Biology MCQs

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Biology MCQs

Practice complete Biology MCQs covering Introduction to Biology, Cell Biology, Cell Structure, Cell Division, Biomolecules, Plant Physiology, Human Physiology, Genetics, Evolution, Biotechnology, Ecology, Classification of Living Organisms, Plant Kingdom, Animal Kingdom, Microbiology, Human Diseases, Nutrition, Reproduction, Environmental Biology, and all other important topics. Includes chapter-wise and exam-oriented multiple-choice questions with detailed answers and explanations for JKSSB, SSC, Banking, Railway, UPSC, CUET, NEET, State PSCs, and other competitive exams.

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Page 63 of 103
Question #1241
The disease caused by the bacterium Neisseria meningitidis is:
A. Tuberculosis
B. Pneumonia
C. Gonorrhea
D. Meningitis
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Correct Answer: Option D

Explanation:
Neisseria meningitidis (meningococcus) causes bacterial meningitis, an inflammation of the meninges. N. gonorrhoeae causes gonorrhea. Pneumonia is often Streptococcus pneumoniae.
This question belongs to: Science Biology
Question #1242
The scientist who discovered the bacterium Helicobacter pylori and its role in ulcers was:
A. Robert Koch
B. Louis Pasteur
C. Barry Marshall and Robin Warren
D. Alexander Fleming
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Correct Answer: Option C

Explanation:
Marshall and Warren discovered H. pylori in 1982 and proved it causes peptic ulcers, earning the 2005 Nobel Prize. Koch discovered TB, Pasteur vaccines, Fleming penicillin.
This question belongs to: Science Biology
Question #1243
The process of movement of molecules from high to low concentration without energy is:
A. Endocytosis
B. Active transport
C. Osmosis
D. Passive diffusion
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Correct Answer: Option D

Explanation:
Passive diffusion is the net movement of molecules down their concentration gradient without energy. Osmosis is water diffusion, active transport uses energy, endocytosis is vesicular uptake.
This question belongs to: Science Biology
Question #1244
The vitamin that is required for the conversion of prothrombin to thrombin is:
A. Vitamin C
B. Vitamin K
C. Vitamin A
D. Vitamin D
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Correct Answer: Option B

Explanation:
Vitamin K-dependent carboxylation allows prothrombin and other clotting factors to bind calcium and participate in coagulation. Deficiency prolongs clotting time.
This question belongs to: Science Biology
Question #1245
The hormone that stimulates the pancreas to secrete bicarbonate is:
A. Cholecystokinin
B. Gastrin
C. Secretin
D. Motilin
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Correct Answer: Option C

Explanation:
Secretin is released from the duodenum when acidic chyme enters, stimulating the pancreas to secrete bicarbonate-rich fluid, neutralizing the acid.
This question belongs to: Science Biology
Question #1246
The pigment that gives red and purple color to some fruits like grapes and berries is:
A. Chlorophyll
B. Anthocyanin
C. Lycopene
D. Carotenoid
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Correct Answer: Option B

Explanation:
Anthocyanins are water-soluble vacuolar pigments that appear red, purple, or blue depending on pH. They are flavonoids. Chlorophyll is green, carotenoids yellow/orange, lycopene red.
This question belongs to: Science Biology
Question #1247
The scientist who first observed the 'cell' under a microscope was:
A. Matthias Schleiden
B. Robert Brown
C. Antonie van Leeuwenhoek
D. Robert Hooke
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Correct Answer: Option D

Explanation:
Robert Hooke, in 1665, observed cork cells under a compound microscope and coined the term 'cell'. Leeuwenhoek later observed live cells.
This question belongs to: Science Biology
Question #1248
The disease caused by the bacterium Corynebacterium diphtheriae is:
A. Typhoid
B. Tetanus
C. Pertussis
D. Diphtheria
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Correct Answer: Option D

Explanation:
Diphtheria affects the throat, forming a pseudomembrane, and releases a toxin affecting the heart and nerves. Tetanus is Clostridium, pertussis Bordetella, typhoid Salmonella.
This question belongs to: Science Biology
Question #1249
The vitamin that is required for the absorption of calcium from the gut is:
A. Vitamin E
B. Vitamin A
C. Vitamin D
D. Vitamin C
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Correct Answer: Option C

Explanation:
Vitamin D stimulates the synthesis of calcium-binding proteins in the intestinal epithelium, promoting calcium absorption. Deficiency leads to rickets/osteomalacia.
This question belongs to: Science Biology
Question #1250
The process of breakdown of glucose to pyruvate is called:
A. Electron transport chain
B. Krebs cycle
C. Fermentation
D. Glycolysis
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Correct Answer: Option D

