85 practice MCQs on carbohydrates, lipids, proteins and nucleic acids, their building blocks, bonds and functions. Every question has the correct answer and an explanation.
Start free — 20 questionsBiological Molecules is part of the MDCAT Biology syllabus. This page collects Biological Molecules MCQs in the style of past MDCAT papers — below are 12 of them with answers and explanations, and the full set of 85 questions is in the HighYield MDCAT QBank.
This chapter covers: carbohydrates, lipids, proteins and nucleic acids, their building blocks, bonds and functions.
Correct answer: B. Transgenic plants
Transgenic plants have foreign DNA (from another species) deliberately incorporated into their genome using genetic engineering techniques.
Correct answer: B. Phospholipids
The fluid mosaic model states that protein molecules float within a fluid phospholipid bilayer that forms the plasma membrane.
Correct answer: A. Uracil
Uracil, a pyrimidine base found in RNA, is absent from DNA, which instead uses thymine as its pyrimidine partner to adenine.
Correct answer: B. Dihydroxy acetone
Dihydroxyacetone is the simplest monosaccharide containing a keto (ketone) group, making it the simplest ketose.
Correct answer: A. Alcohol
Waxes are formed by the combination of fatty acids with long-chain alcohols, rather than glycerol as in fats and oils.
Correct answer: D. Oestrogen
Oestrogen, a lipid-derived hormone synthesized from cholesterol, is classified as a steroid hormone.
Correct answer: C. Plasmids
Plasmids, small circular DNA molecules, are the most commonly used vectors for carrying foreign genes in recombinant DNA technology.
Correct answer: C. cDNA
DNA synthesized from an RNA template by the enzyme reverse transcriptase is called complementary DNA (cDNA).
Correct answer: C. Methionine
The start codon AUG represents the amino acid methionine (Met) in the genetic code. In addition to being the start codon, AUG can also code for methionine within a protein sequence, serving as both the initiation codon and an amino acid codon.
Correct answer: A. Genes
DNA stores biological information in discrete units called genes. Genes are segments of DNA that contain the instructions for building and maintaining an organism. They provide the information needed to produce proteins, which are essential for various biological processes and traits.
Correct answer: B. Hydrolysis
Hydrolysis is a chemical reaction where water is used to break down a compound, resulting in the separation of the compound into its constituent parts.
Correct answer: C. Glucose and fructose
Sucrose, also known as table sugar, is a disaccharide that is hydrolyzed into two monosaccharides: glucose and fructose. This reaction is catalyzed by the enzyme sucrase:Sucrose (C12H22O11) → Glucose (C6H12O6) + Fructose (C6H12O6)
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