6.Besides water, name any two constituents of
human sweat.

Ans. Sodium chloride and urea.

7.What happens is glomerulonephritis?

Ans. Inflammation of glomeruli of kidney.

8.Name the excretory organ of cockroach.

Ans. Malphigian tubules.

9.Name the hormone which controls the
concentration of sodium in the body.

Ans. Aldosterene is a hormone which controls
concentration of sodium in the body.

10.Which gland secrete sebum?

Ans. The sebaceous glands are microscopic
exocrine glands in the skin that secrete an oily or waxy matter, called sebum,

11.ble to water. Name it.

Ans. Ascending limb

12.Besides water, name any two constituents
of human sweat.

Ans. Sodium chloride, Iactic acid, glucose
(any two).

13.Explian the function of vasa rectae.

Ans. It helps to retain reabsorbed ions and
urea in the interstitial fluid of the medulla, to

maintain its high osmotic pressure.

14.Name two types of nephrons found in human
kidney.

Ans. (i) Juxta medullary nephron (ii)
Cortical nephron.

15.Define GPR (Glomerular Filtration Rate)

Ans. The amount of filtrate formed by the
kidney per minute. 

16.The mechanism of is also known as counter
current mechanism justify the statement.

Ans. (in the ascending limb) the out flow
runs parallel to and in the opposite direction of the inflow in the descending limb.

17.What Is maturation?

Ans. the act of passing out urine from
urinary bladder.

18.Write the function of enzyme ‘renin’
produced by kidney.

Ans. Renin is used to convert angiotensinogen
to angiotensin.

19.Name the excretory product of (i) reptiles
(ii) Prawns.

Ans.(i) Uric acid (ii) Ammonia.

SOL99

Photosynthesis in Higher Plants: 1 Marks Questions

1.Expand NADP.

Ans. Nicotinamide adenine dinucleotide phosphate.

2.Name one plant that carries out photosynthesis at night?

Ans. Opuntia, chenopodium.

3.Name the cell – organelles involved in photorespiration.

Ans. Mitcohondria, chloroplast and peroxisomes.

4.Why photosynthesis important?

Ans. (a) Primary source of all food on earth.

(b) O2 is released by green plants into the atmosphere.

5.Define photosynthesis?

Ans. Photosynthesis is an anabolic endergonic as well as oxidation reduction process in which green plants manufacture food by raw materials in sunlight.

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6.What is the site for photosynthesis in Opuntia?

Ans. Stem

7.Explain chlorophyll is an essential photosynthetic pigment?

8.What is the end product of light reaction?

Ans. ATP, NADPH2 and O2

9.Give examples of photosynthetic micro – organisms which also fixes atmospheric nitrogen?

Ans. Anabaena, Notec.

10.Name two photosynthetic pigments belonging to Carotenoids.

Ans. Carotene and Xanthophyll.

SOL99

11.How many molecules of ATP are required for synthesis of one molecule of glucose in and Pathways ?

Ans. In pathway = 18 ATP molecules

In pathway = 30 ATP molecules

12.What part of sunlight is most suitable for photosynthesis?

Ans. Blue and red regions of the light spectrum are the most effective in photosynthesis.

13.Which one of the photosystems can carry on photophosphorylation independently?

Ans. PS-I.

14.Name two plants that can catty out photosynthesis at night.

Ans. Opuntia, Chenopodium, Bougainvillea.

15.Name the enzyme which is found abundantly in the world.

Ans. RuBisCO.

SOL99

16.Name the scientist who Proposed the pathway.

Ans. Hatch and Slack.

17.Where does carbon fixation occur in chloroplast.

Ans. Carbon fixation takes place in stroma.

18.Which compound acts as CO, acceptor in Calvin cycle?

Ans. Ribulose 1,5 bisphosphate.

19.Name the end products of light reaction.

Ans. ATP, NADPH and .O2

Respiration in Plants

1 Marks Questions

1.Define fermentation and aerobic respiration.

Ans. Fermentation is partial breakdown of glucose.

Aerobic respiration glucose is completely degraded into CO2 and H2O.

2.What are the different types of respiration occurs in plants?

Ans. Aerobic respiration and Anaerobic respiration.

3.Name the energy currency of the cells.

Ans. ATP.

4.What are the other two names for kreb’s cycle?

