BBCCT 107 key facts: June 2026
- Course code: BBCCT-107
- Subject: Enzymes
- Programme: B.Sc. (Honours) Biochemistry (BSCBCH), Semester III
- Credits: 4 (theory), taken with BBCCL-108 Enzymes Laboratory (2 credits)
- Blocks and units: 4 blocks, 12 units
- Maximum marks: 70
- Duration: 3 hours
- Questions in the June 2026 paper: 9 of 10 marks each, 19 sub-parts; attempt any 7
- Diagrams required: yes, in Q4(a) and Q7(b)
- Samples shown on this page: 2 (Q1 and Q2); all 9 in the paid file
BBCCT 107 Solved Question Paper for the June 2026 term-end examination gives you the official nine-question paper with complete answers written by our biochemistry team. Two answers are open on this page so you can judge the quality; the other seven are in the full file, available on WhatsApp 9899436384.
1. What the June 2026 Solved Paper Covers
BBCCT 107 Enzymes is a 4-credit core theory course in Semester III of IGNOU's B.Sc. (Honours) Biochemistry (BSCBCH), taught through 4 blocks and 12 units on enzyme structure, kinetics, regulation and use.
The June 2026 paper printed nine questions of 10 marks each and asked for any seven. Every question has two parts or two short notes, so the file answers 19 separate sub-parts in total. There is no compulsory objective section this time, which means each attempt must be a full written answer.
The questions range across the whole course: active site and specificity, metal ions and suicide inhibitors, uncompetitive inhibition, covalent modification, pyridoxal phosphate, a five-pair enzyme and disease match, immobilisation, wine and baking enzymes, IUBMB classification, zymogens, bisubstrate mechanisms, catalysis, temperature, multienzyme complexes, feedback inhibition and FAD/FMN.
If you want to practise older sessions before reading the answers, our IGNOU Previous Year Question Paper collection lets you set a timed mock first and check yourself afterwards.
2. Two Answers Solved in Full, Seven Held Back
Questions 1 and 2 of the June 2026 paper are solved in full below, and Questions 3 to 9 are listed exactly as printed for the full file.
Each sample answer follows the paper's 5 plus 5 mark split, with its own heading for each part.
The active site and enzyme specificity
Question 1 (a): What are the common features of the active site of an enzyme? (5)
Question 1 (b): Explain the term enzyme specificity. Describe the different types of specificity exhibited by enzymes. (5)
(a) Common features of the active site
The active site is the small region of an enzyme where the substrate binds and the chemical change happens. Enzymes differ a lot in size and shape, yet their active sites share a common set of features.
- A small part of the molecule: only a few amino acid residues touch the substrate directly. The rest of the polypeptide acts as a scaffold that holds these residues in exactly the right three-dimensional position.
- A three-dimensional cleft or crevice: residues forming the site often sit far apart in the primary sequence and come together only when the chain folds. In lysozyme, Glu-35 and Asp-52 line the cleft that holds the polysaccharide substrate.
- A special microenvironment: water is largely kept out of the cleft unless it is a reactant, which strengthens the binding forces and helps the catalytic groups act.
- Binding by many weak interactions: hydrogen bonds, ionic bonds, hydrophobic contacts and van der Waals forces hold the substrate. Because these are weak and reversible, the product can leave once the reaction is over.
- Binding site plus catalytic site: some residues only grip the substrate, while others take part in bond making and breaking. Chymotrypsin's catalytic triad, Ser-195, His-57 and Asp-102, is the classic example.
- Complementarity and flexibility: the shape and charge of the site match the substrate, which explains specificity. Koshland's induced fit model (1958) adds that the site changes shape on binding, as hexokinase does when it closes around glucose.
Together, these features explain why an enzyme can bind its substrate tightly enough to act on it, yet release the product quickly and stay unchanged at the end of the reaction.
(b) Enzyme specificity and its types
Enzyme specificity is the ability of an enzyme to act on one substrate, or a small group of closely related substrates, and to catalyse only one kind of reaction. It comes from the precise match in shape, charge and hydrophobicity between the active site and the substrate.
