ENZYME

Which statement about enzymes is true?

• Most enzymes are proteins.

• All enzymes have an optimum temperature of about 38 ⁰C.

• Enzymes are denatured at low temperatures.

• Enzymes are killed at high temperatures.

Which statement is not true for all enzymes?

• Enzymes break down large molecules to small ones.

• Enzymes remain unchanged at the end of a reaction.

• Enzymes are affected by pH.

• Enzymes catalyse reactions.

Where are enzymes found?

• Only in the digestive system

• in animals but not in plants

• in all living cells

• in plants but not in animals

Some catalase was added to some hydrogen peroxide. Bubbles of oxygen were given off. After a while, the reaction stopped.

Why did the reaction stop?

• The catalase was all used up.

• The catalase was denatured by the reaction.

• The hydrogen peroxide was all broken down.

• The oxygen given off inhibited the catalase.

Which types of enzymes digest starch?

• catalase

• amylase

• lipase

• protease

A student investigated the effect of temperature on the rate of activity of a protease enzyme. Which variable should she change, and which should she keep constant?

• Change: Enzyme concentration; Keep constant:substrate concentration

• Change: substrate concentration; Keep constant: temperature

• Change: temperature; Keep constant: pH

• Change: pH; Keep constant: enzyme concentration

Catalase catalyses a reaction in which hydrogen peroxide is

broken down to water and oxygen.

What are the substrate and product in this reaction?

• Substrate: catalase; Product: hydrogen peroxide

• Substrate: hydrogen peroxide; Product: water and oxygen

• Substrate: oxygen and water; Product: catalase

• Substrate: water; Product:oxygen

Tags

NGSS.HS-PS1-2

What is an active site?

• A gland that secretes a particular enzyme

• A part of an enzyme molecule into which a substrate molecules fits

• A part of the substrate to which an enzyme molecules attaches

• A place in the body where an enzyme works

Why does the rate of an enzyme-catalysed reaction increase as temperature is raised from 0–40 °C?

• The enzyme and substrate molecules have more kinetic energy, so they collide more frequently.

• The shape of the active site changes so that the substrate fits into it better.

• Enzymes are denatured at low temperatures.

• The shape of the substrate changes at high temperatures.

Why does pH affect enzyme activity?

• Changes in pH affect the shape of the active site.

• Changes in pH affect the frequency of collisions between enzyme and substrate.

• Changes in pH affect enzyme concentration.

• Changes in pH affect the enzyme's optimum temperature.