(1st Year Syllabus) Test-2

Explanation: A

Explanation: C

Explanation: B

Explanation: B
Total time = 3 + 2 = 5
Total displacement = 100 – 50= 50
Average velocity = 50/5 = 10m/s.
For speed
Total distance = 100 + 50 = 150
Average speed = 150/5 = 30 m/s

Explanation: B
For one complete revolution,
angle in radians = 2π, angle in degrees = 360°.
Therefore,
radians/degrees = 2π/360 = π/180.
Note:  π/180 is the general conversion factor from degrees to radians (i.e., 1° = π/180 rad). Option D, 360/2π = 180/π, is the inverse (degrees per radian).

Explanation: A
Terminal velocity is given by the formula
V = 2gpr²/9n, if r = constant, V is directly proportional to density, so the ball with more density will have more Terminal velocity.

Explanation: D
L = nλ
Wavelength = total length/ no of waves= 10/20 = 0.5m.

Explanation: B
In SHM, a=−ω²x: acceleration always points toward the mean, so its direction flips when x changes sign. Over one full oscillation the mass crosses the mean position twice, so acceleration reverses direction two times

Explanation: C
In Isobaric all the heat is not converted into internal energy as some part of heat is also converted into work therefore more heat is required to raise the temperature
In Isochoric all the heat is converted into internal energy and therefore less heat is required.

Explanation: B
For angle we use, angle = tan^–1 y/x = tan^–1 2/2= 45 degrees
As both x and y are negative vector is lying in 3^rd quadrant
For 3^rd quadrant, angle = 180 + 45 = 225 degrees.

Explanation: C
• Concept and Explanation: Energy is scalar; it is conserved (transferred/ transformed) but not created/destroyed.
Energy has no direction (so A is false), total energy includes many forms—kinetic, potential, thermal, etc. (so B is false), and it’s conserved—not created or destroyed—only transformed or transferred (so D is false).

Explanation: C
A displacement of 2r means the initial and final points are diametrically opposite, so the chord between them is a diameter. The shortest arc connecting opposite points is a semicircle, whose length is half the circumference:
distance = 1/2 (2πr) = πr.
Circular Motion: Displacement vs Distance
distance along arc = πr.

Explanation: B
All the hands of clock when compared with same hand of any other clock have same angular velocity
If angular velocity is constant
Linear velocity is directly proportional to radius (v = ωR)
If R_a > R_b than V_a > V_b.

Explanation: C
The more the velocity, the more will be the drag force acting on it and flow of the fluid across it will be Turbulent.

Explanation: D
In a longitudinal wave, particles oscillate back and forth along the line of travel. Where they move opposite the wave’s propagation, they spread out, creating a low-density, low-pressure region—a rarefaction. (Compressions occur where particles move with the wave and crowd together.)

Explanation: C

Explanation: C
Thermally insulated = Adiabatic = Q = 0
For Adiabatic
W = change in internal energy
New internal energy = Initial internal energy – work = 100 – 80 = 20.

Explanation: D
If magnitude of dot product between vector A and B is AB this means that the angle between A and B is 0 degrees because: A.B = ABcos(θ) = AB
When angle between two vectors is zero their cross product is:
A × B = ABsin(θ)ń    = 0ń (null vector).

Explanation A

Explanation: D
Increasing slope means that velocity is increasing
If acceleration is increasing Positive = velocity increases
If acceleration is decreasing positive = velocity increases
If acceleration is uniform Positive = velocity increases.

Explanation: A
Because for rigid rotation: v=ω × r.
Order matters (A is ω × r, not r × ω)
and dot products (C, D) would give a scalar, not a velocity vector.
Why B is wrong:
Because the order in a cross product matters (it’s anti-commutative):
a × b = –(b × a)
For rigid rotation the kinematics give
v = ω × r
If you swap the order (option B),
r × ω = –( ω × r) = –v.

Explanation: C
According to equation of continuity
Product of area and velocity = volume/ time (flow rate) or
Av = V/t.

Explanation: C
Frequency is set by the source and remains the same across media. When sound goes from a rarer to a denser medium, the speed and thus the wavelength change, and the amplitude can change due to reflection/transmission—but the frequency does not.

Explanation: B
Time to reach from mean to mid of mean and extreme = T/12 = 24/12 = 2s.

Explanation: C
In isothermal change in internal energy is zero and all the heat supplied is converted into work.
For an ideal gas, Q = ΔU + W.
• Isothermal: ΔU = 0 ⇒ W = Q → all added heat becomes work (max conversion).
• Isobaric: part of Q raises ΔU.
• Isochoric: W = 0.
• Adiabatic: Q = 0 (no heat-to-work conversion).

