Pleas hel Which of the following explains the flexible nature of plant stems?
a. Cell volume of parenchyma cells
b. Thickness of cell wall in collenchyma cells
c. Lack of nucleus in sclerenchyma cells
d. Presence of cellulose in plant cell wall

D. I.

maybe its D, I think it might be D

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.

the most common type of reef is the fringing reef. this type of reef grows seaward directly from the shore. they form borders along the shoreline and surrounding islands.