Respiration in Plants - Questions & Answers

1. Write the important aspects about the overall chemical equation of respiration, pertaining to the following :
(i) number of steps for glucose to break down into CO2 and H2O.
It does not occur in a single step, but in a series of chemical steps.
(ii) involvement of enzymes.
Each breakdown step is strictly due to a particular enzyme.
(iii) forms of energy liberated.
Energy is liberated as chemical energy in the form of ATP and some heat.

2. List three ways in which respiration is different from burning.
(1) Respiration is a cellular process, whereas burning is non-cellular. (2) Respiration occurs at body temperature in a series of chemical steps, while burning occurs at high temperature (ignition point) in a single step. (3) Respiration is carried out by enzymes and energy is liberated as ATP and some heat, whereas burning is carried out by heat and all energy is liberated as massive heat and light.

3. Name the three inlets of oxygen for respiration in plants.
(1) Stomata in leaves, (2) Lenticels in stems, (3) General surface of the roots.

1. Give the overall chemical equation for the two kinds of respiration in plants :
(i) Aerobic
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP
(ii) Anaerobic
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2 ATP

2. Mention any one difference other than those reflected in the two chemical equations given above.
Aerobic respiration occurs normally throughout life, whereas anaerobic respiration occurs temporarily for short periods.

3. Certain organisms respire only anaerobically throughout their lives. Name any two such organisms.
Certain bacteria and fungi.

1. In experiments on respiration, the seeds taken as control are boiled. Why ?
Boiling kills the seeds. They are used as a control to prove that the process of respiration (like consuming oxygen, releasing carbon dioxide, or producing heat) is carried out only by living organisms.

2. What is the use of the following in the experiments on respiration ?
(i) Soda lime
It is used to absorb any carbon dioxide present in the incoming air or released by the seeds.
(ii) Limewater
It is used to test for the presence of carbon dioxide, as it turns milky when carbon dioxide passes through it.

3. Suppose we conduct an experiment to demonstrate respiration in a green plant. What special precaution is required to be taken in it ?
The experiment must be carried out in the dark, or the apparatus must be completely covered with a piece of black cloth to prevent photosynthesis. Otherwise, the carbon dioxide liberated in respiration will be used up in the synthesis of starch.

4. In experiment no. 5, we are using mercury in the test tube and the beaker. Why can't we use water instead ?
We cannot use water because water absorbs/dissolves some of the carbon dioxide produced, which would affect the results, and water contains dissolved oxygen. Mercury does not react with or dissolve carbon dioxide and completely blocks air.

1. Fill in the blanks :
In anaerobic respiration in plants, the end product is ethanol (ethyl alcohol) and carbon dioxide instead of lactic acid in animals.

2. The table below is intended to give certain differences between photosynthesis and respiration, but a few points are given wrongly. Strike out the wrong ones and write the correct words instead.
Corrected Table:
PHOTOSYNTHESIS
(i) Results in gain in weight
(ii) Glucose is the product
(iii) Occurs in green cells only (Correct)
(iv) Uses water and carbon dioxide

RESPIRATION
(i) Results in loss in weight
(ii) Glucose is broken down
(iii) Occurs in all cells (Correct)
(iv) Uses glucose and oxygen (Correct)

1. Choose the correct answer from the options given below :

(i) Glycolysis is a process
(a) in which glycogen is broken down into glucose
(b) which occurs in mitochondria
(c) in which glucose is broken down into pyruvate
(d) that occurs next to Krebs cycle.
(c) in which glucose is broken down into pyruvate

(ii) In plants, a common function is performed by?
(a) Stomata and veins
(b) Stomata and lenticels
(c) Lenticels and sepals
(d) Lenticels and hydathodes
(b) Stomata and lenticels

(iii) Anaerobic respiration normally occurs in
(a) Grass
(b) Cactus
(c) Coconut
(d) Baker's yeast
(d) Baker's yeast

(iv) On oxidation of 1 molecule of glucose, .............. ATP is produced through aerobic respiration.
(a) 2
(b) 20
(c) 18
(d) 38
(d) 38