- Absolute specificity: the enzyme acts on a single substrate only. Urease hydrolyses urea to ammonia and carbon dioxide and acts on no other compound.
- Group specificity: the enzyme acts on molecules that carry a particular group. Trypsin cuts peptide bonds on the carboxyl side of lysine and arginine, while chymotrypsin prefers aromatic residues such as phenylalanine, tyrosine and tryptophan. Hexokinase phosphorylates several hexoses, including glucose, fructose and mannose.
- Bond (linkage) specificity: the enzyme attacks one type of chemical bond whatever the rest of the molecule looks like. Lipases hydrolyse the ester bonds of triacylglycerols, and peptidases hydrolyse peptide bonds.
- Stereochemical specificity: the enzyme tells optical or geometrical isomers apart. L-amino acid oxidase acts only on L-amino acids, and fumarase hydrates fumarate (the trans isomer) but not maleate (the cis isomer).
- Reaction specificity: one substrate can be converted to different products by different enzymes. Pyruvate becomes acetyl-CoA through pyruvate dehydrogenase, oxaloacetate through pyruvate carboxylase and lactate through lactate dehydrogenase.
Specificity lets thousands of reactions run side by side in a cell without interfering, and it is the reason enzymes are so useful in clinical tests and industry.
Metal ions in enzyme activity, and mechanism-based inhibitors
Question 2 (a): Discuss the role of metal ions in the biological activity of enzymes. (5)
Question 2 (b): What are mechanism-based inhibitors? With the help of an example, explain how they are used to design drugs. (5)
(a) Role of metal ions in enzyme activity
Nearly one-third of known enzymes need metal ions for activity. They fall into two groups. Metalloenzymes hold a tightly bound transition metal such as Zn2+, Fe2+/Fe3+, Cu2+ or Mn2+, for example carbonic anhydrase and carboxypeptidase A (both zinc). Metal-activated enzymes bind ions such as Na+, K+, Mg2+ or Ca2+ loosely from solution; pyruvate kinase needs both K+ and Mg2+.
- Binding and orienting the substrate: in kinases such as hexokinase the true substrate is the Mg-ATP complex, and the metal holds the phosphate groups in the right position.
- Shielding negative charge: Mg2+ neutralises the negative charges on the phosphates of ATP, so the phosphorus atom becomes easier for a nucleophile to attack.
- Lewis acid (electrophilic) catalysis: in carbonic anhydrase, Zn2+ lowers the pKa of a bound water molecule to about 7. The zinc-bound hydroxide formed at body pH attacks CO2 to give bicarbonate.
- Redox reactions: metals that change oxidation state carry electrons, such as iron in cytochromes and catalase and copper in cytochrome c oxidase.
- Structural stability: some ions hold the folded protein together rather than take part in catalysis; calcium ions help keep thermolysin stable at high temperature.
Other examples include Ni2+ in urease, Mn2+ in arginase, Zn2+ in alcohol dehydrogenase and molybdenum in xanthine oxidase and nitrogenase. Removing the metal with a chelating agent such as EDTA inactivates a metalloenzyme, which is a simple laboratory test for metal dependence.
(b) Mechanism-based inhibitors and drug design
Mechanism-based inhibitors, also called suicide inhibitors or suicide substrates, are unreactive compounds that look like the normal substrate. The target enzyme binds them and starts its usual catalytic steps, and these steps turn the inhibitor into a highly reactive intermediate. This intermediate forms a covalent bond with a residue in the active site, so the enzyme destroys itself and is inactivated irreversibly.
Because the reactive form is made only inside the target enzyme, these inhibitors are highly specific and have fewer side effects. This makes them ideal for rational drug design. Designers first learn the catalytic mechanism from kinetic and structural studies, then build a substrate analogue carrying a hidden reactive group that is unmasked only by the enzyme's own catalytic step. A good candidate shows time-dependent, irreversible inactivation that the real substrate can slow down.
Example: 5-fluorouracil and thymidylate synthase. Thymidylate synthase converts dUMP to dTMP, using N5,N10-methylene-tetrahydrofolate as the carbon donor. Inside cells the anticancer drug 5-fluorouracil is converted to FdUMP, which the enzyme accepts like dUMP.
