Chapter 5: The Structure and Function of Large Biological Molecules

Vocabulary practice flashcards covering biological macromolecules, protein structures, nucleic acids, and molecular sequencing concepts from Chapter 5.

Peptide bond

A covalent bond in which two amino acids are joined by a dehydration reaction.

Dipeptide

A polymer of two amino acids linked together by a peptide bond.

Polypeptide

A polymer of many amino acids linked together by peptide bonds.

Dehydration synthesis

The synthesis of monomers into polymers through the removal of water molecules.

Nonpolar R groups

Hydrophobic amino acid side chains that commonly include hydrocarbons or methyl groups.

Polar R groups

Hydrophilic amino acid side chains that contain polar chemical groups.

Electrically charged R groups

Hydrophilic amino acid side chains that include positively or negatively charged groups (acidic or basic).

Enzymatic proteins

Proteins that accelerate chemical reactions; examples include maltase, pepsin, and sucrase.

Storage proteins

Proteins responsible for storing amino acids, such as casein in milk and ovalbumin in egg whites.

Defensive proteins

Proteins such as antibodies that protect against disease by inactivating and helping destroy viruses and bacteria.

Primary structure

The linked series of amino acids with a unique sequence in a protein, illustrated by transthyretin.

Secondary structure

Coils and folds in a polypeptide resulting from hydrogen bonds between repeating constituents of the polypeptide backbone, forming $\text{α}$ helices and $\text{β}$ pleated sheets.

Alpha ($\text{α}$) helix

A delicate coil in a protein's secondary structure held together by hydrogen bonding between every fourth amino acid.

Beta ($\text{β}$) pleated sheet

A secondary structure where two or more strands of the polypeptide chain lie side by side, connected by hydrogen bonds between parallel backbones.

Tertiary structure

The overall three-dimensional shape of a polypeptide resulting from interactions between side chains (R groups) of various amino acids.

Quaternary structure

The overall protein structure resulting from the aggregation of two or more polypeptide subunits, such as in collagen, hemoglobin, and globular transthyretin.

Disulfide bridge

A strong covalent link between the sulfhydryl groups of two cysteine amino acids (sulfur to sulfur) that stabilizes tertiary protein structure.

Sickle-cell disease

An inherited blood disorder caused by the substitution of valine for glutamic acid in hemoglobin, causing red blood cells to crystallize into long fibers and assume a sickle shape.

Denaturation

The process in which a protein unravels and loses its native shape due to the destruction of weak chemical bonds caused by alterations in pH, salt concentration, temperature, or solvents.

Ribosome

A tiny structure in the cytoplasm of eukaryotic cells that serves as the site of protein synthesis by translating genetic instructions conveyed by mRNA.

Nucleotide

The monomer of a nucleic acid, composed of a five-carbon sugar (pentose), a nitrogen-containing base, and one to three phosphate groups.

Deoxyribose

The pentose sugar found in DNA nucleotides that lacks an oxygen atom on the second carbon in the ring.

Double helix

The three-dimensional shape of DNA proposed by James Watson and Francis Crick, consisting of sugar-phosphate uprights and nitrogenous base pair rungs.

Antiparallel

The structural arrangement of the DNA double helix where the two complementary strands run in opposite $5' \rightarrow 3'$ directions.

Genomics

An area of study involving the complete sequencing and analysis of genomes across numerous species to understand evolutionary connections.

Proteomics

The large-scale analysis of protein data sets resulting from genome translation, applied in personalized medical care such as sequencing tumor genes.

Polysaccharides

Carbohydrate polymers acting as fuel storage (starch in plants, glycogen in animals) or structural support (cellulose in plant cell walls, chitin in exoskeletons and fungal walls).

Phospholipids

Lipids consisting of a glycerol bonded to two fatty acids and a phosphate group, forming hydrophilic heads and hydrophobic tails that assemble into membrane bilayers.

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings, functioning as cell membrane components (cholesterol) or signaling molecules (hormones).