Explanation: C

Explanation: B

Explanation: D
Power = P = F.V = (2 × 0) + (3 × 3) + (0 × 2) = 0 + 9 + 0 = 9W.

Explanation: B

Explanation: C
For steady, incompressible flow in a vertical pipe of uniform diameter, continuity gives Av = const Since A is constant, the speed v is the same at all heights.
Bernoulli’s equation along the pipe (neglecting losses) is
P + 1/2 ρv² + ρgz = constant.
As height z increases, P decreases to compensate, while the kinetic-energy term 1/2 ρv² stays constant. Hence the kinetic energy per unit volume remains the same with height.
In horizontal pipe PE/volume = ρgh remains same
In vertical pipe KE/volume = 1/2 ρv² remains same.

Explanation: B
Source used to form wave in the organ pipe is not kept precisely on the opening of the pipe. There is a small space between the open end and the source this is called as end effect
Due to this we say that fundamental note Wavelength is slightly larger than 4l.

Explanation: C
That’s the essence of thermal equilibrium: when two bodies have the same temperature, there’s no net heat flow between them.
A and B are statements of the second law (Clausius form / source → sink idea), not the law of thermal equilibrium.

Explanation C
V_H = u cosθ is independent of g.
Gravity is vertical; it does not alter v_x.
A, B. Confuse effect of g on v_x. D. v_x ≠ 0 at the top anywhere.
Important formula(s)/law(s): a_x = 0, v_x = u cosθ.
Hints/shortcuts: Change g → affects v_y and time, not v_x.

Explanation: C

Explanation: C
When a heavy body collides with a light body at rest then
Velocity of heavy body after collision = remains same
Velocity of light body after collision = 2 times of velocity of heavy body.

Explanation: B
λ for a string fixed at both ends with n loops is λ = 2L/n.
Here L = 5m and n = 5, so
λ = 2×5/5 = 2m.

Explanation: C
1. During a sprint (200 m race):
The muscles require rapid delivery of oxygen and nutrients (especially glucose).
The heart rate increases → more blood is pumped per minute → more oxygen and glucose are delivered to muscle cells.
Waste products (like CO₂ and lactic acid) are removed faster.
2. Looking at options:
A. Increase digestion of carbohydrates → Not correct. Digestion is slowed during exercise because blood is diverted away from the gut to the muscles.
B. Increase ventilation of the lungs with fresh air → This is mainly due to increased breathing rate, not directly an effect of increased heart rate (though both are coordinated). Heart rate rise itself doesn’t increase ventilation.
C. Reduce the need for anaerobic respiration Correct. By pumping more oxygen-rich blood to the muscles, the increased heart rate helps supply sufficient oxygen, thereby delaying or reducing the need for anaerobic respiration (which produces lactic acid).
D. Reduce the need for sweating to cool the body → Incorrect. Sweating is mainly controlled by body temperature, not heart rate.
Correct Answer: C. To reduce the need for anaerobic respiration:
The indirect effect of increased heart rate is enhanced oxygen delivery to muscles. This allows muscles to rely more on aerobic respiration, which is efficient and prevents early buildup of lactic acid, thus reducing the reliance on anaerobic respiration.

Explanation: A
1. Classification of hormones by chemical nature:
• Steroid hormones: Derived from cholesterol (e.g., testosterone, estrogen, progesterone, cortisol, aldosterone).
• Amino acid derivatives: From tyrosine or tryptophan (e.g., thyroxine, adrenaline, melatonin).
• Protein/Polypeptide hormones: Chains of amino acids (e.g., insulin, glucagon, growth hormone).
2. Testosterone, estrogen, progesterone → all are sex hormones derived from cholesterol → hence steroid hormones.
3. Check options:
A. Steroid nature  Correct.
B. Amino acid nature  Wrong.
C. Protein nature  Wrong.
D. Polypeptide nature  Wrong.
Correct Answer: A. Steroid nature
Sex hormones such as testosterone, estrogen, and progesterone belong to the steroid family, synthesized from cholesterol, and are lipid-soluble. They pass through cell membranes and act via intracellular receptors to regulate gene expression.

