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 56 of 103
Question #1101
The element that is a component of DNA and ATP is:
A. Phosphorus
B. Nitrogen
C. Sulfur
D. Iron
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Correct Answer: Option A

Explanation:
Phosphorus is part of the phosphate backbone of DNA/RNA and the high-energy bonds of ATP. Nitrogen is in bases and amino acids, iron in hemoglobin, sulfur in some amino acids. Phosphorus is essential for energy transfer and genetic material.
This question belongs to: Science Biology
Question #1102
The disease caused by the protozoan Entamoeba histolytica is:
A. Malaria
B. Sleeping sickness
C. Amoebic dysentery
D. Leishmaniasis
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Correct Answer: Option C

Explanation:
Amoebic dysentery (amoebiasis) is characterized by bloody, mucus-containing stools, caused by Entamoeba histolytica, transmitted through contaminated food/water. Malaria is Plasmodium, sleeping sickness Trypanosoma, leishmaniasis Leishmania.
This question belongs to: Science Biology
Question #1103
The vitamin that is required for the formation of the visual pigment rhodopsin is:
A. Vitamin D
B. Vitamin C
C. Vitamin A
D. Vitamin B₁
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Correct Answer: Option C

Explanation:
Vitamin A (retinal) combines with opsin to form rhodopsin in rod cells, necessary for vision in dim light. Deficiency causes night blindness. B₁ is for carbohydrate metabolism, C for collagen, D for calcium.
This question belongs to: Science Biology
Question #1104
The organelle that contains ribosomes attached to its surface is:
A. Smooth ER
B. Lysosome
C. Golgi apparatus
D. Rough ER
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Correct Answer: Option D

Explanation:
Rough endoplasmic reticulum is studded with ribosomes on its cytoplasmic surface, giving it a rough appearance. It is involved in protein synthesis and processing. Smooth ER lacks ribosomes and is for lipid synthesis.
This question belongs to: Science Biology
Question #1105
The process by which plants release oxygen is:
A. Photosynthesis
B. Respiration
C. Nitrogen fixation
D. Transpiration
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Correct Answer: Option A

Explanation:
During photosynthesis, water is split (photolysis), releasing oxygen as a byproduct. Respiration consumes oxygen, nitrogen fixation uses nitrogenase, transpiration releases water vapor.
This question belongs to: Science Biology
Question #1106
The structure that carries urine from the kidney to the bladder is the:
A. Urethra
B. Ureter
C. Calyx
D. Renal pelvis
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Correct Answer: Option B

Explanation:
The ureters are two muscular tubes that propel urine from the renal pelvis of each kidney to the urinary bladder via peristaltic contractions. Urethra exits bladder, renal pelvis and calyces are within the kidney.
This question belongs to: Science Biology
Question #1107
The scientist who discovered the cell nucleus was:
A. Matthias Schleiden
B. Theodor Schwann
C. Robert Hooke
D. Robert Brown
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Correct Answer: Option D

Explanation:
Robert Brown, a Scottish botanist, discovered and named the nucleus in 1831 while studying orchid epidermal cells. Hooke coined 'cell', Schleiden and Schwann formulated cell theory. Brown's observation was pivotal.
This question belongs to: Science Biology
Question #1108
The vitamin that is a coenzyme in the metabolism of carbohydrates and branched-chain amino acids is:
A. Pantothenic acid
B. Thiamine
C. Riboflavin
D. Niacin
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Correct Answer: Option B

Explanation:
Thiamine pyrophosphate (TPP) is a coenzyme for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase, playing a key role in carbohydrate metabolism. Riboflavin is FAD, niacin NAD, pantothenic acid CoA.
This question belongs to: Science Biology
Question #1109
The disorder characterized by repetitive seizures due to abnormal brain electrical activity is:
A. Stroke
B. Meningitis
C. Epilepsy
D. Multiple sclerosis
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Correct Answer: Option C

Explanation:
Epilepsy is a neurological disorder marked by recurrent seizures caused by excessive and synchronous neuronal firing. Stroke is from interrupted blood supply, MS is demyelination, meningitis is inflammation of meninges.
This question belongs to: Science Biology
Question #1110
The process of converting food into energy in cells is:
A. Fermentation
B. Transpiration
C. Cellular respiration
D. Photosynthesis
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Correct Answer: Option C

