How Temperature Affects Enzyme Activity

Enzymes are specialized proteins that help chemical reactions happen faster inside living things. They work best only within a certain temperature range, and even small changes in temperature can speed them up, slow them down, or stop them from working completely. Because all cells rely on enzymes for processes like digestion, respiration, and DNA replication, maintaining the right body temperature is essential for survival.

At low temperatures, enzyme activity slows down. The enzymes themselves don’t change shape, but the molecules move more slowly, which reduces how often enzymes collide with their substrates. When these collisions decrease, reactions happen much more slowly. For example, when a person becomes dangerously cold or hypothermic, their enzymes slow down, and basic processes—like shivering, thinking clearly, or maintaining heart rate—start to decline.

Each enzyme also has an optimal (optimum) temperature, the temperature at which it works fastest. In humans, most enzymes have an optimum temperature close to 37°C (98.6°F), which is our normal body temperature. At this point, enzyme and substrate molecules are moving at just the right speed for the highest number of successful collisions, allowing reactions to proceed quickly and efficiently.

If the temperature becomes too high, enzymes can denature. Denaturation means the enzyme loses its shape due to heat breaking the bonds that hold it together. Because an enzyme’s shape determines how it fits with its substrate, a denatured enzyme can no longer function. This is why a high fever can be dangerous. When body temperature rises significantly—usually above 40°C (104°F)—some enzymes begin to denature. If enough enzymes lose their shape, essential body processes slow or stop, which can lead to organ failure.

Both high and low temperatures can disrupt enzyme activity, but in different ways. Cold temperatures slow enzymes down without changing their structure, while high temperatures permanently change their shape. To stay healthy, humans must maintain a stable internal temperature so that enzymes can continue carrying out the chemical reactions needed for life.

Directions: Draw the relationship between temperature and enzyme activity on the graph below. Hit the envelope button in the top right corner to send your answers to us. 

Exit Ticket

Over the weekend, Mr. Pinho and Ms. Angarola entered a charity hamburger-eating contest at White Castle, and during the chaos of trying to beat each other’s slider record, grease and ketchup splattered all over Mr. Pinho’s white shirt. The next morning, he tried to clean it quickly by soaking it in boiling hot water mixed with enzymatic cleaner, assuming the extreme heat would help the enzymes break down the stain. But after twenty minutes, the ketchup and grease were still clearly visible, leaving him confused about why the cleaner didn’t work. 

1) Why didn’t the enzymatic cleaner work in boiling water?
(1) The enzymes became denatured by the high temperature.
(2) The enzymes froze and could not move.
(3) The enzymes became stronger and dissolved too quickly.
(4) The hot water caused the stain molecules to evaporate.

2) What happens to enzymes when the temperature gets too high?
(1) They multiply rapidly.
(2) They change shape and can no longer bind to their substrate.
(3) They freeze and stop moving.
(4) They become stronger and work faster.

3) Enzymes in detergents work best at warm temperatures, not boiling temperatures. What is the term for this “best temperature”?
(1) Minimum temperature
(2) Denature temperature
(3) Optimal (optimum) temperature
(4) Maximum temperature

4) What would likely happen if Mr. Pinho had used very cold water instead?
(1) The enzymes would melt the stain.
(2) The enzymes would freeze and disappear.
(3) The enzymes would slow down and work less effectively.
(4) The enzymes would denature even faster.