Explanation: A
1. Aorta:
• Carries blood from the left ventricle to the body.
• Blood is oxygen-rich (just pumped from lungs via left atrium/ventricle).
• CO₂ is low.
• Pressure is highest because it receives blood directly from the left ventricle’s powerful contraction.
2. Pulmonary artery:
• Carries blood from right ventricle → lungs.
• Blood is deoxygenated (low O₂, high CO₂).
3. Pulmonary vein:
• Carries blood from lungs → left atrium.
• Blood is oxygenated and low in CO₂, but pressure is much lower than in the aorta.
4. Vena cava:
• Carries blood from body → right atrium.
• Blood is low in O₂, high in CO₂, and under low pressure. 
Correct Answer: A. Aorta.

Explanation: B
Both plant and animal cells are eukaryotic and contain mitochondria, endoplasmic reticulum, and Golgi apparatus. Plastids and large vacuoles are specific to plants; centrioles are typical of animals.

Explanation: A
Rough ER is continuous with the nuclear envelope and plays a role in transporting proteins.

Explanation: B
Hemoglobin has 4 subunits (quaternary).

Explanation: B
Higher substrate concentration outcompetes inhibitor.

Explanation: C
Each acetyl-CoA yields 3 NADH, 1 FADH₂, 1 ATP (or GTP), and 2 CO₂.

Explanation: B
The variable region at the tips of the antibody arms determines antigen specificity.

Explanation: D
Most mammalian enzymes show their maximum activity near 40°C, which is close to the normal body temperature of mammals (around 37°C). At this temperature, the enzymes maintain their proper shape and catalytic efficiency. Below or above this range, their activity decreases, and very high temperatures can denature them permanently.

Explanation: B
1. Blood from the ileum contains digested nutrients (glucose, amino acids, some vitamins, toxins if present, etc.).
• These nutrients go via the hepatic portal vein directly to the liver before entering general circulation.
2. Checking options one by one:
A. Amino acids → urea before circulation 
The liver deaminates excess amino acids, but not immediately all amino acids. Useful ones are kept for protein synthesis. Urea production happens when there is surplus amino acid metabolism, not the main advantage.
B. Excess glucose → glycogen 
The liver stores glucose as glycogen (glycogenesis). This prevents large fluctuations of blood glucose and avoids wastage. This is a major advantage of portal blood going through the liver.
C. Fat products
Fats are absorbed into lacteals (lymphatic system), not directly into the hepatic portal vein, so this option is wrong.
Final Key: B
Explanation: The hepatic portal vein ensures that absorbed glucose from the ileum is first regulated by the liver. Excess glucose is stored as glycogen, preventing it from being lost or causing harmful spikes in blood sugar levels.

Explanation: B
1. In the pancreas, the endocrine part is the Islets of Langerhans.
• Alpha cells → secrete glucagon (raises blood glucose).
• Beta cells → secrete insulin (lowers blood glucose).
• Delta cells → secrete somatostatin (inhibits both insulin & glucagon).
• Acinar cells → part of the exocrine pancreas, secreting digestive enzymes, not hormones.
2. Since insulin is secreted by beta cells, the correct option is B.
Correct Answer: B. Beta cells
Beta cells of the islets of Langerhans produce insulin, which decreases blood glucose by promoting glucose uptake into cells and conversion of glucose into glycogen (glycogenesis) in liver and muscles.

Explanation: B
1. Right ventricle contraction (systole):
• Blood is pumped from the right ventricle → pulmonary artery through the pulmonary valve.
• To prevent backflow into the right atrium, the tricuspid valve (between right atrium and right ventricle) must be closed.
2. Check the options:
A. Bicuspid valve (mitral valve): Found between the left atrium and left ventricle, not involved in right ventricle contraction.
B. Tricuspid valve: Located between right atrium and right ventricle → must close during right ventricular systole.
C. Aortic valve: Found at the exit of the left ventricle → not related here.
D. Pulmonary valve: This one opens during right ventricular contraction to allow blood into pulmonary artery, not close. 
Correct Answer: B. Tricuspid valve.

Explanation: C
Prokaryotes lack a true nucleus. Their circular DNA is located in the nucleoid region.

Explanation: C
Like prokaryotes, mitochondria have circular DNA and 70S ribosomes → evidence of endosymbiotic origin.

Explanation: A
RNA has ribose, uracil, usually single-stranded.

Explanation: B
Low temperature reduces kinetic energy, slowing enzyme-substrate collisions.

Explanation: B
Acetyl-CoA (2C) combines with oxaloacetate (4C) to form citrate (6C).

Explanation: B
The bicuspid valve is present between the left atrium and ventricle.

Explanation: C
Chief cells (zymogenic cells) of the gastric glands secrete pepsinogen, the inactive precursor of pepsin. Once released, pepsinogen is converted to active pepsin by the action of hydrochloric acid.

