Biology MCQs

Question #421

Share Report

The energy currency of the cell is:

A. ATP

B. Glucose

C. FADH₂

D. NADH

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Adenosine triphosphate (ATP) stores and transfers energy in cells via high-energy phosphate bonds. Hydrolysis of ATP to ADP releases energy for endergonic reactions. Glucose and NADH/FADH₂ are energy sources but not direct energy carriers usable by most enzymes; ATP is the immediate energy donor.

This question belongs to: Science Biology

Question #422

Share Report

Which of the following is a plant hormone that promotes seed germination?

A. Ethylene

B. Abscisic acid

C. Gibberellin

D. Cytokinin

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Gibberellins stimulate seed germination by activating synthesis of hydrolytic enzymes (amylase) that break down stored food reserves. They also promote stem elongation. Abscisic acid inhibits germination and promotes dormancy. Ethylene is for ripening, cytokinins for cell division. The GA:ABA ratio determines germination vs dormancy.

This question belongs to: Science Biology

Question #423

Share Report

The human spinal cord extends from the:

A. Midbrain to sacrum

B. Pons to coccyx

C. Medulla oblongata to first lumbar vertebra

D. Cerebellum to lumbar region

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
The spinal cord is a long tubular bundle of nervous tissue extending from the medulla oblongata to the level of the first/second lumbar vertebra (L1-L2), where it tapers into the conus medullaris. Below this, nerves form the cauda equina. It transmits impulses between the brain and body and coordinates reflexes.

This question belongs to: Science Biology

Question #424

Share Report

The type of muscle tissue present in the walls of blood vessels and intestine is:

A. Smooth muscle

B. Cardiac muscle

C. Voluntary muscle

D. Skeletal muscle

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Smooth muscle is non-striated, spindle-shaped, involuntary muscle found in the walls of hollow organs like intestines, blood vessels, uterus, and bladder. It controls peristalsis, vasoconstriction, and other autonomic functions. Skeletal muscle is voluntary and striated, cardiac muscle is striated but involuntary.

This question belongs to: Science Biology

Question #425

Share Report

The human disease caused by the deficiency of vitamin B₃ (niacin) is:

A. Pellagra

B. Scurvy

C. Beriberi

D. Rickets

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Pellagra, characterized by dermatitis, diarrhea, dementia (three D's), results from niacin deficiency. Beriberi is due to B₁ deficiency, scurvy to C, rickets to D. Niacin is part of NAD and NADP, essential in redox reactions. Foods rich in niacin include meat, fish, whole grains. Pellagra historically associated with corn-based diets.

This question belongs to: Science Biology

Question #426

Share Report

The process by which white blood cells squeeze through capillary walls to reach infection sites is:

A. Chemotaxis

B. Phagocytosis

C. Diapedesis

D. Opsonization

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Diapedesis (extravasation) is the migration of leukocytes through the endothelial junctions of capillaries into tissues in response to inflammation. Chemotaxis is the directed movement along a chemical gradient, phagocytosis is ingestion, opsonization is coating for phagocytosis. Both diapedesis and chemotaxis are part of the inflammatory response.

This question belongs to: Science Biology

Question #427

Share Report

The number of chromosomes in a human zygote is:

A. 44

B. 23

C. 46

D. 22

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
A human zygote is diploid (2n = 46), formed by the fusion of a haploid sperm (23) and a haploid ovum (23). It contains 22 pairs of autosomes and one pair of sex chromosomes (XX or XY). Mitotic division then produces all somatic cells. Gametes are haploid (23).

This question belongs to: Science Biology

Question #428

Share Report

The phenomenon where a single gene influences multiple phenotypic traits is called:

A. Polygenic inheritance

B. Codominance

C. Epistasis

D. Pleiotropy

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Pleiotropy occurs when one gene affects multiple seemingly unrelated traits. Example: phenylketonuria (PKU) affects mental development, skin pigmentation, and musty odor. Marfan syndrome affects skeleton, eyes, and heart. Polygenic is many genes affecting one trait, epistasis is gene interaction, codominance is both alleles expressed.

This question belongs to: Science Biology

Question #429

Share Report

Which of the following is an example of a heterotrophic plant?

A. Neem

B. Cuscuta

C. Sunflower

D. Mango

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
Cuscuta (dodder) is a parasitic plant that lacks chlorophyll and derives nutrients from the host plant through haustoria. It is a total stem parasite. Mango, neem, and sunflower are autotrophic plants performing photosynthesis. Heterotrophic plants include parasites (Cuscuta, Rafflesia) and saprophytes (Monotropa).

This question belongs to: Science Biology

Question #430

Share Report

The movement of pollen grains from anther to stigma of the same flower is called:

A. Self-pollination

B. Anemophily

C. Cross-pollination

D. Hydrophily

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Self-pollination (autogamy) occurs within the same flower or between flowers of the same plant. Cross-pollination (allogamy) involves different plants. Hydrophily is pollination by water, anemophily by wind. Self-pollination ensures genetic uniformity, while cross-pollination promotes variation. Cleistogamous flowers (e.g., groundnut) are obligate self-pollinators.

