HBSE Class 11 Biology Question Paper 2024 Answer Key

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HBSE Class 11 Biology Question Paper 2024 Answer Key

Section – A (1 Mark)

1. Albugo belongs to :
(a) Ascomycetes
(b) Phycomycetes
(c) Basidiomycetes
(d) Deuteromycetes
Answer – (b) Phycomycetes

2. Segmentation in the body is first observed in which of the following?
(a) Platyhelminthes
(b) Aschelminthes
(c) Annelida
(d) Arthropoda
Answer – (c) Annelida

3. In which of the following ovary is inferior?
(a) Mustard
(b) Brinjal
(c) China-rose
(d) Guava
Answer – (d) Guava

4. Parietal placentation is present in :
(a) Tomato
(b) Sunflower
(c) Pea
(d) Mustard
Answer – (d) Mustard

5. Which of the following organelles does not surrounded by any membrane?
(a) Ribosome
(b) Nucleus
(c) Mitochondria
(d) Endoplasmic reticulum
Answer – (a) Ribosome

6. In citric acid cycle, which of the following step is not catalysed by dehydrogenase enzyme?
(a) Oxaloacetic acid to citric acid
(b) Citric acid to α-ketoglutaric acid
(c) Succinic acid to fumaric acid
(d) Malic acid to oxaloacetic acid
Answer – (d) Malic acid to oxaloacetic acid

7. Ethylene is used for :
(a) Slowing down ripening of Apples
(b) Slowing down ripening of Tomato
(c) Hastening of ripening in Fruits
(d) Both (b) & (c)
Answer – (c) Hastening of ripening in Fruits

8. PEP is primary CO2 acceptor in :
(a) C2 plants
(b) C3 plants
(c) C4 plants
(d) Both (b) & (c)
Answer – (c) C4 plants

9. Which of the following auxin has been isolated from plants?
(a) Naphthalene acetic acid (NAA)
(b) 2, 4-dichlorophenoxy acetic acid (2, 4-D)
(c) Indole acetic acid (IAA)
(d) None of these
Answer – (c) Indole acetic acid (IAA)

10. Which of the following is a glucocorticoid?
(a) Cortisol
(b) Epinephrine
(c) Nor-epinephrine
(d) Aldosterone
Answer – (a) Cortisol

11. Gout is caused due to the accumulation of :
(a) Oxalic acid
(b) Uric acid crystals
(c) Lactic acid
(d) Calcium carbonate
Answer – (b) Uric acid crystals

12. Node of Ranvier is found in :
(a) Non-myelinated nerve fibres
(b) Myelinated nerve fibre
(c) Both (a) and (b)
(d) None of these
Answer – (b) Myelinated nerve fibre

13. Oxygen dissociation curve is :
(a) Parabolic
(b) Hyperbolic
(c) Sigmoid
(d) Straight
Answer – (c) Sigmoid

14. One molecule of haemoglobin can carry a maximum of how many molecules of oxygen?
(a) 2
(b) 4
(c) 6
(d) 8
Answer – (b) 4

15. Assertion (A) : In muscle contraction, length of both A-bands and I-band decreased.
Reason (R) : Both myosin of A-band and actin of I-band are contractile proteins and decrease in size during muscle contraction.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true but Reason (R) is not correct explanation of Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Both Assertion (A) and Reason (R) are false.
Answer – (d) Both Assertion (A) and Reason (R) are false.

16. Assertion (A) : Vasopressin released by posterior pituitary is also called Anti-diuretic Hormone (ADH).
Reason (R) : ADH increases the permeability of (PCT) Proximal Convoluted Tubule and collecting tubules to increase reabsorption of water and decrease the urine output.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true but Reason (R) is not correct explanation of Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Both Assertion (A) and Reason (R) are false.
Answer – (a) Both Assertion (A) and Reason (R) are true and Reason (R) is correct explanation of Assertion (A).

17. Assertion (A) : C4 photosynthetic pathway is more efficient than the C3 pathway.
Reason (R) : In C4 plants photorespiration does not occur.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true but Reason (R) is not correct explanation of Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Both Assertion (A) and Reason (R) are false.
Answer – (a) Both Assertion (A) and Reason (R) are true and Reason (R) is correct explanation of Assertion (A).

