What is the molar mass of the dipeptide glycylglycine formed from two glycine molecules (glycine = 75 g mol⁻¹, H₂O = 18 g mol⁻¹)?
Correct answer D. 132 g mol⁻¹
Topic / 35 questions
Macromolecules MCQs
Macromolecules MCQs are multiple-choice questions on proteins and enzymes, covering amino acids, peptide bonds, the levels of protein structure, the nutritional importance of proteins and how enzymes act as biological catalysts. They follow the MDCAT chemistry curriculum, and every question on MCQs360 shows its correct answer instantly.
- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
Amino acids in a protein chain are joined together by which type of bond?
Correct answer D. Peptide bond
The α-helix secondary structure of a protein is mainly stabilised by ____.
Correct answer B. hydrogen bonds between C=O and N−H groups
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Which bond is a covalent link that helps stabilise the tertiary structure of many proteins?
Correct answer A. Disulfide bridge
Essential amino acids are those that ____.
Correct answer C. cannot be made by the body and must be supplied in the diet
Enzymes increase the rate of biochemical reactions by ____.
Correct answer A. lowering the activation energy
The high specificity of an enzyme for its substrate is explained by the ____.
Correct answer C. lock and key model
Why does enzyme activity fall sharply at high temperatures such as 70 °C?
Correct answer A. The enzyme is denatured and its active site changes shape
At its isoelectric point, an amino acid exists mainly as a ____.
Correct answer A. zwitterion
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How many peptide bonds are present in a linear polypeptide made of 50 amino acids?
Correct answer C. 49
Which statement describes non-competitive inhibition?
Correct answer D. The inhibitor binds at an allosteric site and alters the active site
An adult needs about 0.8 g of protein per kg of body mass each day. What is the daily protein requirement of a 65 kg adult?
Correct answer D. 52 g
How many different linear tripeptides can be made using glycine, alanine and valine, each used exactly once?
Correct answer A. 6
Take molar mass of glycine = 75 g/mol, water = 18 g/mol. What is the molar mass of the dipeptide glycylglycine?
Correct answer A. 132 g/mol
How many water molecules are released when four amino acids join to form a linear tetrapeptide?
Correct answer B. 3
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How many peptide bonds are present in a single unbranched polypeptide chain of 120 amino acids?
Correct answer D. 119
Urease catalyses the hydrolysis of urea but has no effect on other amides. This illustrates which property of enzymes?
Correct answer D. Specificity
An inactive protein part of an enzyme combines with a non-protein cofactor to give the active enzyme. What are these called?
Correct answer B. Apoenzyme + cofactor = holoenzyme
How does a competitive inhibitor reduce the rate of an enzyme-catalysed reaction?
Correct answer A. It resembles the substrate and occupies the active site
Pepsin, a protein-digesting enzyme in the stomach, has its optimum activity at a pH of about ____.
Correct answer B. 2
About Macromolecules MCQs
Protein questions cover the zwitterion form of amino acids, the formation of peptide bonds by condensation, counting peptide bonds in a polypeptide, the molar mass of simple peptides and the primary, secondary, tertiary and quaternary levels of structure. You will also classify proteins as fibrous or globular and link their structure to their function. Nutrition and enzyme questions ask about daily protein requirements, enzyme specificity, the lock-and-key and induced fit models, the effect of temperature and pH on enzyme activity, denaturation and the action of competitive inhibitors.
Key facts to remember
- Proteins are polymers of α-amino acids joined by peptide (–CO–NH–) bonds formed by condensation; a chain of n amino acids has n − 1 peptide bonds.
- Near neutral pH, amino acids such as glycine exist mainly as zwitterions, ⁺H₃N–CH₂–COO⁻.
- The primary structure of a protein is the sequence of amino acids in its polypeptide chain; α-helices and β-pleated sheets are secondary structures held by hydrogen bonds.
- Enzymes are biological catalysts, mostly proteins, that lower the activation energy of reactions and are highly specific for their substrates.
- Most human enzymes work best near 37 °C and lose activity at high temperatures because the protein is denatured.
- A competitive inhibitor resembles the substrate and binds to the active site; its effect can be reduced by increasing substrate concentration.
Exams that include Macromolecules MCQs
Pakistan
- MDCAT
- ECAT
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Macromolecules MCQs
- Learn the four levels of protein structure with the type of bonding that holds each one.
- For dipeptide molar mass questions, add the amino acid masses and subtract 18 g mol⁻¹ for each water molecule lost.
- Compare competitive and non-competitive inhibition in a short table.
- Revise this unit alongside the enzymes chapter in Biology, since MDCAT questions often overlap.
Frequently asked questions
What does the MDCAT syllabus include in Macromolecules?
The PMDC MDCAT chemistry curriculum for Macromolecules covers the classification of proteins and the link between their structure and function, the biological and nutritional importance of proteins, and enzymes as biocatalysts. It overlaps closely with the enzymes and biomolecules chapters in MDCAT Biology.
Which exams ask Macromolecules MCQs?
Protein and enzyme questions appear in MDCAT, ECAT, NUMS and AKU entry tests and in FSc board papers in Pakistan. Biomolecules are also part of NEET and JEE Main in India and of HSC and medical admission tests in Bangladesh.
What is denaturation of a protein?
Denaturation is the loss of a protein's secondary, tertiary and quaternary structure when hydrogen bonds and other weak interactions are broken by heat, extreme pH or certain chemicals. The amino acid sequence stays the same, but the protein loses its shape and usually its biological activity.
Last reviewed October 2026