Lesson 04: Biological Macromolecules

Biological Macromolecules

Large, complex molecules synthesized by cells from small molecule subunits; organic molecules with carbon as the framework.

Proteins

Macromolecules making up roughly 15\% of a cell's mass; serve as enzymes, provide structural support, and perform a wide range of other functions.

Polysaccharides and Lipids

Macromolecules each comprising about 2\% of a cell's mass.

Nucleic Acids

Macromolecules comprising 7\% of a cell's mass, mostly RNA; DNA stores genetic information, RNA is involved in its expression.

Hydrocarbons

Molecules composed entirely of hydrogen and carbon (e.g., butane, fatty acids), which store energy in their many carbon-hydrogen bonds and are nonpolar.

Functional Groups

Polar regions in molecules containing oxygen, nitrogen, sulfur, and phosphorus, due to electronegativity, exhibiting specific chemical properties.

Carbohydrates

Energy storage molecules that provide structural support, assembled from monosaccharide subunits.

Lipids

Macromolecules utilized in energy storage, providing the structure of cell membranes, and acting as signals for cell communication; assembled from fatty acid subunits.

Polymers

Carbohydrates, proteins, and nucleic acids are often termed polymers because they are formed from the end-to-end linkage of monomeric subunits.

Monosaccharides

Simple sugars, the subunits from which carbohydrates are assembled, containing carbon, hydrogen, and oxygen in a 1:2:1 ratio.

Isomers

Molecules with the same chemical formula but differing in structure or position of attached chemical groups.

Structural Isomers

Isomers that differ in the location of the carbonyl group (e.g., glucose vs. fructose).

Stereoisomers

Isomers that have the same chemical groups but in opposite orientations (e.g., glucose vs. galactose).

Dehydration Reaction

The reaction forming disaccharides by the covalent linkage of two monosaccharides with the removal of a water molecule, requiring a cellular enzyme.

Disaccharides

Formed by the covalent linkage of two monosaccharides, acting as transport forms of sugars (e.g., sucrose, lactose).

Polysaccharides

Long polymers formed by the assembly of monosaccharides, often linked C1 of one subunit to C4 of the next (e.g., starches, glycogen, cellulose, chitin).

Nucleotide

The subunit of nucleic acids, containing a five-carbon pentose sugar, a nitrogenous base, and at least one phosphate group.

Ribose

The sugar found in RNA, containing a hydroxyl group (-OH) on the 2' carbon.

2'-deoxyribose

The sugar found in DNA, lacking an oxygen atom on the 2' carbon, containing only a hydrogen atom.

Purines

Double-ring nitrogenous bases; Adenine (A) and Guanine (G).

Pyrimidines

Single-ring nitrogenous bases; Cytosine (C), Thymine (T - found only in DNA), and Uracil (U - found only in RNA).

Phosphodiester Bonds

Covalent bonds linking nucleotides in a nucleic acid polymer, connecting the 3'-carbon of one subunit to the 5'-carbon of the next, generating a directional polymer.

Sugar-phosphate backbone

Composed of the sugars and phosphate groups that link nucleotides together in a nucleic acid strand, with bases projecting outward.

Hydrogen Bonds

Interactions between complementary bases in DNA strands (A-T, G-C) that hold the double helix together.

Double Helical Arrangement

The twisted structure formed by two DNA strands interacting via hydrogen bonds.

Anti-parallel

The orientation of the two strands in DNA, running in opposite directions (e.g., 5'-end of one strand aligns with the 3'-end of the other).

ATP (Adenosine Triphosphate)

Considered the energy currency of the cell; contains adenine, ribose, and three phosphate groups, with chemical energy stored in the linkage between the second and third phosphate groups.

Amino Acid

The subunit of proteins, characterized by a central carbon atom, an amino group, an acidic carboxyl group, a hydrogen atom, and a unique R-group (side chain).

R-group (side chain)

The unique part of an amino acid that determines its specific chemical properties and classification (nonpolar, polar uncharged, acidic, basic).

Peptide Bonds

Covalent bonds linking amino acids in a polypeptide, formed through a dehydration reaction catalyzed by a ribosome.

Polypeptide

A polymer longer than ~10 amino acids, typically ~300 amino acids long, with a unique amino acid sequence.

Primary Structure

The unique, linear sequence of amino acids in a polypeptide chain, determined by covalent peptide bonds.

Secondary Structure

Local folding patterns generated by hydrogen bonds forming between atoms within the peptide backbone (not side chains), resulting in beta sheets or alpha helices.

Tertiary Structure

The overall three-dimensional shape of a single polypeptide chain, generated by interactions (hydrogen bonds, ionic, disulfide, hydrophobic) between amino acid side chains, often representing the functional form.

Quaternary Structure

Formed by the association of two or more polypeptide chains (subunits) to form a functional protein, with interactions similar to those in tertiary structure.

Denaturation

The process by which a protein loses its correct three-dimensional structure and becomes deactivated due to alterations in the environment (e.g., pH, temperature), resulting in unfolding.

Renaturation

The process by which a denatured protein refolds into its original, active shape if normal environmental conditions are restored.