2.5 Enzymes- Paper 1 questions

What effect do changes in pH have on enzymes?

• All enzymes increase in activity as pH increases.

• The activity of all enzymes is reduced by a pH below or above 7.

• Low pH causes reversible denaturation in all enzymes

• Extreme pH can alter the active site of all enzymes.

Lactose intolerance occurs when the enzyme, lactase, that digests lactose is not produced after infancy in humans. The incidence of lactose intolerance varies in different racial groups. The graph shows the distribution of lactose intolerance in different human populations. What can be hypothesized from the graph?

• Native American people produce most lactase after infancy

• Most Indian people do not produce lactase after infancy.

• Lactase is not produced after infancy in most Caucasian people.

• One quarter of Afro-Caribbean people will probably experience digestive problems when drinking milk.

The graph shows the effect of changing the substrate concentration on the early stages of an enzyme-catalysed reaction. What can be interpreted about the rate of reaction from the graph?

• Rate of reaction increases up to a point and then remains constant.

• Rate of reaction increases linearly with increasing substrate concentration.

• Rate of reaction increases non-linearly with increasing substrate concentration.

• Rate of reaction is not affected by any change in the substrate concentration.

What is the advantage of using lactase in an immobilized state in the food manufacturing industry?

• It functions within cells.

• It dissolves in multiple solvents.

• It converts cellulose into glucose.

• It is less likely to become denatured.

Three flasks were prepared for an analysis of the activity of amylase. At time zero, each of the substances indicated in the diagrams was added.Which flask(s) could provide support for the hypothesis that heat denatures enzymes?

• Flasks I and II after 15 minutes

• Flasks II and III after 15 minutes

• Flasks I and III after 15 minutes

• . Flask III at time zero and again after 15 minutes

The graph shows the effect of increasing the substrate concentration on the rate of an enzyme-catalysed reaction. What is occurring during the phase indicated by section Y of the graph?

• The active site of the enzyme is saturated.

• The enzyme becomes denatured.

• The substrate concentration has risen too high.

• The optimum rate is reached.

In an experiment the effect of changing pH on an enzymatic reaction is tested. Which could be a dependent variable in this kind of experiment?

• Changing substrate concentration

• Rate of formation of product

• Variation in temperature

• Change in pH

What is decreased when lactase is added to milk?

• A. Sweetness

• Disaccharides

• Calcium

• Monosaccharides

Why does exposure to high temperatures cause an enzyme to lose its biological properties?

• The substrate blocks the active site at high temperatures

• The three dimensional structure of the enzyme becomes changed.

• Chemical reactions cannot take place at high temperatures.

• High temperatures increase the activation energy of reactions.

It is possible to attach β-galactosidase to alginate beads for use in the production of lactose-free milk. What are enzymes that have been attached in this way called?

• Inhibited

• Immobilized

• Catalysed

• Activated