Explanation: C
1. Phagocytosis = “cell eating” → intake of solid particles (like bacteria or food particles).
2. Pinocytosis = “cell drinking” → intake of extracellular fluid and dissolved substances into small vesicles.
3. Exocytosis = expulsion/secretion of materials out of the cell (reverse of endocytosis).
4. Chloroplast = organelle for photosynthesis in plants, not a process.
Correct Answer: C. Pinocytosis
Pinocytosis is a type of endocytosis where the cell engulfs droplets of extracellular fluid. It’s called the “cell drinking” process, as opposed to phagocytosis (cell eating).

Explanation: D
1. One glucose molecule (C₆H₁₂O₆) in aerobic respiration:
• Glycolysis: produces 2 pyruvate (3C each).
• Link reaction (pyruvate → acetyl-CoA): each pyruvate (2 per glucose) produces 1 CO₂ → total 2 CO₂.
• Krebs cycle: each acetyl-CoA (2 per glucose) produces 2 CO₂ → total 4 CO₂.
• Total per glucose = 2 + 4 = 6 CO₂.
2. For 2 glucose molecules:
• 6 × 2 = 126 × 2 = 12 CO₂.
Correct Answer: D. 12
In aerobic respiration, each glucose molecule is completely oxidized into 6 CO₂ molecules. Therefore, for 2 glucose molecules, the total CO₂ released is 12 molecules.

Explanation: C
1. Types of enzyme inhibition:
• Competitive inhibition: Inhibitor competes with substrate for the active site.
• Non-competitive inhibition: Inhibitor binds to an allosteric site (a site other than the active site).
2. Effect of non-competitive inhibition:
• Changes the shape of the enzyme (including active site).
• Substrate can still bind (sometimes), but enzyme cannot catalyze reaction effectively.
• Rate of reaction decreases regardless of substrate concentration.
3. Check options:
A. Competing with the substrate at the active site → This is competitive inhibition.
B. Increasing substrate concentration → This increases rate, not decreases it.
C. Binding to a site other than the active site → Correct, definition of non-competitive inhibition.
D. Denaturing the enzyme → Denaturation is caused by heat/pH extremes, not inhibitors.
Correct Answer: C. Binding to a site other than the active site

Explanation: B
Glycogen is the animal storage form, and centrioles are typical of animal cells. Plants/algae store starch instead, while bacteria lack centrioles

Explanation: B
They are hybrid molecules: protein backbone + covalently attached carbohydrates.

Explanation: B
Adenine pairs with Thymine (2 H-bonds), Guanine with Cytosine (3 H-bonds).

Explanation: A
Each round of β-oxidation removes 2 carbons as acetyl-CoA. An 18-carbon fatty acid → 18 ÷ 2 = 9 acetyl-CoA molecules. These enter the Krebs cycle, producing a much higher ATP yield than glucose.

Explanation: C
ETC complexes are embedded in inner mitochondrial membrane.

Explanation: D
In bacterial cells, RNA is present in a much higher quantity than DNA. The ratio of RNA to DNA is about 6:1, meaning RNA content is nearly six times more than DNA. This is because bacteria require large amounts of RNA (particularly ribosomal RNA) to support rapid protein synthesis and growth, whereas DNA is relatively stable and present in smaller amounts

Explanation: A
Normal sequence is SA → AV → AV bundle  → bundle branches → Purkinje → ventricular muscle.

Explanation: D
1. Gluconeogenesis = formation of glucose from non-carbohydrate sources (like amino acids, lactate, glycerol).
2. Glycogenolysis = breakdown of glycogen into glucose (for energy release).
3. Glycolysis = breakdown of glucose to pyruvate with ATP release (first step of respiration).
4. Glycogenesis = synthesis of glycogen from glucose molecules for storage in liver and muscle.
Correct Answer: D. Glycogenesis
When blood glucose levels are high (after a meal), glucose is converted into glycogen in the liver and muscle cells through glycogenesis. This process is stimulated by insulin.

Explanation: A
Option A (Correct):
A chromosome is made of a single, long DNA molecule coiled around proteins (histones). This DNA is divided into smaller functional units called genes.
Option B (Incorrect):
This suggests that a chromosome is made of many separate small DNA molecules, each forming a gene. That’s wrong — a chromosome contains one continuous DNA molecule, not many small ones.
Option C (Incorrect):
This flips the relationship. Genes are parts of chromosomes, not the other way around.
Option D (Incorrect):
Genes are not entire long DNA molecules. They are specific segments of DNA that carry instructions for proteins or RNA.

