Important Questions Class 11 Biology Chapter 11

Class 11 Biology Chapter 11 Important Questions: Transport in Plants

Biology is a subject that all of us should study to  understand the world in a better way where  we live , and it is a key subject for careers in the life sciences and healthcare domain. Chapter 11 of CBSE Class 11 Biology deals with Transport in Plants. Plants transport various substances like gases, minerals, water, hormone, and organic solutes from one cell to another in a short distance or as water from roots to the tips of the stem, which is a long distance. Long-distance transport occurs through the vascular system, xylem and phloem and is called translocation through mass flow.

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Important Questions Class 11 Biology Chapter 11 Transport in Plants – With Solutions

Solving all the questions given in our question bank of Biology Class 11 Chapter 11 Important Questions helps students enhance their knowledge and upgrade their understanding of this topic by strengthening their concepts. Our  subject experts  at Extramarks with years of experience know how to handle students’ dilemma by  imparting education in an easy and understandable manner to enrich their learning experience and help them get excellent scores. Therefore, we focus on developing content that includes all the necessary questions and solutions for the topics studied in the chapter. Our question bank of Class 11 Biology Chapter 11 Important Questions covers all questions from the chapter Transport in Plants. .

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Given below are some of the important questions and solutions from our Important Questions Class 11 Biology Chapter 11.

Question 1.

What is the process of osmosis?

Answer 1: 

Osmosis is the movement of water molecules from a region of high concentration to a region of low concentration through the semipermeable plasma membrane. It is a vital process, and many  physiological processes in plants take through osmosis.

Question 2. What do you mean by active transport of water?

Answer 2- 

Active transport is the transport of water molecules against the concentration gradient with the help of energy through ATP. The molecules move from low to high concentrations in the active transport of water.

Question 3 

What are the necessary conditions for imbibition to take place?

Answer 3- 

There are two necessary conditions for imbibition to occur:

Firstly, the water potential gradient occurs between the surface of the adsorbent and the liquid imbibed in it.

Secondly, it’s  the affinity between the adsorbent and the imbibed liquid. It is also a type of diffusion by which water movement occurs.

Question 4.

Describe the water relations of a plant cell briefly when it is placed in the following solutions- 

(a) Hypertonic solution

(b) Hypotonic solution 

Answer 4

1. a) Hypertonic solution

The exosmosis process occurs when the cell is kept in a hypertonic solution. In this process, the protoplast contracts and the cell membrane detaches itself from the cell wall, which results in a contracted protoplast. This contraction of the protoplast by the osmosis process is termed plasmolysis.

(b) Hypotonic solution.

Endosmosis occurs when a plasmolysed cell is placed in a hypotonic solution, and the protoplast regains its original position. This phenomenon is termed de-plasmolysis.

Question 5.

Describe the ascent of sap briefly.

Answer 5:

Water and minerals are absorbed by plants through roots (diffusion) from the soil and are transported to different parts of the plant, as water plays a vital role in their growth and development. Water, along with various dissolved inorganic substances, is called sap. This upward translocation of sap containing water and dissolved inorganic substances from the roots to the plant’s aerial parts is known as sap’s ascent.

Question 6.

What are the various advantages of transpiration?

Answer6- 

Ascent of sap: Firstly, the transpiration pull created in leaves is responsible for the ascent of sap.

Absorption of water: The Transpiration pull is also responsible for the passive absorption of water through the roots.

Transmission of minerals in different parts of the plant is also done by transpiration.

Cooling effect: Transpiration causes a cooling effect by lowering the temperature of the leaf.

The increased rate of transpiration favours the growth and development of tissue, which provides strength and stability to the plant.

Excessive transpiration induces hardness which results in resistance of plants in a drought.

Q7. Describe why osmosis is a special case of diffusion. 

Answer 7: 

The uptake and distribution of water, solutes, and gases occur through diffusion. The diffusion of water occurs through a semipermeable membrane. This process of diffusion is known as osmosis. Also, the diffusion of water molecules continues across the semipermeable membrane until an equilibrium condition is attained. Osmosis can also be demonstrated by a simple experiment as follows:

A thistle funnel is taken and then tied with a semipermeable membrane. For example, parchment paper is tight and attached to the thistle funnel’s wide mouth.

