In yeast cells, the process that occurs when there is not enough oxygen for aerobic respiration is called
a) fermentation.
b) mastication.
c) phagocytosis.
d) transcription.

the three components of a nucleotide are the nitrogenous base, the phosphate group and the five-carbon sugar.

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.

well the answer is 2!

answer: b

coz red blood cells marrow and circulates the body for 120 days.