- A cysteine residue of the enzyme attacks C-6 of FdUMP, and the methylene group from the folate is attached to C-5, exactly as in the normal reaction.
- To finish, the enzyme must remove the group at C-5. In dUMP this is a hydrogen, but in FdUMP it is fluorine, which cannot be removed.
- The enzyme is therefore trapped in a stable covalent enzyme-FdUMP-folate complex. dTMP is no longer made, DNA synthesis stops and fast-dividing cancer cells die.
Other drugs built on the same idea include eflornithine (DFMO), which inactivates ornithine decarboxylase and is used against African sleeping sickness, and clavulanic acid, which inactivates bacterial β-lactamase and is given with amoxicillin.
3. Questions Answered Only in the Full File
The seven questions below are printed exactly as they appear in the June 2026 paper. Their answers, diagrams and plots are available only in the complete file.
Question 3 (a): How does the presence of an uncompetitive inhibitor affect the kinetic parameters of an enzyme-catalysed reaction? (5)
Question 3 (b): Discuss the regulation of enzyme activity by reversible covalent modification with a suitable example. (5)
Question 4 (a): Draw the structure of pyridoxal phosphate. Describe its role in amino acid metabolism. (5)
Question 4 (b): Match the name of the enzyme in Column A with the associated disease in Column B. (5)
| Column A | Column B |
|---|---|
| (i) Creatine kinase | (1) Phenylketonuria |
| (ii) AST | (2) Tay-Sachs disease |
| (iii) Glycogen phosphorylase | (3) Liver disease |
| (iv) Phenylalanine 4-monooxygenase | (4) Glycogen storage disease type V |
| (v) β-N-acetyl-D-hexosaminidase | (5) Brain and muscle disorder |
Question 5 (a): Explain the purpose of enzyme immobilisation. What kind of effects does it have on the stability of an enzyme? (5)
Question 5 (b): Discuss the applications of enzymes in the wine and baking industry. (5)
Question 6: Write short notes on the following. (2 × 5 = 10)
(a) IUBMB system of enzyme classification
(b) Competitive inhibition of enzymes
Question 7 (a): What are zymogens? Explain with a suitable example. (5)
Question 7 (b): Describe the different mechanisms of sequential reactions with the help of suitable diagrams. (5)
Question 8: Explain any two of the following. (2 × 5 = 10)
(a) Acid-base catalysis
(b) Effect of temperature on enzyme activity
(c) Multienzyme complexesQuestion 9: Write short notes on the following. (2 × 5 = 10)
(a) Feedback inhibition of enzymes
(b) FAD/FMN as coenzyme
4. Syllabus by Block and Unit
BBCCT 107 Enzymes is taught through 4 blocks and 12 units that move from what enzymes are, to kinetics, to regulation and finally to industrial and medical use.
