class-x biology-questions- photosynthesisx+qs.d… · web viewglucose produced during...

CLASS-X BIOLOGY-Questions- PHOTOSYNTHESIS 2012

Class X- Biology

Questions and Answers

PROGRESS CHECK

1. Answer the following in “Yes” or “No”

I. All parts of a green plant carry out photosynthesis- Yes

II. Photosynthesis is the only biological process that releases oxygen into the air. Yes

III. Out of nine types of chlorophyll, chlorophyll a and b are most abundant.-Yes

IV. Too much light destroys chlorophyll. – Yes

V. No transpiration occurs during photosynthesis. No

VI. During sunlight, the guard cells turn flaccid to open the stomata.- No

PROGRESS CHECK

1. Write the overall chemical equation of photosynthesis

-6CO2 + 12H2O C6H12O6 + 6H2O + 6O2

2. Which substance in the above equation is repeated in raw materials as well as the end

products?

- Water

3. What is the source of oxygen released in the photosynthesis- CO2 or H2O?

- Water

4. What happens in photolysis?

- The water molecules split into its components in the presence of light.

5. Dark reaction involves utilization of CO2 in producing C6H12O6 (glucose). Why is this called

dark phase?

- Since this reactions are independent of light. It does not mean that the reaction occurs in

dark or at night.

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6. Glucose produced during photosynthesis is soon polymerized into starch. What does

polymerization mean?

- The process of conversion of smaller molecules into larger molecules (polymers) is

called polymerization.

7. Why is better to call the dark phase of photosynthesis as “light- independent phase”?

- The dark phase does not mean that it occurs when it is dark or at night. It only meant

that the reactions not dependent on light. That’s why, it is now better to called it “light-

independent phase”

PROGRESS CHECK

1. How do the following favor increased photosynthesis?

I. Large surface of the leaf

- Larger the surface area maximum light absorption occurs. Therefore the rate of

photosynthesis is more.

II. Thinness of the leaf

-it reduces the distance between cells facilitating the rapid transport. Thereby

increases the rate of photosynthesis.

III. More numerous stomata

- More numerous the stomata allow the exchange of gases (CO2 and O2). So the rate of

photosynthesis is increased.

2. Name three end- products of photosynthesis and mention the fate of each of them in the

plant

I. Name………Glucose

Fate……….. Utilized by the cells or store in the form of starch/ sucrose.

II. Name……...Water

Fate………. It’s re-utilized in the continuance of photosynthesis.

III. Name…….. Oxygen

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Fate ……… Used for respiration and releases into the atmosphere.

3. If we keep on increasing CO2 concentration in the air, will the rate of photosynthesis also

keep on increasing in the direct proportion?

Yes/No. Explain

No, the rate of photosynthesis will not increase in the direct proportion if we keep on

increasing the CO2 concentration. It’s due to the fact that the light intensity and CO2

concentration are both limiting factors for each other. The rate of the photosynthesis will

increase with the increase in CO2 concentration provided there should also increase in the

light intensity and vice versa.

PROGRESS CHECK

1. Why is it necessary to de-starch a plant before performing any experiment on

photosynthesis?

- The removal of starch will not show the presence of starch and to give correct result

from the experiment.

2. Why do we perform the iodine-test?

- To indicate the presence starch.

3. What chemical do you use to remove CO2 from inside a flask in certain experiments on

photosynthesis?

-KOH

4. All food chains start with a plant. Why is this so?

- It the producers as it provides food for all living beings

5. The honey bee produced honey. In terms of the food chain, is the honey bee a producer

or consumer?

- consumer

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REVIEW QUESTIONS

A. VERY SHORT ANSWER TYPE.

1. Name the following:

I. The category of organisms that prepare their own food from basic raw materials.

- Plants

II. The kind of plastids found in the mesophyll cells of the leaf.

- Chlorophyll

III. The compound which stores energy in the cells.

- Mitochondria

IV. The first form of food substance produced during photosynthesis.

-glucose

V. The organisms that can be called “natural purifiers” of the air.

- Plants

VI. The source of O2 for aquatic plants.

-water

VII. The part of the chloroplast where dark reaction of the photosynthesis takes place.

-stoma

VIII. The tissue that transports manufactured type of starch from leaves to all parts of the

plants.