Explanation: C
1. Structure of DNA:
• DNA is a double helix made of repeating units called nucleotides.
• Each nucleotide = deoxyribose sugar + phosphate group + nitrogenous base.
2. Backbone composition:
• The sugar (deoxyribose) and phosphate groups link together in a chain.
• Nitrogenous bases (A, T, G, C) project inward and pair by hydrogen bonds.
• Thus, the backbone = deoxyribose + phosphate.
3. Check options:
A. Nucleotides and amino acids → Amino acids make proteins, not DNA backbone.
B. Ribose and phosphate → Ribose is in RNA, not DNA.
C. Deoxyribose and phosphate → Correct.
D. Bases and deoxyribose → Bases are not part of the backbone; they are the rungs of the ladder.
Correct Answer: C. Deoxyribose and phosphate.

Explanation: A
The centromere holds sister chromatids and attaches to spindle fibers, ensuring proper chromosome segregation.

Explanation: B
Carbohydrates (especially glucose) are the main instant energy source.

Explanation: B
Strands are complementary and antiparallel for replication fidelity.

Explanation: C
Bacteriophages are viruses that parasitize bacteria. Example: T4 phage infects E. coli.

Explanation: A
The liver secretes bile but never comes in direct contact with food. All others are parts of the alimentary canal where food passes .

Explanation: A
Fibrous proteins are elongated, insoluble proteins that mainly serve structural roles in cells and tissues. Keratin is a classic fibrous protein found in hair, nails, horns, and the outer layer of skin. In contrast, antibodies, haemoglobin, and albumin are globular proteins, which are compact, soluble, and function mainly in transport, defense, and metabolism.

Explanation: B
The Islets of Langerhans are clusters of endocrine cells in the pancreas that secrete important hormones like insulin, glucagon, and somatostatin. Despite their vital role in glucose metabolism, they make up only about 2% of the total pancreatic mass, with the remaining bulk consisting of exocrine tissue that produces digestive enzymes.

Explanation: D
1. Maltose = Glucose + Glucose → disaccharide
2. Sucrose = Glucose + Fructose → disaccharide
3. Lactose = Glucose + Galactose → disaccharide
4. Fructose = a monosaccharide (single sugar, along with glucose and galactose)
Correct Answer: D. Fructose
Disaccharides are formed by the condensation of two monosaccharides. Maltose, sucrose, and lactose all belong to disaccharides, while fructose is a monosaccharide (a simple sugar).

Explanation: C
1. Right atrium → receives blood from vena cavae and pushes it only into the right ventricle → requires little force → thin wall.
2. Right ventricle → pumps blood into the lungs through pulmonary artery → requires more pressure than the atrium (though less than the left ventricle, which pumps to the whole body).
3. Wall thickness is due to the force required for pumping, not O₂ concentration or blood volume.
Correct Answer: C. Right ventricle must exert greater force
The ventricle walls are thicker than atria because ventricles must generate more pressure to pump blood out of the heart (to lungs or body), whereas atria only push blood into nearby ventricles.

Explanation: C
Mitochondria oxidize fatty acids and glucose to release ATP. SER synthesizes lipids; Golgi modifies proteins; nucleolus makes rRNA/ribosomes

Explanation: A
1. Metabolism of fatty acids:
• Fatty acids are broken down in the mitochondria by a process called β-oxidation.
• This process sequentially removes 2-carbon fragments from the fatty acid chain.
2. Product of β-oxidation:
• Each 2-carbon fragment is converted into Acetyl-CoA.
• Acetyl-CoA then enters the Krebs cycle (citric acid cycle) to produce NADH, FADH₂, and ATP.
3. Check options:
A. Acetyl-CoA → Correct; direct product of β-oxidation.
B. Glucose → Fatty acids cannot be converted back into glucose (except glycerol part of triglycerides).
C. Pyruvate → Pyruvate is formed from glucose (glycolysis), not fatty acids.
D. Citrate → Citrate is formed inside the Krebs cycle from Acetyl-CoA + oxaloacetate, not directly from fatty acids.
Correct Answer: A. Acetyl-CoA

Explanation: B
Lipids yield ~9 kcal/g, almost double carbohydrates/proteins.

Explanation: B
Cholesterol is converted into steroid hormones like estrogen, testosterone.

Explanation: C
Viruses lack metabolic machinery. They rely on host cell enzymes and ribosomes for replication.

Explanation: B
The pyloric sphincter is a muscular valve that controls the movement of partially digested food (chyme) from the stomach into the duodenum.

