Respiration in Plants

Progress Check 1

Question 1

Write the important aspects about the overall chemical equation of respiration, pertaining to the following :

1. number of steps for glucose to break down into CO₂ and H₂O.
2. involvement of enzymes.
3. forms of energy liberated.

Answer

1. The breakdown of glucose to carbon dioxide and water does not occur in a single step, but in a series of chemical steps. These steps occur in two major phases — (i) glycolysis (glucose → pyruvate) occurring in cytoplasm and (ii) Krebs cycle (pyruvate → CO₂ + 6H₂O + ATP) occurring in mitochondria.
2. Each breakdown step occurs due to a particular enzyme.
3. The energy liberated in the breakdown of glucose molecule is not all in the form of heat, but a large part of it is converted into chemical energy in the form of ATP.

Question 2

List three ways in which respiration is different from burning.

Answer

Question 3

Name the three inlets of oxygen for respiration in plants.

Answer

The three inlets of oxygen for respiration in plants are:

1. Stomata in leaves.
2. Lenticels in stem.
3. General surface of the roots.

Progress Check 2

Question 1

Give the overall chemical equation for the two kinds of respiration in plants :

1. Aerobic
2. Anaerobic

Answer

1. Aerobic respiration
   C₆H₁₂O₆ + 6O₂ $\xrightarrow{\text{enzyme}}$ 6CO₂ + 6H₂O + 38ATP

2. Anaerobic respiration
   C₆H₁₂O₆ ⟶ 2C₂H₅OH + 2CO₂ + 2ATP

Question 2

Mention any one difference other than those reflected in the two chemical equations given above.

Answer

Aerobic respiration is the primary and the most efficient way for plants to generate energy. On the other hand, Anaerobic respiration is a backup mechanism for plants when oxygen is limited and occurs temporarily for short periods.

Question 3

Certain organisms respire only anaerobically throughout their lives. Name any two such organisms.

Answer

Bacteria and fungi.

Progress Check 3

Question 1

In experiments on respiration, the seeds taken as control are boiled. Why?

Answer

In experiments on respiration, the seeds taken as control are boiled to kill them. It is done in order to compare the live seeds that can respire to dead seeds that cannot respire.

Question 2

What is the use of the following, in the experiments on respiration?

1. Soda lime
2. Limewater

Answer

1. Soda lime is used to absorb any carbon dioxide released by the seeds.
2. Limewater is used to test for the presence of carbon dioxide as carbon dioxide turns limewater milky.

Question 3

Suppose we conduct an experiment to demonstrate respiration in a green plant. What special precaution is required to be taken in it?

Answer

It is necessary that this experiment is carried out in dark in order to stop the process of photosynthesis so that the carbon dioxide liberated in respiration is not used up for photosynthesis.

Question 4

In experiment no. 5, we are using mercury in the test tube and the beaker. Why can't we use water instead?

Answer

We can't use water because it has some dissolved gases like oxygen and carbon dioxide.

Progress Check 4

Question 1

Fill in the blanks:

In anaerobic respiration in plants, the end product is ............... and ............... instead of ............... in animals.

Answer

In anaerobic respiration in plants, the end product is ethanol and carbon dioxide instead of lactic acid in animals.

Question 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.

Answer

Multiple Choice Type

Question 1

Glycolysis is a process

1. in which glycogen is broken down into glucose
2. which occurs in mitochondria
3. in which glucose is broken down into pyruvate
4. that occurs next to Krebs cycle.

Answer

in which glucose is broken down into pyruvate

Reason — Glycolysis is the first phase of respiration in which glucose is broken down into pyruvate.

Question 2

In plants, a common function is performed by?

1. Stomata and veins
2. Stomata and lenticels
3. Lenticels and sepals
4. Lenticels and hydathodes

Answer

Stomata and lenticels

Reason — Stomata are tiny pores present on surface of leaves and lenticels are present on stems. Both are responsible for gaseous exchange.

Question 3

Anaerobic respiration normally occurs in

1. Grass
2. Cactus
3. Coconut
4. Baker’s yeast

Answer

Baker’s yeast

Reason — Anaerobic respiration normally occurs in fungi.

Question 4

On oxidation of 1 molecule of glucose, .............. ATP is produced through aerobic respiration.

1. 2
2. 20
3. 18
4. 38

Answer

38

Reason — Oxidation of 1 molecule of glucose gives 38 ATP.

Question 5

Respiration in plants occurs

1. Only in stomata
2. Only in leaves
3. Only in lenticels
4. In all the parts

Answer

In all the parts

Reason — Leaves respire through stomata, stems respire through lenticel and roots respire through their general surface.

Question 6

Which of the following is produced during anaerobic respiration in plants?