(v) Respiration in plants occurs :
(a) Only in stomata
(b) Only in leaves
(c) Only in lenticels
(d) In all the parts
(d) In all the parts

(vi) Which of the following is produced during anaerobic respiration in plants?
(a) Soda lime
(b) Ethyl alcohol
(c) Lime water
(d) None of these
(b) Ethyl alcohol

(vii) Glycolysis takes place in :
(a) Chloroplast
(b) Mitochondria
(c) Cytoplasm
(d) Ribosomes
(c) Cytoplasm

(viii) Lime water turns milky upon absorption of carbon dioxide gas due to the formation of :
(a) Calcium carbonate
(b) Sodium carbonate
(c) Calcium chloride
(d) Sodium chloride
(a) Calcium carbonate

(ix) Which of the following is the main substrate for any kind of respiration ?
(a) Starch
(b) Oxygen
(c) Glucose
(d) Sucrose
(c) Glucose

(x) Which of the following is a catabolic process ?
(a) Photosynthesis
(b) Respiration
(c) Both (a) and (b)
(d) None of these
(b) Respiration

(xi) The two major phases during the breakdown of glucose in respiration are (P) .................. and (Q) .................. .
(a) P — Glycogenesis Q — Kreb's cycle
(b) P — Aerobic respiration, Q — Anaerobic respiration
(c) P — Anoxybiotic respiration Q — Oxybiotic respiration
(d) P — Glycolysis Q — Kreb's cycle
(d) P — Glycolysis Q — Kreb's cycle

(xii) A biology teacher aksed her students to give the end products of anaerobic respiration in plants/animals.
John said : Carbon dioxide and water.
Kabir said : Glucose and water vapour.
Sukhvinder said : Carbolic acid and lactic acid.
Aayush said : Lactic acid.
Who were correct ?
(a) John and Kabir
(b) Kabir and Sukhvinder
(c) Sukhvinder and Aayush
(d) John and Aayush
Aayush correctly named the product of anaerobic respiration in animals (lactic acid). Note: None of the students correctly named the plant products (ethyl alcohol and carbon dioxide).

1. Fill in the blanks :
(a) Lenticels are the openings found on older stems.
(b) Glycolysis occurs in the cytoplasm of the cells.
(c) Glucose is a respiratory substance.
(d) Rate of photosynthesis is more than the rate of respiration in the daytime in the case of green plants.
(e) Alkaline pyrogallol is a chemical which absorbs oxygen of the air.
(f) Mercury is used to create vacuum to show anaerobic respiration.

2. Name the following :
(a) Energy currency of cell.
ATP (Adenosine Triphosphate)
(b) Oxidative breakdown of carbohydrates to release energy.
Respiration
(c) An organism which respires throughout life anaerobically.
Certain bacteria / Fungi (yeast)
(d) A common phase in both aerobic and anaerobic respiration.
Glycolysis
(e) A chemical which removes CO2 from the air.
Soda lime / Potassium hydroxide

3. Do the plants respire all day and all night or only at night ?
Plants respire all day and all night.

4. Mention if the following statements are true or false. If false, rewrite them correctly.
(a) Aerobic respiration of one mole of glucose yields 138 ATP (T/F)
False. Aerobic respiration of one mole of glucose yields 38 ATP.
(b) Anaerobic respiration in plants yields lactic acid. (T/F)
False. Anaerobic respiration in plants yields ethanol (ethyl alcohol) and carbon dioxide.
(c) Carbon dioxide readily dissolves in lime water. (T/F)
True.
(d) All leaves of a green plant normally respire anaerobically at night. (T/F)
False. All leaves of a green plant normally respire aerobically at night.

1. Define :
(a) Respiration
Respiration is a breaking down process by which a living cell oxidises organic substances (glucose) and releases carbon dioxide, water vapour and energy.
(b) Combustion
Combustion (burning) is a non-cellular, physico-chemical process that occurs at high temperature in a single step, liberating energy as heat and light.
(c) ATP
ATP (Adenosine Triphosphate) is the chemical compound that acts as the "energy currency of the cell", storing chemical energy liberated during respiration.

