal energy supply. Activities such as growth, absorption of minerals, movement of substances across membranes, repair of tissues, and synthesis of new molecules all require energy. Food contains this energy in stored chemical form, but the cell must release it through respiration before it becomes useful. This is why respiration is essential even in non-moving organisms like plants. The need is not limited to visible growth alone. It supports nearly every active function carried out by living cells.
5. Which of the following is true about respiration in plants?
ⓐ. It occurs only in green tissues during daylight
ⓑ. It occurs only when photosynthesis stops at night
ⓒ. It occurs only in roots because leaves make food
ⓓ. It occurs in all living cells of the plant
Correct Answer: It occurs in all living cells of the plant
Explanation: Respiration is a universal process for living plant cells because every living cell needs energy to remain active and maintain metabolism. Leaves, roots, stems, flowers, fruits, and seeds all carry out respiration as long as their cells are alive. It is not restricted to green parts, and it does not depend on the presence of sunlight. Photosynthesis may occur only in chlorophyll-containing tissues, but respiration is much more general. Since energy is needed throughout the plant body, respiration is widespread. Therefore all living cells participate in this process.
6. The main difference between photosynthesis and respiration in plants is that respiration:
ⓐ. releases energy from food, whereas photosynthesis stores energy in food
ⓑ. stores oxygen in leaves, whereas photosynthesis removes all gases
ⓒ. forms chlorophyll, whereas photosynthesis breaks down pigments
ⓓ. occurs outside cells, whereas photosynthesis occurs inside cells
Correct Answer: releases energy from food, whereas photosynthesis stores energy in food
Explanation: Photosynthesis and respiration are related but opposite in their main energy roles. Photosynthesis captures light energy and stores it in the chemical bonds of food molecules such as glucose. Respiration, on the other hand, breaks down food and releases that stored energy in a usable form. This energy is then transferred mainly into ATP for cellular functions. Both are cellular processes, but their energy directions differ clearly. One builds and stores, while the other breaks down and releases. That contrast makes this distinction fundamental in plant physiology.
7. Which statement correctly explains why respiration is essential even in plants?
ⓐ. Plants need respiration only to absorb carbon dioxide
ⓑ. Plants need respiration because living cells require usable energy
ⓒ. Plants need respiration mainly to prepare glucose in chloroplasts
ⓓ. Plants need respiration only when leaves lose water rapidly
Correct Answer: Plants need respiration because living cells require usable energy
Explanation: Although plants do not move from place to place like animals, their cells are highly active and constantly require energy. They absorb ions, transport materials, synthesize compounds, divide, grow, and maintain internal organization. The energy for these functions must be supplied in a usable form, and respiration provides that supply. This is why respiration is an essential life process in plants as well as animals. It is not limited to gas uptake or food formation. Its importance lies in meeting the continuous energy demands of living cells.
8. What happens to the energy present in food during respiration?
ⓐ. It is destroyed after carbon dioxide is formed
ⓑ. It is turned completely into plant pigments
ⓒ. It is released in a controlled way and trapped for cell use
ⓓ. It is stored again as water inside the vacuole
Correct Answer: It is released in a controlled way and trapped for cell use
Explanation: The energy present in food is not released all at once during respiration because a sudden release would be inefficient and harmful to the cell. Instead, the breakdown occurs through a series of controlled reactions, allowing energy to be captured step by step. Much of this energy is stored in ATP, which can then be used as needed. This controlled transfer makes respiration biologically useful. It ensures that the cell can direct energy toward specific functions. Thus respiration is both an energy-releasing and an energy-conserving process in practical terms.
9. Which of the following best identifies the direct source of energy used in plant respiration?
ⓐ. Sunlight captured at the leaf surface
ⓑ. Soil water moving through the xylem
ⓒ. Stored chemical energy present in food molecules
ⓓ. Heat energy absorbed from the atmosphere
Correct Answer: Stored chemical energy present in food molecules
Explanation: The energy used in respiration comes from the chemical bonds of food molecules such as glucose. Plants manufacture food during photosynthesis and store energy in that form. When the plant needs energy for cellular work, respiration breaks these molecules down and releases the stored chemical energy. This energy is then transferred into ATP for immediate use. External heat or water movement does not serve as the main direct source for respiration. The process fundamentally depends on the energy already locked within organic food.