18. Assertion (A) : Mitochondria and chloroplast are semi-autonomous organelles.
Reason (R) : They are formed by division of pre-existing organelles and contain DNA but lack protein synthesizing machinery.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true but Reason (R) is not correct explanation of Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Both Assertion (A) and Reason (R) are false.
Answer – (b) Both Assertion (A) and Reason (R) are true but Reason (R) is not correct explanation of Assertion (A).

Section – B (2 Marks)

19. What are the universal rules of nomenclature?
Answer – The universal rules of nomenclature are as follows :
(i) Biological names are in Latin and are written in italics.
(ii) The first word in the name indicates the genus, while the second word denotes its specific epithet.
(iii) The name of the genus should start with a capital letter and the name of the species with a small letter.
(iv) When the name is handwritten, both the words are separately underlined.

20. What is the basis of classification of Algae?
Answer – The absence or presence of pigments is the prime basis for algae classification.
• Chlorophyceae (Green Algae) : Contain chlorophyll a and b, which gives them their characteristic green color.
• Phaeophyceae (Brown Algae) : Contain chlorophyll a, c, and fucoxanthin, which gives them a brownish color.
• Rhodophyceae (Red Algae) : Contain chlorophyll a, d, and phycobilins (phycocyanin and phycoerythrin), which give them their red color.

21. What do you mean by secondary and tertiary structure of protein?
Answer : Secondary Structure – Local folding patterns of the polypeptide backbone (α-helices, β-sheets, and turns/loops) stabilized primarily by hydrogen bonds.
• Tertiary Structure – The overall three-dimensional shape of a single polypeptide chain, stabilized by various interactions between the side chains (hydrophobic interactions, hydrogen bonds, ionic bonds, disulfide bridges, and van der Waals interactions).

22. Define Respiratory Quotient. What is the Respiratory Quotient of fat?
Answer – Respiratory Quotient (RQ) is defined as the ratio of carbon dioxide released and the oxygen used during the process of respiration. i.e. RQ = volume of CO2 produced / volume of O2 consumed
Respiratory Quotient of fat is 0.7

23. Write down the functions of Lymph.
Answer – Functions of lymph :
(i) It drains excess tissue fluid from the extracellular spaces back into the blood.
(ii) Some of the fluid from the digestive tract is absorbed in the lymph. The lymphatic vessels store this fluid temporarily, and release it gradually so that the kidneys do not face a sudden pressure of urine excretion.
(iii) It carries carbon dioxide and nitrogenous waste materials that diffuse into the tissue fluid to the blood.
(iv) It takes lymphocytes and antibodies from the lymph nodes to the blood.

24. What are the functions of Gibberellins?
Answer – Gibberellin (GA) is one of the plant hormones that regulate a wide range of processes involved in plant growth, organ development, and environmental responses. These include seed germination, stem elongation, leaf expansion, transition to flowering, and the development of flowers, fruits, and seeds.


What are the crucial events in aerobic respiration?
Answer – Aerobic respiration is a multi-step process in which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water. The crucial events in aerobic respiration include Glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation (including the electron transport chain and chemiosmosis).

25. What are the main functions of the root system?
Answer – The root system is essential for :
• Providing stability to the plant.
• Uptaking water and essential nutrients from the soil.
• Storing carbohydrates and other nutrients.
• Moving water, nutrients, and synthesized food throughout the plant.
• Facilitating vegetative propagation.
• Maintaining soil structure and preventing erosion.


What is Venation? What are various types of it?
Answer – The arrangement of veins and veinlets in the leaf lamina is known as venation.
There are two types of venation in leaf: Reticulate venation and Parallel venation.

Section – C (3 Marks)

26. Explain with suitable examples different type of phyllotaxy.
Answer – The arrangement of leaves on the stem of a plant is called phyllotaxy.

