Cholesterol is a lipid molecule produced by the liver, then transported to the membranes of animal cells. Cholesterol, which is found embedded in the plasma membrane of animal cells alongside other molecules like phospholipids, plays a vital role there.
The cholesterol of animal cell membranes help increase the fluidity of the membrane and also helps prevent the membrane from freezing during low temperatures.
"An organism in which the two copies of the gene are identical — that is, have the same allele — is called homozygous for that gene. An organism which has two different alleles of the gene is called heterozygous."