Explanation:
Glycolysis is a cytoplasmic pathway that converts glucose into two pyruvate molecules, producing a net of 2 ATP and 2 NADH. Krebs cycle and ETC are in mitochondria.
This question belongs to: Science Biology
Question #1251
The structure that stores sperm and allows maturation is the:
A. Epididymis
B. Seminal vesicle
C. Vas deferens
D. Prostate gland
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Correct Answer: Option A

Explanation:
The epididymis is a coiled tube on the testis where sperm mature and are stored. Seminal vesicles and prostate add fluid, vas deferens transports sperm.
This question belongs to: Science Biology
Question #1252
The hormone that stimulates the growth and development of the mammary glands during puberty is:
A. Estrogen
B. Progesterone
C. Oxytocin
D. Prolactin
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Correct Answer: Option A

Explanation:
Estrogen promotes ductal growth in breasts and deposition of fat, contributing to breast development at puberty. Progesterone develops alveoli, prolactin synthesizes milk, oxytocin ejects milk.
This question belongs to: Science Biology
Question #1253
The technique used to produce monoclonal antibodies involves fusion of B cells with:
A. Myeloma cells
B. T cells
C. Macrophages
D. Dendritic cells
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Correct Answer: Option A

Explanation:
Hybridoma technology fuses antibody-producing B cells with immortal myeloma cells to create hybridomas that produce monoclonal antibodies. Developed by Kohler and Milstein.
This question belongs to: Science Biology
Question #1254
The organ that is the site of T-cell maturation is the:
A. Bone marrow
B. Lymph node
C. Thymus
D. Spleen
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Correct Answer: Option C

Explanation:
The thymus gland is a primary lymphoid organ where T lymphocytes mature and become self-tolerant. Bone marrow is where B cells mature; spleen and lymph nodes are secondary.
This question belongs to: Science Biology
Question #1255
The pigment that is responsible for the green color of leaves is:
A. Chlorophyll
B. Carotene
C. Xanthophyll
D. Anthocyanin
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Correct Answer: Option A

Explanation:
Chlorophyll a and b absorb red and blue light and reflect green, giving leaves their color. Carotenoids are yellow/orange, anthocyanins red/purple.
This question belongs to: Science Biology
Question #1256
The scientist who discovered the sex chromosomes was:
A. Thomas Hunt Morgan
B. Gregor Mendel
C. Nettie Stevens
D. Walter Sutton
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Correct Answer: Option C

Explanation:
Nettie Stevens (1905) discovered that sex is determined by the XY chromosomes in beetles. Morgan later confirmed chromosomal theory. Mendel discovered laws of inheritance.
This question belongs to: Science Biology
Question #1257
The enzyme that breaks down acetylcholine in the synaptic cleft is:
A. Acetylcholinesterase
B. Choline acetyltransferase
C. Monoamine oxidase
D. Catechol-O-methyltransferase
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Correct Answer: Option A

Explanation:
Acetylcholinesterase degrades acetylcholine into acetate and choline, terminating the synaptic signal. Choline acetyltransferase synthesizes ACh, MAO and COMT degrade monoamines.
This question belongs to: Science Biology
Question #1258
The disease caused by the fungus Histoplasma capsulatum is:
A. Histoplasmosis
B. Aspergillosis
C. Coccidioidomycosis
D. Candidiasis
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Correct Answer: Option A

Explanation:
Histoplasmosis is a respiratory fungal infection caused by inhaling spores of Histoplasma capsulatum, often found in bird or bat droppings. It can be severe in immunocompromised.
This question belongs to: Science Biology
Question #1259
The hormone that stimulates the kidney to convert 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D is:
A. ACTH
B. PTH
C. TSH
D. Calcitonin
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Correct Answer: Option B

Explanation:
Parathyroid hormone (PTH) activates the enzyme 1-α-hydroxylase in the kidney, converting vitamin D to its active form, which then increases calcium absorption.
This question belongs to: Science Biology
Question #1260
The process of making a complementary DNA (cDNA) from mRNA using reverse transcriptase is called:
A. Replication
B. Reverse transcription
C. Transformation
D. Translation
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Correct Answer: Option B

Explanation:
Reverse transcription synthesizes DNA from an RNA template, catalyzed by reverse transcriptase in retroviruses and used in molecular biology for cDNA synthesis.
This question belongs to: Science Biology

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