Types of Phyllotaxy :
• Opposite Phyllotaxy – In this type of arrangement, a pair of leaves opposite to each other develops at each node of the stem. Example: Guava
• Alternate Phyllotaxy – In this type of arrangement, only one single leaf develops at each node of the stem alternatively. Example: Rose
• Whorled Phyllotaxy – In this type of arrangement, more than two leaves develop at each node of the stem to form a whorl of leaves. Example: Sunflower

27. Describe the steps of catalytic cycle of an enzyme action.
Answer – The catalytic cycle of the enzyme is as follows:
• Firstly the substrate binds to the active site of the enzyme.
• This binding induces the active site to change its shape fitting more tightly around the substrate.
• The active site then breaks the chemical bonds of the substrate and the enzyme-product complex is formed.
• The enzyme then releases the products of the reaction and the enzyme becomes free to bind to another molecule of the substrate and pass through the cycle again.

28. Write down the functions of Endoplasmic Reticulum.
Answer – Endoplasmic Reticulum (ER) is a complex network of tubular membranes exclusively present in the cytoplasm of the eukaryotic cell. It comes in two forms: Rough ER (RER) and Smooth ER (SER).
The Endoplasmic Reticulum performs following functions :
• It is responsible for the production and secretion of steroid hormones.
• It is also responsible for the synthesis of essential lipids such as phospholipids and cholesterol.
•It is responsible for the metabolism of carbohydrates.
• It releases calcium ions, which are necessary for the nervous system and muscular system.

29. What are the various steps of glycolysis?
Answer – Steps of glycolysis :
• Reaction 1 : Glucose is converted to glucose-6-phosphate by using enzyme hexokinase.
• Reaction 2 : Glucose-6-phosphate is converted to fructose-6-phosphate by using isomerase enzyme.
• Reaction 3 : Fructose-6-phosphate is converted to fructose-1,6-bisphosphate by using enzyme Phosphofructokinase.
• Reaction 4 : Fructose-1,6-bisphosphate is converted to two triose sugars that is, glyceraldehyde-3-phosphate (GA3P) and dihydroxyacetone phosphate (DHAP) by using enzyme fructose-bisphosphate aldolase.
Here, the first phase of glycolysis ends and 2 ATP molecules are consumed.
• Reaction 5 : Dihydroxyacetone phosphate (DHAP) is converted to glyceraldehyde-3-phosphate (GA3P). And both reactions proceed further in glycolysis.
• Reaction 6 : Glyceraldehyde-3-phosphate (GA3P) is converted to 1,3-bisphosphoglycerate (1,3-BPG) by using enzyme glyceraldehyde phosphate dehydrogenase. Yields a molecule of NADH from reduction of NAD+.
• Reaction 7 : 1,3-bisphosphoglycerate (1,3-BPG) is converted to 3-phosphoglycerate (3PG) by using enzyme phosphoglycerate kinase. Leads to generation of a molecule of ATP.
• Reaction 8 : 3-phosphoglycerate (3PG) is converted to 2-phosphoglycerate (2PG) by using enzyme phosphoglycerate mutase.
• Reaction 9 : 2-phosphoglycerate is converted to phosphoenolpyruvate using enzyme enolase.
• Reaction 10 : Phosphoenolpyruvate gets converted into pyruvate with the help of pyruvate kinase. With the release of ATP molecules.
This is the whole process of glycolysis.


Describe cyclic photophosphorylation.
Answer – Cyclic photophosphorylation is a process in photosynthesis where light energy is used to generate ATP without the production of NADPH or oxygen. This occurs in the thylakoid membranes of chloroplasts and involves only Photosystem I (PSI).
Here are the key steps of cyclic photophosphorylation :
1. Light Absorption by Photosystem I – Light energy is absorbed by chlorophyll molecules in Photosystem I, which excites electrons to a higher energy level.
2. Electron Transport – The excited electrons are transferred from the reaction center chlorophyll (P700) of PSI to a primary electron acceptor.
3. Electron Flow Through the Electron Transport Chain – The high-energy electrons are then passed through a series of carriers, including ferredoxin (Fd), and eventually back to the PSI reaction center via the cytochrome b6f complex and plastocyanin (Pc).
4. Proton Gradient Formation – As electrons move through the cytochrome b6f complex, protons (H+) are pumped from the stroma into the thylakoid lumen, creating a proton gradient across the thylakoid membrane.
5. ATP Synthesis – The proton gradient drives the synthesis of ATP from ADP and inorganic phosphate (Pi) via ATP synthase, a process called photophosphorylation.

