Biology MCQs

Question #1221

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The process by which water moves up the xylem against gravity is mainly due to:

A. Active pumping

B. Capillarity

C. Transpiration-cohesion-tension

D. Root pressure

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Correct Answer: Option C

Explanation:
The cohesion-tension theory states that transpiration from leaves creates tension, pulling water up the xylem; water molecules cohere, forming a continuous column. Root pressure is minor.

This question belongs to: Science Biology

Question #1222

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The vitamin that is part of coenzyme A and is involved in acyl group transfer is:

A. Biotin

B. Thiamine

C. Riboflavin

D. Pantothenic acid

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Correct Answer: Option D

Explanation:
Pantothenic acid (vitamin B₅) is a component of coenzyme A (CoA), essential for the Krebs cycle and fatty acid metabolism. Thiamine is TPP, riboflavin FAD, biotin for carboxylation.

This question belongs to: Science Biology

Question #1223

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The disease caused by the deficiency of vitamin B₁₂ and folate leads to:

A. Megaloblastic anemia

B. Sickle cell anemia

C. Thalassemia

D. Microcytic anemia

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Correct Answer: Option A

Explanation:
Megaloblastic anemia is characterized by large, immature RBCs due to impaired DNA synthesis from B₁₂ or folate deficiency. Microcytic is iron deficiency, sickle cell is genetic.

This question belongs to: Science Biology

Question #1224

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The technique used to detect specific proteins in a tissue section using labeled antibodies is:

A. Flow cytometry

B. Immunohistochemistry

C. Western blotting

D. ELISA

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Correct Answer: Option B

Explanation:
Immunohistochemistry (IHC) uses enzyme- or fluorophore-linked antibodies to visualize specific antigens in tissue sections. ELISA is for liquid samples, Western blot for membrane, flow cytometry for cells.

This question belongs to: Science Biology

Question #1225

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The organ that produces the hormone thrombopoietin is the:

A. Liver

B. Bone marrow

C. Spleen

D. Kidney

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Correct Answer: Option A

Explanation:
Thrombopoietin, which stimulates platelet production, is primarily produced by the liver and to some extent by the kidney. Erythropoietin is mainly from kidneys.

This question belongs to: Science Biology

Question #1226

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The hormone that relaxes the pubic symphysis during childbirth is:

A. Progesterone

B. Estrogen

C. Oxytocin

D. Relaxin

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Correct Answer: Option D

Explanation:
Relaxin, produced by the corpus luteum and placenta, softens and relaxes the pelvic ligaments and pubic symphysis to facilitate childbirth. Oxytocin stimulates contractions.

This question belongs to: Science Biology

Question #1227

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The process of taking in solid particles by a cell is called:

A. Phagocytosis

B. Exocytosis

C. Osmosis

D. Pinocytosis

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Correct Answer: Option A

Explanation:
Phagocytosis ('cell eating') is the engulfment of large particles or microbes by the cell membrane forming a phagosome. Pinocytosis is 'cell drinking' of liquids. Exocytosis is secretion.

This question belongs to: Science Biology

Question #1228

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The pigment that gives brown algae their color is:

A. Phycocyanin

B. Chlorophyll b

C. Phycoerythrin

D. Fucoxanthin

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Correct Answer: Option D

Explanation:
Fucoxanthin is a carotenoid that masks the green chlorophyll in brown algae (Phaeophyceae). Phycoerythrin is red, phycocyanin blue, chlorophyll b green.

This question belongs to: Science Biology

Question #1229

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The disease caused by the fungus Candida albicans is called:

A. Ringworm

B. Histoplasmosis

C. Aspergillosis

D. Candidiasis

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Correct Answer: Option D

Explanation:
Candidiasis (thrush) is an opportunistic infection caused by Candida albicans, affecting mucous membranes and sometimes systemic. Ringworm is dermatophytes.

This question belongs to: Science Biology

Question #1230

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The scientist who developed the oral polio vaccine was:

A. Jonas Salk

B. Louis Pasteur

C. Albert Sabin

D. Edward Jenner

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Correct Answer: Option C

Explanation:
Albert Sabin developed the attenuated oral polio vaccine (OPV), which is easier to administer and provides intestinal immunity. Salk developed the inactivated vaccine (IPV).

