MDCAT Biology — Enzymes
Enzymes is a core Biology topic in the PMDC MDCAT syllabus, covering 5 subtopics. Below are the subtopics to revise, how often the topic appears in past papers, and real past-paper MCQs to try.
Subtopics (5)
- Characteristics of Enzymes
- Co-factors of Enzymes
- Enzyme Inhibitors
- Factors Affecting Enzyme Action
- Mode of Enzyme Action
How Enzymes is tested
Across the 16 MDCAT past papers on ParhaiKrlo, Enzymes accounts for 70 questions. It appears in all 16, about 4.4 questions a paper. The heaviest was MDCAT 2014, with 10 questions, and the most recent is MDCAT 2025, with 5.
| Paper | Questions |
|---|---|
| MDCAT 2025 | 5 |
| MDCAT 2024 | 3 |
| MDCAT 2023 | 4 |
| MDCAT 2022 | 5 |
| MDCAT 2019 | 5 |
| MDCAT 2018 | 6 |
| MDCAT 2017 | 9 |
| MDCAT 2016 | 4 |
| MDCAT 2015 | 3 |
| MDCAT 2014 | 10 |
| MDCAT 2013 | 5 |
| MDCAT 2012 | 3 |
| MDCAT 2011 | 3 |
| MDCAT 2010 | 2 |
| MDCAT 2009 | 2 |
| MDCAT 2008 | 1 |
Enzymes MCQs from the MDCAT past papers
Try each one before opening the answer. Each comes with a short explanation.
- Q1 · MDCAT 2025 · Enzymes
Enzyme activity decreases at very low or high pH because:
- A.Substrate concentration increases
- B.Enzymes become denatured
- C.Product formation increases
- D.Temperature becomes constant
Show answer
Answer: B. Enzymes become denatured — Extreme pH denatures enzymes, destroying their activity.
- Q2 · MDCAT 2024 · Enzymes
Enzyme NADP reductase is responsible for:
- A.Reducing NADP⁺
- B.Oxidizing NADP⁺
- C.Reducing Ferredoxin
- D.Reducing P₇₀₀
Show answer
Answer: A. Reducing NADP⁺ — NADP reductase reduces NADP+ to NADPH — that's what 'reductase' means.
- Q3 · MDCAT 2023 · Enzymes
The enzyme which can work on pH 7 of the medium is:
- A.Pepsin
- B.Sucrase
- C.Chymotrypsin
- D.Pancreatic lipase
Show answer
Answer: C. Chymotrypsin — Chymotrypsin works best at pH 7–8, so it is the enzyme that works at pH 7. The printed key marks sucrase, whose optimum (pH 4.5 in the FSc table) is acidic.