Explanation C 
They are rings of smooth muscle at the entrance to capillary beds (metarteriole–capillary junction).

Explanation: C
The Human Immunodeficiency Virus (HIV) possesses about 72 glycoprotein spikes on its envelope. Each spike is made of gp120 and gp41 glycoproteins, which help the virus attach to and fuse with host cells (mainly CD₄⁺ T-lymphocytes). These spikes are critical for viral infectivity and are major targets for neutralizing antibodies.

Explanation: D
1. Enzyme structure:
• Many enzymes need a cofactor (non-protein helper, e.g., metal ion or organic molecule) to work.
• The complete, active form of enzyme = Holoenzyme = Apoenzyme + Cofactor.
2. Definitions:
• Active site = region on enzyme where substrate binds
• Coenzyme = organic, non-protein cofactor (like NAD⁺, FAD)
• Prosthetic group = tightly bound cofactor to enzyme
• Apoenzyme = the protein part of enzyme, inactive without cofactor
Correct Answer: D. Apoenzyme
An apoenzyme is the inactive protein part of an enzyme. When the required cofactor (metal ion, coenzyme, or prosthetic group) binds, it becomes a holoenzyme, which is catalytically active.

Explanation: B
1. Role of the gall bladder:
• The gall bladder does not produce bile; it only stores and releases bile made by the liver.
• Bile contains bile salts which emulsify fats (break large fat globules into smaller droplets).
• This emulsification increases the surface area for lipase enzymes to act, improving fat digestion.
2. If the gall bladder is removed (cholecystectomy):
• The liver still produces bile normally.
• But bile will no longer be stored and concentrated in the gall bladder.
• Instead, bile will drip continuously into the small intestine in small amounts.
• As a result, digestion of large fatty meals becomes less efficient (reduced fat digestion).
3. Why not the other options?
A. Carbohydrates: Their digestion depends on amylase (saliva and pancreatic), not bile.
C. Liver’s ability to convert glucose to glycogen: This is a liver metabolic function, not related to the gall bladder.
D. Stored urine: This is the function of the urinary bladder, not the gall bladder.
Correct Answer: B. Reducing the digestion of fats.

Explanation: C
1. Causative agent of AIDS:
• AIDS (Acquired Immunodeficiency Syndrome) is caused by HIV (Human Immunodeficiency Virus).
• HIV is a retrovirus (RNA virus).
2. Target cells:
• HIV specifically attacks Helper T-lymphocytes (CD₄⁺ T-cells).
• These cells are critical for coordinating the immune response.
3. Effect of infection:
• Destruction of helper T-cells → weakened immune system.
• Body becomes vulnerable to opportunistic infections and certain cancers.
4. Check options:
A. Red blood cells → HIV does not infect RBCs; they lack a nucleus and CD4 receptors.
B. Neurons → Not the main target; though HIV can indirectly affect the nervous system, it does not primarily infect neurons.
C. Helper T-lymphocytes → Correct, main target cells.
D. Platelets → Platelets are cell fragments, not infected by HIV. 

Explanation: B
Chromosomes house DNA, which encodes hereditary information passed from one generation to the next.

Explanation: B
Polar H₂O dissolves polar and ionic substances.

Explanation: C
Enzymes accelerate biochemical reactions but remain unchanged after reaction.

Explanation: A
HIV has structural proteins: gp120 (attachment), gp41 (fusion), p24 (capsid), and p17 (matrix).

Explanation: A
Enterokinase from the duodenum activates trypsinogen into active trypsin, which then digests proteins.

Explanation: A
The brain and nervous tissue are especially rich in glycolipids, which form key parts of the myelin sheath around nerve fibers. They play a vital role in electrical insulation, nerve impulse conduction, and cell recognition in the nervous system. While nucleoproteins, lipoproteins, and glycoproteins are important biological molecules, they are not the major specialized components of brain tissue compared to glycolipids.

Explanation: B
The “lub” sound occurs when AV valves (tricuspid & bicuspid) close at the beginning of ventricular contraction.

Explanation: A
Coenzymes are small organic non-protein molecules that bind to enzymes and assist them in catalyzing reactions.
Most coenzymes are derived from vitamins (especially the B-complex vitamins).
Example:
NAD⁺ and NADP⁺ from niacin (Vitamin B3)
FAD from riboflavin (Vitamin B2)
Coenzyme A from pantothenic acid (Vitamin B5)
Minerals (like Mg²⁺, Zn²⁺, Fe²⁺/³⁺, Cu²⁺) act as cofactors, not coenzymes.
Hormones are signaling molecules, not enzyme helpers.

