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Released STAAR Biology EOC · 2026 · Item 7 · 1 point

Walkthrough: Biology 2026, Item 7

B.11B · Enzymes · unscored study

A line graph of enzyme activity in units per milliliter from 20 to 80 degrees Celsius. Activity is about 340 at 20 °C, 510 at 30 °C, 1,060 at 40 °C, peaks near 1,200 around 45 °C, is 1,160 at 50 °C, then falls to 600 at 60 °C, 400 at 70 °C, and about 110 at 80 °C.
Enzyme activity versus temperatureOriginal visual from the released STAAR test.

A graph of enzyme activity is shown. Which statement is BEST supported by the data?

  1. The enzyme is denatured and can no longer bind to its substrate between 20 and 40 °C.
  2. The enzyme is able to optimally function and bind to its substrate at around 45 °C.
  3. The enzyme can only bind to its substrate at temperatures between 30 and 60 °C.
  4. The enzyme can no longer bind to its substrate at temperatures greater than 60 °C.

1. Understand the question

Read the enzyme-activity graph. The highest point on the curve is the enzyme's optimal temperature.

Try the question on your own first, then reveal one step at a time.

2. Solve it step by step

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Question, artwork, answer key and rationale: Texas Education Agency released STAAR test. Walkthrough steps written by TEKSForge. Studying here does not change your mastery or scores.