1. Soda lime
2. Ethyl alcohol
3. Lime water
4. None of these

Answer

Ethyl alcohol

Reason — Anaerobic respiration in plants leads to the formation of Ethyl alcohol.

Question 7

Glycolysis takes place in :

1. Chloroplast
2. Mitochondria
3. Cytoplasm
4. Ribosomes

Answer

Cytoplasm

Reason — Glycolysis takes place in cytoplasm whereas Krebs cycle takes place in mitochondria.

Question 8

Lime water turns milky upon absorption of carbon dioxide gas due to the formation of:

1. Calcium carbonate
2. Sodium carbonate
3. Calcium chloride
4. Sodium chloride

Answer

Calcium carbonate

Reason — Calcium carbonate is formed when carbon dioxide reacts with lime water.

Question 9

Which of the following is the main substrate for any kind of respiration ?

1. Starch
2. Oxygen
3. Glucose
4. Sucrose

Answer

Glucose

Reason — Glucose is the simplest sugar. Any sugar first breaks to form glucose, which further breaks down to release energy.

Question 10

Which of the following is a catabolic process ?

1. Photosynthesis
2. Respiration
3. Both (a) and (b)
4. None of these

Answer

Respiration

Reason — Photosynthesis (anabolic process) leads to formation of glucose while respiration(catabolic process) leads to break down of the glucose molecules.

Very Short Answer Type

Question 1

Fill in the blanks:

1. ............... are the openings found on older stems.

2. Glycolysis occurs in the ............... of the cells.

3. ............... is a respiratory substance.

4. Rate of ............... is more than the rate of ............... in the daytime in the case of green plants.

5. ............... is a chemical substance which absorbs oxygen of the air.

6. ............... is used to create vacuum to show anaerobic respiration.

Answer

1. Lenticels are the openings found on older stems.

2. Glycolysis occurs in the cytoplasm of the cells.

3. Glucose is a respiratory substance.

4. Rate of Photosynthesis is more than the rate of Respiration in the daytime in the case of green plants.

5. Pyrogallate of potash is a chemical substance which absorbs oxygen of the air.

6. Caustic potash (KOH) is used to create vacuum to show anaerobic respiration.

Question 2

Name the following:

1. Energy currency of cell.
2. Oxidative breakdown of carbohydrates to release energy.
3. An organism which respires throughout life anaerobically.
4. A common phase in both aerobic and anaerobic respiration.
5. A chemical which removes CO₂ from the air.

Answer

1. ATP (Adenosine triphosphate)
2. Respiration
3. Fungus
4. Glycolysis
5. Soda lime

Question 3

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

Answer

Respiration is an essential life process for all living organisms. Therefore, plants also respire all day and all night.

Question 4

Mention if the following statements are true or false. If false, rewrite them correctly.

1. Aerobic respiration of one mole of glucose yields 138 ATP.
2. Anaerobic respiration in plants yields lactic acid.
3. Carbon dioxide readily dissolves in lime water.
4. All leaves of a green plant normally respire anaerobically at night.

Answer

1. False
   Corrected Statement — Aerobic respiration of one mole of glucose yields 38 ATP.

2. False
   Corrected Statement — Anaerobic respiration in plants yields ethanol.

3. True

4. False
   Corrected Statement — All leaves of a green plant normally respire aerobically at night.

Short Answer Type

Question 1

Define

(a) Respiration

(b) Combustion

(c) ATP

Answer

(a) Respiration — Respiration is a catabolic process of releasing energy from glucose for carrying out life processes.

(b) Combustion — Combustion or burning is defined as a physio-chemical process in which energy is liberated in the form of heat and light.

(c) ATP — ATP is defined as energy currency of the cell as it acts as the immediate source of energy for different life processes.

Question 2

Name:

(a) Two raw materials of respiration.

(b) Two end products of aerobic respiration.

(c) Two microbes which normally respire anaerobically

Answer

(a) Glucose and Oxygen

(b) Carbon dioxide and water

(c) Bacteria and Fungi

Question 3

Write the full form of ATP and ADP.

Answer

Full form of ATP — Adenosine triphosphate

Full form of ADP — Adenosine diphosphate

Question 4

What happens to the energy liberated in respiration?

Answer

The energy liberated in respiration is stored in the form of ATP inside the cells. Some part of it is lost as heat to the surroundings.

Question 5

How is the tilling of the soil useful for the crops growing in it?

Answer

Tilling makes the soil porous and airy. The parts of the plant present below the ground receive adequate oxygen supply to respire. This way tilling facilitates faster crop growth.

Question 6

Why is it usually difficult to demonstrate respiration in green plants?

Answer

During day time, both photosynthesis and respiration takes place in green plants. Evolution of carbon dioxide is an indicator to demonstrate respiration in living organisms. Carbon dioxide produced during respiration in plants gets utilized during photosynthesis and thus, there is no evolution of carbon dioxide. Consequently, it becomes difficult to demonstrate respiration in green plants as there in no evolution of carbon dioxide during day time.

