Ch 2 - Chemical Components of Cells Flashcards
acid
a molecule that releases a proton when dissolved in water; this dissociation generates hydronium (H3O+) ions, thereby lowing the pH
amino acid
small organic molecule containing both an amino group and a carboxyl group; it serves as the building block of proteins
atom
the smallest particle of an element that still retains its distinctive chemical properties; consists of a positively charged nucleus surrounded by a cloud of negatively charged electrons
atomic weight
the mass of an atom relative to the mass of a hydrogen atom; equal to the number of protons plus the number of neutrons that the atom contains
ATP
activated carrier that serves as the principal carrier of energy in cells; a nucleoside triphosphate composed of adenine, ribose and three phosphate groups
Avogadro’s number
the number of molecules in a mole, the quantity of a substance equal to its molecular weight in grams; approx. 6 x 10 power 23
base
molecule that accepts a proton when dissolved in water; also used to refer to the nitrogen-containing purines or pyrimidines in DNA and RNA
buffer
mixture of weak acids and bases that maintains the pH off a solution by releasing and taking up protons
chemical bond
a sharing or transfer of electrons that holds two atoms together (covalent / non - covalent)
chemical group
a combination of atoms, such as a hydroxyl group (-OH) or an amino group (-NH2) with distinct chemical and physical properties that influence the behaviour of the molecule in which it resides
condensation reaction
chemical reaction in which a covalent bond is formed between two molecules as water is expelled; used to build polymers, such as proteins, polysaccharides and nucleic acids
conformation
precise, three-dimensional shape of a protein or other macromolecule, based on the spatial location of its atoms in relation to one another
covalent bond
stable chemical link between two atoms produced by sharing one or more pairs of electrons
DNA (deoxyribonucleic acid)
Double stranded polynucleotide formed from two separate chains of covalently linked deoxyribonucleotide units. it serves as the cell’s store of genetic information that is transmitted from generation to generation.
electron
negatively charged subatomic particle that occupies space around an atomic nucleus (e-)
electronegativity
the tendency of an atom to attract electrons
electrostatic attraction
force that draws together oppositely charged atoms. examples include ionic bonds and the attractions between molecules containing polar covalent bonds
fatty acid
molecule that consists of a carboxylic acid attached to a long hydrocarbon chain. used as a major source of energy during metabolism and as a starting point for the synthesis of phospholipids
hydrogen bond
a weak noncovalent interaction between a positively charged hydrogen atom in one molecule and a negatively charged atom, such as nitrogen or oxygen, in another; hydrogen bonds are key to the structure and properties of water
hydrolysis
chemical reaction that involves cleavage of a covalent bond with the accompanying consumption of water (its -H being added to one product of the cleavage and its -OH to the other); the reverse of a condensation reaction
hydronium ion
the form taken by a proton (H+) in aqueous solution
hydrophobic
nonpolar, uncharged molecule or part of a molecule that forms no hydrogen bonds with water molecules and therefore does not dissolve; literally water fearing
hydrophillic
molecule or part of a molecule that readily forms hydrogen bonds with water, allowing it to readily dissolve; literally water loving
hydrophobic force
a noncovalent interaction that forces together the hydrophobic portions of dissolved molecules to minimize their disruption of the hydrogen-bonded network of water; causes membrane phospholipids to self-assemble into a bilayer and helps to fold proteins into a compact, globular space
ionic bond
interactions formed when one atom donates electrons to another; this transfer of electrons causes both atoms to become electrically charged.
inorganic
not composed of carbon atoms
ion
an atom carrying an electrical charge, either positive or negative
lipid bilayer
thin pair of closely juxtaposed sheets, composed mainly of phospholipid molecules, that forms the structural basis for all membranes
macromolecule
polymer built from covalently linked subunits; includes proteins, nucleic acids and polysaccharides with a molecular mass great than a few thousand dalton
lipid
an organic molecule that is insoluble in water but dissolves readily in nonpolar organic solvents; typically contains long hydrocarbon chains or multiple rings. One class, the phospholipids, forms the structural basis for biological membranes
molecule
group of atoms joined together by covalent bonds
molecular weight
sum of atomic weights of the atoms in a molecule; as a ratio of molecular masses, it’s a number without units
monomer
small molecule that can be linked to other of a similar type to form a larger molecule (polymer)
noncovalent bond
chemical association that does not involve the sharing of electrons; singly they are relatively weak, but they can sum together to produce strong, highly specific interactions between molecules. examples are hydrogen bonds and van der Waals attractions.
nucleotide
basic building block of the nucleic acids, DNA and RNA; a nucleoside linked to a phosphate
organic molecule
chemical compound that contains carbon and hydrogen
pH scale
concentration of hydrogen ions in a solution, expressed as a logarithm. an acidic solution with ph3 will contain 10 power -3 M hydrogen ions.
polar
in chemistry, describes a molecule or bond in which electrons are distributed unevenly
polymer
long molecule made by covalently linking multiple identical or similar subunits (monomers)
protein
macromolecule built from amino acids that provides cells with their shape and structure and performs most of their activities
proton
positively charged particle found in the nucleus of every atom; also, another name for a hydrogen ion (H+)
RNA
molecule produced by the transcription of DNA; usually single-stranded, it is a polynucleotide composed of covalently linked ribonucleotide subunits. Serves a variety of information, structural, catalytic and regulatory functions in cells.
sequence
the linear order of monomers in a large molecule -for example, amino acids in a protein or nucleotides in DNA; encodes information that specifies a macromolecule’s precise biological function
subunit
a monomer that forms part of a larger molecule, such as an amino acid residue in a protein or a nucleotide residue in a nucleic acid. can also refer to a complete molecule that forms part of a larger molecule. many proteins, for example, are composed of multiple polypeptide chains, each of which is called a protein subunit
sugar
a substance made of carbon, hydrogen and oxygen with the general formula (CH2O)n. a carbohydrate or saccharide. the sugar of everyday use is sucrose, a sweet-tasting disaccharide made of glucose and fructose
van der Waals attraction
weak noncovalent interaction, due to fluctuating electrical charges, that comes into play between two atoms within a short distance of each other