30. Draw a well labelled diagram of T. S. Dicot root (Primary).
Answer –


Draw a well labelled diagram of T. S. of Monocot stem.
Answer –

31. Identify the animals A and B shown below in the figure and answer the following questions :

(a) Which type of circulatory system is present in these animals? (1 Mark)
Answer – Closed circulatory system

(b) Which are osmoregulatory and excretory organs present in these animals? (1 Mark)
Answer – Nephridia

(c) What are the scientific name of animals A and B? (2 Marks)
Answer : Animal A → Neries
Animal B → Hirudinaria


Which one of the animals is monoecious & which one is dioecious?
Answer : Monoecious → Animal B
Dioecious → Animal A

32. Different types of Leucocytes are shown below in figure. Identify these and answer the following questions :

(a) Which one is the most abundant cell of total leucocytes? (1 Mark)
Answer – Neutrophils

(b) Which is least in number? (1 Mark)
Answer – Basophils

(c) Name two types of phagocytic cells in leucocytes. (2 Marks)
Answer – Monocytes and Neutrophils


Which type of leucocyte is involved in allergic and inflammatory reactions?
Answer : Allergic → Eosinophils
Inflammatory Reaction → Basophils

Section – D (5 Marks)

33. Differentiate between Chordates and Non-chordates.
Answer –

Chordates Non-chordates
1. A notochord is present at some stage in the life of a chordate. 1. Notochord is not present at any stage in the life of a non-chordate.
2. Central nervous system is dorsal and hollow. 2. Central nervous system is ventral and solid.
3. Gill slits are present in the pharynx either in the embryo or adult. 3. Gill slits are absent.
4. Tail is present at some stage in the life of the chordate. 4. Tail is absent.
5. Heart is ventral. 5. Heart is dorsal (if present).
6. Pharyngeal gill-slits are present in them. 6. Pharyngeal gill slits are absent in them.



Write down the salient features of phylum Echinodermata and give examples.
Answer – Salient features of phylum Echinodermata are :
(i) They are exclusively marine organisms.
(ii) Their body appearance is star like.
(iii) They are triploblastic, i.e., they possess three germ layers.
(iv) They exhibit Organ level of organization.
(v) Their skeleton is made of calcium carbonate.
(vi) They are spiny skinned organisms.
(vii) Circulatory systems in these organisms are open type.
(viii) Respiration occurs through gills or cloacal respiratory tree.
(ix) Nervous system is simple and radial in them.
(x) Excretory system is absent in those organisms.
(xi) Unsegmented body with mouth on the ventral side and anus on the dorsal side.
(xii) Tube feet help them in locomotion.
(xiii) Asexual reproduction is through regeneration and sexual reproduction is through gametic fusion. External fertilization occurs.
(xiv) Power of regeneration is very high in those organisms.
(xv) Development is indirect.
e.g. Sea star (Asterias), Sea cucumber (Cucumaria), Brittle star (Ophiothrix), Sea urchin (Echinus).

34. Describe Meiosis-II of cell division.
Answer – The four stages of Meiosis-II are as follows :
• Prophase II – It immediately sets off after the cytokinesis when the daughter cells are formed. The chromosomes begin to condense accompanied by the dissolution of the nuclear membrane and the disappearance of the Golgi apparatus and ER complex.
• Metaphase II – The chromosomes are connected to the centriole poles at the kinetochores of sister chromatids through the microtubules. They also get aligned at the equator to form the metaphase plate.
• Anaphase II – In this phase of meiosis II, there is a simultaneous splitting of the centromere of each chromosome and the sister chromatids are pulled away towards the opposite poles. As the chromatids move towards the poles, the kinetochore is at the leading edge with the chromosomal arms trailing.
• Telophase II – The chromosomes dissolve again into an undifferentiated lump and a nuclear envelope develops around it. Followed by cytokinesis, telophase II marks the end of meiosis. Four haploid daughter cells are formed as a result.