| Block | Unit | Unit focus | Topics to know for the exam |
|---|---|---|---|
| Block 1: Enzymes as Biocatalysts | Unit 1 | Introduction to enzymes | Enzyme nomenclature, the six IUBMB classes with EC numbers, apoenzyme, holoenzyme and prosthetic group |
| Block 1: Enzymes as Biocatalysts | Unit 2 | Principles and theories of enzyme catalysis | Activation energy and transition state, Fischer lock-and-key versus Koshland induced fit, active site features |
| Block 1: Enzymes as Biocatalysts | Unit 3 | Factors affecting enzyme activity | Effect of pH and temperature, substrate and enzyme concentration, activators such as metal ions |
| Block 2: Enzyme Kinetics | Unit 4 | Kinetics of mono-substrate reactions | Michaelis-Menten derivation, meaning of Km, Vmax and kcat, Lineweaver-Burk double-reciprocal plot |
| Block 2: Enzyme Kinetics | Unit 5 | Kinetics of bisubstrate reactions | Ordered and random sequential mechanisms, ping-pong (double displacement) reactions, Cleland notation |
| Block 2: Enzyme Kinetics | Unit 6 | Enzyme inhibition | Competitive, uncompetitive and mixed inhibition, reversible versus irreversible inhibitors, substrate inhibition |
| Block 3: Mechanisms and Regulation of Enzyme Activity | Unit 7 | Mechanisms of enzyme action | Acid-base catalysis, covalent catalysis, proximity and orientation effects |
| Block 3: Mechanisms and Regulation of Enzyme Activity | Unit 8 | Regulation of enzyme activity | Allosteric control, feedback inhibition types, reversible covalent modification and zymogen activation |
| Block 3: Mechanisms and Regulation of Enzyme Activity | Unit 9 | Multienzyme complexes | Pyruvate dehydrogenase complex, substrate channelling, advantages of enzyme clustering |
| Block 4: Applications of Enzymes | Unit 10 | Coenzymes | NAD+/NADP+, FAD/FMN, pyridoxal phosphate and coenzyme A in named reactions |
| Block 4: Applications of Enzymes | Unit 11 | Applications of enzymes | Food, wine, baking and detergent uses, diagnostic enzymes such as AST and creatine kinase |
| Block 4: Applications of Enzymes | Unit 12 | Advances in enzyme technology | Immobilisation by adsorption, entrapment, covalent binding and cross-linking, enzyme electrodes |
You can open the official self-learning material for each block on eGyanKosh, IGNOU's course repository for BBCCT-107. Unit 10 on coenzymes is worth extra time, because PLP and FAD/FMN both appeared in June 2026.
For unit-wise notes that follow this same block order, see our BBCCT 107 Study Material, which pairs each unit summary with the question types it tends to produce.
5. Paper Pattern and Marks Split
The June 2026 paper had 9 questions of 10 marks each, and students had to answer any seven for 70 marks in 3 hours.
| Feature | June 2026 | December 2023 | December 2022 |
|---|---|---|---|
| Questions printed | 9 | 8 | 8 |
| Questions to attempt | Any 7 | Q1 plus any 5 of Q2 to Q8 | Any 5 |
| Marks per question | 10 (split 5 + 5 or 2 × 5) | Q1: 20; Q2 to Q8: 10 each | 14 each |
| Compulsory objective section | None | Yes, one-word answers, differences and definitions in Q1 | None |
| Diagram instruction | In the note and in Q4(a) and Q7(b) | Not stated in the note | Asked inside Q1(a) |
All three sessions kept the same 70 marks and 3 hours, but the number of answers changed from five to six to seven. With seven answers in June 2026, you have roughly 25 minutes per 10-mark question, so each 5-mark part needs about 12 minutes of writing.
This paper sits inside a wider programme set; our BSCBCH Question Paper page lists the other Biochemistry core papers of the same session for side-by-side practice.
6. Enzyme Topics That Keep Returning
Across the three official BBCCT 107 papers we could verify, metal ions, feedback regulation, immobilisation, multienzyme complexes and coenzymes appeared in every session.
We used the December 2022 and December 2023 papers from webservices.ignou.ac.in and the June 2026 paper you see here. IGNOU's June 2024 index lists BBCCT-107 without a paper, and we could not find official June 2023, December 2024, June 2025 or December 2025 papers, so this is a three-session count, not a five-year one.
