Amino acids are named after two of their functional groups: the amino group (NH2), which acts like a base, and the carboxyl group (COOH), which acts like an acid. A third functional group, often called the R group, varies among the different types of amino acids. In alanine, the R group is a methyl group (CH3). In serine, the R group is a methyl alcohol (-CH2OH).

the backbone of the dna and rna compound is sugar phosphate.

the correct answer is - d. china has a large and growing population.

the fact that china has a large (the biggest) population, and it is still growing, doesn't hinder the agriculture production in the country. in fact, it can for increased production in the agriculture, since there's more labor force, as well the sheer mass of people produces lots of scientists that come up with new inventions as to how to improve this sector. nice example is the inner mongolia region in china, in general dominated by the gobi desert, but few scientist came up with a nice idea as to how to make the region productive by using plants that are very resistant to droughts, so lots of people have been employed, and the region is becoming greener and greener each year, and the production of food in this region is also increasing.

a scenario where a cell may be needed to perform a form of endocytosis is when transporting large molecules. a scenario where a cell may be needed to perform a form of exocytosis is when releasing the large molecule from the cell.