Write down the classification of Enzymes.
Answer – Enzymes are classified into six major classes :
1. Oxidoreductases – These enzymes catalyze oxidation-reduction reactions, where electrons are transferred from one molecule (the reductant) to another (the oxidant).
2. Transferases – These enzymes transfer functional groups (such as methyl, glycosyl, or phosphoryl groups) from one molecule to another.
3. Hydrolases – These enzymes catalyze the hydrolysis of various bonds by the addition of water.
4. Lyases – These enzymes catalyze the addition or removal of groups to form double bonds or the breaking of various chemical bonds by means other than hydrolysis and oxidation.
5. Isomerases – These enzymes catalyze the rearrangement of atoms within a molecule to form isomers.
6. Ligases – These enzymes catalyze the joining of two molecules with the formation of a new chemical bond, usually with the hydrolysis of ATP or another nucleotide.

35. Describe the transmission of nerve impulse.
Answer – The transmission of a nerve impulse occurs when a neuron is stimulated by a signal, such as a touch or sound, and it sends an electrical signal down its axon. This process involves several steps :
1. Resting potential – When the neuron is at rest, it has a negative charge inside the cell and a positive charge outside. This difference in charge is maintained by the sodium-potassium pump and potassium leak channels.
2. Depolarization – When the neuron is stimulated, channels on the cell membrane open, allowing sodium ions to rush into the cell. This causes the inside of the cell to become more positive, leading to depolarization.
3. Action potential – If the depolarization reaches a certain threshold, it triggers an action potential, which is a rapid and temporary reversal of the membrane potential. This causes an electrical signal to travel down the axon.
4. Repolarization – After the action potential passes, potassium channels open, allowing potassium ions to leave the cell, which restores the negative charge inside the cell.
5. Transmission – The action potential travels down the length of the axon, jumping from one node of Ranvier to the next in a process called saltatory conduction in myelinated neurons. In unmyelinated neurons, the action potential travels continuously along the axon.
6. Synaptic transmission – When the action potential reaches the end of the axon (the presynaptic terminal), it triggers the release of neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic neuron, initiating a new electrical signal in that neuron.
Overall, the transmission of a nerve impulse is a complex process involving changes in membrane potential and the release of neurotransmitters at synapses.


Describe various disorders of circulatory system.
Answer – There are several disorders of the circulatory system that can affect the heart, blood vessels, and blood flow. Some common disorders include :
1. Hypertension (High Blood Pressure) – High blood pressure can damage the blood vessels over time and increase the risk of heart disease, stroke, and other health problems. It is often referred to as a “silent killer” because it may not have noticeable symptoms.
2. Heart Failure – Heart failure occurs when the heart is unable to pump enough blood to meet the body’s needs. This can lead to symptoms such as shortness of breath, fatigue, and swelling in the legs and abdomen.
3. Coronary Artery Disease – This condition occurs when the blood vessels that supply the heart muscle become narrowed or blocked by a buildup of plaque, leading to reduced blood flow to the heart. This can result in chest pain (angina), heart attack, or other serious complications.
4. Arrhythmias – Arrhythmias are abnormal heart rhythms that can cause the heart to beat too fast, too slow, or irregularly. This can disrupt the normal pumping function of the heart and lead to symptoms such as palpitations, dizziness, or fainting.
5. Peripheral Artery Disease (PAD) – PAD occurs when there is a buildup of plaque in the arteries outside of the heart, usually in the legs. This can result in reduced blood flow to the extremities, causing symptoms such as leg pain, numbness, or weakness.
6. Stroke – A stroke occurs when there is a blockage or rupture of a blood vessel in the brain, leading to a lack of oxygen and nutrients to brain tissue. This can cause sudden weakness, numbness, difficulty speaking, or other neurological symptoms.
7. Deep Vein Thrombosis (DVT) – DVT is a blood clot that forms in a deep vein, usually in the legs. If the clot breaks loose and travels to the lungs, it can cause a life-threatening condition known as pulmonary embolism.


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