MDCAT Biology MCQs with answers
Practise MDCAT Biology (PMDC 2025-26) with 592 exam-style MCQs, each with the answer and a short explanation. Every test is marked the moment you finish and shows your score chapter by chapter, so you know what to revise next. It is free and needs no sign-up.
592 questions · 16 chapters
What each chapter covers 16 chapters
The questions follow the syllabus chapter by chapter. You can test the whole subject or one chapter at a time.
- Biology · Acellular life 26 questionsViruses: structure and classification, Viral replication and disease
- Biology · Bioenergetics 35 questionsPhotosynthesis, Cellular respiration
- Biology · Biological molecules 62 questionsWater and carbohydrates, Proteins and lipids, Nucleic acids
- Biology · Cell structure and function 52 questionsCell membrane and transport, Organelles, Prokaryotic and eukaryotic cells
- Biology · Coordination and control 57 questionsNeurons and the nerve impulse, The nervous system, Chemical coordination
- Biology · Enzymes 28 questionsEnzyme action, Factors and inhibition
- Biology · Evolution 31 questionsTheories of evolution, Evidence and speciation
- Biology · Reproduction 31 questionsHuman reproductive systems, Reproductive cycle and development
- Biology · Support and movement 30 questionsSkeleton and joints, Muscles and contraction
- Biology · Inheritance 46 questionsMendelian inheritance, Beyond simple dominance, Sex linkage and chromosomes
- Biology · Circulation 48 questionsThe heart, Blood and blood vessels, Lymphatic system and disorders
- Biology · Immunity 28 questionsInnate and adaptive immunity, Types of immunity and vaccination
- Biology · Respiration 26 questionsRespiratory system and breathing, Gas transport and disorders
- Biology · Digestion 27 questionsAlimentary canal and enzymes, Absorption, liver and disorders
- Biology · Homeostasis 35 questionsOsmoregulation and the kidney, Thermoregulation and excretion
- Biology · Biotechnology 30 questionsRecombinant DNA techniques, Applications of biotechnology
Sample MDCAT Biology MCQs with answers 12 questions
12 questions from the test, one or two from each chapter. Try each one, then open the answer.
1. In the name AIDS (acquired immune deficiency syndrome), the word "acquired" means that the disease
- A
is inherited from a parent through a faulty gene
- B
is caught by infection during life, not inherited
- C
appears only in old age as immunity weakens
- D
is caused by a lack of a vitamin in the diet
Show answer
Answer: B. AIDS follows infection with HIV picked up during a person's life; it is not an inherited immune deficiency. Even a baby who catches HIV from its mother has acquired it by infection.
2. Three similar plants are grown for two weeks under red, blue and green light of the same intensity. The plant under green light grows least because
- A
chlorophyll reflects or transmits most green light, so little is absorbed
- B
green light carries too much energy and damages the chlorophyll
- C
chlorophyll absorbs green light strongly but cannot use it in photolysis
- D
green light is absorbed only by carotenoids, which cannot pass energy on
Show answer
Answer: A. Only light that is absorbed can drive photosynthesis. Chlorophyll absorbs red and blue light strongly but little green; most green light is reflected or passes through the leaf, which is also why leaves look green.
3. Starch from a potato is a mixture of amylose and amylopectin. Which statement about them is correct?
- A
Both are polymers of α-glucose, but only amylopectin is branched.
- B
Both are polymers of α-glucose, but only amylose is branched.
- C
Amylose is a polymer of β-glucose and amylopectin of α-glucose.
- D
Both are branched polymers of β-glucose, like cellulose.
Show answer
Answer: A. Amylose is an unbranched chain of α-glucose units linked 1,4, which coils into a helix; amylopectin has similar chains with 1,6 branch points. β-glucose is the monomer of cellulose, not of starch.
4. Living cells can be watched under a light microscope but not under an electron microscope, mainly because
- A
living cells move too fast to be seen at such a high magnification
- B
the specimen must be in a vacuum, which living cells cannot survive
- C
living cells are transparent to electrons and so give no image
- D
the glass lenses would focus the heat of the beam onto the cells
Show answer
Answer: B. The electron beam can travel only through a vacuum, so specimens must be dried, fixed and therefore dead. Electron microscopes focus the beam with magnetic lenses, not glass ones.
5. A frog kept on a dark background slowly turns darker as pigment spreads out through the pigment cells of its skin. Which pituitary hormone brings about this change?