10. Which statement best matches the idea of “need for energy release” in plants?
ⓐ. Food is useful to cells only after its stored energy is made available
ⓑ. Food is important only because it gives colour to plant tissues
ⓒ. Food is required only to increase the water content of cells
ⓓ. Food is useful mainly because it prevents gas diffusion
Correct Answer: Food is useful to cells only after its stored energy is made available
Explanation: Food molecules contain potential energy, but cells cannot make proper use of that energy unless it is released through respiration. The phrase “need for energy release” means that merely storing food is not enough for life processes to continue. Cells must obtain accessible energy to drive metabolic reactions, transport, growth, and maintenance. Respiration converts the stored chemical energy into a form the cell can actually use. This is why the breakdown of food is as important as its synthesis. The biological value of food lies in the energy that can be released from it.
11. A germinating seed kept in complete darkness for several days still shows slight growth. Which statement best explains this?
ⓐ. It continues making glucose by using light stored earlier
ⓑ. It absorbs ready-made energy directly from water around it
ⓒ. It uses stored food and releases energy through respiration
ⓓ. It converts mineral ions into carbohydrates without chlorophyll
Correct Answer: It uses stored food and releases energy through respiration
Explanation: A germinating seed does not depend immediately on sunlight for its early growth because it already contains stored food. The cells of the seed break down this reserve material through respiration and release energy in a usable form. That energy supports cell division, elongation, and other metabolic activities needed for germination. This shows that respiration can continue even in darkness as long as living cells and stored food are present. The process is therefore essential for early seedling growth before photosynthesis begins effectively. This is a clear practical example of the need for energy release in plants.
12. Which plant structure would normally not carry out respiration?
ⓐ. Dead cork cells of the outer bark
ⓑ. Root hair cells in the absorption zone
ⓒ. Guard cells surrounding a stoma
ⓓ. Embryo cells inside a viable seed
Correct Answer: Dead cork cells of the outer bark
Explanation: Respiration is a metabolic activity of living cells, so only cells with active protoplasm can perform it. Dead cork cells in the outer bark serve mainly a protective role and do not have living contents to carry out metabolic reactions. In contrast, root hairs, guard cells, and embryo cells are living and require energy for their functions. This question highlights that respiration is not a property of all plant structures equally, but of living tissues only. The presence of life within the cell is the key condition. Therefore dead cork cells do not normally respire.
13. A container of soaked germinating seeds becomes warm after some time. This warmth is mainly due to:
ⓐ. rapid absorption of heat from the surrounding air
ⓑ. continuous production of chlorophyll in the young embryo
ⓒ. conversion of carbon dioxide into stored starch
ⓓ. partial release of respiratory energy as heat
Correct Answer: partial release of respiratory energy as heat
Explanation: During respiration, the energy stored in food is not converted entirely into ATP for cellular work. A part of the released energy appears as heat, especially when respiration is active, as in germinating seeds. Because many seeds respire intensely at the same time, the cumulative heat becomes noticeable and the container feels warm. This observation is often used as practical evidence that respiration is occurring. The heat is therefore not coming mainly from the outside environment. It arises from the energy-releasing breakdown of stored food inside living seed cells.
14. Which statement is correct for a green leaf during the night?
ⓐ. Both photosynthesis and respiration stop in the absence of light
ⓑ. Photosynthesis stops, but respiration continues in living cells
ⓒ. Respiration stops, but photosynthesis continues using stored ATP
ⓓ. Only gas exchange occurs, while cellular activity remains absent
Correct Answer: Photosynthesis stops, but respiration continues in living cells
Explanation: Photosynthesis requires light, so in darkness a green leaf cannot continue synthesizing food through that process. Respiration, however, does not depend on light and continues as long as the cells remain alive and need energy. The leaf uses available food and releases energy to maintain its cellular functions throughout the night. This is why respiration is a continuous life process, whereas photosynthesis is limited by light conditions. The contrast helps students avoid the common error of linking respiration only with daytime or only with photosynthetic tissues. Nighttime leaves still respire actively.
15. When root cells absorb mineral ions against a concentration gradient, the required energy is mainly supplied by:
ⓐ. movement of water through the cell wall spaces
ⓑ. direct use of sunlight reaching the underground roots
ⓒ. respiration occurring in the living root cells
ⓓ. passive diffusion through the plasma membrane
Correct Answer: respiration occurring in the living root cells
Explanation: Absorption of mineral ions against a concentration gradient is an active process, and active processes require energy. Root cells obtain this energy by breaking down food through respiration and transferring the released energy into usable cellular form. This energy allows membrane proteins to transport ions even when the movement is not naturally favorable. The question applies the concept of respiration to a real plant function rather than asking for a definition alone. It shows that respiration supports internal work throughout the plant body. Thus living root cells depend on respiration for active mineral uptake.
