Biology Review: Proteins, Nucleic Acids, and Carbohydrates

Vocabulary practice flashcards covering fundamental concepts of proteins, nucleic acids, and carbohydrates from Chapters 3, 4, and 5.

Carboxyl Group (in Amino Acids)

A functional group ($-\text{COOH}$) present on every amino acid that acts as an acid by donating a proton at cellular pH (about pH $7$).

Amino Group (in Amino Acids)

A functional group ($-\text{NH}_2$) present on every amino acid that acts as a base by accepting/gaining a proton at cellular pH (about pH $7$).

R-Group (Side Chain)

The variable component attached to the central carbon of an amino acid that distinguishes the $20$ different amino acids from one another and determines their chemical properties (such as polar, nonpolar, hydrophobic, or hydrophilic).

Hydrophobic Amino Acid

An amino acid whose R-group consists only of hydrogen and carbon atoms; when folded in aqueous solutions, these side chains congregate together and are stabilized by van der Waals interactions.

Hydrophilic Amino Acid

An amino acid whose R-group exhibits affinity for water, such as a short chain of hydrogen and carbon atoms terminated by a negatively charged carboxylic acid.

Peptide Bond

A covalent linkage formed between amino acid monomers through a condensation reaction that releases a water molecule, establishing the primary structure of proteins.

Primary Structure (Protein)

The linear sequence of amino acids joined by peptide bonds; it is the highest structural level of a completely linear protein and the level least affected or preserved when all hydrogen bonds are disrupted.

Secondary Structure (Protein)

Localized structural conformations—specifically the $\alpha$-helix and $\beta$-pleated sheet (predominant in keratin)—that are stabilized by hydrogen bonds.

Tertiary Structure (Protein)

The fully folded, $3\text{D}$ polypeptide conformation governed primarily by interactions among the side chains (R-groups).

Protein Denaturation

The structural unraveling of proteins caused by conditions such as a rising fever, which severely impairs biological functions.

Nucleotide

The monomer of nucleic acids, consisting of three components: a nitrogenous base, a pentose sugar, and a phosphate group.

Ribonucleotide vs. Deoxyribonucleotide

Ribonucleotides possess a hydroxyl group ($-\text{OH}$) on the second carbon atom of their pentose sugar, whereas deoxyribonucleotides lack this oxygen atom and have a hydrogen atom ($-\text{H}$) instead.

Phosphate Group (in Nucleic Acid Formation)

The feature of single nucleotides that supplies the necessary energy for polymerization when nucleic acids are synthesized.

Phosphodiester Bond

A covalent bond in nucleic acids formed between the sugar of one nucleotide and the phosphate group of a second (via a condensation reaction releasing water), analogous to a peptide bond in polypeptides.

Pyrimidines

A class of nitrogenous bases found in DNA and RNA, comprising uracil, cytosine, and thymine.

Histones

Large proteins around which DNA wraps to organize and form the tertiary structure of DNA.

Adenosine Triphosphate (ATP)

An energy-rich molecule that is structurally similar to individual nucleotides.

Complementary Base Pairing

The structural pairing of nitrogenous bases via hydrogen bonding (e.g., $5'\text{-ATTGCA-}3'$ pairing with $3'\text{-TAACGT-}5'$) that stabilizes DNA's double-stranded secondary structure and enables replication.

RNA (Ribonucleic Acid)

A typically single-stranded nucleic acid involved primarily in protein synthesis; thought to be the first self-replicating molecule because it can both store genetic information and act as a catalyst.

Aldose vs. Ketose

The classification of monosaccharides determined by the location of the carbonyl group ($-\text{C=O}$) along the carbon backbone.

$\alpha$ and $\beta$ Forms of Glucose

Two conformational isomers of glucose ($\text{C}_6\text{H}_{12}\text{O}_6$) that differ in the spatial position/location of their hydroxyl group ($-\text{OH}$).

$$\alpha\text{-1,6-glycosidic Linkage}$$

The type of covalent linkage found specifically at branch points in complex carbohydrates such as glycogen and amylopectin.

Peptidoglycan

A complex carbohydrate containing at least one peptide bond, commonly studied as a target for developing new antibacterial antibiotics.

Starch vs. Glycogen

Storage polysaccharides whose primary structural difference lies in their degree of branching.

Chitin

A structural polysaccharide that serves as an important component in the anatomy and cell walls of many animals and fungi.

Lactose

A milk disaccharide composed of one glucose molecule joined to one galactose molecule by a glycosidic linkage.