Biology MCQs for MDCAT

This page has over 3,300 multiple-choice questions for Biology (MDCAT), arranged in 18 chapters and 67 topics. The chapters include Acellular Life, Bioenergetics and Cellular Respiration, Biological Molecules, Cell Structure and Function and Coordination and Control. Every question has four options, an instant answer and, where available, a short explanation.

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Chapters and topics

  • Acellular Life 2 topics · 179 MCQs
  • Bioenergetics and Cellular Respiration 8 topics · 142 MCQs
  • Biological Molecules 8 topics · 474 MCQs
  • Cell Structure and Function 5 topics · 504 MCQs
  • Coordination and Control 4 topics · 295 MCQs
  • Enzymes 4 topics · 120 MCQs
  • Evolution 4 topics · 119 MCQs
  • Reproduction 3 topics · 151 MCQs
  • Support and Movement 6 topics · 187 MCQs
  • Inheritance 3 topics · 240 MCQs
  • Circulation 4 topics · 222 MCQs
  • Immunity 1 topic · 126 MCQs
  • Respiration 1 topic · 96 MCQs
  • Digestion 1 topic · 177 MCQs
  • Homeostasis 4 topics · 169 MCQs
  • Biotechnology 1 topic · 168 MCQs
  • Plant Physiology and Diversity 5 topics · 9 MCQs
  • Animal Diversity and Development 3 topics · 21 MCQs

Sample Biology MCQs

Try these questions, then open the full practice to work through every chapter. Tap “Show the answer” after you choose.

Q1. Which of the following infectious particles consists of only an RNA molecule?

  1. Virion
  2. Virus
  3. Prion
  4. Viroid
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Answer: D. Viroid

Viroids are small, naked circular RNA molecules.

Q2. In ATP, the ratio of high-energy to low-energy bonds is:

  1. 3 : 1
  2. 1 : 2
  3. 1 : 3
  4. 2 : 1
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Answer: D. 2 : 1

ATP has two high-energy phosphoanhydride bonds and one low-energy phosphoester bond.

Q3. Which polysaccharide has an amino group?

  1. Cellulose
  2. Glycogen
  3. Starch
  4. Chitin
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Answer: D. Chitin

Chitin is made of N-acetylglucosamine units that carry an amino (acetylamino) group.

Q4. The factory of ribosomal synthesis is the:

  1. Cytoplasm
  2. Endoplasmic reticulum
  3. Nucleus
  4. Nucleolus
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Answer: D. Nucleolus

Ribosomal RNA is synthesised and assembled into subunits in the nucleolus.

Q5. Which ion is involved in the release of acetylcholine from the pre-synaptic fibre into the extracellular fluid?

  1. Calcium
  2. Potassium
  3. Sodium
  4. Magnesium
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Answer: A. Calcium

Ca²⁺ entry triggers vesicles to release neurotransmitter.

Q6. The lock and key model was proposed by:

  1. Koshland
  2. Robin Williams
  3. Emil Fischer
  4. Rudolph Virchow
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Answer: C. Emil Fischer

Emil Fischer proposed the lock and key hypothesis in 1894.

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