Explanation: C
1. Nature of viruses:
• Viruses have either DNA or RNA as their genetic material, but never both.
• They may be single-stranded or double-stranded, depending on the virus type.
2. Check each option:
A. Smallpox is an RNA virus → Incorrect.
• Smallpox (variola virus, family Poxviridae) is a large, double-stranded DNA virus.
B. Bacteriophages always contain RNA →  Incorrect.
• Most bacteriophages (like T4 phage) have DNA genomes, not RNA.
C. Smallpox is a DNA virus →  Correct.
D. Plant viruses never contain DNA →  Incorrect.
• Most plant viruses are RNA viruses (e.g., Tobacco mosaic virus = RNA), but some plant viruses do contain DNA (e.g., Geminiviruses).
Correct Answer: C. Smallpox is a DNA virus.

Explanation: D
1. Role of B-lymphocytes:
• B-cells are a type of lymphocyte that mature in the bone marrow.
• When activated by an antigen (often with help from helper T-cells), they differentiate into plasma cells.
• Plasma cells produce and secrete antibodies (immunoglobulins) specific to the antigen.
2. Check other options:
A. T-lymphocytes → They regulate immunity (helper T-cells) or kill infected cells (cytotoxic T-cells), but they do not produce antibodies.
B. Neutrophils → These are phagocytes that engulf pathogens, not antibody producers.
C. Macrophages → Also phagocytes; they present antigens but don’t make antibodies.
D. B-lymphocytes → Correct; they are the source of antibody production.
Correct Answer: D. B-lymphocytes.

Explanation: B
Histones compact DNA into nucleosomes. Without them, long DNA molecules cannot be packed into the tiny nucleus.

Explanation: B
Sucrose = glucose + fructose.

Explanation: C
1. Tobacco mosaic virus (TMV):
• It was the first virus discovered (by Ivanovsky, later studied by Beijerinck).
• Structure: rod-shaped, rigid, and helical.
• Made of a single-stranded RNA genome surrounded by protein subunits arranged helically.
2. Check options:
A. Spherical That describes viruses like polio virus.
B. Tadpole-like That’s typical of bacteriophages (head + tail).
C. Rod-shaped Correct, TMV is rod-shaped.
D. Polyhedral Example: Adenovirus.
Correct Answer: C. Rod-shaped
TMV is a rigid rod-shaped plant virus with helical symmetry. Its discovery was key in understanding that viruses are non-cellular infectious agents made of nucleic acid and protein.

Explanation: D
1. Proteins in diet:
• The body cannot make all the essential amino acids.
• Proteins in food are broken down into amino acids → used to build new proteins for growth, repair, and enzymes.
2. Check each option:
A. They are an energy source → Not their main role. Although proteins can be used for energy (4 kcal/g), this happens mainly in starvation, not their essential function.
B. They are used in synthesizing hormones → Partly true (many hormones like insulin are proteins), but this is not the primary reason they are essential.
C. They can be stored as a food reserve → Proteins are not stored; excess amino acids are converted to fat or glucose.
D. They provide amino acids for cell growth → Correct. This is the fundamental reason proteins are essential.
Correct Answer: D. They provide amino acids for cell growth.

Explanation: C
1. Vena cava (superior & inferior):
• Bring deoxygenated blood from the body → right atrium.
2. Pulmonary artery:
• Carries deoxygenated blood from right ventricle → lungs for oxygenation.
3. Check other options:
A. Aorta + pulmonary artery → Aorta carries oxygenated blood.
B. Aorta + pulmonary vein → Both carry oxygenated blood.
C. Vena cava + pulmonary artery → Both carry deoxygenated blood.
D. Vena cava + pulmonary vein → Pulmonary vein carries oxygenated blood from lungs to left atrium.
Correct Answer: C. Vena cava and pulmonary artery.

Explanation: A
Primary = amino acid sequence. Higher structures = folding.

Explanation: B
Enzymes are reusable catalysts and remain intact.

Explanation: B
NAD⁺ accepts electrons, forming NADH. Without regeneration of NAD⁺, glycolysis stops.

Explanation: B
B-lymphocytes differentiate into plasma cells which produce antibodies, mediating humoral immunity.

Explanation: B
HIV destroys CD₄⁺ T-helper cells, impairing immunity. Patients become vulnerable to opportunistic infections like tuberculosis, pneumonia, and cancers.

