Large Biological Molecules and Cell Membrane Transport Vocabulary

A comprehensive vocabulary review of carbon chemistry, functional groups, macromolecules (carbohydrates, lipids, proteins, nucleic acids), cell structures, and membrane transport concepts from Chapters 4, 5, 6, and 7.

Hydrocarbon

An organic molecule consisting solely of carbon and hydrogen atoms, which is nonpolar, hydrophobic, and capable of storing large amounts of energy.

Structural Isomer

Compounds that possess the same molecular formula but differ in the covalent arrangement of their constituent atoms.

Geometric Isomer

Compounds that have identical covalent bonds but differ in the spatial arrangement of atoms or groups around a double bond.

Enantiomer

Molecules that are non-superimposable mirror images of each other due to the presence of an asymmetric carbon.

Functional Group

A specific configuration of atoms attached to a carbon skeleton that directly participates in chemical reactions and determines molecular properties.

Hydroxyl Group

A polar functional group ($-OH$) consisting of a hydrogen atom bonded to an oxygen atom, characteristic of alcohols and sugars, which increases water solubility.

Carbonyl Group

A functional group ($>C=O$) consisting of a carbon atom double-bonded to an oxygen atom, found in aldehydes at the end of a carbon skeleton and ketones within a carbon skeleton.

Carboxyl Group

An acidic functional group ($-COOH$) combining carbonyl and hydroxyl groups that donates $H^+$ ions in solution.

Amino Group

A basic functional group ($-NH_2$) containing nitrogen that acts as a base by accepting $H^+$ ions to become positively charged ($-NH_3^+$).

Sulfhydryl Group

A functional group ($-SH$) containing sulfur and hydrogen that can form covalent disulfide bridges to stabilize protein structure.

Phosphate Group

A negatively charged functional group ($-PO_4^{2-}$) that contributes negative charge, plays an essential role in ATP energy transfer, and forms part of nucleic acid backbones.

Methyl Group

A nonpolar functional group ($-CH_3$) consisting of a carbon atom bonded to three hydrogen atoms that affects gene expression and molecular shape.

Adenosine Triphosphate (ATP)

An organic molecule consisting of adenine, ribose, and three phosphate groups that releases usable cellular energy when hydrolyzed to ADP and inorganic phosphate.

Monomer

A small chemical subunit that serves as a building block for a larger polymer.

Polymer

A long chain molecule consisting of many similar or identical monomer subunits linked together by covalent bonds.

Dehydration Reaction

A chemical reaction in which two monomers become covalently bonded to each other with the simultaneous loss of a water molecule.

Hydrolysis

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

Monosaccharide

The simplest carbohydrate monomer, with a general molecular formula $(CH_2O)_n$, occurring in linear or ring forms in aqueous solution.

Disaccharide

A double sugar consisting of two monosaccharides joined together by a glycosidic linkage formed via a dehydration reaction.

Glycosidic Linkage

A covalent bond formed between two monosaccharides by a dehydration reaction.

Starch

A plant energy storage polysaccharide consisting entirely of $\text{α}$-glucose monomers, stored in plastids as unbranched amylose or branched amylopectin.

Glycogen

An extensively branched animal energy storage polysaccharide made of $\text{α}$-glucose monomers, stored primarily in liver and muscle cells.

Cellulose

An unbranched structural polysaccharide component of plant cell walls consisting of $\text{β}$-glucose monomers connected by $\text{β}$-1,4 glycosidic linkages.

Chitin

A structural polysaccharide containing modified glucose monomers with nitrogen, found in arthropod exoskeletons and fungal cell walls.

Lipid

A diverse group of hydrophobic biological molecules that are not polymers or macromolecules, primarily composed of carbon and hydrogen.

Triglyceride

A fat molecule consisting of one glycerol bonded to three fatty acid chains via ester linkages formed through dehydration synthesis.

Saturated Fatty Acid

A fatty acid chain containing only single covalent bonds between carbon atoms, resulting in a straight chain saturated with hydrogen that is solid at room temperature.

Unsaturated Fatty Acid

A fatty acid chain containing one or more double bonds that produce kinks in the chain, rendering it liquid at room temperature.

Phospholipid

An amphipathic lipid composed of glycerol attached to two hydrophobic fatty acid tails and a hydrophilic polar phosphate head group.

Amphipathic

Describing a molecule that contains both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

Steroid

A lipid characterized by a carbon skeleton consisting of four fused rings, such as cholesterol and steroid hormones.

Peptide Bond

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

Polypeptide

A linear polymer chain of amino acids connected by peptide bonds, synthesized in direction from the N-terminus to the C-terminus.

Primary Structure

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

Secondary Structure

Repetitive coiling ($\text{α}$-helix) or folding ($\text{β}$-pleated sheet) of a polypeptide chain formed by hydrogen bonds between backbone atoms.

Tertiary Structure

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

Quaternary Structure

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

Denaturation

A process in which physical or chemical conditions (such as pH, salt concentration, or temperature) cause a protein to unravel and lose its active native conformation.

Chaperonin

A protein complex consisting of a hollow cylinder and cap that provides a hydrophilic environment for the proper folding of unfolded polypeptides.

Polynucleotide

A polymer of nucleic acids consisting of multiple nucleotide monomers linked together by a sugar-phosphate backbone.

Nucleotide

A nucleic acid monomer consisting of a 5-carbon pentose sugar, a nitrogenous base, and a phosphate group.

Pyrimidine

A family of nitrogenous bases characterized by a single six-membered ring, including cytosine (C), thymine (T, DNA only), and uracil (U, RNA only).

Purine

A family of nitrogenous bases characterized by a six-membered ring fused to a five-membered ring, including adenine (A) and guanine (G).

Antiparallel

The structural arrangement of the two complementary strands in a DNA double helix, running in opposite $5' \rightarrow 3'$ and $3' \rightarrow 5'$ directions.

Fluid Mosaic Model

The model depicting cell membrane structure as a flexible phospholipid bilayer containing a mosaic of diverse embedded and attached proteins.

Selective Permeability

The property of biological membranes that allows some substances to cross more easily than others.

Diffusion

The passive net movement of particles down their concentration gradient toward lower concentration without energy expenditure.

Osmosis

The diffusion of free water molecules across a selectively permeable membrane toward a higher solute concentration.

Facilitated Transport

The passive movement of molecules across a membrane down their concentration gradient via specific channel or carrier transport proteins.

Active Transport

The movement of a substance across a membrane against its concentration gradient, requiring carrier proteins and cellular energy expenditure (ATP).

Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+$-ATPase)

A primary active transport protein that pumps $3\text{​Na}^+$ ions out of the cell and $2\text{​ K}^+$ ions into the cell per cycle using ATP.

Electrochemical Gradient

The combined effect of a chemical concentration gradient and an electrical force (voltage) across a membrane acting on an ion.

Phagocytosis

A form of endocytosis ('cellular eating') in which a cell engulfs large particles or whole cells into a vesicle.

Pinocytosis

A form of endocytosis ('cellular drinking') in which a cell continuously gulps droplets of extracellular fluid into small vesicles.

Receptor-Mediated Endocytosis

A specialized type of endocytosis where specific bulk transport is triggered by ligands binding to membrane-bound receptors.