The thistle funnel is filled with concentrated sugar solution while its wide mouth is dipped in water in a beaker. The semipermeable membrane allows the water molecules to pass through but stops the sugar molecules. Due to this, the level of sugar solution rises in the funnel. This demonstrates the process of osmosis.

A demonstration of the osmosis process can be done easily. A thistle funnel is taken and filled with sucrose solution. Then it is kept inverted in a beaker containing water.

(a) Water will diffuse across the semipermeable membrane to raise the level of the solution in the funnel

(b) Pressure will be applied to stop the water movement into the funnel.

Q8. What is the major factor which affects the rate of transpiration?

Answer 8:

Two major factors affect the transpiration rate.

1. External or Environmental factors.
2. Internal or Living factors.

     A.External factors:

It is also called environmental factors. The light source causes stomatal opening.

Based on temperature: High temperature decreases the relative humidity, which increases transpiration.

Based on humidity: Humidity directly affects the rate of transpiration which is related to the vapour pressure of the atmosphere.

The wind: High velocity of wind results in the closure of stomata.

Soil moisture: The transpiration rate is directly proportional to the quantity of available moisture in the soil.

     B.Internal factor:

Root Shoot Ratio: Roots absorb water and should transpire water. Hence their ratio affects the transpiration rate.

Leaf area: Due to the surface area, smaller plants tend to transpire more rapidly per unit area than larger plants.

Leaf Anatomy: Modification of leaves affects transpiration.

Question 9 Explain facilitated diffusion briefly.

Answer 9- 

In facilitated diffusion, special proteins are presented that help move substances across membranes without the expenditure of ATP or energy. While the special proteins help, the facilitated diffusion cannot cause the net transport of molecules from a low to a high concentration because this would require the input of ATP or energy.

The transport rate reaches a maximum value when all the protein transporters are being used, i.e., at saturation point. Facilitated diffusion is also very specific: it allows the cell to select substances for the uptake. It is also very sensitive to inhibitors that react with protein side chains.

Question 10.

What do you mean by active transport? Explain it with the help of an appropriate example.

Answer 10- 

Active transport is the process which is carried out by membrane proteins. Hence different proteins present in the membrane play a major role in active and passive transport processes. Pumps are specialised proteins that use energy to carry substances across the cell membrane. These pumps can also transport substances from a low concentration to a high concentration but with energy expenditure.

The transport rate reaches a maximum when all the protein transporters are being used or at saturation. Like enzymes, the carrier protein is also very specific in what it carries across the membrane. These proteins are also sensitive to inhibitors that react with protein side chains.

Question 11.

What is imbibition?

Answer 11:

Imbibition is a unique type of diffusion that occurs when water is absorbed by solids-colloids-causing them to increase enormously in volume. The classic examples of imbibition are water absorption by seeds and dry wood. Prehistoric people have used the pressure generated by the swelling of wood to split rocks and boulders.

Also, if it were not for the pressure due to imbibition, seedlings could not have emerged from the soil into the open surrounding; they probably would not have been able to establish themselves.

Question 12.

What do you mean by turgor pressure? Give its two roles in plants.

Answer 12:

Turgor pressure is the pressure exerted by the cell sap on its cell wall when it has absorbed the maximum amount of water.

Due to the turgor pressure, leaves stand erect and look fresh.

Also, the movement of soluble food in the phloem is due to turgor pressure.

Q13. Briefly describe water potential. What are the factors affecting it?

Answer 13:

Water potential describes the tendency of water to move from one area to another due to various factors like osmosis, gravity, and mechanical pressure.

It is estimated in units of pressure which is the pascal. At a standard temperature and pressure, pure water possesses zero water potential as pure water is neutral. Also, when solutes are added to pure water, solute potential lowers, and there is an increase in pressure, which increases water potential.

Factors that affect the water potential:

Solute potential

Pressure potential

Matric potential

Pressure

Temperature

Gain/loss of water

1. 14 What happens when a pressure that exceeds the atmospheric pressure is applied to the pure water of a solution?

Answer 14- 

When a pressure that exceeds the atmospheric pressure is applied to pure water or a solution, its potential water increases.

