Which sequence shows cells of increasing size (from left to right)?
A. E. coli → human red blood cell → onion epidermal cell
B. human red blood cell → E.coli → onion epidermal cell
C. E. coli → onion epidermal cell → human red blood cell
D. onion epidermal cell → human red blood cell → E. coli
E. onion epidermal cell → E. coli → human red blood cell
The correct answer is A.
Escherichia coli is a bacteria that lives, in physiological conditions, inside the intestines of warm-blooded organisms. Knowing that it is a bacteria helps you identify that this is the smallest structure among the 3 options. Its size is around 1 to 2 µm long.
Human red blood cells (RBC) transport the oxygen to the body’s tissues. Its size is about 7 to 8µm.
Onion epidermal cells are pretty large : they are around 0.25mm.