MDCAT Biology: Biological Molecules MCQs

Practice MDCAT Biology Biological Molecules MCQs with explanations — PMC, ETEA, NUMS entry test preparation.

MDCAT Biology: Biological Molecules MCQs

  1. Question 1

    Q1. A researcher analyzing the chemical composition of a prokaryotic cell finds that a specific inorganic compound dominates the mass. What is its percentage?

    • A) 15%
    • B) 70%
    • C) 90%
    • D) 20%

    Answer: 70%

    Explanation: Bacterial cells consist of 70% water by weight. 90% is the water content found specifically in mammalian brain cells.

  2. Question 2

    Q2. During a laboratory experiment, a student measures the energy required to convert 1kg of liquid water into gas. Which PTB value matches this?

    • A) 540 kcal/kg
    • B) 580 kcal/kg
    • C) 564 kcal/kg
    • D) 574 kcal/kg

    Answer: 574 kcal/kg

    Explanation: PTB specifies water's heat of vaporization as 574 kcal/kg. 540 kcal/kg is a general value not used in the PTB textbook.

  3. Question 3

    Q3. A nutritionist explains that the digestion of starch initially yields a disaccharide. What specific bond holds the two monomers of this disaccharide together?

    • A) Alpha 1-4 glycosidic linkage
    • B) Beta 1-4 glycosidic linkage
    • C) Alpha 1-2 glycosidic linkage
    • D) Alpha 1-6 glycosidic linkage

    Answer: Alpha 1-4 glycosidic linkage

    Explanation: Maltose consists of two glucose units joined by an alpha 1-4 glycosidic linkage. Beta 1-4 linkages are found in cellulose.

  4. Question 4

    Q4. In the metabolic pathway of glycolysis, an intermediate is identified as a ketonic sugar containing only three carbon atoms. Name this molecule.

    • A) Glyceraldehyde
    • B) Ribulose
    • C) Dihydroxyacetone
    • D) Glucose

    Answer: Dihydroxyacetone

    Explanation: Dihydroxyacetone is a keto-triose, while glyceraldehyde is an aldo-triose. Ribulose is a pentose, and glucose is a hexose.

  5. Question 5

    Q5. A patient with a sweet tooth consumes large amounts of cane sugar. Upon enzymatic hydrolysis in the digestive tract, which products are released?

    • A) Glucose and Galactose
    • B) Glucose and Fructose
    • C) Glucose and Glucose
    • D) Fructose and Galactose

    Answer: Glucose and Fructose

    Explanation: Sucrose (cane sugar) hydrolyzes into glucose and fructose. Glucose and galactose are the components of lactose, which is milk sugar.

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