Respiration in Plants Practice Questions
20 free Respiration in Plants practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is respiration in plants?
- A The process of making food using sunlight
- B The process of absorbing minerals only
- C The process of producing flowers
- D The process of releasing energy from food
Correct answer: The process of releasing energy from food
Respiration is the process by which plant cells break down food to release energy. This energy is used for growth, repair, transport, and other life processes.
Which gas is usually taken in by plants during aerobic respiration?
- A Nitrogen
- B Carbon monoxide
- C Oxygen
- D Helium
Correct answer: Oxygen
In aerobic respiration, oxygen is used to break down glucose completely. This process releases energy and produces carbon dioxide and water.
Which gas is released by plants during respiration?
- A Oxygen
- B Nitrous oxide
- C Nitrogen
- D Carbon dioxide
Correct answer: Carbon dioxide
During respiration, glucose is broken down and carbon dioxide is released as a waste product. Plants respire all the time, both during day and night.
Which food molecule is mainly broken down during respiration in plants?
- A Chlorophyll
- B Cellulose
- C Glucose
- D Minerals
Correct answer: Glucose
Glucose is the main respiratory substrate used by plant cells. It is broken down to release usable energy for cellular activities.
In which cell organelle does most aerobic respiration occur?
- A Chloroplast
- B Central vacuole
- C Cell wall
- D Mitochondrion
Correct answer: Mitochondrion
Mitochondria are the main sites of aerobic respiration in plant cells. They help release energy from glucose in the presence of oxygen.
Which of the following is the correct word equation for aerobic respiration?
- A Carbon dioxide + water + light energy → glucose + oxygen
- B Oxygen + water + sunlight → glucose + nitrogen
- C Glucose + oxygen → carbon dioxide + water + energy
- D Glucose + sunlight → oxygen + minerals + energy
Correct answer: Glucose + oxygen → carbon dioxide + water + energy
Aerobic respiration uses glucose and oxygen to produce carbon dioxide, water, and energy. This is different from photosynthesis, which makes glucose using carbon dioxide and water.
When do plants carry out respiration?
- A Only during the day
- B Only at night
- C Only during flowering
- D All the time
Correct answer: All the time
Plants respire continuously because all living cells need energy at all times. Photosynthesis occurs only when light is available, but respiration occurs day and night.
How do most leaves exchange gases for respiration?
- A Through roots
- B Through flowers
- C Through stomata
- D Through seeds
Correct answer: Through stomata
Leaves exchange gases mainly through tiny pores called stomata. Oxygen enters and carbon dioxide exits through these openings during respiration.
Which part of a plant root helps in the exchange of gases with soil air?
- A Root cap
- B Xylem vessels
- C Root hairs
- D Phloem
Correct answer: Root hairs
Root hairs are in close contact with soil particles and soil air spaces. They help roots take in oxygen needed for respiration.
Why is loose soil helpful for plant respiration?
- A It stops roots from absorbing water
- B It prevents all microorganisms from living
- C It allows air to reach the roots easily
- D It converts oxygen into glucose
Correct answer: It allows air to reach the roots easily
Loose soil contains air spaces that allow oxygen to reach the roots. Compacted or waterlogged soil can reduce oxygen supply and affect root respiration.
What happens to plant roots in waterlogged soil for a long time?
- A They begin photosynthesis faster
- B They no longer need any energy
- C They may not get enough oxygen
- D They begin absorbing only sunlight
Correct answer: They may not get enough oxygen
Waterlogged soil fills air spaces with water and reduces oxygen availability. Without enough oxygen, roots cannot respire properly and may die.
Which process in plants uses oxygen and releases energy?
- A Photosynthesis
- B Transpiration
- C Anaerobic respiration
- D Aerobic respiration
Correct answer: Aerobic respiration
Aerobic respiration uses oxygen to break down glucose and release energy. It occurs in living plant cells throughout the day and night.
Which of the following statements is true about respiration and photosynthesis in plants?
- A Respiration only occurs in animals
- B Photosynthesis releases energy from glucose
- C Respiration occurs in all living plant cells
- D Photosynthesis occurs in roots without chlorophyll
Correct answer: Respiration occurs in all living plant cells
Respiration occurs in all living plant cells because they need energy. Photosynthesis occurs mainly in green parts containing chlorophyll.
Which plant structure allows gas exchange in older woody stems?
- A Cork layer
- B Cambium
- C Lenticels
- D Pith cells
Correct answer: Lenticels
Lenticels are small openings in the bark of woody stems. They allow exchange of gases between internal tissues and the outside air.
What is anaerobic respiration?
- A Food production using sunlight energy
- B Movement of water through xylem tissue
- C Respiration that occurs without oxygen
- D Loss of water vapor from leaf surfaces
Correct answer: Respiration that occurs without oxygen
Anaerobic respiration is the breakdown of food without using oxygen. It releases less energy than aerobic respiration.
Which organism commonly performs anaerobic respiration and is useful in fermentation?
- A Mango tree
- B Earthworm
- C Yeast
- D Frog
Correct answer: Yeast
Yeast can respire anaerobically and convert sugars into alcohol and carbon dioxide. This process is useful in baking and brewing.
During anaerobic respiration in yeast, which products are formed?
- A Water and carbon dioxide
- B Water vapor and chlorophyll
- C Alcohol and carbon dioxide
- D Nitrogen gas and starch
Correct answer: Alcohol and carbon dioxide
Yeast breaks down sugar anaerobically to produce alcohol and carbon dioxide. The carbon dioxide helps dough rise during bread making.
Why do germinating seeds show a high rate of respiration?
- A They do not contain living cells
- B They only absorb sunlight
- C They need energy for rapid growth
- D They release no gases
Correct answer: They need energy for rapid growth
Germinating seeds need energy for cell division and growth of the young plant. Therefore, their rate of respiration is usually high.
Which simple test can show that germinating seeds release carbon dioxide?
- A Iodine turns starch blue-black
- B Litmus paper turns white
- C Lime water turns milky
- D Salt dissolves in water
Correct answer: Lime water turns milky
Carbon dioxide turns lime water milky due to the formation of calcium carbonate. Germinating seeds release carbon dioxide during respiration.
Why is respiration necessary in plants even though they can make their own food?
- A To stop the natural movement of water
- B To help produce new soil minerals
- C To convert stored food into usable energy
- D To slowly remove chlorophyll from leaves
Correct answer: To convert stored food into usable energy
Photosynthesis makes food, but respiration breaks down that food to release usable energy. Plants need this energy for all living activities.