Barrier Breakers

6. Look at the table above. Which enzyme saves more total energy: Catalase or Sucrase? By how many kilojoules?

7. In your own words, why does lowering the energy hurdle allow food to digest in seconds instead of years?

5 Part 5: Easy Graph Drawing Challenge

Student Coordinate Grid Sketch both curves

Energy [kJ] Progress \(\rightarrow\)

Sketch an Endergonic Reaction:

Use these super-simple target numbers:

• Start (Reactants) = \(20\text{ kJ}\)

• End (Products) = \(60\text{ kJ}\)

• High Peak (No Enzyme) = \(100\text{ kJ}\)

• Lower Peak (With Enzyme) = \(50\text{ kJ}\)

Label which curve is "With Enzyme" and which curve is "Without Enzyme".

Barrier Breakers • Biology Instructional Series Page 2 of 2 • Assessment Ready

Rubric: 1 pt for explaining shape change/detaching; 1 pt for stating enzyme is undamaged and reusable.

Teaching Tip: Use the "speed bump" analogy. An uncatalyzed reaction is a massive hill that requires a lot of gas to climb; an enzyme bulldozes the hill into a small speed bump.

Barrier Breakers • Teacher Guide Page 1 of 2 • Solutions Continued →

Teacher Key • Page 2

Parts 3, 4 & 5 Solutions

Standards-Aligned Solutions

3 Part 3 Solutions: Understanding Energy Rules (4 pts)

4. Why Net Energy Released Never Changes (2 pts)

Solution: The net energy released depends only on the starting fuel (\(50\text{ kJ}\)) and the final products (\(30\text{ kJ}\)). Because an enzyme only speeds up the middle step and never changes what the starting or ending molecules are, the net difference is always \(50 - 30 = \mathbf{20\text{ kJ}}\).

5. Why Cells Cannot Just Heat Up (2 pts)

Solution: Heating a cell to \(100^\circ\text{C}\) would cook and denature its proteins and melt its cell membranes, destroying the cell. Enzymes allow reactions to happen at high speeds at safe, moderate body temperatures (\(37^\circ\text{C}\)).

4 Part 4 Solutions: Real-World Energy Numbers (4 pts)

6. Comparison Calculation (2 pts)

• Catalase: \(75 - 10 = 65\text{ kJ saved}\)

• Sucrase: \(100 - 30 = 70\text{ kJ saved}\)

Answer: Sucrase saves more total energy by \(5\text{ kJ}\) (\(70 - 65 = 5\)).

7. Speed Explanation in Plain Words (2 pts)

Solution: When the hurdle is tall (\(100\text{ kJ}\)), almost no molecules have enough natural energy to get over it, so the reaction is extremely slow. When the enzyme cuts the hurdle to \(30\text{ kJ}\), almost every molecule has enough natural heat energy to jump over immediately.

5 Part 5: Easy Graph Drawing Solution (6 pts)

Energy [kJ] Progress \(\rightarrow\) Start: 20 kJ End: 60 kJ No Enzyme: 100 kJ With Enzyme: 50 kJ

Grading Checklist (6 pts):

• 1 pt: Starting level at \(20\text{ kJ}\)

• 1 pt: Ending level higher at \(60\text{ kJ}\)

• 1 pt: Red curve reaches \(100\text{ kJ}\)

• 1 pt: Green curve reaches \(50\text{ kJ}\)

• 1 pt: Clearly labeled "With" and "Without"

• 1 pt: Clean curves starting & ending together

Simple Check: Did Students Subtract Correctly?

Make sure students subtract from the reactant baseline (\(50\text{ kJ}\)) rather than from zero. The hurdle without enzyme is \(150 - 50 = \mathbf{100\text{ kJ}}\), not \(150\text{ kJ}\).

Barrier Breakers • Teacher Guide Scoring Solutions Complete