| Topic | Dec 2022 | Dec 2023 | Jun 2026 | Sessions (of 3) |
|---|---|---|---|---|
| Metal ions in enzyme activity | Q5(b) | Q4(a) | Q2(a) (Sample 2) | 3 |
| Feedback regulation and inhibition | Q7(b) | Q6 | Q9(a) | 3 |
| Enzyme immobilisation | Q5(a) | Q1(a)(iii), Q7 | Q5(a) | 3 |
| Multienzyme complexes | Q3(b) | Q1(a)(ii), Q8(b) | Q8(c) | 3 |
| Coenzymes (NAD, CoA, PLP, FAD/FMN) | Q3(a) | Q2 | Q4(a), Q9(b) | 3 |
| Enzyme inhibition types | Q2(a), Q7(a) | Q1(b)(i), Q4(b)(ii) | Q3(a), Q6(b) | 3 |
| Km, Vmax and the double-reciprocal plot | Q4(a) | Q1(a)(vi), Q3 | Q3(a) | 3 |
| Bisubstrate and sequential reactions | Q8(a) | Q4(b)(i) | Q7(b) | 3 |
| Enzyme classes and the IUBMB system | Q8(b) | Q1(c)(ii) | Q6(a) | 3 |
| Industrial, food and medical uses | Q6(a) | Q8(a) | Q5(b) | 3 |
| Active site and catalysis models | Q1(b) | Q1(a)(v) | Q1(a) (Sample 1) | 3 |
| Catalytic mechanisms (acid-base, covalent) | — | Q5 | Q8(a) | 2 |
| Effect of pH and temperature | Q1(a) | — | Q8(b) | 2 |
| Allosteric and covalent control | Q4(b) | — | Q3(b) | 2 |
| Pyridoxal phosphate (PLP) | — | Q2(ii) | Q4(a) | 2 |
Topics seen in all three sessions are the safest places to prepare a full answer. For a ready shortlist of likely questions across courses, our IGNOU Solved Guess Paper page groups them by course code.
7. How the Answers Were Written and Checked
Every BBCCT 107 answer was written by a biochemistry writer from the IGNOU study material and then checked by a second reviewer against the printed June 2026 paper.
The answers were written after reading all four blocks and the earlier December 2022 and December 2023 papers. Each 5-mark part runs to roughly 250 words, opens with a one-line definition and then moves to named enzymes, residues or drugs, because vague answers lose marks in this course.
The review matched question numbers, marks and sub-part letters with the June 2026 paper, and checked every structure and graph label. Where the paper says "with the help of suitable diagrams", the file includes a drawn diagram, not a description of one.
8. Solved File Index and BBCCL-108 Practical Links
BBCCT 107 is studied together with the 2-credit BBCCL-108 Enzymes Laboratory, so this index links every June 2026 question to its course unit and to the lab skill behind it.
The lab column names skill areas from the BBCCL-108 manual's focus on assays, kinetics and inhibition, not official experiment numbers. Use it to revise the practical record and the theory answer together.
| Question and topic | Course unit | Linked BBCCL-108 lab skill | Where the answer is |
|---|---|---|---|
| Q1: active site and specificity | Units 1 and 2 | Substrate specificity checks in an enzyme assay | Sample 1 above |
| Q2: metal ions and mechanism-based inhibitors | Units 3 and 6 | Effect of activators and chelating agents on activity | Sample 2 above |
| Q3: uncompetitive inhibition and covalent modification | Units 6 and 8 | Plotting inhibited and uninhibited Lineweaver-Burk lines | Full file |
| Q4: PLP structure and the enzyme-disease match | Units 10 and 11 | Serum enzyme estimation such as AST and creatine kinase | Full file |
| Q5: immobilisation and wine or baking enzymes | Units 11 and 12 | Entrapping an enzyme in calcium alginate beads and reusing it | Full file |
| Q6: IUBMB classification and competitive inhibition | Units 1 and 6 | Reading EC numbers on reagent labels; Km shift with inhibitor | Full file |
| Q7: zymogens and sequential reactions | Units 5 and 8 | Activating a proenzyme before assay; two-substrate rate curves | Full file |
| Q8: acid-base catalysis, temperature, multienzyme complexes | Units 3, 7 and 9 | Activity versus temperature curve and optimum temperature | Full file |
| Q9: feedback inhibition and FAD/FMN | Units 8 and 10 | Following a flavoprotein reaction by absorbance change | Full file |
That is 2 answers on this page and 7 in the paid file, which covers all 9 questions.
9. Programmes That Study BBCCT 107
BBCCT 107 Enzymes is a core course of IGNOU's B.Sc. (Honours) Biochemistry (BSCBCH), studied in Semester III alongside its lab partner BBCCL-108.
In the IGNOU Bachelor of Science (Honours) Biochemistry programme, BBCCT 107 sits between BBCCT-105 Proteins and BBCCT-109 Metabolism of Carbohydrates and Lipids, so a strong grip on enzyme kinetics here makes the metabolism courses much easier. The programme runs for a minimum of 3 and a maximum of 6 years.
