Factors that affect enzyme action · ⁨影响酶作用的因素⁩

What changes an enzyme's speed

• Change the conditions and you change how fast an enzyme works.
• First, you need a fair way to measure the rate.
• Then we'll see how temperature, pH and concentration each affect it.

Measuring the rate

• Follow how fast product forms (e.g. collect the oxygen gas from catalase) or how fast substrate disappears (e.g. the iodine colour fading as amylase digests starch).
• A colorimeter 比色计 turns a colour change into an exact number you can plot.
• The reaction is fastest at the start (most substrate present), so the initial rate 初始速率 — the slope at time zero — is the fairest value to compare.

The initial rate — the slope at the very start — is the fairest value to compare.

Temperature

• Heating gives molecules more kinetic energy, so they collide more often — the rate rises.
• But past the optimum 最适, the heat breaks the bonds holding the enzyme's shape: it denatures 变性, the active site no longer fits, and the rate crashes.

pH

• Each enzyme has an optimum pH. Move too far either side and it denatures, so the rate drops.
• To study pH fairly, hold it steady with a buffer 缓冲液 solution.

Enzyme and substrate concentration

• More enzyme (with substrate to spare) means more active sites, so the rate rises in proportion.
• More substrate speeds things up at first — but once every active site is busy, adding more makes no difference and the rate levels off.
• More inhibitor 抑制剂 lowers the rate.
• Explore it below: drag the substrate slider and watch the rate climb, then flatten once every active site is full.

You've got it