-Phloem

B. MULTIPLE CHOICE TYPE

2. The statements given below are followed by four options each. Tick- mark the correct

option in each case.

a) Production of starch, and not glucose, is often used as a measure of photosynthesis in

the leaves.

i. Starch is the immediate product of photosynthesis

ii. Glucose formed in photosynthesis soon gets converted into starch

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iii. Starch is soluble in water.

iv. Sugar cannot be tested

-ii. Glucose formed in the photosynthesis soon gets converted into starch.

b) The number of water molecules required in the chemical reactions to produce one

molecule of glucose during photosynthesis is.

i. Six ii. Twelve iii. Eighteen iv. Twenty-four

- i. Six

c) The rate of photosynthesis is NOT affected by.

i. Light intensity ii. Humidity

ii. Temperature iv. CO2 concentration

-ii. Humidity.

d) Chlorophyll in a leaf is required for

i. Breaking down water into hydrogen and oxygen

ii. Emitting green light

iii. Trapping light energy

iv. Storing starch in the leaves

- iii. Trapping light energy.

e) If the rate of respiration becomes more than the rate of photosynthesis, plants will:

i. Continue to live, but will not be able to store food

ii. Be killed instantly

iii. Grow more vigorously because more energy will be available

iv. Stop growing and die gradually of starvation.

- iv. Stop growing and die gradually of starvation.

f) Which one of the following reactions occurs during photosynthesis?

i. Carbon dioxide is reduced and water is oxidized

ii. water is reduced and carbon dioxide is oxidized

iii. both carbon dioxide and water are oxidized

iv. both carbon dioxide and water are reduced

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-ii. Water is reduced and carbon dioxide is oxidized.

g) the specific function of light energy in the process of photosynthesis is to

i. reduce carbon dioxide

ii. synthesis glucose

iii. activate chlorophyll

iv. split water

- split water

h) a plant is kept in a dark cupboard for about 48 hours before conducting any

experiment on photosynthesis in order to

i. remove chlorophyll from the leaves

ii. remove starch from the leaves

iii. ensure that no photosynthesis occurs

iv. ensure that leaves are free from starch

-ii. Remove starch from the leaves.

i) during photosynthesis, oxygen in glucose comes from

i. CO2 ii. water

ii. Both CO2 and water iv. Oxygen via air

- ii. water

C. SHORT ANSWER TYPE

3. Mention one difference between the following on the basis of what is given in the

brackets.

a. Respiration and photosynthesis( gas released)

-respiration releases carbon dioxide and photosynthesis releases oxygen.

b. Light and dark reactions (products formed)

- Light reactions produces more molecules of ATP and no NADP production and dark

reactions produces less ATP and NADP is produced

c. Producers and consumers (mode of nutrition)

-producers are autotrophs and consumers are heterotrophs

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d. Grass and grasshopper (mode of nutrition)

-Grass- autotrophs and grasshopper- heterotrophs.

e. Chlorophyll and chloroplast (part of the plant cell)

-Chlorophyll- upper part of the mesophyll cells (palisade cells) / walls of thylakoids and

chloroplast- in mesophyll cells between upper and lower epidermis.

4. Identify the false statements and rewrite them correctly by changing the first or the last

word only

i. The dark reaction of photosynthesis occurs during night time. (False)

- The dark reaction of photosynthesis occurs are not dependent on the light.

ii. The immediate product of photosynthesis is glucose. (True)

iii. All the starch produced in a leaf remains stored in it for 2-3 weeks before it is used by

other parts of the plant. (True)

iv. Photosynthesis requires enzymes. (False)

- Photosynthesis requires light energy.

v. All green plants are consumers. (False)

- All green plants are producers.

vi. Photosynthesis results in loss of dry weight of the plants. (False)

- Transpiration results in the lost of dry weight of the plants.

vii. Photosynthesis stops at a temperature at about 350C. (True)

viii. Photosynthesis occurs only in cells containing chloroplast. ( True)

ix. All green plants perform photosynthesis. (True)

x. All algae are autotrophs. (False)

- All algae are heterotrophs

5. Fill in the blanks with the appropriate word from the choices given in the brackets

a. The site of light reaction in the cells of a leaf is………………………( cytoplasm, stoma)

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b. The chemical substance used to test the presence of starch in the cell of a leaf

is……………..( CaCl2, iodine solution, Benedict solution)

c. Stoma is ground substance in………………………(cytoplasm, chloroplast, ribosomes)

d. The dark reaction of photosynthesis is known as…………….. (Hill reaction, cyclic

phosphorylation, Calvin cycle)

e. In the flowering plants, food is transported in the form of………………………….

i. Sucrose ii. Glucose iii. Starch

6. Are the following statements true or false? Give reason in support of your answer.

a. The rate of photosynthesis continues to rise as long as the intensity of the light rises.

-False. The rate of photosynthesis increases with increase of intensity of light provided the CO 2

concentration also increases. Not simply a rise in intensity of the light will increase the intensity

of the light but CO2 too is necessary.

b. The outside atmospheric temperature has no effect on the rate of photosynthesis.

-False. With the rise in the outside atmospheric temperature, the rate of the photosynthesis rises.

The rise up to optimum temperature is suitable yet it the outside temperature is above the

optimum temperature the rate falls as the enzymes will be destroyed.

c. If I immerse a leaf intact on the plant in ice water, it will continue to photosynthesize

only at night.