Ans. Citric acid cycle (CAC), Tricarboxylic acid cycle (TCA)

5.In which organelle does kreb’s cycle occur in living cells?

Ans. Mitochondria.

6.Mention the conditions under which

(i) RQ is 1 (ii) R.Q is less than 1

Ans. (i) If carbohydrates are used as substrate and are fully oxidized the R.Q will be 1.

(ii) If fats are used in respiration, the R.Q well be less than 1.

1

7.What is respiration?

Ans. A process of physiochemical change by which environmental oxygen is taken into, to

oxidize the stored food, for release of CO2, water and energy. The energy released is used for

doing various life activities, whereas CO2 is used by the plants.

8.Give two types of cellular respiration.

Ans. (a) Aerobic (b) Anaerobic

9.How many carbon atoms are present in the molecule of each of :

Ans. (i) 6 carbon in glucose (ii) 3 carbon in pyruvate.

(i)Glucose and (ii) Pyruvate?

SOL99

10.Nain the molecule which is terminal acceptor of electron.

Ans. Oxygen.

11.How many ATP mo1ecuIe am produced from a molecule of glucose on i complete

oxidation in eukaryotes.

Ans. 36 ATP.

12.Where does ETC found in eukaryotic cell?

Ans. Mitochondrial membrane.

13.Name the enzyme which convert sugar into glucose and fructose.

Ans. Invertase.

14.How many molecules of ATP are produced by the oxidation of one molecule of FADH2?

Ans. 2 ATP molecules.

15.Why do the person with sufficient while fibres get fatigued ma short period ?

Ans. due to formation of Lactic acid.

16.Write the name of end product of glycolysis.

Ans. Pyruvic acid

17.Name the first product formed in Kerb’s cycle.

Ans. Citric acid.

SOL99

Cell Cycle and Cell Division: 1 Marks Questions

1.Name the stage of cell division in which paired homologous chromosomes get

shortened & thickened?

Ans. Pachytene

2.Which structure of animal cell forms the asters of spindle?

Ans. Centrosome

3.Name the cells in which meiosis occurs?

Ans. Reproductive cells or germ cells.

4.At which stage of meiosis crossing over of genetic material takes place?

Ans. pachytene.

5.What is Go phase?

Ans. A stage when cell cycle is arrested during interphase is called Go phase

6.Name the cell division concerned with cancer?

Ans. Mitosis

7.What are kinetochores ?

1

Ans. Small disc-shaped structure at the surface of the centromeres.

8.What is interkinesis ?

Ans. The stage between two meiotic dividions.

9.Why is mitosis called equational division ?

Ans. The chromosome number in daughter cells is equal to that of the parent cell.

10.Name the stage of meiosis during which synaptonemal complex is formed.

Ans. Zygotene.

SOL99

11.What is Go phase of cell cycle?

Ans. Cells which enter a stage where they are metabolically active but no longer proliferate.

12.Where does mitosis take place in plants and animals?

Ans. Plants – Meristematic tissue; Animals – somatic cells.

SOL99

Breathing and Exchange of Gases

1 Marks Questions

1.Define partial pressure of a gas.

Ans. Pressure contributed by an individual gas in a mixture of gases is called partial

pressure of gas and it is represented as PO2 for O2 and PCO2 for CO2.

2.Name the other pigments which are present in animals besides haemoglobin.

Ans. Haemocyanin and haemoerythrin.

3.What is the difference between alveolar air and inspired air?

Ans. Alveolar air – The air present in the alveoli.

Inspired air – The amount of air inspired at a time.

4.Define vital capacity.

Ans. Vital Capacity is the volume of air breathed out by a maximum forceful expiration.

5.What is the role of carbonic anhydrase in RBC’s?

Ans. About 70% of CO2 reacts with water to form carbonic acid in RBCs in the presence of

enzyme carbonic anhydrase. CO2 + H2O H2CO3

SOL99

6.What is carbamino haemoglobin?

Ans. Carbaminohaemoglobin is formed when CO2 combines with globin is reduced haemoglobin.

7.Name the place where actual exchange of gases takes place in insects.

Ans. Tracheoles.

8.What is the percentage of O2 in inspired & expired air?

Ans. Inspired air has 21% O2 and expired air has 16% O2.