2. Name :
(a) Two raw materials of respiration.
Glucose and Oxygen.
(b) Two end products of aerobic respiration.
Carbon dioxide and Water.
(c) Two microbes which normally respire anaerobically.
Certain bacteria and fungi.

3. Write the full form of ATP and ADP.
ATP: Adenosine Triphosphate.
ADP: Adenosine Diphosphate.

4. What happens to the energy liberated in respiration ?
A large part of the energy liberated is converted into chemical energy in the form of ATP, and some of it is released as heat.

5. How is the tilling of the soil useful for the crops growing in it ?
Ploughing or tilling of the soil creates tiny air spaces around soil particles and provides the source of oxygen for the roots to respire.

6. Why is it usually difficult to demonstrate respiration in green plants ?
During daytime, the carbon dioxide produced during respiration in the leaves serves as a raw material for photosynthesis, making it difficult to detect its release.

7. Can cell respiration occur in any organism at a temperature of about 65°C ? Give reason.
No. Respiration is carried out by enzymes, and high temperatures like 65°C would denature (destroy) these enzymes, stopping the process.

1. Distinguish between the following pairs :
(a) Aerobic and anaerobic respiration
Aerobic respiration proceeds in the presence of oxygen, completely breaks down glucose, and produces 38 ATP, CO2, and water. Anaerobic respiration proceeds without oxygen, incompletely breaks down glucose, and produces 2 ATP, ethanol, and CO2 (in plants).
(b) Respiration and combustion
Respiration is a cellular, biochemical process at body temperature in a series of steps via enzymes, yielding ATP and heat. Combustion is non-cellular, physico-chemical at high temperature in a single step, yielding huge heat and light.
(c) Stomata and lenticels
Stomata are tiny openings found mainly on leaves, while lenticels are openings found on older stems. Both act as inlets for oxygen.
(d) Photosynthesis and respiration
Photosynthesis is an anabolic process occurring only in green cells in light, utilizing CO2 and water to manufacture glucose and release oxygen. Respiration is a catabolic process occurring in all living cells at all times, utilizing glucose and oxygen to release energy, CO2, and water.
(e) Anaerobic respiration in plants and animals
In plants, anaerobic respiration produces ethanol (ethyl alcohol) and carbon dioxide. In animals, it produces lactic acid.

2. How do the following structures help in respiration in plants?
(a) Lenticels
They provide an inlet on the stem for oxygen from the atmosphere to diffuse in.
(b) Stomata
They provide an inlet on the leaves for oxygen from the atmosphere to diffuse in.
(c) Root hairs
The general surface of the roots (including root hairs) absorbs oxygen trapped in the air spaces of the soil.

3. How are aerobic and anaerobic respirations different in plants ?
Aerobic respiration uses oxygen, causes complete breakdown of glucose, produces CO2 and water, yields 38 ATP per glucose, and occurs normally throughout life. Anaerobic respiration occurs without oxygen, causes incomplete breakdown of glucose, produces ethyl alcohol and CO2, yields 2 ATP, and occurs temporarily for short periods.

4. Explain why respiration is said to be the reverse of photosynthesis. (HOTS)
The requirements of one are the products of the other. Photosynthesis uses CO2 and H2O to produce glucose and O2, resulting in a gain in weight. Respiration uses glucose and O2 to produce CO2 and H2O, resulting in a loss in weight. One is a constructive (anabolic) process, and the other is a destructive (catabolic) process.

5. What is respiration ? How are respiration and burning similar and how are they different?
Respiration is a catabolic process of releasing energy from glucose for life processes. They are similar because both liberate energy and both give end products CO2 and water vapour. They are different because respiration is a cellular, multi-step enzymatic process occurring at body temp producing ATP, while burning is non-cellular, single-step without enzymes, requiring high heat and producing massive heat and light.

