What You Need to Know

Key Concept Diagram

Enzymes are proteins that act as biological catalysts, speeding up reactions without being consumed

Each enzyme has an active site that fits a specific substrate (lock and key model)

Enzyme activity is affected by temperature and pH; extremes cause denaturation

Denaturation changes the shape of the active site, preventing the substrate from binding

Key Vocabulary

Enzyme

A biological catalyst made of protein that speeds up specific chemical reactions

Substrate

The specific molecule that binds to an enzyme's active site

Active site

The region of an enzyme where the substrate binds

Denaturation

The permanent change in an enzyme's shape caused by extreme heat or pH

Knowledge Check

Select the correct answer for each question. Click "Check Answer" to see if you are right.

Question 1

Why does body temperature (37 degrees C) matter for enzyme function?

Enzymes only work in cold conditions Temperature has no effect on enzymes Most human enzymes have an optimal temperature of around 37 degrees C; higher temperatures cause denaturation Enzymes work faster at 100 degrees C

Question 2

The "lock and key" model describes:

How DNA replicates How genes are expressed How cells divide How a specific substrate fits into a specific enzyme's active site

Question 3

A student tests enzyme activity at pH 2, pH 7, and pH 12. At pH 2 and 12, the enzyme barely works. What explains this?

Extreme pH values denature the enzyme, altering the shape of the active site The enzyme is inactive at room temperature The enzyme needs sunlight to work The substrate is too large at extreme pH

Enzymes and Biological Catalysts