9.What is the utility of chloride shift?

Ans. It maintains the ionic balance and electrochemical neutrality.

10.Name the organ in human respiratory system which produces sound.

Ans. Larynx (Sound box)

SOL99

11.How many oxygen molecules can be carried out by one hemoglobin molecule.

Ans. Four molecules

12.Give the name and function of a fluid filled double membranous layer

which surrounds the lungs.

Ans. Fleuron. It reduces the friction and keeps the two pleura together and the lungs

inflated.

13.Which organ of our respiratory system acts as primary site of exchange of gases?

Ans. Alveoli of Lungs.

14.Cigarette smoking causes emphysema. Give reason.

Ans. Cigarette smoking damages alveolar walls due to alveolar sacs remaining filled with air

leading to decreased respiratory surface fore

15.Name the principle of exchange of gases.

Ans. Diffusion.

SOL99

16.What is the role of oxyhaernoglobin after releasing molecular oxygen in the

Ans. Amino group of refuced hoemoglobin combines with CO2 forming

carbaminohaemoglobin to transport CO2.

17. Name the museles which facilitate breathing.

Ans. External and internal intercostals muscles, situated between ribs.

18.How is the entry of food pivoted in the respiratory tract?

Ans. Ans. During swallowing a cartilaginous flap like structure called epiglottis covers the glottis and prevents the entry of food into respiratory tract.

19. About 97% of O2 is transported by RBCs in the blood. How does the remaining 3% of O2 transported?

Ans. In simple solution form through plasma.

SOL99

Body Fluids and Circulation: 1 Marks Questions

1.Which of the four chambers of the human heart has the thickest muscular wall?

Ans. Left ventricle.

2.Where are RBCs formed from in an adult human?

Ans. RBCS are formed from the bone marrow.

3.What is ECG technique?

Ans. It is a technique to record and photograph the various electric cal changes in the working of the heart.

4.In which mammal, the RBC are nucleated?

Ans. Camel.

5.Name any two substances which prevent blood coagulation in uninjured blood

vessels.

Ans. Heparin, Antithrombin.

6.Name the type of granulocytes that play an important role in detoxification?

Ans. Eosinophils.

7.A cardiologist observed an enlarged QR wave in the ECG of a patient. What does it indicate?

Ans. Enlarged Q and R waves are the indication of myocardial infraction.

8.Name the double layered membranous covering of the heart.

Ans. Pericardium.

9.Why lymphatic circulation takes place very slowly?

Ans. Lymphatic circulation occurs due to squeezing action of surrounding muscles and not

heart.

10.Name the instrument used for measuring blood pressure.

Ans. Sphygmomanometer.

SOL99

11.What is a pace-naked?

Ans. A patch of modified heart muscle that initiates a wave of contraction.

12.Why is SA node called pace-maker of the heart?

Ans. SA node being self excitatory, initiates a wave of contraction in the heart.

13.Write the full form of SA node.

Ans. Sinu Auricular Node (Pace-maker)

14.What is lymph node?

Ans. A lymph node is specialized structure in lymphatic vessel concerned with the filteration

of foreign bodies by the lymphocytes.

15.A cardiologist observed an cntargc4 QRS wave in the ECU of a patient. What does it indicate?

Ans. QRS wave denotes ventricular contraction of heart which may be normal or abnormal.

SOL99

16.Name the enzyme that catalyses the formation of carbonic acid in erythtocytes.

Ans. Carbonic anhydrase.

17.What is systemic circulation?

Ans. the kind of blood circulation that is concerned with the supply of oxygenated blood

from the left the left ventricle to all body parts and return of oxygenated blood to the right

atrium of heart.

18.Give two examples of extra-cellular fluids.

Ans. Interestitial fluid and blood plasma.

19.What name is given to the blood vessels which generally brine blood to an organ?

Ans. Afferent blood vessel.

20.Which adrenal hormone accelerales the heart beat under normal conditions.

Ans. Noradrenalin.

SOL99

21.Name the blood that carries blood from the intestine to liver.

Ans. Hepatic portal vein.

22. Define cardiac cycle.

Ans. A regular sequence of three events (i) auricular systole (ii) ventricular systole and (iii)

joint diastole duing the completion of one heart beat.

23. Name the protein found in RBCs.

Ans. Haemoglobin.