16. Why do meristematic regions usually show a higher rate of respiration than old woody dead parts?
ⓐ. They contain more chlorophyll for food manufacture
ⓑ. They are always exposed directly to atmospheric oxygen
ⓒ. They store more water and therefore release more energy
ⓓ. Their living cells divide and synthesize materials rapidly
Correct Answer: Their living cells divide and synthesize materials rapidly
Explanation: Meristematic tissues are made of actively dividing living cells, so their demand for energy is very high. These cells constantly carry out biosynthesis, growth, repair, and cell division, all of which require a steady supply of ATP. Since respiration provides that usable energy, such tissues usually respire more actively than less active or dead regions. Old woody dead parts lack living protoplasm and therefore do not show comparable metabolic intensity. This makes respiration closely related to the level of cellular activity in a tissue. Highly active growing regions naturally need more respiration.
17. Which statement correctly distinguishes gas exchange from cellular respiration in plants?
ⓐ. Gas exchange moves respiratory gases, while respiration releases energy inside cells
ⓑ. Gas exchange forms ATP, while respiration only opens and closes stomata
ⓒ. Gas exchange occurs in chloroplasts, while respiration occurs in the soil
ⓓ. Gas exchange is a food-making process, while respiration stores glucose
Correct Answer: Gas exchange moves respiratory gases, while respiration releases energy inside cells
Explanation: Gas exchange and respiration are related but not identical. Gas exchange refers to the movement of oxygen and carbon dioxide between plant tissues and the surroundings, while respiration is the internal biochemical process that breaks down food to release energy. A plant may exchange gases through surfaces like stomata or lenticels, but the actual energy-releasing reactions take place inside living cells. This distinction is important because many students incorrectly use both terms as if they mean the same thing. One is mainly about movement of gases, and the other is about cellular metabolism. Therefore the correct distinction is between external exchange and internal energy release.
18. Which statement best removes the misconception that only green parts of a plant respire?
ⓐ. Respiration is limited to leaves because only leaves make food
ⓑ. Non-green living tissues also respire because respiration does not require chlorophyll
ⓒ. Roots respire only when exposed to light for several hours
ⓓ. Stems respire only after they begin carrying out photosynthesis
Correct Answer: Non-green living tissues also respire because respiration does not require chlorophyll
Explanation: Respiration does not require chlorophyll, so it is not confined to green tissues. Any living plant cell that needs energy can carry out respiration, including cells in roots, seeds, fruits, and non-green stems. These tissues may not photosynthesize, but they still break down available food to obtain usable energy. This makes respiration a much more general process than photosynthesis. The misconception arises when students connect all plant metabolism only with green parts. In reality, respiration is a basic activity of living tissues throughout the plant.
19. Which of the following is the best example of respiration as a breakdown process?
ⓐ. Formation of cellulose in a developing cell wall
ⓑ. Synthesis of chlorophyll in a young expanding leaf
ⓒ. Conversion of sugars into stored starch in a tuber
ⓓ. Breakdown of stored food in a seed to release energy
Correct Answer: Breakdown of stored food in a seed to release energy
Explanation: Respiration is a catabolic process because it involves the breakdown of complex food substances to release energy. In a seed, stored reserve material is degraded during germination so that the embryo receives usable energy for growth. This clearly shows the energy-releasing side of plant metabolism. The other kinds of changes mentioned involve building or storing substances rather than breaking them down for immediate energy needs. The question therefore tests whether the student can recognize respiration in a practical example. Breakdown with energy release is the key feature here.
20. Assertion (A): Dead plant cells do not respire. Reason (R): Respiration is a metabolic activity carried out by living protoplasm.
ⓐ. Both A and R are true, and R is the correct explanation of A.
ⓑ. Both A and R are true, but R is not the correct explanation of A.
ⓒ. A is true, but R is false.
ⓓ. A is false, but R is true.
Correct Answer: Both A and R are true, and R is the correct explanation of A.
Explanation: The assertion is correct because dead cells do not have active protoplasm and therefore cannot carry out metabolism. The reason is also correct, since respiration is fundamentally a metabolic process taking place in living cellular material. It is not just a physical event but a series of organized biochemical reactions requiring enzymes and intact living contents. Because the reason directly explains why dead cells cannot respire, the relationship between the two statements is logically correct. This item reinforces the living-cell basis of respiration. Thus both statements are true and properly connected.
