Solved Exercise, Bio-11, Ch-14


(i) In the process of facilitated diffusion, the carrier molecules are ________. (proteins)

(ii) Pure water has a water potential which is equal to ________. (zero)

(iii) The insects which feed on the phloem of plants are the ________. (fluid feeders)

(iv) The substance produced by basophils which inhibits blood-clotting is ________. (heparin)

(v) The most abundant compound of blood plasma of man is ________. (water)

(vi) ________ in 1874 suggested that water molecules move along the cells walls of xylem vessels due to imbibition. (Sacks)


(i) The intercellular openings in the blood capillaries are larger than the openings in the lymph capillaries. (FALSE)

CORRECT: The intercellular openings in the lymph capillaries are larger than the openings in the blood capillaries.

(ii) Between the left auricle and the left ventricle in human heart, the valve present is called tricuspid valve. (FALSE)

CORRECT: Between the left auricle and the left ventricle in human heart, the valve present is called bicuspid valve.

(iii) The pacemaker of the heart of man is the AV node. (FALSE)

CORRECT: The pacemaker of the heart of man is the SA node.

(iv) Each sieve tube member is associated with one or more tracheid cells. (FALSE)

CORRECT: Each sieve tube member is associated with one or more companion cells.

(v) The method of active immunization is used to combat active infections of tetanus and rabies. (FALSE)

CORRECT: The method of passive immunization is used to combat active infections of tetanus and rabies.


(i) Which of the following is not true of guard cells? 

(a)   They are present in the epidermis of leaf

(b)   They are connected with plasmodesmata with other epidermal cells.

(c)   They contain chloroplasts.

(d)   They are kidney shaped.

EXPLANATION: In young developing plants, plasmodesmata are present between guard cells and epidermal cells. While, in most mature plants, plasmodesmata disappear or become non-functional, isolating the guard cells from direct communication with the epidermis. The cell walls of guard cells and epidermal cells are always physically adjacent.

(ii) The Casparian strips are present in: 

(a)   Cortex cells of roots

(b)   Endodermis cells of roots

(c)   Cells of pericycle

(d)   Cells of phloem

EXPLANATION: Casparian strips are found in the endodermis cells of roots. These are specialized, impermeable cell wall structures that surround the radial and transverse walls of endodermal cells. They prevent the free flow of water and solutes between adjacent cells, forcing substances to pass through the selectively permeable cell membranes, enabling the plant to regulate nutrient uptake and prevent the entry of harmful substances.

(iii) Lymph most closely resembles with:     

(a)   Blood

(b)   Interstitial fluid

(c)   Plasma

(d)   Urine

EXPLANATION: Lymph most closely resembles plasma because it is derived from blood plasma. Lymph is a colorless fluid that originates from the interstitial fluid surrounding cells, which is essentially plasma without red blood cells. Both plasma and lymph contain water, electrolytes, and proteins, although the concentrations may differ. The main distinction is that lymph lacks red blood cells, making it similar in composition to the liquid component of blood.

(iv) Hydathodes are associated with:

(a)   Transpiration

(b)   Guttation

(c)   Conduction

(d)   None of these

EXPLANATION: Hydathodes are specialized structures in plant leaves that are associated with guttation. Guttation is the process by which water, along with dissolved minerals, is exuded from the tips or edges of leaves, especially in the morning. Hydathodes play a role in this process by allowing the release of water through pores in the leaf epidermis, driven by root pressure. Guttation occurs when the rate of water absorption by roots exceeds the rate of transpiration (loss of water through stomata) and is often observed in conditions of high soil moisture.

(v) According to pressure flow theory, which of the followings serves as sink: 

(a)   Leaves

(b)   Stem

(c)   Roots

(d)   None of these

EXPLANATION: According to the pressure flow theory, roots are considered sinks because they receive and accumulate the sugars produced through photosynthesis in the source leaves. Sugars are actively transported from source (usually leaves) to sink tissues, such as roots, through the phloem. The movement is driven by a pressure gradient established by the active loading of sugars into the phloem at source regions and their unloading at sink regions, where they are utilized or stored. Therefore, roots act as a sink for the transported sugars, utilizing them for growth, energy, or storage.

(vi) Which of the followings is not true about mammals? 

(a)   They have right aortic arch only.

(b)   They have left aortic arch only.

(c)   They have left and right aortic arches only.

(d)   They do not have aortic arch.

EXPLANATION: Mammals typically have a left aortic arch as the primary structure in their circulatory system. The right aortic arch is usually small and degenerates during embryonic development.

(vii) The process that most likely/directly enables root hair cell to absorb minerals by active transport and enables a muscle cell to contract is: 

(a)   Circulation

(b)   Excretion

(c)   Respiration

(d)   Assimilation

EXPLANATION: Minerals in the soil require energy to be transported against their concentration gradient into the root hair cell. This energy comes from ATP, produced by aerobic respiration in the cell’s mitochondria. Similarly, muscle contraction relies on proteins like myosin and actin interacting. This interaction requires energy, also provided by ATP generated through anaerobic respiration. 

(viii) Which of the following processes causes substances to move across membranes without the expenditure of cellular energy?          

(a)   Endocytosis

(b)   Active transport

(c)   Diffusion

(d)   None of these

EXPLANATION: Diffusion is a passive process that causes substances to move across membranes without the expenditure of cellular energy. It relies on the natural movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached. This spontaneous movement occurs due to the random thermal motion of molecules, and it does not require energy input from the cell.

(ix) Cardiac muscle can be distinguished from other muscle fibres because cardiac muscle: 

(a)   Contain only actin

(b)   Voluntary in action

(c)   Lacks regular arrangement of sarcomeres

(d)   Has intercalated discs

EXPLANATION: Cardiac muscle can be distinguished by the presence of intercalated discs, specialized structures that connect adjacent cardiac muscle cells. Intercalated discs facilitate rapid electrical communication between cells and allow the synchronized contraction of the heart. The discs contain gap junctions, which enable the passage of ions and electrical signals, ensuring coordinated contraction and pumping of blood in the heart.


Consult textbook at page 278 — 282.

Consult textbook at page 290 — 291.

Consult textbook at page 296 — 297.

Consult textbook at page 284 — 285.

Consult textbook at page 281 — 282.

Consult textbook at page 282 — 283.

Consult textbook at page 307 — 310.

Consult textbook at page 325 — 327.

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