24. What happen to a person suffering from hemophilia.

Ans. The person suffering from haemophilia lacks clotting factors in blood, which result the defective clotting mechanism. In case of injury the person is at risk of blood loss.

Body Fluids and Circulation

1. Name the components of the formed elements in the blood and mention one major function of each of them.

Solution: Blood corpuscles are the formed ele-ments in the blood, they constitute 45% of the blood. Formed elements are – (erythrocytes, RBCs or red blood corpuscles), (leucocytes, WBCs or white blood corpuscles) and throm¬bocytes or blood platelets. The major function of RBCs is to transport oxygen from lungs to body tissues and COz from body tissues to the lungs. White blood cells provide immunity to the body. Blood platelets play important role in blood clotting.

2. What is the importance of plasma proteins?

Solution: Plasma proteins constitute about 7 to 8% of plasma. These mainly include albumin, globulin, prothrombin and fibrinogen. Prothrombin and fibrinogen are needed for blood clotting. Albumins and globulins retain water in blood plasma and helps in maintaining osmotic balance. Certain globulins

3. Match Column I with Column II.

Column I                          Column II

(a) Eosinophils               (i) Coagulation

(b) RBC                            (ii) Universal recipient

(c) AB Group                  (iii) Resist infections

(d) Platelets                    (iv) Contraction of heart

(e) Systol                         (v) Gas transport

Solutlion.(a) – (iii); (b) – (v); (c) – (ii); (d) – (i); (e) – (iv).

4. Why do we consider blood as a connective tissue?

Solution: A connective tissue connects different tissues or organs of the body. It consists of living cells and extracellular matrix. Blood is vascular connective tissue, it is a mobile tissue consisting of fluid matrix and free cells. Blood transports materials from one place to the other and thereby establishes connectivity between different body parts.

What is the difference between lymph and blood?
Solution: The differences between blood and lymph are given below:

What is meant by double circulation? What is its significance?
Solution: The type of blood circulation in which oxygenated blood and deoxygenated blood do not get mixed is termed double circulation. It includes systemic circulation and pulmonary circulation. The circulatory pathway of double circulation is given in the following flow chart.

 Write the differences between:
(a) Blood and lymph
(b) Open and closed system of circulation
(c) Systole and diastole
(d) P-wave and T-wave
Solution: (a) Refer answer 5.
(b) The differences between open and closed circulatory system are given below:

(c) Systole is contraction of heart chambers in order to pump out blood while diastole is relaxation of heart chambers to receive blood. The contraction of a chamber or systole decreases its volume and forces the blood out of it, whereas its relaxation or diastole brings it back to its original size to receive more blood.
(d) P wave is a small upward wave of elec-trocardiograph that indicates the atrial depolarisation (contraction of atria). It is caused by the activation of SA node. T-wave is a dome shaped wave of electro-cardiograph which represents ventricular repolarisation (ventricular relaxation).

Neural Control and Coordination

Briefly describe the structure of the following:

(a) Brain (b) Eye (c) Ear

Solution: (a) Brain: The brain acts as control and command system of the body. It is protected by skull and is covered by three meninges. It is divisible into three main regions: forebrain, midbrain and hindbrain.

(i) Forebrain – It consists of three regions:

(a) Olfactory lobes: These are a pair of very small, solid club-shaped bodies which are widely separated from each

other. They are fully covered by cerebral hemispheres.

(b) Cerebrum – It is the largest and most complex of all the parts of human brain. A deep cleft divides the cerebrum into right and left cerebral hemispheres, connected by myelinated fibres, the corpus callosum.

(c) Diencephalon – It encloses a slit-like cavity, the third ventricle. The thin roof of this cavity is known as the epithalamus, the thick right and left sides as the thalami, and floor as the hypothalamus.

(ii) Midbrain – It is located between thalamus/ hypothalamus of forebrain and pons of hindbrain. Its upper surface has two pairs of rounded protrusious called corpora quadrigemina and two bundles of fibres called crura cerebri.

(iii) Hindbrain – It consists of:

(a) Cerebellum – The second largest part of the human brain is the cerebellum. It consists of two lateral cerebellar hemispheres and central worm-shaped part, the vermis. The cerebellum has its grey matter on the outside, comprising three layers of cells and fibres. It also has Golgi cells, basket cells and granule cells.

