BIO 202 - LEC 3

Vocabulary flashcards covering key concepts of protein structure, functions, amino acid properties, levels of protein organization, denaturation, and molecular mutations from Campbell Biology Chapter 5.

Glycosidic Linkage

A covalent bond formed between two monosaccharide monomers through a dehydration reaction.

Phosphodiester Linkage

A covalent bond connecting adjacent nucleotide monomers between the sugar of one nucleotide and the phosphate group of another.

Deoxyribonucleoside Triphosphates (dNTPs)

Nucleotide monomers containing three phosphate groups that enter a growing DNA strand during nucleic acid synthesis.

Pyrophosphate ($\text{PP}_i$)

A molecule consisting of two bound phosphate groups released together during nucleotide addition.

Enzymatic Proteins

Proteins that function in the selective acceleration of chemical reactions, such as digestive enzymes catalyzing bond hydrolysis in food.

Defensive Proteins

Proteins that protect an organism against disease, such as antibodies that inactivate and destroy viruses and bacteria.

Storage Proteins

Proteins that store amino acids for later use, such as casein in milk and ovalbumin in egg whites.

Transport Proteins

Proteins responsible for carrying substances throughout an organism or across cellular membranes, such as oxygen-carrying hemoglobin.

Hormonal Proteins

Proteins that coordinate an organism's activities, such as insulin secreted by the pancreas to regulate blood glucose concentration.

Receptor Proteins

Membrane-embedded proteins that allow cells to respond to external chemical stimuli by binding specific signaling molecules.

Contractile and Motor Proteins

Proteins involved in movement, such as actin and myosin in muscle contraction and motor proteins driving cilia and flagella.

Structural Proteins

Proteins that provide physical framework and support, such as keratin in hair and feathers, or collagen in animal connective tissues.

Alpha ($\alpha$) Carbon

The central carbon atom of an amino acid that is covalently bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R group.

Zwitterion

An amino acid state occurring near neutral $\text{pH}$ having a net charge of $0$, consisting of a protonated amino group ($\text{H}_3\text{N}^+$) and a deprotonated carboxyl group ($\text{COO}^-$).

Non-Polar Side Chains

Hydrophobic amino acid side chains lacking significant charge that tend to cluster away from aqueous environments.

Polar Side Chains

Hydrophilic, uncharged amino acid side chains containing electronegative atoms capable of forming hydrogen bonds with water.

Acidic Side Chains

Hydrophilic amino acid side chains containing carboxyl groups that carry a net negative charge at physiological $\text{pH}$.

Basic Side Chains

Hydrophilic amino acid side chains containing amino groups that carry a net positive charge at physiological $\text{pH}$.

Aliphatic Side Chains

Hydrophobic side chains consisting of straight or branched non-aromatic hydrocarbon chains.

Aromatic Side Chains

Amino acid side chains containing rigid ring structures with conjugated $\pi$-electron systems.

Peptide Bond

The covalent bond linking the carboxyl group of one amino acid to the amino group of another via a dehydration reaction.

Dehydration Reaction

A condensation reaction where two monomers are covalently bonded together with the loss of a water molecule.

Hydrolysis

A chemical reaction that breaks covalent bonds between monomer subunits in a polymer through the addition of a water molecule.

Primary Structure

The unique, linear sequence of amino acids in a polypeptide chain determined by inherited genetic information.

N-terminus (Amino Terminus)

The starting end of a polypeptide chain featuring a free amino group.

C-terminus (Carboxyl Terminus)

The terminating end of a polypeptide chain featuring a free carboxylate group.

Secondary Structure

Repetitive localized coils and folds in a polypeptide backbone caused by hydrogen bonds between repeating backbone constituents.

Alpha ($\alpha$) Helix

A delicate helical coil secondary structure held together by hydrogen bonding between every fourth amino acid in the polypeptide backbone.

Beta (\target{\beta}) Pleated Sheet

A secondary protein structure formed by hydrogen bonds between two or more parallel or antiparallel polypeptide strands.

Tertiary Structure

The overall three-dimensional shape of a single polypeptide chain determined by interactions among variable amino acid side chains (R groups).

Disulfide Bridges

Strong covalent bonds formed when the sulfhydryl groups of two cysteine monomers react, reinforcing protein tertiary structure.

Quaternary Structure

The overall protein structure resulting from the association of two or more individual polypeptide subunits.

Collagen

A fibrous structural protein consisting of three helical polypeptides coiled around one another like a rope.

Hemoglobin

A globular transport protein consisting of four polypeptide subunits (two $\alpha$ and two $\beta$) that carries oxygen in vertebrate blood.

X-Ray Crystallography

An experimental technique used to determine the 3D molecular structure of a protein by analyzing the diffraction pattern of X-rays passed through a crystal.

Denaturation

The process in which a protein loses its native shape and becomes biologically inactive due to disruption of weak bonds by changes in $\text{pH}$, salt concentration, or temperature.

Renaturation

The refolding of an unfolded or denatured protein back into its functional, native three-dimensional conformation once denaturing conditions are removed.

Conservative Substitution

An amino acid substitution where a original residue is replaced by one with similar chemical properties, resulting in minor structural impacts.

Non-Conservative Substitution

An amino acid substitution where a residue is replaced by one with distinctly different chemical properties (size, charge, or polarity), frequently disrupting protein folding or function.

Sickle-Cell Disease

An inherited blood disorder caused by a single amino acid substitution (valine substituted for glutamic acid at position 6) in the $\beta$ subunit of hemoglobin, causing hemoglobin aggregation and cell deformation.