The tertiary structure of a protein is created by various interactions between the R groups in the chain. This makes the protein fold three-dimensionally.

One example would be ionic bonds forming between a positively charged R group and a negatively charged R group. Covalent disulfide bonds will create a tertiary shape between two cysteine amino acids. Hydrophobic R groups will also contribute to the structure, bending toward one another to avoid contact with the aqueous environment.

The four basic biological macromolecules carry out virtually every metabolic process of living organisms. Keep in mind that these molecules work together to achieve common goals. For example, enzymes (proteins) are used to help break down glucose (carbohydrate) in glycolysis. One product of glycolysis is energy in the form of ATP. ATP can be used to polymerize nucleotides (nucleic acids) to copy DNA.

The functions of specific types of macromolecules are highly dependent on their structures. For example, firbous proteins are used to provide structural support, while globular proteins are better suited to catalyze reactions as enzymes. The variety of macromolecular structures is directly related to the multitude of functions these molecules can facilitate.

Proteins are synthesized through dehydration synthesis reactions, which is the removal of water between two amino acids. In this case, two hydrogen atoms are removed from the amine group and one oxygen is removed from the carboxyl group, forming a peptide bond between the carbon atom of one amino acid and the nitrogen atom of the other amino acid.

All amino acids contain carbon, hydrogen, oxygen, and nitrogen. These elements create a carboxylic acid group and an amine group, which can fuse to form a peptide bond. Peptide bonds hold amino acids together and generate the primary structure of the protein.

Cysteine, a specific amino acid, also contains sulfur. Thus, the correct answer is that carbon, oxygen, hydrogen, nitrogen, and sulfur can all be found in amino acids.

Phosphorus is never found in amino acids, but plays an important role in the structure of nucleic acids, such as DNA, and in the modification and activation of proteins.

A quaternary protein structure is made up of two or more polypeptide chains that fit together based on their shape and polarities, like a jigsaw puzzle. The subunits also fit together by forces of attraction between positively charged regions and negatively charged regions. Not all proteins have quaternary structure.

DNA—deoxyribonucleic acid—is found in chromosomes within a cell’s nucleus. A complete set of DNA (i.e. 46 chromosomes) is called a genome. DNA contains instructions that make humans different from other species and other individuals. DNA provides instructions for all the proteins that the body makes and is passed from adults to offspring. DNA cannot get out of the nucleus; however, RNA can. RNA is used to get the instructions from DNA out of the nucleus and into the site of protein synthesis: the ribosomes within the cytoplasm. Proteins are made of amino acids and determine the structure and function of all of the body’s cells; therefore, this process can be simplified into “DNA to RNA to protein.”

The sequence of amino acids is called a protein's primary structure. Each protein has a unique sequence of amino acids. A difference of just one amino acid in a chain of hundreds can be deadly to the organism. For example, mutation leading to a single amino acid change is responsible for sickle cell anemia.

Active transport is used to carry amino acids from the lumen of the small intestine into the blood stream. Active transport requires the use of energy (ATP) in order to transport molecules. In this case, amino acids are large, blulky, and frequently polar. All of these characteristics make them hard to transport across a plasma membrane.

The pH of a solution is defined as the the concentration of H+ ions in the solution. The pH of a solution declines as H+ concentration increases. On the pH scale, ranging from 0 to 14, 7 is neutral. Substances below 7 are more acidic, 0 being the most acidic. Substances above 7 are more basic, 14 being the most basic.

“Composed of plutonium” is not a characteristic of a living organism. The other three choices are characteristics of living organisms. Organisms use energy in their metabolic processes. Organisms reproduce either asexually or sexually to make offspring for the next generation. Organisms from the simplest prokaryote to the human species contain DNA—the universal genetic code.