Explain enzymes

Supplied materials

• All measurements and observations below are supplied classroom examples. They are not data from actual learners or a claim about a particular real site.
• Paper or a browser document for a labeled drawing, table or explanation.
• Worked problem inputs: Catalyzed and uncatalyzed models have the same products and overall energy difference but different rates. Explain the mechanism.
• Assessment case 1: A catalyst lowers the activation barrier but reactant/product energy levels stay fixed. What follows? Which inference or prediction is best supported?
• Assessment case 2: Which scientific label fits the specifically described step or feature? Supplied case: Binding region of modeled enzyme.
• Assessment case 3: Which scientific label fits the specifically described step or feature? Supplied case: Energy barrier before reaction proceeds.
• Assessment case 4: Which scientific label fits the specifically described step or feature? Supplied case: Enzyme speeds repeated reactions.
• Assessment case 5: Which scientific label fits the specifically described step or feature? Supplied case: Molecule converted in enzyme reaction.
• Assessment case 6: An enzyme remains after repeated model reactions while products accumulate. What is supported? Which inference or prediction is best supported?

Learn the idea

Enzymes accelerate reactions by lowering activation-energy barriers. They do not change the reaction’s overall free-energy difference or get used up in the net reaction. Conditions can alter their activity.

Substrate means molecule acted on by enzyme. Active site means region interacting with substrate. Activation energy means barrier the catalyst helps lower. Catalyst means agent increasing reaction rate without net consumption.

For the supplied mechanism problem, Catalyzed and uncatalyzed models have the same products and overall energy difference but different rates. Explain the mechanism. The enzyme lowers the activation barrier, enabling faster reaction under the stated conditions. It does not change the products’ overall energy difference or create energy.

1. Read the supplied problem and mark the structures, processes or quantities named: Catalyzed and uncatalyzed models have the same products and overall energy difference but different rates. Explain the mechanism.
2. Draw the relevant boundary, pathway or comparison and label it using the scientific ideas above.
3. Write a causal explanation or calculation, showing how each observation supports the result.
4. Compare your reasoning with the worked solution; name a condition that would change or limit the inference.

Check your reasoning

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Take it further

New comparison: enzyme lowers the activation barrier while initial and final free-energy levels stay fixed. Expected: faster reaction under the supplied conditions without changing overall free-energy difference or consuming the enzyme in the net reaction.

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