MCDB Textbook UNIT 1

ch 2-5 gemini

Matter

Anything that takes up space and has mass.

Element

A substance that cannot be broken down to other substances by chemical reactions.

Compound

A substance consisting of two or more different elements combined in a fixed ratio.

Trace Element

An element that is essential for life but required in extremely minute amounts.

Atom

The smallest unit of matter that still retains the properties of an element.

Proton

A subatomic particle with a single positive electrical charge.

Neutron

A subatomic particle having no electrical charge.

Electron

A subatomic particle with a single negative electrical charge.

Isotope

One of several atomic forms of an element, each with the same number of protons but a different number of neutrons.

Valence Shell

The outermost energy shell of an atom, containing the valence electrons.

Covalent Bond

A type of strong chemical bond in which two atoms share one or more pairs of valence electrons.

Electronegativity

The attraction of a given atom for the electrons of a covalent bond.

Nonpolar Covalent Bond

A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.

Polar Covalent Bond

A bond between atoms that differ in electronegativity; the shared electrons are pulled closer to the more electronegative atom.

Ionic Bond

A chemical bond resulting from the attraction between oppositely charged ions.

Hydrogen Bond

A type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule.

Van der Waals Interactions

Weak attractions between molecules or parts of molecules that result from transient local partial charges.

Cohesion

The linking together of like molecules, often by hydrogen bonds.

Adhesion

The clinging of one substance to another, such as water to plant cell walls.

Specific Heat

The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1 degree Celsius.

Hydration Shell

The sphere of water molecules surrounding each dissolved ion.

Hydrophilic

Having an affinity for water.

Hydrophobic

Having no affinity for water; tending to coalesce and form droplets in water.

Buffer

A solution that contains a weak acid and its corresponding base; it minimizes changes in pH when acids or bases are added to the solution.

Hydrocarbon

An organic molecule consisting only of carbon and hydrogen.

Isomer

One of two or more compounds that have the same numbers of atoms of the same elements but different structures and hence different properties.

Structural Isomer

One of several compounds that have the same molecular formula but differ in the covalent arrangements of their atoms.

Cis-Trans Isomer

One of several compounds that have the same molecular formula and covalent bonds between atoms but differ in the spatial arrangements of their atoms owing to the inflexibility of double bonds.

Enantiomer

One of two compounds that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon.

Functional Group

A specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and involved in chemical reactions.

Hydroxyl Group

-OH; characteristic of alcohols; polar.

Carboxyl Group

-COOH; acts as an acid; contributes H+ to a solution.

Amino Group

-NH2; acts as a base; picks up H+ from a solution.

Phosphate Group

-OPO3^2-; contributes negative charge; important in ATP.

Polymer

A long molecule consisting of many similar or identical monomers linked by covalent bonds.

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 process that splits molecules by the addition of water.

Monosaccharide

The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides.

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 the number of hydrogen atoms attached.

Unsaturated Fatty Acid

A fatty acid that has one or more double bonds between carbons in the hydrocarbon tail, reducing the number of hydrogen atoms.

Phospholipid

A lipid made up of a glycerol joined to two fatty acids and a phosphate group; the hydrocarbon chains of the fatty acids act as nonpolar tails, while the phosphate group and its attachments form a polar head.

Amphipathic

Having both a hydrophilic region and a hydrophobic region.

Polypeptide

A polymer of amino acids connected by peptide bonds.

Primary Structure

The level of protein structure referring to the specific linear sequence of amino acids.

Secondary Structure

Regions of repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bonding between constituents of the backbone (not the side chains).

Tertiary Structure

The overall shape of a protein molecule due to interactions of amino acid side chains (R-groups), including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

Quaternary Structure

The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits.

Denaturation

In proteins, a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, becoming biologically inactive.

Nucleotide

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.

Purine

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring (e.g., Adenine, Guanine).

Pyrimidine

One of two types of nitrogenous bases found in nucleotides, characterized by a single six-membered ring (e.g., Cytosine, Thymine, Uracil).

Phosphodiester Linkage

The connection in a nucleic acid polymer that consists of a phosphate group that links the sugars of two nucleotides.