6. Describe one experiment each you would perform to demonstrate the following phenomena : The germinating seeds (a) produce heat, (b) give out carbon dioxide, (c) can respire even in total absence of air.
(a) Produce heat: Place germinating seeds in a flask and boiled seeds in a control flask. Insert a thermometer into each. After a few hours, the thermometer in the germinating seeds flask will show a higher reading.
(b) Give out CO2: Keep germinating seeds in a flask connected to a test tube containing limewater. The gas released flows into the tube and turns the limewater milky.
(c) Absence of air: Fill a test tube with mercury, invert it over a beaker of mercury. Insert soaked, peeled seeds into it. After a few days, the mercury level drops as CO2 gas is liberated, proving respiration occurs without air.

7. Draw a neat and labelled diagram showing the experimental set up (initial and final stages) to demonstrate anaerobic respiration in germinating seeds.
(Diagram based on text: A test tube filled with mercury inverted in a beaker of mercury. Peeled germinating seeds are pushed up into the inverted tube. In the final stage after 2-3 days, the mercury level in the tube falls as the liberated CO2 gas collects at the top.)

1. The following two chemical reactions are supposed to indicate a certain process occurring in the green plants under two different conditions :
(a) C6H12O6 + 6O2 → 6CO2 + ....... + 38 ATP
(b) C6H12O6 → ............... + 2CO2 + 2ATP
(i) Fill in the blanks of each reaction.
(a) 6H₂O
(b) 2C₂H₅OH
(ii) Name the process represented by the two chemical equations.
(a) Aerobic respiration.
(b) Anaerobic respiration.
(iii) What are the conditions under which the two reactions (a) and (b) are occurring ?
Reaction (a) occurs in the presence of free oxygen. Reaction (b) occurs in the absence of oxygen.

2. The experimental set-up given below demonstrates anaerobic respiration in germinating seeds. Read the information below the figure and answer the following questions : (EL)
(a) Why do we fill mercury in the test tube ? Can we do the same experiment in water or air ?
Mercury completely blocks air/oxygen and does not react with or dissolve the CO2 gas produced. We cannot do this in water because water would dissolve some CO2 and contains dissolved oxygen. Air cannot be used as we need to prove respiration occurs without it.
(b) Name the gas released by the germinating seeds, shown (A) in the figure.
Carbon dioxide.
(c) Can we do the above experiment with the seeds without peeling them ?
Yes, but peeling off the seed coat hastens the outward diffusion of CO2.
(d) How can we test the gas released in the above set-up ? Explain in short.
Introduce a stick of potassium hydroxide into the test tube. It will float up through the mercury and absorb the carbon dioxide gas, causing the level of mercury to rise again.
(e) How can we set the 'control set-up' for the above experiment ?
Set up a similar experiment, but use dead seeds killed by heating and sterilized with an antiseptic like carbolic acid to prevent bacterial decay.

3. In order to study and prove a particular physiological process in plants, the following experiment was set up. Study the same and then answer the questions that follow :
(a) Name the physiological process being studied.
Respiration (specifically proving carbon dioxide is given out by germinating seeds).
(b) What is the function of soda lime in the bottle 'A' and why is limewater placed in bottle 'B'?
Soda lime in 'A' absorbs any carbon dioxide present in the incoming air. Limewater in 'B' confirms that the air passing through to the next flask is completely free of carbon dioxide (as it remains clear).
(c) What change would you expect to observe in bottle 'D'?
The limewater in bottle 'D' will turn milky.
(d) Represent the physiological process named in (a) above in the form of a chemical equation.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP
(e) In order to obtain accurate results, the bottle 'C' should be covered with a piece of black cloth. Why?
To prevent photosynthesis, which would use up the carbon dioxide liberated during respiration.
(f) If bottle 'C' was fitted with a 3-holed rubber stopper and a thermometer were introduced in such a way that its bulb reaches close to the germinating seeds, what would you observe? Why?
The thermometer would show a higher temperature reading, indicating that heat is evolved during respiration.

