Prokaryotes and Enzymes

The bacterium Sorangium cellulosum and the fungus Armillaria mellea are both found in soil.

Which of the rows in the table, A to D, correctly shows the structures present in each organism?

• Row A

• Row B

• Row C

• Row D

Which of the options, A to D, occurs in the nucleus of a cell?

• synthesis of enzymes

• synthesis of RNA

• modification of polypeptides

• synthesis of carbohydrates

Which of the following, A to D, is an incorrect statement about enzymes?

• amylase and trypsin catalyse extracellular reactions

• catalase catalyses intracellular reactions

• extracellular enzymes are produced outside the cell

• Intracellular enzymes work inside the cell

Cyanobacteria are photoautotrophs and fossil records confirm their existence 3.5 billion years ago.

Which row in the table describes the structure of cyanobacteria?

• Row A

• Row B

• Row C

• Row D

Fig. 2.1 shows the shapes of an enzyme molecule, its substrate and the molecules of three substances, P, Q and R. Each substance could bind either to the enzyme or to the substrate to cause an effect. Four tubes were set up:

·         The control contained enzyme and substrate only

·         Tube P contained enzyme, substrate and substance P

·         Tube Q contained enzyme, substrate and substance Q

·         Tube R contained enzyme, substrate and substance R.

Which option in the table describes the most likely effect on the rate of reaction in each tube compared with the control?

• Row A

• Row B

• Row C

• Row D

Which of the following factors does not affect the shape of the active site of an enzyme?

• a drop in temperature

• non-competitive inhibitor

• a change in pH

• binding of substrate

Enzymes are capable of affecting the metabolism and structure of whole organisms. Which of the following enzymes will have the greatest effect on the development of an organism as a whole?

• Methyltransferase: adds methyl groups to DNA allowing genes to be switched on or off

• Reverse transcriptase: generates complementary DNA from an RNA template

• Deoxyribonuclease: digests free DNA molecules outside of the nucleus

• Telomerase: lengthens ends of chromosomes by adding DNA sequences, preventing them from being degraded

A group of students monitored the substrate concentration during an enzyme-controlled reaction.

Select the graph that correctly shows how the substrate concentration changes during the course of the reaction

• Graph A

• Graph B

• Graph C

• Graph D

A chemical produced by a metabolic pathway binds to the initial enzyme in the pathway. The chemical binds to the enzyme at a site away from the active site and inhibits the enzyme action. Which of the following statements about the mode of action of the chemical is / are correct?

Statement 1: It is an end product inhibitor.

Statement 2: It is a competitive inhibitor.

Statement 3: It binds to the allosteric site of the enzyme.

• 1, 2 and 3

• Only 1 and 2

• Only 1 and 3

• Only 1

A student investigated the effect of pH on the rate at which an enzyme breaks down a substrate. What would be a suitable control for this investigation?

An identical tube set up with.......

• no buffer

• no buffer and no enzyme

• no enzyme

• no substrate