atomic mass
total number of protons and neutrons in an atom
isotopes
atoms with the same number of protons but different numbers of neutrons; they share almost the same chemical properties, but differ in mass and therefore in physical properties
atomic number
number of protons in the nucleus
the elements of life
hydrogen (H), carbon (C), nitrogen (N), & oxygen (O)
atoms form molecules
through chemical bonds; by combining to fill their outermost shells
valence
the number of missing or extra electrons in the outermost shell
molecules hold together
because the valence electrons of the combining atoms form attractive forces, called chemical bonds, between the atomic nuclei
compound
molecule that contains two or more kinds of atoms
cations
atoms that lose electrons & become positively charged ions
anions
atoms that gain electrons & become negatively charged ions
ionic bonds
attractions between ions of opposite charge; one atom loses electrons & another gains electrons (aka transfer of electrons)
in neutral atoms
the number of protons equals the number of electrons
ions
charged atoms that have gained or lost electrons
covalent bonds
form when 2 atoms share one or more pairs of electrons; stronger & more common in organisms
molecular mass
the sum of the atomic masses in a molecule
one mole of a substance equals
its molecular mass in grams
dalton (da)
unit of molecular mass
water
inorganic, polar molecule, solvent, hydrogen bonding (absorbs heat)
hydrogen bonds
form when a hydrogen atom that is covalently bonded to an O or N atom is attracted to another N or O atom in another molecule
chemical reactions
involve the making or breaking of bonds between atoms
a change in chemical energy
occurs during a chemical reaction
endergonic
reactions absorb energy
exergonic
reactions release energy
synthesis reactions
occur when atoms, ions, or molecules combine to form new, larger molecules (ex: A + B → AB)
anabolism
the building up (or synthesis) of molecules in a cell; endergonic
decomposition reactions
occur when a molecule is split into smaller molecules, ions, or atoms (ex: AB → A + B)
catabolism
the breakdown (or decomposition) of molecules in a cell; exergonic
pH
expresses the concentration of H+ in a solution
acidity correlates with
the H+ concentration; lower pH
alkalinity (basicity) correlates with
the OH- concentration; higher pH
range most organisms grow best
pH of 6.5-8.5
acids
substances that dissociate into one or more hydrogen ions & one or more negative ions (ex: HCl → H+ + Cl-); has proton (H+) by itself
bases
substances that dissociate into one or more hydroxide ions & one or more positive ions (ex: NaOH → Na+ + OH-); has hydroxyl (OH-) group by itself
salts
substances that dissociate into cations and anions, neither of which is H+ or OH- (ex: NaCl → Na+ + Cl-)
inorganic compounds
typically lack carbon; usually small & structurally simple
organic compounds
commonly contain hydrogen, oxygen, and/or nitrogen in addition to carbon
carbon skeleton
the chain of carbon atoms in an organic molecule
functional groups
bond to carbon skeletons & are responsible for most of the chemical properties of a particular organic compound
hydrocarbons are an example of
organic compounds
Hydrogen atomic number & atomic mass
1 & 1
Carbon atomic number & atomic mass
6 & 12
Nitrogen atomic number & atomic mass
7 & 14
Oxygen atomic number & atomic mass
8 & 16
small organic molecules
can combine into large macromolecules
macromolecules
polymers consisting of many repeating molecules call monomers
monomers join by
dehydration synthesis or condensation reactions
carbohydrates
serve as cell structures and cellular energy sources; include sugars and starches, consist of C, H, and O with the formula (CH2O)n; many carbohydrates are isomers
isomers
molecules with the same chemical formula, but different structures
monosaccarhides
simple sugars with 3 to 7 carbon atoms
examples of common monosaccharides
glucose & deoxyribose
disaccharides
formed when 2 monosaccharides are joined in a dehydration synthesis
dehydration synthesis
the creation of larger molecules from smaller monomers where a water molecule is released
hydrolysis
breaks the bonds of polymers by the addition of water
disaccharides can be broken down by
the chemical process of hydrolysis
polysaccharides
consists of tens or hundreds of monosaccharides joined through dehydration synthesis
polymers of glucose that differ in their bonding & function
starch, glycogen, dextran, & cellulose
lipids
fats or triglycerides; contain glycerol & fatty acids; formed by dehydration synthesis
saturated fat
no double bonds in the fatty acids
unsaturated fat
one or more double bonds in the fatty acids
cis
H atoms on the same side of the double bond
trans
H atoms on the opposite sides of the double bond
complex lipids
contain C,H and O + P, N and/or S
cell membranes are made up of
complex lipids, called phospholipids
phospholipids contain
glycerol, two fatty acids, and a phosphate group; also has polar & nonpolar regions
steriods
type of lipid; part of membranes that keeps them fluid; has 4 carbon rings with an —OH group attached to one ring
proteins
made of C, H, O, N & sometimes S; essential in cell structure and function; examples include enzymes, transporter proteins, compose flagella & pili, and some bacterial toxins and cell structures
enzymes
speed up chemical reactions
transporter proteins
move chemicals across membranes
flagella & pili
aid in movement
amino acids
proteins consist of these; contain an alpha-carbon that has an attached: carboxyl group (—COOH), amino group (NH2), & side group; exist in either of 2 stereoisomers D or L
L-form stereoisomers are
most often found in nature
peptide bonds
are between amino acids and formed by dehydration synthesis
primary structure of a protein
a polypeptide chain
secondary structure of a protein
occurs when the amino acid chain folds and coil in a helix or pleated sheet
tertiary structure of a protein
occurs when the helix or sheet folds irregularly, forming disulfide bridges, hydrogen bonds, & ionic bonds between amino acids; folds into 3D shape
quaternary structure of a protein
the arrangement of multiple polypeptide chains (subunits) within a protein complex, where these subunits are held together by non-covalent interactions like hydrogen bonds, ionic bonds, and hydrophobic interactions, forming the final functional structure of the protein
conjugated proteins consist of
amino acids and other organic molecules
proteins can undergo
denaturation
denaturation occurs
when proteins encounter hostile environments such as temperature & pH, and therefore lose their shapes and functions
nucleic acids
consist of nucleotides
nucleotides
consist of a 5-carbon (pentose) sugar, phosphate group, & nitrogen-containing base
purines
A & G
pyrimidines
T, C, & U
nucleosides
consist of pentose & nitrogen-containing base
DNA
deoxyribonucleic acid; contains deoxyribose, exists as a double helix, Adenine hydrogen bonds with Thymine, Guanine hydrogen bonds with Cytosine
the order of the nitrogen-containing bases
forms the genetic instructions fo the organism (organized into codons)
RNA
ribonucleic acid; contains ribose, is single-stranded, Adenine hydrogen bonds to Uracil, Guanine hydrogen bonds to Cytosine
the types of RNA that play a specific role in protein synthesis
rRNA, mRNA, tRNA
adenosine triphosphate (ATP)
made of ribose, adenine, and 3 phosphate groups; is formed from ATPase complex
functions of ATP
stores chemical energy released by some chemical reactions, releases phosphate groups by hydrolysis to liberate useful energy for the cell
components of central dogma
ATP, DNA, amino acids, codons, & ribosomes