Learners in other IGNOU biochemistry degrees may also carry this course code. Confirm it against your own programme guide before you order, because the answers are written to the BSCBCH paper printed above.
10. How to Get the Full Solved Question Paper
Send "BBCCT 107 June 2026" on WhatsApp 9899436384 to get the full solved paper with all 9 answers, including the 7 not shown here.
The complete file is shared as a PDF on WhatsApp after you confirm the order with our team. You get every answer from Q1 to Q9 in the paper's own numbering, the drawn PLP structure and the kinetics plots, ready for revision before the December 2026 term-end examination.
11. BBCCT 107 Enzymes FAQs
These are the questions BBCCT 107 students ask most often before ordering the solved paper.
Is this solved paper based on the official June 2026 paper?
Yes. It uses the official BBCCT-107 Enzymes term-end examination paper of June 2026, with all 9 questions kept in IGNOU's own numbering and wording. Our biochemistry writers answered each part at the length a 5-mark sub-question needs. Two answers, Q1 and Q2, are open on this page so you can judge the depth before you ask for the full file on WhatsApp.
How do I get the full file on WhatsApp and how many answers does it contain?
Send a message saying "BBCCT 107 June 2026" to WhatsApp 9899436384. Our team replies with the price and delivery details for the complete file. It contains answers to all 9 questions of the June 2026 Enzymes paper: the 2 shown on this page and the 7 that are listed here only as question text, including the drawn PLP structure and kinetics plots.
Which BBCCT 107 topics repeat most often in IGNOU papers?
In the three official papers we checked (December 2022, December 2023 and June 2026), five topics appeared every time: metal ions in enzyme activity, feedback regulation, enzyme immobilisation, multienzyme complexes and coenzymes such as NAD, PLP or FAD. Enzyme inhibition, bisubstrate reactions and enzyme classification also came up in all three sessions, in slightly different wording each time.
How many questions must I attempt in the June 2026 paper?
You had to attempt any seven of the nine questions, and every question carried 10 marks, giving a total of 70 marks in 3 hours. This differs from December 2023, when the paper had a compulsory 20-mark objective Question 1 and then any five of Questions 2 to 8, so always read the instructions line before you plan your time.
Are diagrams included in the BBCCT 107 answers?
Yes. The June 2026 paper asks for diagrams in two places, the structure of pyridoxal phosphate in Q4(a) and sequential reaction mechanisms in Q7(b), and both are drawn in the full file. Inhibition answers also carry labelled Lineweaver-Burk plots, because examiners in this course reward a clear graph that shows how Km and Vmax shift.
Is BBCCT 107 paired with a practical course?
Yes. In the BSCBCH programme structure, BBCCT 107 Enzymes (4 credits) is taken together with BBCCL-108 Enzymes Laboratory (2 credits). The lab builds hands-on skill with enzyme assays, pH and temperature studies, kinetics and inhibition, so the practical index on this page links each June 2026 question to the lab skill that supports it.
Who wrote and reviewed the BBCCT 107 answers?
The answers were written by Prateek Talwar and the Unnati Educations biochemistry team, working from the IGNOU study material for all four blocks. Sheetal Kirola then reviewed every answer against the printed June 2026 paper, checking question numbers, marks, named examples and diagram labels before the file was released.
How should I use this paper for December 2026 preparation?
Treat the June 2026 paper as a mock test. Attempt seven questions in 3 hours without notes, then compare your answers with the solved file. Mark the units where you lost marks and revise those blocks first. Topics seen in every session, such as metal ions and feedback regulation, deserve a full practice answer each.
12. Who Wrote and Checked the BBCCT 107 Answers
The BBCCT 107 answers were written by Prateek Talwar and the Unnati Educations biochemistry team, and reviewed by Sheetal Kirola.
Prateek Talwar, founder of Unnati Educations, prepares IGNOU science solved papers from the course blocks and the official term-end paper. Sheetal Kirola, Academic Head (M.Ed.), checks every question number, mark split, named example and diagram label against the printed paper before release.