(b) Pons varolii – An oval mass, called the pons varolii, lies above the medulla oblongata. It consists mainly of nerve fibres which interconnect different regions of the brain.

(c) Medulla oblongata – It extends from the pons varolii above and is continuous with the spinal cord below. The mid brain, pons varolii and medulla oblongata are collectively called brain stem.

(b) Eye: Eye is a hollow spherical structure composed of three coats:

– Outer fibrous coat

– Middle vascular coat

– Inner nervous coat

(i) Fibrous coat: It is thick and protects the eyeball. It has two distinct regions – sclera and cornea. Sclera covers most of the eye ball. The sclera or white of the eye contains many collagen fibres. Cornea is a transparent portion that forms the anterior one – sixth of the eyeball. The cornea is avascular (i.e., lacks blood supply).

(ii)Vascular coat: It comprises of 3 regions : choroid, iris, ciliary body.

(a) Choroid : It lies adjacent to sclera and contains numerous blood vessels and pigmented cells.

(b) Iris: The iris is a circular muscular diaphragm containing the pigment giving eye its colour. It extends from the ciliary body across the eyeball in front of the lens. It 2. has an opening in the centre called the pupil.

It contains two types of smooth muscles, circular muscles (sphincters) and radial muscles (dilators), of ectodermal origin.

(c) Ciliary body: Behind the peripheral margin of the iris, the vascular coat is thickened to form the ciliary body. It is composed of the ciliary muscles and the ciliary processes.

(iii) Nervous coat: It consists of retina which is neural and sensory layer of an eye ball. It consists of three layers; ganglion cells, bipolar cells and photoreceptor cells (rods and cones).

Lens: It is a transparent, biconvex, elastic structure that bends light waves as they pass through its surface. It is composed of epithelial cells that have large amounts of clear cytoplasm in the form of fibres.

Chambers of eyeball: The lens, suspensory ligament and ciliary body divide the eye into an anterior aqueous chamber and a posterior vitreous chamber which are filled with aqueous humour and vitreous humour respectively.

c) Ear: There are three portions in an ear:

(i) External ear: It further has 2 regions: pinna and external auditory canal or meatus.

(a) Pinna: The pinna is a projecting elastic cartilage covered with skin. Its most prominent outer ridge is called the helix. The lobule is the soft pliable part at its lower end composed of fibrous and adipose tissue richly supplied with blood capillaries. It is sensitive as well as effective in collecting sound waves.

(b) External auditory canal: It is an S-shaped tube leading inward from the pinna. It is a tubular passage supported by cartilage in its exterior part and by bone in its interior part.

(ii) Middle ear: It consists of 3 small bones called ear ossicles – malleus, incus and stapes, which are attached to one another and increase efficiency of transmission of sound waves to inner ear.

(iii) Internal ear: It consists of bony 

Explain the following processes:

(a) Polarisation of the membrane of a nerve fibre.

(b) Depolarisation of the membrane of a nerve fibre.

(c) Conduction of a nerve impulse along a nerve fibre.

(d) Transmission of a nerve impulse across a chemical synapse.

 Differentiate between

(a) Myelinated and non-myelinated axons

(b) Dendrites and axons

(c) Rods and cones

(d) Thalamus and Hypothalamus

(e) Cerebrum and Cerebellum

 Distinguish between

(a) Afferent neurons and efferent neurons

(b) Impulse conduction in myelinated nerve fibre and unmyelinated nerve fibre

(c) Aqueous humour and vitreous humour

(d) Blind spot and yellow spot

(e) Cranial nerves and spinal nerves

Class 11 Biology Excretory Products and their Elimination

1.Define Glomerular Filtration Rate (GFR).

Solution. The amount of filtrate formed by the kidneys per minute is called glomerular filtration rate (GFR). It is approximately 125 mL/min. in a healthy person.

2.Explain the autoregulatory mechanism of GFR.

Solution. The kidneys have built-in mechanisms for the regulation of glomerular filtration rate. One such efficient mechanism is carried out by juxta glomerular apparatus (JGA). JGA is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact. A fall in GFR can activate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR back to normal.

4.Give a brief account of the counter current mechanism.

