Fundamental Macromolecules and Concepts - 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.

Cohesion is defined as attraction between the same type of molecule. Water attracts other water molecules because it is polar and has partial charges. This attraction means that water has strong intermolecular forces even at room temperature and more thermal energy is required to vaporize it. Adhesion involves the attraction of a substance with a container or surface.

Two orthophosphates are connected via anhydride linkage to form the high energy pyrophosphate. This is the "" bond. Glycosidic linkage describes a bond between two or more sugar molecules, not between orthophosphates. This anhydride linkage is made up of single bonds, and not double or triple bonds. An amide bond is the specific chemical name for a peptide bond.

All DNA contains 50% purines and 50% pyrimidines due to Watson-Crick base pairing.

However, doing the calculations based on the information given can also give the correct answer. Adenine (A) and guanine (G) are purines. Cytosine (C) and thymine (T) are pyrimidines. Chargaff's rules state that in DNA, G = C and A = T. If the sample is 15% G, then it must also be 15% C. This leaves 70% for A and T, or 35% each. 15% C + 35% T = 50% pyrimidines.

Chargaff's rules state that guanine (G) = cytosine (C) and adenine (A) = thymine (T). Therefore, since the sample contains 35% C, it must also contain 35% G. 100% - 70% (G + C) leaves 30% left for A and T, or 15% T.

The lagging strand is made up of Okazaki fragments due to discontinuous replication. Each of the fragments has its own primer made from RNA that needs to be removed and replaced with dNTPs. The exonuclease performs this function. A ligase comes through immediately after the exonuclease and joins the fragments together. Helicase is the enzyme that separates the DNA strands.

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.