Question

why is the correct answer is D? please simple and short explanation

Number of live cells (log) tooted Time Refer to the figure above. Which of the following statements is CORRECT regarding the figure. Cells are actively growing only during the stage represented by B. B) No cells are reproducing during the stage represented by D. C) Cells are most susceptible to antibiotics during the stage represented by A.D) Cells are alive but not reproducing during the stage represented by A. E) No new cells are being produced during the stage represented by C.

Answer 1

The correct answer among the given statements is option D.

Let us understand why the other options are wrong.

A) Cells are actively growing only during the stage represented by B

In this case, definitely B represents the exponential/log phase where rapid growth occurs with ideal environment and nutrients present in excess. It is important to note here that curve C also represents active growth, but here the number of new cells produced is equal to the number of cells dying. This is known as the stationary phase where the population runs out of essential nutrient or growth is inhibited by certain by-products of its own metabolism.

B) No cells are reproducing during the stage represented by D.

Certain number of cells do reproduce but overall the viability is decreasing.

C) Cells are most susceptible to antibiotics during the stage represented by A

Cells in the phase A are actually preparing to adapt to the environmental conditions. It is known as the lag phase where cells are synthesizing RNA, essential enzymes or metabolites, adjusting to pH, temperature and oxygen available and repairing the injured cells. This is not ideal for antibiotics.

Antibiotics act best when cells are in the log phase (stage B) when cells are actively diving.

D) Cells are alive but not reproducing during the stage represented by A

This statement is true as explained in option C

E) No new cells are being produced during the stage represented by C.

This statement is wrong, as growth occurs but number of cells being produced is equal to number of cells dying.