Explanation: C
Suppressor (regulatory) T-cells keep immune reactions in check to avoid excessive damage to host tissue.

Explanation: C
The Lock and Key model was proposed by Emil Fischer in 1894. According to this model, the enzyme’s active site has a specific shape that exactly fits the substrate, just like a key-fits into a lock. This explains the high specificity of enzymes. Later, Koshland introduced the Induced Fit model to refine this concept.

Explanation: C
Each cardiac cycle (systole + diastole) lasts about 0.8 seconds, allowing rhythmic pumping of blood.

Explanation: B
They compete with substrate for active site.

Explanation: C
Both the thoracic and right lymphatic ducts empty lymph into the subclavian veins, just before the blood enters the right atrium

Explanation: C
Catalase is an important enzyme that breaks down hydrogen peroxide into water and oxygen. Its optimum pH is around 7 (neutral pH), which allows it to function most efficiently in living cells. At pH values much lower or higher than 7, the enzyme’s activity decreases due to denaturation or alteration of the active site.

Explanation: C
Cervical nodes are located along the neck and drain lymph from the scalp, face, and pharyngeal region.

Explanation: A
Cis face (convex) receives ER vesicles; trans face (concave) modifies, sorts, and releases them

Explanation: C
From units of rate constant, reaction B & D are zero order reactions so changing conc. of reactants has no effect on such reactions. In reaction A & C, the reaction C has greater rate constant so doubling reactant increases its rate the most.
Units reveal order:
k in s^–1 → first order (A, C): doubling [reactant] doubles rate.
k in mol dm^–3 s^–1 → zero order (B, D): rate does not depend on concentration → no increase.
Among first‑order, Reaction C has the larger  k (2.3 s^–1 vs 0.11 s^–1), so for the same starting [A] the absolute rate increase is greatest for C.

Explanation: D
For a positive particle, the greater the positive charge & lesser the mass, e/m value is large.
The e/m ratio means charge-to-mass ratio q/m. For a positive particle (like a nucleus or positive ion), q = +Ze and m ≈ Amu, so
e/m ∝ Z/A.
This ratio is larger when the particle is lighter (small A ).
• A (uncharged): q = 0 ⇒ e/m = 0 – smallest possible.
• B (more neutrons): increases A without increasing Z → decreases e/m.
• C (more protons): increases Z but also increases A; in heavier nuclei Z/A ≈ 0.5, so e/m does not get larger overall.
• D (small nucleus): small A gives larger Z/A (max for ¹H, where Z/A = 1 ), hence largest e/m.
Example: proton q/m = e/m_p ; alpha particle q/m=2e/4m_p = 1/2 (e/m_p ) –  smaller nucleus ⇒ larger e/m.

Explanation: A

Explanation: D
London forces depend strongly on size, the greater the size the greater the IM forces.
A: Intermolecular forces are weaker than intramolecular bonds.
B: London (dispersion) forces are present in all molecules (polar and nonpolar).
C: H‑bonding in NH₃ is weaker than the strong dispersion forces that hold solid I₂ together at room temperature — so this is false.
D: True — dispersion forces grow with polarizability/size (more electrons).

Explanation: C
CO₂ is AX₂ with no lone pairs on C → linear. Among the options, BeCl₂ is also linear. (SO₂, NO₂ are bent; CH₄ is tetrahedral.).

Explanation: B
For a reversible elementary reaction, K_c = k_fwd/k_rev. so if the forward rate constant k_f is larger than the reverse rate constant k_r, then Kc>1 and the equilibrium “lies to the right,” meaning the forward reaction progresses to a greater extent.
A. “Its rate increases to a maximum at equilibrium.”
Typically, if you start with reactants only, the forward rate is highest at the start (when reactant concentrations are largest) and decreases as reactants are consumed. At equilibrium it is nonzero but not maximal.
C. “It is faster if reactants are stable.”
Reaction rate depends on the activation energy. More stable (lower‑energy) reactants often imply a higher barrier to the transition state, so there is no general rule that “more stable reactants → faster forward reaction.” Often it’s the opposite.
D. “It is not equal to reverse reaction at equilibrium.”
By definition of dynamic equilibrium, forward and reverse rates are equal (though each is nonzero). Hence this statement is false.

Explanation: B
Species whose oxidation state increases is oxidized itself so it is a reducing agent.

Explanation: C
Heat capacity is energy per unit mass per kelvin. SI uses kg (J kg⁻¹ K⁻¹), but among the given choices the correct form is per gram: J g⁻¹ K⁻¹.
A is heat capacity; B is molar heat capacity.