- A
calcitonin
- B
melatonin
- C
prolactin
- D
melanocyte-stimulating hormone (MSH)
Show answer
Answer: D. MSH from the intermediate lobe of the pituitary makes melanin granules spread through the pigment cells, so the skin darkens. Melatonin, from the pineal gland, has the opposite effect in amphibians and lightens the skin, while prolactin is a pituitary hormone that acts on milk production.
6. A human enzyme is kept at 70 °C for ten minutes and then cooled to 37 °C. Its activity at 37 °C will most likely be
- A
higher than before, because heating activated it
- B
very low, as heat has denatured it permanently
- C
normal, because the enzyme recovers on cooling
- D
normal, because 70 °C is its optimum temperature
Show answer
Answer: B. High temperature breaks the bonds holding the enzyme's three-dimensional shape, so the active site is lost; for most enzymes this denaturation is irreversible and activity does not return on cooling. Most human enzymes work best near 37 °C.
7. Charles Darwin published 'On the Origin of Species', setting out his theory of evolution by natural selection, in
- A
1809
- B
1859
- C
1865
- D
1900
Show answer
Answer: B. The Origin of Species appeared in 1859. 1809 is the year of Lamarck's 'Philosophie Zoologique' (and of Darwin's birth), 1865 the year Mendel presented his work, and 1900 the year Mendel's work was rediscovered.
8. The umbilical cord joins the foetus to the placenta. Which statement about the blood vessels in the cord is correct?
- A
two veins carry deoxygenated blood to the placenta; one artery carries oxygenated blood to the foetus
- B
two arteries carry oxygenated blood to the foetus; one vein carries deoxygenated blood to the placenta
- C
two arteries carry deoxygenated blood to the placenta; one vein carries oxygenated blood to the foetus
- D
one artery and one vein carry the mother's blood into and out of the foetus
Show answer
Answer: C. The foetal heart pumps deoxygenated blood to the placenta along the two umbilical arteries, and the single umbilical vein brings back blood that has been oxygenated in the placenta. Names follow the direction relative to the heart, not the oxygen content, and maternal and foetal blood do not mix.
9. The synovial fluid inside a freely movable joint mainly
- A
lubricates the joint, reducing friction between the cartilages
- B
binds the bones of the joint tightly together, as a ligament does
- C
lays down new bone at the ends of the two articulating bones
- D
attaches the tendons of the muscles firmly to the bones
Show answer
Answer: A. Synovial fluid, secreted by the synovial membrane, lubricates and nourishes the articular cartilages. Ligaments hold the bones together and tendons attach muscles to bones.
10. In a certain squash, a dominant allele W of one gene gives white fruit whatever the alleles of a second, unlinked gene. Plants that are ww are yellow if they carry a dominant Y allele and green if they are yy. What fraction of the offspring of WwYy × WwYy is expected to be white?
- A
3/4
- B
1/4
- C
9/16
- D
15/16
Show answer
Answer: A. Any plant with at least one W allele is white, and W_ makes up 3/4 of the offspring (12/16); the ww plants are yellow (3/16) or green (1/16). This is epistasis: the W gene hides the effect of the Y gene. The fraction 9/16 counts only W_Y_ plants.
11. The largest white blood cells, which leave the blood and become macrophages in the tissues, are the
- A
neutrophils
- B
lymphocytes
- C
monocytes
- D
basophils
Show answer
Answer: C. Monocytes are the largest leucocytes, with a kidney-shaped nucleus; in the tissues they become macrophages that engulf microbes and debris. Neutrophils are the most numerous phagocytes but are smaller.
12. A virus infects some cells of the nasal lining. Within hours, neighbouring uninfected cells become resistant to this and other viruses, long before any antibodies are made. This is due to
- A
histamine released by the mast cells
- B
antibodies made by the plasma cells
- C
interferon released by the infected cells
- D
memory cells formed in the lymph nodes
Show answer
Answer: C. Interferon is a non-specific protein released by virus-infected cells; it helps nearby cells resist viral multiplication. Antibodies and memory cells take days to appear and act against one particular virus only.
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Common questions
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Are these past paper questions?
The 592 MCQs are our own, written to the syllabus in the style of the exam.
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Instantly. You get your score, the right answer and an explanation for every question, and a list of the topics to work on.
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