Question 15. (a) Describe the plasmolysis process in plants and give appropriate examples.

(b) Explain briefly what will happen to a plant cell if it is kept in a solution with a high-water potential.

Answer 15-

1. a) When water moves out of the cell through the cell membrane of a plant, the cell shrinks away from the cell wall, and the process of plasmolysis in the cell occurs. Water moves out from the protoplasm when the cell is kept in a hypertonic solution. Water first moves from the cytoplasm and then afterwards from the vacuole. This results in the cell’s shrinkage, which becomes plasmolysed.
2. b) As the plant cell is kept in a solution with a high water potential, the plant cell absorbs water through endosmosis, and the cell becomes puffy or swollen. This swollen protoplast develops a wall pressure equal to the system’s water potential, resulting in endosmosis stopping.

Question 16. Describe in detail the transpiration pulls model of water transport in plants. What are the factors influencing transpiration? How is it useful to plants?

Answer 16:

Transpiration pull is a process that helps water rise in tall trees, and water loss creates this phenomenon. The process of transpiration occurs from the pores of the stomata of leaves, known as the cohesion-tension model of water transport. The water lost during the day through this process of transpiration results in the flaccid nature of epidermal cells and guard cells.

In turn, these cells take water from the xylem vessel creating a negative tension or pressure in the xylem vessels from the leaves surface to the root tips through the stems. Subsequently, water in the xylem gets pulled from the stem as a single column. The adhesion and cohesion forces on the water molecules and cell walls of the xylem vessels restrict the splitting of the water molecules.

Factors that majorly affect the transpiration pull are

Temperature, relative humidity, light, wind and, plant factors such as the number and distribution of stomata, their canopy structure, water status of plants, number of open stomata

Importance of transpiration pull

i)It has a cooling effect on plants.

ii)Transpiration pull exerts the ascent of sap which helps in the even distribution of mineral salts.

iii)It also helps in retaining shape and structure by keeping the cells turgid.

iv)Transpiration also helps in the removal of excess water absorbed by plants.

V)Provides water for photosynthesis.

Question 17. Explain why xylem transport is unidirectional while phloem transport is bi-directional.

Answer 17- 

Water generally moves only in the upward direction when absorbed by roots through diffusion through the xylem. Hence water transport is unidirectional. On the other hand, food is transported by the phloem tissue. We know that food is synthesised in leaves and is required by both root and shoot systems; thus, the phloem sap moves upwards and downwards, making food transport bidirectional so that it can reach other parts of the plant..

Question 18. Explain the pressure flow hypothesis that occurs in the translocation of sugars in plants.

Answer 18- 

Food is prepared continuously in plants in the mesophyll cells of the leaves in the form of carbohydrates like glucose. The prepared food is then converted into sucrose and is further passed to the source cells, which are in the phloem. Water contained in the xylem vessels moves to the nearest phloem causing a rise in the hydrostatic pressure in the phloem. This results in sucrose’s movement via the phloem’s sieve cells. The sucrose already present in the sink region converts into starch or cellulose, hence causing a reduction in the hydrostatic pressure present in the sink cells. Subsequently, the pressure difference between the source and the sink cells permits the sugars to be translocated from the former to the latter.

Question 19. Mark the mismatched pair.

(a) Amyloplast—Store protein granule

(b) Elaioplast—Store oils or fats

(c) Chloroplasts—Contain chlorophyll pigments

(d) Chromoplasts—Contain coloured pigments other than chlorophyll

Answer 19: the correct option is (a)

Explanation – Aleuroplasts store proteins, while Amyloplast stores carbohydrates, also known as starch.

Question 20.

1. Which statements do not apply to the reverse osmosis process?

(a) It is used for the purification of water

(b) In the reverse osmosis technique, a pressure greater than the osmotic pressure is applied to the system.

(c) It is also called a passive process

(d) It is an active process

Answer 20: Option ( c) is the right answer.

Explanation: Osmosis is a passive process, so due to that, the water follows down the gradient, but in the process of reverse osmosis, the water molecules go against the osmotic pressure due to the cumulative pressure gradient. Hence reverse osmosis requires energy to transport molecules. Hence it is an active process.