-False. An immersed leaf intact on the plant in ice water will continue to photosynthesize even on

during the day if it’s in ice water because all the necessary requirements for photosynthesis are

present.

d. Destarching of the leaves of a potted plant can occur only at night.

-False. Destarching if the leaves of a potted plant do not occur simply at night but it occurs even

in day but in dark areas as there is no light for photosynthesis to occur.

e. The starting point of carbon cycle is the release of CO2 by the animals during respiration.

(True)

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f. If a plant is kept at bright light all the 24 hours for few days, the dark reaction

(biosynthetic phase) will fail to occur.

-The intensity of light required by photosynthetic process is optimum. The intensity of light

become more when its expose more and continuously. Therefore, dark reaction will fail to occur.

7. Given below are five terms. Rewrite the terms in the correct order so as to be in logical

sequence with regard to photosynthesis: water molecules, oxygen, grana, hydrogen and

hydroxyl ions, photons.

-grana, photons, water molecules, hydrogen and hydroxyl ions, , oxygen.

8. State any four differences between photosynthesis and respiration.

Sl no. Photosynthesis Respiration

1 Uses CO2 and produces O2 Uses O2 and produces CO2

2 Occurs only in plants Occurs in both plants and animals

3 Produces

carbohydrates(energy

producers)

Uses carbohydrates( energy consumers)

4 Occurs during day Occurs throughout 24 hours

9. “Oxygen is a waste product of photosynthesis”. Comment

-Oxygen is a waste product of photosynthesis. Some of the oxygen produced may used in

respiration in the leaf cells but major portion of it not required by and difuse in to the

atmosphere through the stomata.

10. Why is it necessary to place a plant in the dark before starting an experiment on

photosynthesis? Explain.

-It is necessary to place a plant in the dark before staring an experiment on photosynthesis to

destarch the leaf so that the destrached parts of the plants won’t show the presence of starch.

Whereas other non-desatrched parts will indicate the presence of starch.

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11. In most of the experiment on photosynthesis, we use a de-starched leaf or plant? What is

the purpose of destarching?

-The purpose of destarching is to remove the starch form the leaf.

12. Why is it not possible to demonstrate respiration in a green plant kept in sunlight?

-The green plant in sunlight would perform photosynthetic process faster. During this process

CO2 produced by respiration will be used up quickly by the green plants as it requires for the

process.

13. Most leaves have upper surface more green and shiny than lower one. Why?

-It is due to the fact that on the upper surface of the leaves photosynthetic process occurs only in

presence of chlorophyll which are found only in green parts of the plants mostly leaves.

14. How would you demonstrate that green plants release oxygen when exposed to light?

The green plants that release oxygen when exposed to light can be demonstrated by:

1. A water plant either Elodea or hydrilla to place in a beaker containing pond water and

cover them by a short-stemmed funnel.

2. Invert a test tube full of water over the stem of the funnel provided the water level in the

beaker is above the level of stem of the inverted funnel.

3. Place the apparatus in the sun for a few hours. Bubbles of the gas will collect in the test

tube

4. Test the gas in the test tube. Glowing splinter burst into the flame indicates the presence

of oxygen.

15. Describe the main chemical changes which occur during photosynthesis in

i. Light reaction- after the activation of chlorophyll by photons it splits the water

molecule into two components (Hydrogen and Oxygen)a s show below

2H2O energy of 4 photons 4H+ + 4e- + O2.

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H+ ions are picked up by a compound NAPD to form NADPH.

NADP+ + e- + H+ enzyme NADPH

Oxygen (O) produced is given out as molecular Oxygen (O2).

The electrons (e-) are used in converting ADP into ATP by adding one phosphate group.

ADP + P ATP this process is called phosphorylations.

ii. Dark reaction- the hydrogen of NADPH is combined with CO2 utlising ATP for

produce glucose (C6H12O6).

The CO2 is fixed in number of steps by a compound RuBP and it’s catalyzed by RuBP

carboxylase.

16. Complete the following food chains by writing the names of appropriate organisms in

the blanks.

i. Grass Rat Snake Hawk

ii. Grass mouse……..Snake peacock

17. How do non- green plants such as fungi and bacteria obtain their nourishment?

-The non-green plants such as bacteria and fungi obtain their nourishment from organic matter

like dead remains of plants and animals through decomposition process.

18. All life owes its existence to chlorophyll. Give reason.

-Chlorophyll is the site of the leaves where photosynthesis takes place. This process occurs in the

green plants and produces the glucose/ carbohydrates the food for the survival all living beings.