Solution. The kidneys have a special mechanism for concentrating the urine, it is called counter current mechanism. The mechanism is said to be a counter current mechanism because the out flow (in the ascending limb) of Henle’s loop runs parallel to and in the opposite direction of the inflow (in the descending limb) and vasa recta. As the mechanism begins to function, the ascending limb of loop of Henle actively transports chloride and sodium ions out into the vasa recta from where it is secreted into the interstitial fluid. As a result the interstitial fluid around the loop of Henle contains large quantities of NaCl. The filtrate passes from the ascending limb of loop of Henle and enters a collecting duct. The collecting duct passes adjacent to the loop of Henle where the interstitial fluid contains large amounts of NaCl. The high osmotic pressure created by NaCl causes water to diffuse out of the collecting duct in the interstitial fluid and eventually to the blood of vasa recta. The filtrate becomes greatly concentrated and is now called urine. A similar counter current mechanism, operates between the interstitial fluid and blood passing through the vasa recta. As the blood capillary runs along the ascending limb of loop of Henle, NaCl diffuses out of the blood. The direction is reversed as the blood capillary passes along the descending limb of Henle. The blood flows in the vasa recta around the loop of Henle from ascending to the descending side while the fluid passing through the loop of Henle goes in the opposite direction. The arrangement helps to maintain the concentration gradient of NaCl.

The ‘overall function of counter current mechanism is to concentrate sodium chloride in the interstitial fluid and thereby cause water to diffuse out of the collecting ducts and concentrate the urine.

What is the significance of juxta glomerular apparatus (JGA) in kidney function?

Solution. Juxta glomerular apparatus (JGA) is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact. The JGA plays a complex regulatory role. A fall in glomerular blood flow/ glomerular blood pressure/GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II. Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the adrenal cortex to release aldosterone. Aldosterone causes reabsorption of  Na+ and water from the distal parts of the tubule. This also leads to an increase in blood pressure and GFR.

Class 11 Biology Locomotion and Movement

1. Draw the diagram of a sarcomere of skeletal muscle showing different regions.
Solution: 

2. Define sliding filament theory of muscle contraction.
Solution: According to sliding filament theory of muscle contraction, the actin and myosin filaments slide past each other with the help of cross-bridges to reduce the length of the sarcomeres.

Solution: (a) Actin filaments and myosin filaments can be differentiated as follows:

(b) Differences between red muscle fibres and white muscle fibres are given in the following table:

(c) Differences between pectoral and pelvic girdles are given in the following table:

6. Match Column I with Column II:
Column I                            Column II
(a) Smooth muscle          (i) Myoglobin
(b) Tropomyosin             (ii) Thin filament
(c) Red muscle                (iii) Sutures
(d) Skull                            (iv) Involuntary
Solution.(a) – (iv), (b)-(ii), (c)-(i), (d)-(iii)

CBSE Class 11 Biology 

DIVERSITY IN THE LIVING WORLD

1 : The Living World

2 : Biological Classification

3 : Plant Kingdom

4 : Animal Kingdom

STRUCTURAL ORGANISATION IN PLANTS AND ANIMALS

5 : Morphology of Flowering Plants

6 : Anatomy of Flowering Plants

7 : Structural Organisation in Animals

PLANT PHYSIOLOGY

11 : Transport in Plants

12 : Mineral Nutrition

13 : Photosynthesis in Higher Plants

14 : Respiration in Plants

15 : Plant Growth and Development

1.What are the factors affecting the rate of diffusion?

HUMAN PHYSIOLOGY

16 : Digestion and Absorption

17 : Breathing and Exchange of Gases

18 : Body Fluids and Circulation

19 : Excretory Products and their Elimination

20 : Locomotion and Movement

21 : Neural Control and Coordination

22 : Chemical Coordination and Integration

Human physiology

(a) Why are villi present in the intestine and not in the stomach?

(b) How does pepsinogen change into its active form?

(c) What are the basic layers of the wall of alimentary canal?

(d) How does bile help in the digestion of fats?

4. State the role of pancreatic juice in digestion of proteins.

5. Describe the process of digestion of protein in stomach.

6. Give the dental formula of human beings.

7. Bile juice contains no digestive enzymes, yet it is important for digestion. Why?

8. Describe the digestive role of chymotrypsin. What two other digestive enzymes of the same category are secreted by its source gland?