Question 21. Why is solute potential always negative? Also, explain yw=ys+yp

Answer 21: When a solute is dissolved in water, it reduces the water potential as the water concentration in a solution reduces to that in pure water. This measure of reduction in water pollution because of the addition of solute is called solute potential.  Since solute potential hurts the water potential, its value is always negative.

yw=ys+yp

Here, yw represents water potential, ys represents solute potential, and yp represents pressure potential.

Question 22. Transpiration is a necessary evil in plants. Explain. 

Answer 22: Transpiration is said to be a necessary evil because it, too, has two sides. One that has a certain disadvantage and another that can be advantageous. One of the major disadvantages of it is that it causes the loss of a large amount of water from the plant body, stops the proper growth of the plant and causes leaves to wilt. But suppose it occurs in more than a required quantity. In that case, it helps in removing the excess amount of water from the plant body to maintain the negative pressure for the ascent of sap in the xylem by producing suction pressure, to help in cooling the plant body, to make minerals and water available for all parts of the plant body and very important for the proper growth of the plant. Considering all these, we can say that even though transpiration is affecting the plant, at the same time, it is necessary for the plant for its overall growth and development. Hence transpiration is called a necessary evil.

Question 23. Describe the three main physical properties of water, which briefly helps in the ascent of water in the xylem.

Answer 23- 

Below are the three major physical properties of water that help in the ascent of water in the xylem.

Cohesion: Cohesion is the ability of water molecules to remain linked with each other. In other words, they stick to each other.

Adhesion: Adhesion is the ability of water molecules to stick to a surface.

Surface Tension: Surface tension is the property of any liquid that tends to occupy the smallest possible surface area possible. Water also makes a continuous column of water in the xylem vessels by adhesion cohesion and surface tension. With the help of these three forces, the transpiration pull pushes the water into a column.

Question 24. Water is indispensable for life. What properties of water make it useful for all biological processes on the earth?

Answer 24: The properties of water make it useful for all biological processes on the earth.

(i) Water is called the Universal Solvent, which can dissolve most substances. Also, water is a major component of the cells, so it is an important ingredient.

(ii) External fertilisation also occurs in some aqueous animals like frogs and fishes. There, external fertilisation takes place, and there, water is the main medium for the transportation of the male gamete to reach the female gamete.

(iii) Aquatic organisms also require oxygen for breathing. So, water helps them by containing dissolved oxygen

(iv) Water acts as the pollination agent in most aquatic plants.

(v) Water also helps maintain the temperature of living beings by attaining a cooling effect.

Question 25. Various types of transport mechanisms are needed to fulfil the mineral requirements of a plant. Why are they not fulfilled by diffusion alone? 

Answer 25: Diffusion cannot fulfil the mineral requirements as the concentration of minerals in the roots is always greater than in the soil. Hence diffusion alone cannot lead to the movement of mineral ions across the walls of the root.

Question 26. Describe the following terms active diffusion, facilitated diffusion and imbibition. 

Answer 26:

Active transport is the process which is carried out by membrane proteins. Hence different proteins present in the membrane play a major role in active and passive transport processes. Pumps are specialised proteins that use energy to carry substances across the cell membrane. These pumps can also transport substances from a low concentration to a high concentration but with energy expenditure.

In facilitated diffusion, special proteins are presented that help move substances across membranes without the expenditure of ATP or energy. While the special proteins help, the facilitated diffusion cannot cause the net transport of molecules from a low to a high concentration because this would require the input of ATP or energy.

Imbibition is a unique type of diffusion that occurs when water is absorbed by solids-colloids-causing them to increase enormously in volume. The classic examples of imbibition are water absorption by seeds and dry wood. A prehistoric person used the pressure generated by the swelling of wood to split rocks and boulders.

Question 27. Explain why transpiration in plants is important. 

Answer 27. Transpiration plays a very important role in plants. The process of transpiration helps with dispersing water from the aerial plant parts uniformly, and it also helps to keep cells well-hydrated and turgid. The process of transpiration also causes cooling in the leaf surface, aids in the growth and development of plants regulates the temperature of a plant, and facilitates the movement of minerals from the soil to different plant parts.

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