Explanation:
Cellular respiration breaks down glucose and other nutrients in the presence of oxygen to produce ATP. Photosynthesis builds glucose, fermentation is anaerobic energy production, transpiration is water loss.
This question belongs to: Science Biology
Question #1111
The structure that forms the physical barrier between the blood and the brain is the:
A. Blood-brain barrier
B. Choroid plexus
C. Corpus callosum
D. Meninges
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Correct Answer: Option A

Explanation:
The blood-brain barrier (BBB) is formed by tight junctions between endothelial cells of brain capillaries, restricting the passage of pathogens and large molecules. Meninges cover the brain, choroid plexus makes CSF, corpus callosum connects hemispheres.
This question belongs to: Science Biology
Question #1112
The disease caused by the variant Creutzfeldt-Jakob disease is linked to:
A. Prion
B. Virus
C. Bacteria
D. Fungus
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Correct Answer: Option A

Explanation:
Variant CJD is a fatal prion disease linked to consumption of beef from cattle with bovine spongiform encephalopathy (mad cow disease). Prions are misfolded proteins that induce other proteins to misfold. Not viral, bacterial, or fungal.
This question belongs to: Science Biology
Question #1113
The hormone that stimulates the formation of red blood cells is:
A. Thrombopoietin
B. Interleukin
C. Erythropoietin
D. Colony-stimulating factor
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Correct Answer: Option C

Explanation:
Erythropoietin (EPO), mainly from kidneys, promotes erythropoiesis in bone marrow. Thrombopoietin stimulates platelets, interleukins are immune cytokines, CSFs for white blood cells. EPO is used to treat anemia.
This question belongs to: Science Biology
Question #1114
The type of joint between the teeth and the jawbone is:
A. Suture
B. Cartilaginous joint
C. Synovial joint
D. Fibrous joint (gomphosis)
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Correct Answer: Option D

Explanation:
A gomphosis is a specialized fibrous joint where a peg-like tooth fits into a socket in the jawbone, connected by the periodontal ligament. Sutures are between skull bones, synovial are movable, cartilaginous slightly movable.
This question belongs to: Science Biology
Question #1115
The pigment that is found in red algae and helps in deep-water photosynthesis is:
A. Chlorophyll b
B. Phycoerythrin
C. Carotenoid
D. Fucoxanthin
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Correct Answer: Option B

Explanation:
Phycoerythrin absorbs blue-green light, which penetrates deeper water, allowing red algae to photosynthesize at greater depths. Fucoxanthin is in brown algae, chlorophyll b green, carotenoids orange.
This question belongs to: Science Biology
Question #1116
The disease that is caused by a deficiency of niacin is:
A. Scurvy
B. Pellagra
C. Rickets
D. Beriberi
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Correct Answer: Option B

Explanation:
Pellagra, with the 3 Ds (dermatitis, diarrhea, dementia), is due to deficiency of niacin (vitamin B₃) or tryptophan. Beriberi is B₁, scurvy C, rickets D. Niacin is part of NAD and NADP.
This question belongs to: Science Biology
Question #1117
The organ that produces the hormone gastrin is the:
A. Duodenum
B. Pancreas
C. Stomach
D. Liver
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Correct Answer: Option C

Explanation:
Gastrin is a hormone secreted by G cells in the stomach antrum, stimulating parietal cells to secrete HCl and promoting gastric motility. It is released in response to food in the stomach.
This question belongs to: Science Biology
Question #1118
The process of sperm fusing with an egg to form a zygote is:
A. Pollination
B. Fertilization
C. Cleavage
D. Implantation
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Correct Answer: Option B

Explanation:
Fertilization is the union of a haploid sperm and a haploid ovum to form a diploid zygote. Pollination is pollen transfer in plants, implantation is embryo embedding in uterine wall, cleavage early mitotic divisions.
This question belongs to: Science Biology
Question #1119
The enzyme that breaks down cellulose is:
A. Lipase
B. Protease
C. Amylase
D. Cellulase
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Correct Answer: Option D

Explanation:
Cellulase hydrolyzes cellulose into glucose. It is produced by certain bacteria, fungi, and protozoa, enabling them to digest plant material. Herbivores harbor these microbes in their gut. Humans lack cellulase.
This question belongs to: Science Biology
Question #1120
The structure that regulates the size of the pupil is the:
A. Retina
B. Iris
C. Lens
D. Cornea
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Correct Answer: Option B

Explanation:
The iris is the colored part of the eye containing smooth muscles (sphincter and dilator pupillae) that adjust the pupil diameter to control light entry. The cornea and lens focus, retina senses light.
This question belongs to: Science Biology

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