Proteins, Carbohydrates, and Lipids

Vocabulary flashcards covering biological macromolecules, protein folding, carbohydrate structures, and lipid classifications based on lecture notes.

Polymer

A large molecule constructed from smaller repeating subunits called monomers linked by covalent bonds.

Macromolecules

Large polymers composed of thousands or more atoms, including proteins, carbohydrates, and nucleic acids.

Functional Group

A specific combination of atoms attached to a carbon backbone that imparts distinct chemical properties, such as polarity or charge, to biological molecules.

Condensation Reaction

A chemical reaction in which energy is required to form covalent bonds between monomers to construct a polymer, releasing a water molecule ($\text{H}_2\text{O}$) in the process.

Hydrolysis Reaction

A chemical reaction that breaks polymers down into individual monomers by consuming a water molecule ($\text{H}_2\text{O}$) and releasing energy.

Isomers

Molecules that share the exact same chemical formula but have different structural arrangements of their constituent atoms.

Structural Isomers

Molecules with identical chemical formulas that differ in how their atoms are bonded together.

Cis-Trans Isomers

Isomers that differ in the spatial orientation of functional groups attached across a double bond.

Optical Isomers

Molecules that have identical chemical formulas but are non-superimposable mirror images of each other around an asymmetric central carbon atom.

Polypeptide Chain

A single, unbranched polymer chain composed of amino acid monomers connected by peptide bonds.

Amino Acid

An organic monomer featuring an asymmetrical central $\alpha$ carbon bonded to a carboxyl group ($-\text{COOH}$), an amino group ($-\text{NH}_2$), a hydrogen atom, and a variable side chain ($\text{R}$-group).

Disulfide Bridge

A covalent bond ($-\text{S}-\text{S}-$) formed when the terminal sulfhydryl ($-\text{SH}$) group of one cysteine side chain reacts with the sulfhydryl group of another cysteine.

Oligopeptides

Short polymers containing 20 or fewer amino acid monomers joined by peptide linkages.

Peptide Linkage

The covalent amide bond formed through a condensation reaction between the carboxyl group of one amino acid and the amino group of another.

Primary Structure

The precise linear sequence of amino acids in a polypeptide chain.

Secondary Structure

Regular, repeated spatial patterns in a polypeptide chain—such as an $\alpha$ helix or $\beta$ pleated sheet—stabilized by hydrogen bonding between backbone $\text{N}-\text{H}$ and $\text{C}=\text{O}$ groups.

Alpha Helix ($\alpha$ Helix)

A right-handed helical coil secondary structure formed by hydrogen bonding between the $\text{N}-\text{H}$ group of one amino acid and the $\text{C}=\text{O}$ group of another.

Beta Pleated Sheet ($\beta$ Pleated Sheet)

A protein secondary structure formed when two or more aligned polypeptide chains are bound laterally by hydrogen bonds.

Tertiary Structure

The overall three-dimensional shape of a folded polypeptide chain determined by interactions among amino acid $\text{R}$-groups.

Quaternary Structure

The multi-subunit protein assembly resulting from noncovalent and covalent interactions between two or more separate polypeptide chains.

Protein Domain

A distinct, independently folding region of a polypeptide chain that carries out a specific biological function.

Denaturation

The irreversible or reversible loss of a protein's secondary, tertiary, and quaternary structure, rendering it nonfunctional due to disruptive physical or chemical conditions.

Molecular Chaperones

Proteins, such as heat shock proteins, that enclose denatured or newly synthesized unfolded polypeptides to prevent inappropriate binding and assist proper folding.

Monosaccharide

A simple sugar molecule with the basic empirical formula $(\text{C}_1\text{H}_2\text{O}_1)_n$ that serves as the building block for larger carbohydrates.

Glycosidic Bond

A covalent linkage formed between monosaccharide units via a condensation reaction.

Disaccharide

A carbohydrate composed of two monosaccharide units joined covalently by a single glycosidic bond.

Oligosaccharide

A carbohydrate polymer consisting of 3 to 20 monosaccharides linked by glycosidic bonds, often functioning as cell-surface recognition signals when bound to proteins or lipids.

Polysaccharide

A large carbohydrate polymer composed of hundreds or thousands of monosaccharides connected by glycosidic bonds.

Cellulose

An unbranched structural polysaccharide composed of glucose monomers joined by chemically stable $\beta$-1,4 glycosidic bonds found in plant cell walls.

Starch

A branched storage polysaccharide in plants composed of glucose monomers linked by $\alpha$-1,4 and $\alpha$-1,6 glycosidic bonds.

Glycogen

A highly branched storage carbohydrate in animals consisting of glucose polymers connected by $\alpha$-1,4 and $\alpha$-1,6 glycosidic bonds.

Chitin

A chemically modified structural polysaccharide polymer composed of $N$-acetylglucosamine monomers found in arthropod exoskeletons and fungal cell walls.

Triglyceride

A lipid composed of one glycerol molecule linked to three fatty acid chains through ester linkages.

Saturated Fatty Acid

A fatty acid hydrocarbon chain with no carbon-carbon double bonds, fully saturated with hydrogen atoms and typically solid at room temperature.

Unsaturated Fatty Acid

A fatty acid containing one or more carbon-carbon double bonds that introduce kinks into the chain, preventing close packing and keeping it liquid at room temperature.

Trans Fat

An unsaturated fat containing trans carbon-carbon double bonds where hydrogen atoms reside on opposite sides, formed by artificial hydrogenation.

Amphipathic Molecule

A molecule containing both a hydrophilic (polar) domain and a hydrophobic (nonpolar) domain.

Phospholipid Bilayer

A biological membrane structure formed in water where hydrophobic fatty acid tails aggregate interiorly while hydrophilic phosphate heads face outward toward water.

Lipoprotein

A macromolecular particle formed by phospholipids and proteins that transports lipids, such as cholesterol, through the bloodstream.

Carotenoids

Light-absorbing pigment lipids, such as $\beta$-carotene, that capture light energy in plants and break down into Vitamin A in humans.

Steroids

Lipids characterized by a skeleton of four fused carbon rings that function as membrane structural units or signaling hormones.