Chapter 1-5: Introduction to Macromolecules (Proteins, Nucleic Acids, Carbohydrates, Lipids)

A set of Q&A flashcards covering key concepts from the lecture notes on amino acid peptide bonds, nucleotides and nucleic acid structure, base pairing, carbohydrate monomers and glycosidic bonds, sugar conformations, and introductory lipids.

What bond forms to link amino acids into proteins, and how many bonds form when five amino acids are linked?

Peptide bonds; for five amino acids linked, there are four peptide bonds (n−1).

What are the three components of a nucleotide?

A nitrogenous base, a phosphate group, and a five‑carbon sugar (pentose).

What sugar is found in RNA, and what sugar is found in DNA?

RNA contains ribose; DNA contains deoxyribose (lacks the 2' OH on the sugar).

In a nucleotide, where is the phosphate group attached and how does the chain extend?

The phosphate is attached to the 5' carbon of the sugar; nucleotides extend by forming phosphodiester bonds between the 3' hydroxyl of one sugar and the 5' phosphate of the next nucleotide.

What type of bond links nucleotides to form nucleic acids?

Phosphodiester bond.

What is meant by 5' and 3' ends, and where is the next nucleotide added during polymerization?

Directionality is 5' to 3'; the next nucleotide is added to the 3' end.

Which bonds hold the two DNA strands together and why are they suitable for replication?

Hydrogen bonds between complementary bases; they are weak and can be easily separated for replication.

Which bases are pyrimidines, and which are purines?

Pyrimidines: cytosine (C), thymine (T), uracil (U); Purines: adenine (A), guanine (G).

What base-pairing rule is described by Chargaff’s rule for DNA and RNA?

In DNA, A pairs with T and G pairs with C; in RNA, A pairs with U and G with C.

Which bases pair in DNA and which are single-ring vs double-ring structures?

Pyrimidines (C, T, U) are single-ring; Purines (A, G) are double-ring.

Name the three common monosaccharides and their chemical formula.

Glucose, galactose, and fructose; all have the formula C6H12O6 and are isomers.

Which of the three monosaccharides are aldoses and which is a ketose?

Glucose and galactose are aldoses; fructose is a ketose.

What is a glycosidic bond, and what are its possible orientations?

A glycosidic bond links monosaccharides; it can be alpha or beta depending on the orientation.

Do sugars prefer linear or cyclic forms in biological systems, and why?

Sugars predominantly exist in cyclic forms in solution because cyclic structures are more stable biologically.

Are lipids macromolecules? What general features define them in water?

Lipids are not macromolecules; they are biological molecules comprised mainly of hydrocarbons and are largely nonpolar (hydrophobic) in water, though some lipids have polar head groups and can be amphipathic.

What functional group is characteristic at the end of fatty acids in lipids, and what property does this impart?

A carboxyl group; this provides some polarity at one end while the hydrocarbon tail remains hydrophobic.