This question belongs to: Science Biology

Question #1231

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The vitamin that acts as a coenzyme in the synthesis of DNA and red blood cells is:

A. Vitamin K

B. Vitamin C

C. Vitamin B₁₂

D. Vitamin A

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Correct Answer: Option C

Explanation:
Vitamin B₁₂ (cobalamin) is required for DNA synthesis and RBC maturation. Deficiency causes pernicious anemia. It also maintains myelin sheath.

This question belongs to: Science Biology

Question #1232

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The hormone that stimulates the secretion of testosterone from Leydig cells is:

A. LH

B. Inhibin

C. FSH

D. GnRH

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Correct Answer: Option A

Explanation:
Luteinizing hormone (LH) binds to Leydig cells in the testes, stimulating testosterone production. FSH stimulates Sertoli cells for spermatogenesis. GnRH is hypothalamic.

This question belongs to: Science Biology

Question #1233

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The structure that produces sound in the larynx is the:

A. Trachea

B. Vocal cords

C. Epiglottis

D. Pharynx

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Correct Answer: Option B

Explanation:
The vocal cords (folds) in the larynx vibrate as air passes, producing sound. Pitch is controlled by tension. Epiglottis prevents food entry, trachea is airway.

This question belongs to: Science Biology

Question #1234

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The process of destruction of red blood cells is called:

A. Erythropoiesis

B. Hemopoiesis

C. Hemolysis

D. Hemostasis

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Correct Answer: Option C

Explanation:
Hemolysis is the rupture or destruction of red blood cells, releasing hemoglobin. Hemopoiesis is blood cell formation, hemostasis is stopping bleeding, erythropoiesis RBC production.

This question belongs to: Science Biology

Question #1235

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The pigment that is present in the macula lutea of the eye and protects against blue light is:

A. Melanin

B. Carotenoid

C. Lutein and zeaxanthin

D. Rhodopsin

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Correct Answer: Option C

Explanation:
Lutein and zeaxanthin are carotenoids concentrated in the macula lutea of the retina, filtering blue light and acting as antioxidants, protecting photoreceptors.

This question belongs to: Science Biology

Question #1236

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The condition caused by the deficiency of ADH leading to excessive dilute urine is:

A. Diabetes mellitus

B. Glycosuria

C. Uremia

D. Diabetes insipidus

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Correct Answer: Option D

Explanation:
Diabetes insipidus results from insufficient ADH or kidney response, causing polyuria and polydipsia with dilute urine. Diabetes mellitus is hyperglycemia.

This question belongs to: Science Biology

Question #1237

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The scientist who discovered the structure of insulin was:

A. Charles Best

B. Dorothy Hodgkin

C. Frederick Banting

D. Frederick Sanger

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Correct Answer: Option D

Explanation:
Frederick Sanger determined the amino acid sequence of insulin in 1955, showing proteins have a specific sequence. Banting and Best isolated insulin, Hodgkin determined its 3D structure.

This question belongs to: Science Biology

Question #1238

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The vitamin that is essential for the proper development of the fetal nervous system is:

A. Vitamin K

B. Vitamin B₁₂

C. Folic acid

D. Vitamin D

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Correct Answer: Option C

Explanation:
Folic acid prevents neural tube defects like spina bifida. It is recommended during early pregnancy. B₁₂ is for DNA synthesis, D for bone, K for clotting.

This question belongs to: Science Biology

Question #1239

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The hormone that increases the heart rate and blood pressure in stress is:

A. Adrenaline

B. Insulin

C. Melatonin

D. Acetylcholine

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Correct Answer: Option A

Explanation:
Adrenaline (epinephrine) from the adrenal medulla mediates the 'fight-or-flight' response, increasing heart rate, contractility, and blood pressure. Acetylcholine slows heart, insulin lowers glucose, melatonin induces sleep.

This question belongs to: Science Biology

Question #1240

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The organelle that is the site of glycolysis is the:

A. Mitochondria

B. Nucleus

C. Cytoplasm

D. Golgi body

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Correct Answer: Option C

Explanation:
Glycolysis, the breakdown of glucose to pyruvate, occurs in the cytoplasm of cells. The Krebs cycle and oxidative phosphorylation occur in mitochondria.

This question belongs to: Science Biology

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