Enzimas

The diagram shows the effect of an enzyme working in the human digestive system. What would reduce the rate of production of amino acids?

• removing the amino acids as they are formed

• increasing the amount of protein

• raising the temperature to 40 °C

• raising the pH to 7.5

Which group of compounds ensures that metabolic reactions take place effectively?

• carbohydrates

• enzymes

• fatty acids

• hormones

Which effect does a gradual decrease in pH from 13 to 1 have on the action of amylase?

• slows it down only

• slows it down then speeds it up

• speeds it up only

• speeds it up then slows it down

Lactase is a human enzyme that catalyses the breakdown of lactose in milk.At which temperature does lactase work fastest?

• 0°C

• 18°C

• 37°C

• 100°C

13 The graph shows the effect of pH on a particular enzyme-controlled reaction.

When is the enzyme not active?

• at pH 1 and pH 13

• at pH 3 and pH 11

• at pH 5 and pH 9

• at pH 7

What happens to most enzymes above 60°C?

• They are destroyed by white blood cells.

• They are digested.

• They are denatured.

• They are made more active

What is a characteristic of all catalysts?

• They are broken down in the reaction

• They are made of protein.

• They are not changed by the reaction

• They do not change the rate of the reaction.

The diagram shows the lock and key model of enzyme action. Which is the enzyme and which is the substrate?

• Enzyme 1

  Substrate 2

• Enzyme 1

  Substrate 3

• Enzyme 3

  Substrate 1

• Enzyme 3

  Substrate 2

Two enzyme-controlled reactions are shown.

What deduction can be made about enzymes?

• Enzyme 1 has been changed to enzyme 2.

• Enzyme 2 slows down the production of amino acids.

• Enzymes can build up large molecules

• Enzymes only break down large molecules.

In an experiment, the effect of temperature on the action of amylase is investigated.Six different test-tubes are set up, each containing a mixture of amylase and starch solution.Which condition should not be kept the same in each of the six test-tubes?

• concentration of amylase

• pH

• temperature

• volume of starch solution