9. How are polysaccharides and disaccharides digested?

10. What would happen if HCl were not secreted in the stomach?

11. How does butter in your food gets digested and absorbed in the body?

12. Discuss the main steps in the digestion of proteins as the food passes through different parts of the alimentary canal.

13. Explain the term thecodont and diphyodont.

14. Name different types of teeth and their number in an adult human.

15. What are the functions of liver?

Cell: Strucutre and Functions

 Match the following.

Column I                                           Column II

(a) Cristae                                 (i) Flat membranous sacs in stroma

(b) Cisternae                           (ii) Infoldings in mitochondria

(c) Thylakoids                        (iii) Disc-shaped sacs in Golgi apparatus

Soln.a – (ii); b – (iii); c – (i).

What is a mesosome in a prokaryotic cell? Mention the functions that it performs.

Soln. Mesosome is a membranous structure in prokaryotic cell, which is formed by the extensions of the plasma membrane into the cell in form of vesicles, tubules and lamellae. Mesosomes are equal to mitochondria in eukaryotes, as they perform aerobic cellular respiration in prokaryotes. It helps in DNA replication and distribution of genetic material to daughter cells. Mesosomes also help in respiration, increase the surface area of the plasma membrane and enzymatic content and cell wall formation.

6.How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?

Soln. Neutral solutes move across the membrane by the process of simple diffusion along the concentration gradient i.e., from higher concentration to the lower concentration. Polar molecules cannot pass through the nonpolar lipid bilayer, they require carrier proteip of the membrane to facilitate their transport across the membrane. In facilitated diffusion, molecules are transported along concentration gradient by help of ion channels and permeases and it does not involve energy expenditure (passive transport).

Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both?

Solution: Mitochondria and chloroplast are double membrane bound organelles. Mitochondria: Mitochondria are cylindrical or sausage shaped cell organelles and contains two membranes, outer and inner. The inner compartment is called the matrix containing DNA, RNA, ribosomes, enzymes of Krebs cycle etc and outer membrane forms the continuous limiting boundary of the organelle. Inner membrane forms number of infoldings called the cristae which increases the surface area. Oxysomes are present on inner mitochondrial membrane. Mitochondria are semiautonomous organelles, i.e., have their own DNA and ribosomes.

Functions of mitochondria:

:

• Mitochondria are essential for aerobic respiration.
• Mitochondria provide intermediates for synthesis of important biomolecules such as chlorophyll, cytochrome, steroids etc.
• Mitochondria regulate the calcium ion concentration in the cell.
• Mitochondrial matrix contains enzymes for the synthesis of fatty acids.
• Synthesis of many amino acids takes place here

Chloroplast: They are green coloured plastids which are disc shaped. The space limited by inner membrane of chloroplast is called as stroma. Stroma has organised flattened membranous sacs called the thylakoids. Thylakoids are arranged in stacks called grana. Matrix of a chloroplast contains DNA, RNA, ribosomes and enzymes. Chloroplast is also a semiautonomous organelle.

Functions of chloroplast:

1. Photosynthesis is performed by chloroplast.
2. Chloroplast stores starch grains.
3. Maintains balance of C02 concentration in the air.
4. Keeps oxygen balance constant in atmosphere by liberating 02 into the atmosphere, used during respiration and combustion.

8.What are the characteristics of prokaryotic cells?
Solution: Characteristics of prokaryotic cells are as follows:

• The prokaryotic cell is essentially a single – envelope system.
• Prokaryotes lack membrane bound cell organelles.
• Prokaryotes have 70S ribosomes.
• DNA is naked and lies coiled in cytoplasm. It is not covered by nuclear membrane and is termed as nucleoid.
• Nuclear components, like, nuclear envelope, nucleolus, nucleoplasm are absent.
• Cell wall is present in bacteria and cyanobacteria, but absent in mycoplasma.
• Multiplies by asexual reproduction.
• Transcription and translation takes place in cytoplasm.