D. STRUCTURED/ APPLICATION/ SKILL TYPE

19. A candidate studied the importance of certain factors in photosynthesis. He took a potted

plant and kept in the dark for 24 hours. In the early hours of the next morning, he covered

one of the leaves with dark paper in the centre only. Then he placed the plant in sunlight

for few hours and tested the leaf which was covered with black paper for starch.

a. What aspect of photosynthesis was being investigated?

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-He tested to show that sunlight is necessary for photosynthesis.

b. Is there any control in this experiment? If so, state it

-Yes, the rest of the paper he haven’t covered with dark paper was control as he covered only

one of the leaves.

c. Why was the plant kept in the dark before the experiment?

-To destarch the leaf for the experiment to indicvate the presence of the starch.

d. Describe step by step, how the candidate proceeded to test the leaf for the presence of

starch.

The steps proceeded by the candidate are as follows:

1. Fix the paper on one of the one of the destarched leaves

2. Make a sketch of the leaf showing the covered and uncovered parts.

3. The experimental set up is exposed to sunlight for 2-6 hours.

4. The paper is removed and the leaf is tested for starch.

5. Starch is produced only in areas that received light, showing that

light is necessary for photosynthesis.

20. Given below is a schematic diagram to illustrate some aspects of photosynthesis.

a. Fill up the gaps, in the blank spaces (1-4), by writing the names of the correct items.

-1. Sunlight 2. Glucose 3. Oxygen ions 4. Xylem

b. What phenomenon do the thick arrows A and B indicate respectively?

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A. Transpiration B. Translocation

21. Photosynthesis in green plants is directly and indirectly dependent on so many plant

structures. Explain briefly the role of the following structures in this process.

a. Guard cells: the opening and closing of stomata for movement of water in and out.

b. Cuticle: prevent the dehydradation of the leaves.

c. Mesophyll cells: site of photosynthesis due to present of chlorophyll

d. Xylem tissue in the leaf veins: Conduction of water and other dissolved minerals

e. Phloem tissue in the leaf veins: transport the prepared food materials from lea to the

rest of the plants.

f. Stoma: Site of dark reactions.

22. Given below is the representation of a certain phenomenon in nature. With four

organisms 1-4.

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a. Name the phenomenon represented.

-Food chain is represented.

b. Name any one organism that could be shown at No. 5.

-Hawk/Eagle

c. Name biological process which was the starting point of the whole chain.

-Producers

d. Name one natural element which all the organisms 2-4 and even 5 are getting from No. 1

for their survival.

-Glucose/starch/ carbohydrates.

23. Enumerate the steps involved in testing a green leaf for the presence of starch.

The steps involved in testing the presence of starch in green plants:

1. Boil pieces of leaves in a beaker of water TO KILL THE CELLS AND BREAK THE

WALL OF LEAF CELL

2. Heat the pieces of leaf in alcohol for few minutes TO REMOVE CHLOROPHYLL

3. Soak the pieces of leaf in hot water for a little while TO SOFTEN THE LEAF

4. Using a dropper, add a few drops of iodine solution onto the pieces of leaf TO TEST FOR

STARCH

5. On observing the leaves that contains starch turn to DARK BLUE COLOUR

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24. Given alongside is the diagram of experiment set-up:

a. What is the purpose of this experiment?

-The purpose of this experiment is to prove that CO2 is necessary for photosynthesis.

b. Will it work satisfactorily? Give reason

-Yes. It will work satisfactorily because the leaf to be tested is inserted inside the conical flask

containing to KOH which absorbs CO2. The inserted inside will not indicate the presence of CO2

whereas those leaves outside will indicate the presence of starch on testing.

c. What alteration(s) will you make in it for obtaining expected result?

-It can be altered by inserting a leaf half inside and half outside.

d. Would you take any step before starting the experiment? Describe this step and explain

its necessity.

-Before starting the experiment I would destarch the leave by keeping the potted plant in the

room for 24-48 hours. Therefore, it can indicate the presence of starch in the leaf which is the

product of photosynthesis.

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25. Draw a neat diagram of the stomata apparatus found in the epidermis of the leaves and

label the stoma, guard cells, and chloroplast, epidermal cells, cell wall and nucleus.

ANSWER THE FOLLOWING SIMPLY IN “YES” OR “NO”

1. Chloroplast and chlorophyll are one and the same thing. NO

2. Oxygen given out in photosynthesis comes from the atmosphere. NO

3. The dark reaction of photosynthesis occurs during nightmare. NO

4. The immediate product of photosynthesis is glucose. YES

5. Photosynthesis can also occur in artificial light such as that of a 100 watt electric lamp.

YES

6. All the starch produced in a leaf remains stored in it for 2-3 weeks before it is used by

other parts of the plant. NO

7. Photosynthesis requires involvement of enzymes. YES

8. Plant requires several nutrients such as nitrogen sulfur and iron. Yes

9. Every green plant produces glucose as well as proteins and many other compounds. YES

10. All green plants are categorized as consumers. NO

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