Substrate Concentration and Enzyme Activity Flashcards

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What is a substrate in an enzyme-controlled reaction?

A substrate is the substance that an enzyme acts on and changes in a reaction.

What do we mean by substrate concentration?

Substrate concentration is how much substrate there is in a given volume of solution.

What happens to the rate of an enzyme reaction when you increase substrate concentration from a very low level?

The reaction gets faster because more substrate particles can collide with the enzyme’s active sites.

Why does increasing substrate concentration increase enzyme activity at first?

At first there are many free active sites, so more substrate means more successful collisions and more products made each second.

Why does the rate of reaction stop increasing at high substrate concentrations?

It stops increasing because all the enzyme active sites are busy, so adding more substrate makes no difference.

What does it mean if the enzymes are ‘saturated’ with substrate?

Saturated means every active site is filled with substrate all the time, so the enzymes are working at their maximum rate.

At low substrate concentration, what is the limiting factor for the rate of an enzyme reaction?

At low substrate concentration, the amount of substrate is the limiting factor.

At high substrate concentration, what becomes the limiting factor for enzyme activity?

At high substrate concentration, the amount of enzyme (number of active sites) becomes the limiting factor.

In photosynthesis, which gas is a substrate whose concentration can affect enzyme activity?

Carbon dioxide is a substrate in photosynthesis, and its concentration can affect enzyme activity.

If all the photosynthesis enzymes are already working at their maximum rate, what happens if you add more carbon dioxide?

The rate of photosynthesis stays the same because the enzymes are saturated and carbon dioxide is no longer the limiting factor.

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