9.Multicellular organisms have division of labour. Explain.
Soln. Division of labour is differentiation of certain components or parts to perform different functions for increased efficiency and higher survival. Multicellular organisms often possess millions of cells. Various cells are grouped together to form specific tissue, organ or organ system, with each specialised to perform particular function. Every cell of a multicellular organism cannot obtain food from outside. The organism requires a system for obtaining food, its digestion and distribution. Therefore, a digestive system and system of transport are also required. Certain cells of the body take over the function of reproduction. Others take part in repair and replacement of worn out or injured portions. For optimum functioning of cells, a multicellular organism also requires an internal favourable environment. Therefore, multicellular organisms come to have division of labour.

10.Cell is the basic unit of life. Discuss in brief.
Soln. Cell is fundamental, structural and functional unit of life, as no living organism can have life without being cellular. All life begins as a single cell. An organism is either made of single cell (unicellular) or many cells (multicellular). In unicellular organism, single cell is capable of independent existence and perform all essential functions of life, while in multicellular organism, each group of cells is specialised for specific function. Life passes from one generation to the next in form of cells, and new cell always arise from division of pre-existing cells. Cells are totipotent, i.e., single cell has ability to form whole organism. The activities of an organism are sum total of activities of its cells, therefore, cell is the basic unit of life.

11.What are nuclear pores? State their function.
Soln. Nuclear envelope bounds the nucleus from outside and separates it from cytoplasm. It consists of two membranes, with outer membrane continuous with endoplasmic reticulum. The nuclear envelope is interrupted by minute nuclear pores, at a number of places, which are produced by the fusion of its two membranes. These
nuclear pores are the passages through which movement of RNA and protein molecules takes place in both directions between the nucleus and the cytoplasm.

12.Both lysosomes and vacuoles are endomem-brane ‘structures, yet they differ in terms of their functions. Comment.
Soln. Organelles of endomembrane system such as lysosome and vacuoles function in close coordination with one another but are specialised to perform different functions. Lysosomes breakdown the ageing and dead cells, they help in digestion of food as they contain hydrolytic digestive enzymes. They are involved in cell division also. Vacuoles on other hand, help in excretion and osmoregulation in Amoeba (contractile vacuole) or provides buoyancy, mechanical strength in prokaryotes (air vacuoles).

13.Describe the structure of the following withthe help of labelled diagrams.
(i) Nucleus (ii) Centrosome
Soln.(i) Nucleus: Nucleus is double membrane bound principle cell organelle which contains all genetic information for controlling cellular metabolism and transmission of genetic information.
Nucleus is differentiated into following four parts:
(a) Nuclear envelope: It is a double membrane bound envelope that surround the nucleus and separates the latter from the cytoplasm.
(b) Nucleoplasm: Itis clear, non-staining, fluid material present in the nucleus, which contains raw materials (nucleotides), enzymes (DNA/RNA polymerases) and metal ions for the synthesis of RNAs and DNA. The nuclear matrix or the nucleoplasm is composed of nucleolus and chromatin.
(c) Nucleolus: It is a naked, round and slightly irregular structure, which is attached to the chromatin at a specific region. It is a site for active ribosomal RNA synthesis.
(d) Chromatin : It has the ability to get stained with certain basic dyes. It is known to be the hereditary DNA protein fibrillar complex. The chromatin fibres are distributed throughout the nucleoplasm.

(ii) Centrosome: Centrosome is an organelle usually containing two cylindrical structures called centrioles. They are surrounded by amorphous pericentriolar materials. Both the centrioles in a centrosome lie perpendicular to each other. They are made up of nine evenly spaced peripheral fibrils of tubulin protein. Each of the peripheral fibril is a triplet. The adjacent triplets are also linked. The hub of centriole is connected with tubules of the peripheral triplets by radial spokes made of protein.

What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.
Soln. A chromosome consists of two identical halves, the chromatids held together at one point called the centromere. The centromere is also called as primary constriction. On its side a disc shaped structure called kinetochore is present. Chromosomes are classified into four types according to position of centromere on the chromosome.
(i) Metacentric chromosome: In this chromosome, centromere is in the middle and the two arms are almost equal in length.
(ii)Submetacentric chromosome: The centromere is slightly away from middle point so one arm is slightly shorter than the other.
(iii)Acrocentric chromosome: The centromere is near the end and one arm is extremely short and other arm is extremely long.
(iv)Telocentric chromosome: Centromere is at the tip of chromosome. These chromosomes are not present in humans.

Class 11 Biology Cell Cycle and Cell Division

Class 11 Biology Structural Organisation in Animals