Amino acids are the building blocks of proteins and are encoded by sequences of three nucleotides in DNA, known as codons. Each nucleotide is composed of a sugar, a phosphate, and one of four nitrogenous bases (adenine [A], cytosine [C], guanine [G], or thymine [T] in DNA; uracil [U] replaces thymine in RNA). Therefore, it takes 3 base pairs (bp) in the DNA to code for a single amino acid. This rule is part of the genetic code, which is nearly universal across all living organisms, highlighting the fundamental role of DNA in encoding the proteins that perform essential functions in cells.

Creating a polymer membrane in a laboratory setting requires precise steps and attention to detail. Firstly, choose an appropriate polymer based on your application's needs. Common polymers include polyethersulfone (PES), polyvinylidene fluoride (PVDF), and cellulose acetate (CA). Next, dissolve the polymer in a solvent such as N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). The concentration of the polymer solution typically ranges from 10% to 25% by weight. After preparing the polymer solution, degas it under vacuum to remove air bubbles. Then, use a casting knife or a slot-die coater to cast the solution onto a flat, clean surface. Allow the solvent to evaporate naturally at room temperature or control the rate using a water bath. Finally, peel off the dried membrane carefully and store it properly. Consider optimizing parameters like polymer concentration and casting speed to tailor the membrane's properties.

The letter that represents a carbohydrate polymer is "C." Carbohydrate polymers are large, complex molecules composed of long chains of monosaccharide units. These include substances such as starches, cellulose, and glycogen, which play critical roles in biological processes and as energy stores in organisms. Polysaccharides, as they're scientifically known, are integral to both plant and animal life, serving structural functions in plants and energy storage in animals.