This question belongs to: Science Biology

Question #431

Share Report

The organ of the human body that stores glycogen as a reserve carbohydrate is:

A. Liver

B. Pancreas

C. Spleen

D. Kidney

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
The liver is the primary site of glycogen storage and releases glucose into the blood between meals (glycogenolysis) to maintain blood sugar. Muscles also store glycogen but for local use. The pancreas regulates blood sugar via insulin/glucagon, spleen stores blood and recycles iron, kidneys excrete waste.

This question belongs to: Science Biology

Question #432

Share Report

The type of joint found in the shoulder and hip is:

A. Pivot joint

B. Gliding joint

C. Hinge joint

D. Ball and socket joint

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
The ball and socket joint (e.g., glenohumeral, hip) allows movement in multiple axes (flexion, extension, abduction, adduction, rotation). The rounded head of one bone fits into the cup-shaped socket of another. Hinge (elbow, knee) allows movement in one plane, pivot (neck) allows rotation, gliding (wrist) allows sliding.

This question belongs to: Science Biology

Question #433

Share Report

The oxygen-carrying protein in muscles is:

A. Hemoglobin

B. Cytochrome

C. Hemocyanin

D. Myoglobin

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Myoglobin is a red protein in muscle cells that stores oxygen and facilitates its diffusion during muscle contraction. It has a higher affinity for O₂ than hemoglobin, allowing oxygen transfer from blood to muscle. Hemoglobin is in RBCs, hemocyanin is in some invertebrates, cytochromes are electron carriers.

This question belongs to: Science Biology

Question #434

Share Report

The term 'binomial nomenclature' was first introduced by:

A. Aristotle

B. Theophrastus

C. Linnaeus

D. Darwin

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Carolus Linnaeus, in his book 'Species Plantarum' (1753), consistently used the two-word naming system for all organisms, establishing binomial nomenclature. Although the concept existed earlier, Linnaeus formalized and popularized it. The first word is the genus, the second the specific epithet, both in Latin or latinized.

This question belongs to: Science Biology

Question #435

Share Report

The organ that produces bile is the:

A. Duodenum

B. Liver

C. Pancreas

D. Gall bladder

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
Bile is continuously synthesized by hepatocytes in the liver. It contains bile salts, bile pigments, cholesterol, and phospholipids. The gall bladder merely stores and concentrates bile, releasing it upon eating. The pancreas produces digestive enzymes, duodenum is part of the small intestine. Bile emulsifies fats.

This question belongs to: Science Biology

Question #436

Share Report

The part of the brain that connects the two cerebral hemispheres is the:

A. Hypothalamus

B. Corpus callosum

C. Pons

D. Thalamus

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
The corpus callosum is a thick band of nerve fibers that connects the left and right cerebral hemispheres, allowing interhemispheric communication. The thalamus is a sensory relay station, hypothalamus regulates homeostasis, pons is part of the brainstem. Severing the corpus callosum results in split-brain syndrome.

This question belongs to: Science Biology

Question #437

Share Report

The substance that gives skin its pigment and protects against UV radiation is:

A. Keratin

B. Elastin

C. Collagen

D. Melanin

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Melanin, produced by melanocytes in the epidermis, is the primary pigment determining skin, hair, and eye color. It absorbs UV radiation, protecting DNA from damage. Keratin is a structural protein in hair and nails, collagen provides connective tissue strength, elastin elasticity. Albinism results from melanin deficiency.

This question belongs to: Science Biology

Question #438

Share Report

The disease caused by the bacterium Mycobacterium leprae is:

A. Plague

B. Tuberculosis

C. Diphtheria

D. Leprosy

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Leprosy (Hansen's disease) is a chronic bacterial infection caused by Mycobacterium leprae, affecting skin, peripheral nerves, and mucous membranes. Tuberculosis is caused by M. tuberculosis. Diphtheria is Corynebacterium diphtheriae, plague is Yersinia pestis. Leprosy is curable with multidrug therapy.

This question belongs to: Science Biology

Question #439

Share Report

Which of the following organisms is used in the production of ethanol for biofuels?

A. Rhizopus stolonifer

B. Aspergillus oryzae

C. Saccharomyces cerevisiae

D. Lactobacillus

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Saccharomyces cerevisiae (baker's yeast) ferments sugars to ethanol and CO₂, a process used in biofuel production, brewing, and baking. Lactobacillus produces lactic acid, Aspergillus oryzae is used in soy sauce and sake fermentation, Rhizopus is a mold causing bread spoilage. Yeast can utilize various feedstocks like corn, sugarcane.

This question belongs to: Science Biology

Question #440

Share Report

The hormone that regulates the basal metabolic rate is:

A. Cortisol

B. Insulin

C. Thyroxine

D. Glucagon

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Thyroxine (T₄) and triiodothyronine (T₃) from the thyroid gland increase the metabolic rate of most tissues, heat production, and oxygen consumption. Insulin and glucagon regulate glucose, cortisol is a stress hormone with metabolic effects but not the primary basal regulator. Hypothyroidism leads to decreased BMR.

This question belongs to: Science Biology

Practice Questions

More Science Topics