Chapter 5: The Structure and Function of Large Biological Molecules

Vocabulary flashcards covering the key terms and concepts of biological macromolecules, including carbohydrates, lipids, proteins, and nucleic acids.

Macromolecules

Very large biological molecules (generally $> 100,000\text{ daltons}$) that include carbohydrates, proteins, and nucleic acids.

Polymer

A long molecule consisting of many similar building blocks called monomers.

Monomer

A small building-block molecule that forms polymers through condensation reactions.

Dehydration reaction

A condensation reaction in which two monomers form a covalent bond through the removal of a water molecule.

Hydrolysis

A reaction that breaks bonds between monomers in a polymer by adding a water molecule.

Carbohydrates

Biological molecules that include sugars and the polymers of sugars.

Monosaccharides

The simplest carbohydrates, or simple sugars, which usually have molecular formulas that are multiples of $\text{CH}_2\text{O}$.

Disaccharide

A sugar formed when a dehydration reaction joins two monosaccharides together.

Glycosidic linkage

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

Polysaccharides

Macromolecules that are polymers composed of many sugar building blocks, functioning in storage and structure.

Starch

A storage polysaccharide of plants consisting entirely of glucose monomers.

Glycogen

An extensively branched storage polysaccharide found in animals, such as in liver and muscle tissue.

Cellulose

A structural polysaccharide component of plant cell walls composed of $\beta$ glucose monomers that form straight, unbranched molecules.

Chitin

A structural polysaccharide found in the exoskeleton of arthropods and the cell walls of many fungi.

Lipids

A diverse class of large biological molecules that do not form polymers and are hydrophobic due to nonpolar hydrocarbon bonds.

Fat (Triacylglycerol)

A lipid constructed from one glycerol molecule joined to three fatty acids by ester linkages.

Ester linkage

The bond formed between a hydroxyl group of glycerol and a carboxyl group of a fatty acid.

Saturated fatty acid

A fatty acid with no double bonds and the maximum number of hydrogen atoms possible, typically solid at room temperature.

Unsaturated fatty acid

A fatty acid with one or more double bonds (usually cis double bonds creating kinks), typically liquid at room temperature.

Phospholipid

A lipid composed of glycerol attached to two fatty acids and a phosphate group, forming a bilayer structure with a hydrophilic head and hydrophobic tails.

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings.

Cholesterol

An important steroid that serves as a component in animal cell membranes.

Enzymes

Proteins that act as catalysts to selectively accelerate chemical reactions without being consumed in the process.

Polypeptides

Polymers of amino acids linked together by peptide bonds, having an amino end (N-terminus) and a carboxyl end (C-terminus).

Amino acids

Organic molecules containing a carboxyl group, an amino group, an $\alpha$ carbon, and a variable side chain (R group).

Peptide bond

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

Primary structure

The unique, precise sequence of amino acids in a protein.

Secondary structure

Coils ($\alpha$ helix) and folds ($\beta$ pleated sheet) in a polypeptide chain created by hydrogen bonds between repeating constituents of the polypeptide backbone.

Tertiary structure

The overall three-dimensional shape of a protein determined by interactions among side chains (R groups), including hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals interactions, and disulfide bridges.

Quaternary structure

The protein structure that results when two or more polypeptide chains aggregate to form one functional macromolecule.

Sickle-cell disease

An inherited blood disorder resulting from a single amino acid substitution in hemoglobin, causing red blood cells to deform into a sickle shape.

Denaturation

The loss of a protein's native three-dimensional conformation due to environmental alterations in pH, salt concentration, or temperature, rendering it biologically inactive.

Chaperones

Protein molecules that assist in the proper folding of other proteins.

Gene

A unit of inheritance made of DNA that programs the amino acid sequence of a polypeptide.

Nucleic acids

Polymers called polynucleotides (DNA and RNA) that store, transmit, and express hereditary information.

Nucleotides

The monomers of nucleic acids, consisting of a nitrogenous base, a pentose sugar, and a phosphate group.

Pyrimidines

A family of nitrogenous bases (cytosine, thymine, uracil) characterized by a single six-membered ring.

Purines

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

Antiparallel

The arrangement of the two sugar-phosphate backbones in a DNA double helix, running in opposite $5'$ to $3'$ directions.