4. The given diagram refers to an apparatus which is used to demonstrate a physiological process :
(a) What is the purpose of keeping potassium hydroxide solution in the test tubes X and Y?
To absorb the carbon dioxide gas released by the germinating seeds.
(b) Why has the coloured water risen in tubing 1?
The germinating seeds in the flask consume oxygen during respiration, and the potassium hydroxide absorbs the CO2 produced. This creates a partial vacuum in the flask, causing the coloured water to rise in tubing 1.
(c) What is the purpose of keeping boiled peas soaked in a disinfectant in test tube Y?
They serve as a control set-up to prove that respiration only takes place in living seeds.
(d) Name the biological process which causes the above rise.
Respiration.
(e) Define the biological process shown in the experiment.
Respiration is a breaking down process by which a living cell oxidises organic substances (glucose) and releases carbon dioxide, water vapour and energy.

5. Given alongside is a set of six experimental set-ups (A-F), kept in this state for about 24 hours. (EL)
(a) In how many flasks, the different plant parts have been kept under observation?
Five flasks (A, B, C, D, and E).
(b) What is the purpose of keeping a test-tube containing limewater in each flask?
To detect the evolution of carbon dioxide gas, which turns the limewater milky.
(c) In which tube/tubes the limewater will turn milky?
In the tubes placed inside flasks A, B, C, D, and E.
(d) What is the purpose of the set-up F?
It acts as a control (with no plant part) to prove that the CO2 production turning the limewater milky only happens due to the living plant tissues.
(e) What conclusion can you draw from this experiment?
The experiment concludes that every part of a plant (fruits, leaves, flowers, stems, roots) respires and produces carbon dioxide.

(Choose the answer based on the codes given below.)
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

(i) Assertion (A) : All the parts of a plant respire all the time, whether it is day or night.
Reason (R) : Among all the parts of a plant, only the leaves respire because they contain stomata which help in the diffusion of respiratory gases.
(c) A is true but R is false.

(ii) Assertion (A) : Respiration is a catabolic process which produces energy in the form of ATP.
Reason (R) : Respiration is the process in which glucose is broken down in a series of chemical steps to produce energy.
(a) Both A and R are true and R is the correct explanation of A.

(iii) Assertion (A) : End products of anaerobic respiration in plants are ethyl alcohol and carbon dioxide.
Reason (R) : Incomplete breakdown of glucose occurs in the anaerobic respiration of plants.
(a) Both A and R are true and R is the correct explanation of A.

(iv) Assertion (A) : In many respects, respiration and photosynthesis in plants are distinctly opposite processes.
Reason (R) : In photosynthesis, food is oxidised; whereas in respiration, food is manufactured.
(c) A is true but R is false. (Reason is reversed)

(v) Assertion (A) : Kreb's cycle occurs in the mitochondria of a cell and releases energy.
Reason (R) : Glycolysis and kreb's cycle are the two steps of respiration. They both occur in the mitochondria and release energy.
(c) A is true but R is false. (Glycolysis occurs in the cytoplasm)

(vi) Assertion (A) : Lenticels are the openings found on the surface of roots.
Reason (R) : Lenticels help in the diffusion of gases.
(d) A is false but R is true. (Lenticels are found on stems)

1. While helping his mother trim the garden shrubs, Adarsh noticed tiny white dots on the stem of a guava plant. Curious, he gently scratched the bark and saw the spots remained unchanged, unlike normal tissue. Later during his biology class, he understood that these pores are respiratory structures. His biology teacher explained that plants do not have lungs like us but they also respire with the help of pores present on the stem as well as on the surfaces of leaves.
(a) What are these special pores found on the surface of stems and on the surface of leaves called ?
On the surface of stems: Lenticels. On the surface of leaves: Stomata.
(b) Are the main steps of respiration in plants similar to that in humans ?
Yes, the basic aspects of cellular respiration (glycolysis and Krebs cycle) are the same in all organisms.
(c) Name the cell organelle which is mainly involved in the production of energy.
Mitochondria.
(d) Which surface of the leaves contains more number of these respiratory pores and how is it advantageous to the plants ?
The lower surface of the leaves generally contains more stomata. It is advantageous because it prevents direct exposure to sunlight, thereby reducing excessive water loss through transpiration.
(e) Write two more significant processes which occur through these respiratory pores found on the surface of leaves.
Photosynthesis (gaseous exchange of CO2 and O2) and Transpiration.