Biological Macromolecules: Structure, Function, and Properties

Vocabulary practice flashcards covering biological macromolecules, monomer-polymer linkages, nucleic acids, carbohydrates, lipids, and protein structure levels based on the lecture slides.

Carbon

The basic building block of life on Earth; it is the fourth most abundant element in the universe, the second most abundant in the human body, and can form covalent bonds with up to four other atoms.

Monomer

An individual subunit that serves as the repeating building block of a larger molecule.

Polymer

A long molecule made of many monomers or subunits linked together.

Dehydration Synthesis

A chemical reaction that joins monomers together to build polymers through the removal of a hydrogen atom and a hydroxyl group, producing water ($H_2O$).

Hydrolysis Reaction

A chemical reaction that breaks polymers down into monomers by adding a water molecule ($H_2O$) across a covalent bond, catalyzed by a hydrolyase enzyme.

Monosaccharide

The simplest carbohydrate and monomer for complex carbohydrates, generally possessing a molecular formula that is a multiple of the unit $CH_2O$ (such as glucose, $C_6H_{12}O_6$).

Glycosidic Linkage

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

Disaccharide

A double sugar consisting of two monosaccharides joined by a covalent glycosidic linkage (such as maltose or sucrose).

Polysaccharide

A macromolecule composed of a few hundred to a few thousand monosaccharide building blocks joined by glycosidic linkages.

Starch

A plant storage polysaccharide of glucose monomers consisting of unbranched chains (amylose) and branched chains (amylopectin).

Glycogen

An extensively branched storage form of glucose found in animals, humans, and other vertebrates that provides quick energy release when needed.

Cellulose

A structural polysaccharide comprising linear chains of glucose monomers that forms rigid plant cell walls, providing rigidity and strength.

Lipids

A class of nonpolar, hydrophobic biological molecules that mix poorly with water and are not considered true polymers.

Ester Linkage

The covalent bond formed between a hydroxyl group of glycerol and a carboxyl group of a fatty acid in the synthesis of a fat molecule.

Triacylglycerol (Triglyceride)

A fat molecule assembled from one glycerol molecule joined to three fatty acid molecules by ester linkages.

Saturated Fatty Acid

A fatty acid whose hydrocarbon chain contains only single bonds between carbon atoms, allowing molecules to pack closely and remain solid at room temperature.

Unsaturated Fatty Acid

A fatty acid containing at least one double bond between carbon atoms, causing a kink in the carbon chain that prevents close packing and keeps it liquid at room temperature.

Phospholipid

A lipid composed of a glycerol molecule linked to two hydrophobic fatty acid tails and a hydrophilic phosphate head group.

Steroids

A class of lipids characterized by a carbon skeleton consisting of four fused rings, distinguished by attached chemical groups.

Cholesterol

A common steroid found in animal cell membranes that provides structural stability and serves as the precursor from which other steroids are synthesized.

Nucleotide

The monomer of nucleic acids, composed of a 5-carbon pentose sugar, a phosphate group, and a nitrogenous base.

Nucleoside

The structural portion of a nucleotide comprising a nitrogenous base and a five-carbon sugar, lacking a phosphate group.

Phosphodiester Linkage

The covalent bond that links adjacent nucleotides by joining the $3'$ hydroxyl group of one sugar to the $5'$ phosphate group of the next, creating the sugar-phosphate backbone.

Antiparallel

The structural orientation of the two strands in a DNA molecule running in opposite directions ($5' \rightarrow 3'$ and $3' \rightarrow 5'$).

Amino Acid

The monomer of proteins, containing a central carbon bonded to a hydrogen atom, a carboxyl group ($-\text{COOH}$), an amino group ($-\text{NH}_2$), and a variable $R$ group.

Peptide Bond

A covalent bond connecting the carboxyl group of one amino acid to the amino group of another, formed by dehydration synthesis at the carboxyl terminus.

Primary Structure

The linear sequence of amino acids in a protein linked by covalent peptide bonds, determined by inherited genetic information.

Secondary Structure

Localized folding of the polypeptide chain into repeating structures like alpha-helices and beta-pleated sheets, stabilized by hydrogen bonds between atoms of the polypeptide backbone.

Tertiary Structure

The overall three-dimensional shape of a polypeptide resulting from interactions among amino acid side chains ($R$ groups), including hydrogen bonds, hydrophobic interactions, ionic bonds, and disulfide bridges.

Quaternary Structure

The overall protein structure resulting from the aggregation and interaction of multiple polypeptide subunits into a single functional macromolecule.

Disulfide Bridge

A covalent bond formed between the sulfur atoms of two cysteine side chains that helps stabilize the tertiary structure of a protein.

Denaturation

The process in which changes in pH, salt concentration, temperature, or solvent polarity disrupt weak chemical bonds, causing a protein to lose its native shape and become biologically inactive.