Question 7

Can cell respiration occur in any organism at a temperature of about 65°C? Give reason.

Answer

Cell respiration cannot occur in any organism at a temperature of about 65°C because the enzymes involved in respiration become inactivated at high temperatures.

Long Answer Type

Question 1

Distinguish between the following pairs:

(a) Aerobic and anaerobic respiration

(b) Respiration and combustion

(c) Stomata and lenticels

(d) Photosynthesis and respiration

(e) Anaerobic respiration in plants and animals

Answer

(a) Difference between Aerobic and anaerobic respiration:

(b) Difference between Respiration and combustion:

(c) Difference between Stomata and lenticels:

(d) Difference between Photosynthesis and respiration:

(e) Difference between Anaerobic respiration in plants and animals:

Question 2

How do the following structures help in respiration in plants?

(a) Lenticels

(b) Stomata

(c) Root hairs

Answer

Given below are the ways in which the following structures help in plant respiration:

(a) Lenticel — These help the stem to participate in respiration.

(b) Stomata — These help the leaves to participate in respiration.

(c) Root hairs — These help the roots to participate in respiration.

Question 3

How are aerobic and anaerobic respirations different in plants?

Answer

The differences between aerobic and anaerobic respiration in plants are as follows:

Question 4

Explain why respiration is said to be the reverse of photosynthesis.

Answer

Respiration is said to be the reverse of photosynthesis due to the following reasons :

1. In respiration, the organic food is disintegrated into its inorganic compounds, namely –
   Carbon dioxide and Water. In photosynthesis, the organic food is manufactured from its inorganic components, namely - Carbon dioxide and Water.
2. In respiration, Carbon dioxide is released whereas in Photosynthesis Carbon dioxide is consumed.
3. Oxygen is consumed during respiration while Oxygen is evolved in photosynthesis
4. Energy is liberated in Respiration while in Photosynthesis, energy is absorbed.

Question 5

What is respiration? How are respiration and burning similar and how are they different?

Answer

Oxidation of organic food particularly carbohydrates in living cells to release energy is called respiration.

Similarities between burning and respiration are —

1. Oxygen is required by both.
2. Energy is released by both.
3. The outcome of both is water and carbon dioxide.

Differences between burning and respiration:

Question 6

Describe one experiment each you would perform to demonstrate the following phenomena: The germinating seeds

1. Produce heat,
2. Give out Carbon dioxide,
3. Can respire even in total absence of air.

Answer

1. Aim — Experiment demonstrating the fact that germinating seeds produce heat.

Procedure —

1. Name two thermo flasks as 'A' and 'B', keep them aside
2. Approximately 200 pea seeds or beans would be used in the experiment. Soak them in water for more than 24 hours.
3. Split the seeds into two equal groups approximately
4. One group of seeds are killed by boiling them and washing them with dilute formaline in order to restrict bacterial decay
5. The live germinating seeds need to be placed in flask A and the boiled/killed seeds in flask B.
6. Introduce a thermometer into each of the flasks and seal their mouths with cotton wool.
7. Take note of the initial reading observed in the thermometer.

Inference —

1. A few hours later, thermometer in the flask A shows a higher reading depicting that the seeds that germinate generate heat.

2. Flask B shows no rise in the temperature.

3. Aim — Experiment demonstrating the fact that germinating seeds produce Carbon dioxide.

Procedure —

1. Name two thermo flasks as ‘A’ and ‘B’, keep them aside.
2. At the base of both the flasks, place wet cotton wool.
3. In flask A, take a few soaked seeds of pea, simultaneously take equal quantity of boiled seeds in flask B.
4. To flask B, add some carbolic acid so as to inhibit bacterial growth on the dead seeds.
5. Seal the flasks with a cork, leave them undisturbed for a couple of days.
6. Observe the changes.

Inference —

1. Post few days, germination of seeds in flask A is observed.

2. Flask B shows no signs of seed germination.

3. Cork is removed to test the gases in each of the flasks. The flask is toppled over a test tube which carries limewater. The test tube is then shaken up.

4. Indication of carbon dioxide as expected in flask A is observed when lime water turns milky, thereby depicting that germinating seeds produce carbon dioxide.

5. The gas in the flask B shows no effect upon coming in contact with limewater, indicating absence of carbon dioxide.

6. Aim — Experiment demonstrating the fact that seed germination undergoes respiration even in complete absence of air

Procedure and Inference —

1. Fill a test tube with mercury that is inverted into a beaker of mercury.
2. Into this tube, push some soaked and peeled off pea seeds before inverting into the mercury beaker.
3. You will observe that seeds will float up and are entirely girdled by mercury.
4. A few days later, few changes are observed. Mercury level drops, presence of some gases are detected in the tube.
5. Pour in some KOH into the tube.
6. Gas in the tube is absorbed, mercury level rises again, depicting that the gas was carbon dioxide
7. Consequently it is proved that the germinating seeds undergo respiration even in the total absence of air.

