Macromolecule Fundamentals - Biochemistry

The one letter code for asparagine (asn) is N. The one letter code for aspartic acid (asp) is D. The one letter code for histidine (his) is H. The one letter code for glutamine (gln) is Q.

Cysteine is the only amino acid that forms disulfide bonds. Methionine also contains sulfur but does form these bonds.

Most mammals are unable to digest beta glycosidic bonds, such as the bonds in cellobiose and lactose. Maltose and sucrose both are connected via alpha glycosidic bonds, and can be digested by mammals.

Note: Most mammals are unable to digest lactose after infancy. It is only through a genetic mutation that many humans now are able to ingest lactose well into adulthood.

This is a fact question. A lactone is a cyclic ester, which is a ring of two or more carbon atoms and one oxygen atom with a ketone at one of the carbons adjacent to the other oxygen. Lactones are usually formed via a reaction of a carboxylic acid with a hydroxyl group or halogen atom present in the same molecule.

Maltose is a disaccharide formed from two glucose molecules. Mammals use the enzyme maltase to digest maltose. Lactose is a disaccharide formed from one glucose and one galactose molecule. Mammals use the enzyme lactase to digest lactose. Sucrose is a disaccharide formed from one glucose and one fructose molecule. Mammals use the enzyme sucrase to digest sucrose. Mammals cannot digest cellulose because they do not have the necessary enzymes to do so in their digestive tracts.

Glycogen is a multi-branched glucose polysaccharide that functions in energy storage in animals. Its chemical formula is . In contrast, starch is a glucose polymer which functions in energy storage in plants. Glycogen is also not an artificial sweetener (synthetic sugar substitute). As stated, it is the main storage form of glucose in animals.

Typically, nonpolar amino acids have side chains containing only carbons and hydrogens. The side chain on glycine contains only a hydrogen, and is nonpolar. The side chains on leucine and isoleucine contain nothing but carbons and hydrogens, so they are also nonpolar. Finally, the side chain on tryptophan does contain a nitrogen. However, tryptophan is large enough and contains enough carbons to balance out the increased electronegativity of the nitrogen within the side chain. Therefore, tryptophan, along with the rest of the answer choices, is nonpolar.

The word hydrophobic means "water fearing". Knowing this, you can eliminate the answer choice "near water". Typically, the exterior of a protein is surrounded by water, so we can also eliminate that answer choice. It is true that hydrophobic amino acids will cluster away from water. The interior of a protein typically is away from water, so the correct answer is "Both the interior of a protein and away from water."

A peptide bond is the chemical bond formed between two amino acids to create a polypeptide. The carboxyl group of one amino acid reacts with the amino group of the other amino acid, releasing a molecule of water. This is known as a dehydration reaction.

Glucose can be stored as glycogen, mostly in the liver, and fatty acids are stored in adipose cells. Amino acids, though, can not be stored for future anabolic use in the human body. Therefore, any time there is an excess of amino acids, they are broken down into their constituent parts so that they may be recycled into other molecules.

An essential amino acid is one that can not be synthesized by the human body, and so it must be consumed in the diet. Tyrosine can be synthesized, and is therefore not considered to be an essential amino acid.

Different proteins have different optimal temperature and pH ranges, values at which they function best. Outside of these ranges, they can become denatured. Thus, treatments of heat, low pH, or high pH can cause proteins to denature.

Detergents denature proteins in a different way. Detergents are amphipathic, meaning that they have both hydrophobic and hydrophilic regions. Because all membrane proteins are also amphipathic (they must be in order to remain anchored in the lipid bilayer), the detergent can be attracted to these regions and force the membrane proteins apart.

Non-proteinogenic amino acids are those which are not found in the genetic code of any organism. These are also called "unnatural" amino acids, as compared to "natural" amino acids which are found in the genetic code. Isoleucine, proline, and asparagine are three of approximately one hundred and forty "natural" amino acids. Ornithine is a non-proteinogenic amino acid that has a role in the urea cycle.

Methionine and cysteine are the only amino acids that contain sulfur.

Only two cysteine amino acids can come together to form a disulfide bridge. This disulfide bridge is a covalent bond. Disulfide bridges are a component of tertiary structure in proteins. As a side note, the name of a cysteine amino acid changes to cystine after a disulfide bridge is formed.

Only glycine is nonpolar. The rest of the answer choices are polar. Remember that being nonpolar implies that the substance is hydrophobic and, hence, insoluble in water. Besides methionine, you will notice that the rest of the nonpolar and nonaromatic amino acids have R-groups composed solely of carbon and hydrogen. Polarity of amino acids is quite important when looking at the tertiary, or three dimensional, structure of a protein.

There are only three aromatic amino acids. They are phenylalanine, tyrosine, and tryptophan. Histidine has a positively charged R-group. Proline is a nonpolar amino acid. Serine is a polar amino acid. Threonine is a polar amino acid.

Lipids are capable of storing the most energy per unit weight of any molecule. The complete oxidation of a fatty acid yields , compared to about for carbohydrates and proteins.

Triglycerides and cholesterol are not phospholipids, so they can be eliminated from the answer choices. Phosphatidylinositol and phosphatidylserine are present in cellular membranes, but they are typically less abundant than phosphatidylcholine, which is the correct answer.

Glycolipids, phospholipids, and cholesterol are all major components of membranes. Free fatty acids, however, are not found freely in membranes. Free fatty acids are the tails in phospholipids, sphingolipids and other lipid derivatives, but not cholesterol.