Completed biology worksheet illustrating enzyme function, including the lock and key model and definitions of catalysts and amino acids.

The worksheet you've uploaded is about enzymes, and it appears to be a completed version with handwritten answers. Let's go through each section, explain the correct answers, and clarify any potential issues—especially in part (d)ii, which has an incorrect labeling.

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1a) Fill in the gaps:

i) Enzymes are biological catalysts that speed up chemical reactions in living organisms.
✔ Correct: Enzymes are catalysts because they lower activation energy without being consumed.

ii) Enzymes are protein molecules, which are made up of long chains of amino acids.
✔ Correct: Proteins are polymers of amino acids linked by peptide bonds.

iii) The sequence and type of amino acids are different in each protein, so they produce enzymes with many different shapes and functions.
✔ Correct: The primary structure (sequence of amino acids) determines the enzyme’s 3D shape and function.

iv) The shape of an enzyme is very important to its function.
✔ Correct: Enzyme function depends on the shape of the active site, which must match the substrate.

> ✔ All answers here are correct.

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1b) Name one process catalyzed by enzymes in the human body:

Answer: Cellular respiration, digestion
✔ Correct: Both are major processes involving enzymes.
- Digestion: Enzymes like amylase, proteases, lipases break down food.
- Cellular respiration: Enzymes in mitochondria help convert glucose into ATP.

Other valid examples: DNA replication, photosynthesis (in plants), blood clotting.

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1c) Label the image:

The diagram shows:
- A large "E" shape → enzyme
- A smaller puzzle-like piece → substrate (also called reactant)
- The indented area on the enzyme → active site

Your labels:
- Enzyme → ✔️ Correct
- Active site → ✔️ Correct
- Substrate (labeled as "reactant") → ✔️ Correct

Note: "Reactant" is acceptable, but substrate is the more precise term in enzymology.
✔️ All labels are correct.

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1d) i) What is the common name for the above model?

Answer: Lock and key model
✔ Correct: This model describes how the enzyme (lock) has a specific shape that only fits a particular substrate (key).

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1d) ii) Label the two components of this model on the above image.

You have written:
Enzyme X — ✘ Incorrect labeling.

But you already labeled:
- The big "E" → Enzyme ✔️
- The small piece → Substrate ✔️

So, the two components of the lock and key model are:
1. Enzyme (the lock)
2. Substrate (the key)

👉 You should label both on the diagram.

✘ The "X" next to "enzyme" seems to indicate confusion or a correction attempt. But the enzyme is correctly labeled.

✔ So, correct answer:
- Label the large E-shaped molecule as Enzyme (lock)
- Label the smaller puzzle piece as Substrate (key)

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✔ Final Summary of Corrections:

| Section | Your Answer | Evaluation |
|--------|-------------|----------|
| 1a) all | Catalysts, amino acids, different, function | ✔ Correct |
| 1b) | Cellular respiration, digestion | ✔ Correct |
| 1c) Labels | Enzyme, Active site, Substrate | ✔ Correct |
| 1d)i) | Lock and key model | ✔ Correct |
| 1d)ii) | Enzyme X | ✘ Misplaced mark; you already labeled enzyme correctly |

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🛠️ Suggested Fix for 1d)ii):

Write:
- On the large E shape: Enzyme (lock)
- On the small puzzle piece: Substrate (key)

This clearly identifies the two components of the lock and key model.

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🔍 Explanation of the Lock and Key Model:

- The enzyme has a rigid active site shaped precisely to fit one specific substrate.
- Like a lock and key, only the correct substrate can bind.
- Once bound, the reaction occurs.
- Afterward, the products are released, and the enzyme is free to act again.

> ⚠️ Note: While useful, the lock-and-key model is simplified. A more accurate model is the induced fit model, where the enzyme slightly changes shape upon substrate binding.

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✔ Final Answer Summary:

All answers are correct except for 1d)ii), where the "X" may suggest confusion. Simply ensure both components are clearly labeled:
- Enzyme = lock
- Substrate = key

And you're all set!