Question 7

Draw a neat and labelled, diagram showing the experimental set up (initial and final stages) to demonstrate anaerobic respiration in germinating seeds.

Answer

Below diagram shows the experimental set up (initial and final stages) to demonstrate anaerobic respiration in germinating seeds:

Structured / Application / Skill Type

Question 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 + ...... + 38ATP

(b) C₆H₁₂O₆ → ...... + 2CO₂ + 2ATP

1. Fill in the blanks of each reaction
2. Name the process represented by the two chemical equations
3. What are the conditions under which the two reactions (a) and (b) are occurring?

Answer

1. (a) 6H₂O
   (b) 2C₂H₅OH
2. (a) The process observed in this chemical reaction here is aerobic respiration
   (b) The process observed in this chemical reaction is anaerobic respiration
3. The reaction occurring in (a) can take place only in the presence of oxygen as it is aerobic respiration. The reaction occurring in (b) can take place even in the absence of oxygen as it is anaerobic respiration.

Question 2

Given below is a set of six experimental set-ups (A-F), kept in this state for about 24 hours.

(a) In how many flasks, the different plant parts have been kept under observation?

(b) What is the purpose of keeping a test-tube containing limewater in each flask?

(c) In which tube/tubes the limewater will turn milky?

(d) What is the purpose of the set-up F?

(e) What conclusion can you draw from this experiment?

Answer

(a) The different plant parts for observation have been placed in five flasks right from A-E flasks as observed in the diagram.

(b) It is the property of limewater to absorb Carbon dioxide. Hence it is placed in the flask, so as to absorb Carbon dioxide and turn milky in the presence of any Carbon dioxide.

(c) Limewater turns milky in the presence of Carbon dioxide. All five flasks from A to E have plant parts hence respiration takes place in all five parts causing the limewater to turn milky. In flask F, respiration does not take place as there is no plant part, hence no change is observed

(d) In the experiment, the setup F depicts the experiment control, wherein all conditions are maintained in the same way except for the plant part that is absent in flask F.

(e) The experiment clearly shows that Carbon dioxide is produced during the process of respiration.

Question 3

The following 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?

(b) Why has the coloured water risen in tubing 1?

(c) What is the purpose of keeping boiled peas soaked in a disinfectant in test tube Y?

(d) Name the biological process which causes the above rise.

(e) Define the biological process shown in the experiment

Answer

(a) To check the presence of Carbon dioxide, potassium hydroxide is placed in the test tubes X and Y. Potassium hydroxide has a special property of absorbing Carbon dioxide if produced.

(b) In the test tube X, when the process of respiration takes place, the oxygen is consumed that is present in the test tube. Due to respiration, Carbon dioxide that is produced is absorbed by the KOH in the test tube. Due to consumption of Oxygen, a space is developed causing the colored water to rise in the tubing 1.

(c) It is because the seeds die once they are boiled and hence cannot undergo respiration. This is why respiration does not take place in test tube Y.

(d) The biological process that causes a rise is respiration.

(e) It is respiration. It is a catabolic process wherein energy is liberated from simple sugars to be able to carry out life processes.

Question 4

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.

(b) What is the function of soda lime in the bottle 'A' and why is limewater placed in bottle 'B'?

(c) What change would you expect to observe in bottle 'D'?

(d) Represent the physiological process named in (a) above in the form of a chemical equation.

(e) In order to obtain accurate results, the bottle ‘C’ should be covered with a piece of black cloth. Why?

(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?

Answer

(a) The experiment demonstrates that carbon dioxide is produced during the process of respiration in germinating seeds.

(b) Soda lime is placed in bottle ‘A’ as it indicates the passage/presence of Carbon dioxide in bottle A. Another property of soda lime is that is absorbs Carbon dioxide that is present in the air. The clear limewater in bottle B indicates that the air that enters the flask C is free from Carbon dioxide.

(c) The bottle D holding limewater should indicate that carbon dioxide is produced as a result of respiration occurring in bottle ‘C’ possessing the germinating seeds. As carbon dioxide is produced in the bottle C, limewater turns milky that enters the bottle 'D'.

(d) The chemical reaction is as written below:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38ATP (energy)

(e) The bottle 'C' is covered with a black cloth in order to restrict any chance of photosynthesis so as to make sure the process of respiration only is carried out and observed.

(f) A thermometer is inserted in bottle C to observe the changes in temperature. Respiration causes the temperature to rise, if there is no respiration, the temperature will not rise.