Bio Chapter 3-5 Study Guide

Cohesion

The attraction between molecules of the same substance, often due to hydrogen bonding (e.g., water sticking to water).

Adhesion

The attraction between molecules of different substances (e.g., water sticking to plant cell walls).

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid, caused by hydrogen bonding at the surface. Water has one that is unusually high.

Specific Heat

The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C. Water's high specific heat buffers temperature changes. Water has one that is unusually high.

Heat of Vaporization

The quantity of heat a liquid must absorb for 1 g of it to be converted from a liquid to a gas.

Evaporative Cooling

The process in which the surface of an object becomes cooler during evaporation, as the hottest molecules leave the liquid state.

Hydrophilic

Having an affinity for water; typically applies to polar or ionic substances.

Hydrophobic

Having no affinity for water; typically applies to nonpolar substances like oils.

Buffer

A solution containing a weak acid and its conjugate base that minimizes changes in pH when acids or bases are added.

Isomers

Compounds with the same molecular formula but different structures and properties.

Structural Isomers

Compounds that differ in the covalent arrangements of their atoms.

Cis-Trans Isomers

Compounds with the same covalent bonds but differing spatial arrangements due to double-bond rigidity

Enantiomers

Isomers that are mirror images of each other and differ in shape due to an asymmetric carbon.

Hydroxyl Group (-OH)

A functional group consisting of a hydrogen atom bonded to an oxygen atom; forms alcohols and increases solubility in water.

Carbonyl Group (>C=O)

A functional group consisting of a carbon atom double-bonded to an oxygen atom (found in aldehydes and ketones).

Carboxyl Group (-COOH)

A functional group consisting of a single carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group; acts as an acid.

Amino Group (-NH2)

A functional group consisting of a nitrogen atom bonded to two hydrogen atoms; acts as a base.

Sulfhydryl Group (-SH)

A functional group consisting of a sulfur atom bonded to a hydrogen atom; can form cross-linking disulfide bridges in proteins.

Phosphate Group (-OPO3^2-)

A functional group containing phosphorus bonded to four oxygen atoms; plays a major role in energy transfer (e.g., ATP).

Methyl Group (-CH3)

A nonpolar functional group consisting of a carbon bonded to three hydrogen atoms; affects gene expression and molecular shape.

Dehydration Reaction

A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule.

Hydrolysis

A chemical reaction that breaks bonds between two molecules by the addition of water; functions in monomer disassembly.

Glycosidic Linkage

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

Saturated Fatty Acid

A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, maximizing hydrogen attachment (solid at room temperature).

Unsaturated Fatty Acid

A fatty acid that has one or more double bonds between carbons in the hydrocarbon tail, creating a kink (liquid at room temperature).

Phospholipid

A lipid made of glycerol joined to two fatty acids and a phosphate group, forming an amphipathic molecule essential for cell membranes.

Peptide Bond

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

Primary Structure (Protein)

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

Secondary Structure (Protein)

Coils and folds in the polypeptide backbone held together by hydrogen bonds (e.g., alpha helices and beta pleated sheets).

Tertiary Structure (Protein)

The overall 3D shape of a polypeptide resulting from interactions between R-groups (side chains).

Quaternary Structure (Protein)

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

Denaturation

A process in which a protein loses its native shape due to disruption of weak chemical bonds, becoming biologically inactive.

Nucleotide

The monomer of nucleic acids, composed of a 5-carbon sugar, a nitrogenous base, and one to three phosphate groups.

Phosphodiester Linkage

The covalent bond linking nucleotides together in a nucleic acid strand between the sugar of one and the phosphate of another.