C4&5 - Biological Molecules (5078)

Which of this is a role of water in living organisms?

• an energy source

• buoyancy (allowing organisms to float/sink)

• insulation

• transport

What are the subunits of a protein molecule?

• amino acid

• fatty acid

• glucose

• glycerol

A food substance is tested with three reagents. The results are:

- iodine solution turns blue-black

- biuret test gives a purple colour

- ethanol test gives an emulsion

What does the food substance contain?

• starch

• protein

• fat

Which of these properties make water suitable to be used in a blood transport system?

• Water cools a surface from which it evaporates.

• Water is used as a solvent for many chemicals.

• Water is involved in many metabolic reactions.

Which statement is true of enzymes?

• They absorb the sun's energy during photosynthesis.

• They catalyse biological reactions.

• They are destroyed at temperatures below 20 °C.

• They slow down reactions that occur in cells.

Which statement about enzymes is essential to the lock-and-key hypothesis?

• Enzymes are catalysts.

• Enzymes can be denatured by high pH values.

• Enzymes can be denatured at high temperatures.

• Enzymes have a distinct active site shape.

The diagrams represent the activity of an enzyme. What are the labelled structures?

• A

• B

• C

• D

Which statement(s) is/are correct?

• Heating enzymes too high above optimum temperature changes the shape of their active sites.

• An enzyme has the same shape as its substrate.

• When a substrate binds to its enzyme, it becomes permanently attached.

The graph shows the results of an experiment on an enzyme-controlled reaction. Which statement explains the shape of the graph above 40 °C?

• The enzyme-substrate complex does not separate.

• The shape of the enzyme's active site is altered.

• The substrate has been denatured by the heat.

• The enzyme has not reached its optimum temperature.

The graph shows the rate of reaction of three different enzymes. Which conclusion can be made from the graph?

• Each enzyme works best at a different pH.

• Each enzyme works best over a small temperature range.

• The enzymes work best in acidic conditions.

• The enzymes work best in alkaline conditions.