how can only around a dozen chemical elements generate the diversity of molecules that make up living organisms
basic features of chemistry:
- each element contains only 1 types of atom -> basic unit of matter
- C, H, O, N, P
what are the components of an atom
nucleus, protons and neutrons
electrons move around nucleus
electrons move around nucleus in a region of space -> orbitals (can hold max 2 electrons)
how are molecules formed
atoms combining with other atoms
what is atomic number and atomic mass
of protons
of protons + # of neutrons
what are valence electrons
electrons found in outermost orbitals of an atom
determines # of bonds an atom can make
what are covalent bonds
valence electrons shared in a molecular orbital
what is a polar covalent bond
when there is an unequal sharing of electrons
ex. water -> O2 is more electronegative and attracts electrons more than H
what is a cation
atom with positive charge (extra protons relative to electrons)
what is a nonpolar covalent bond
equal sharing of electrons
atoms have the same or nearly the same electronegativity
what is an ionic bond
atom “steals” an electron from another when there is a significant difference in their electronegativity
ex. NaCl -> Cl steals an electron from Na, sodium is positive and Cl is negative
what are the starting substances and ending substances of chemical reactions
reactants and products
what is an anion
atom with negative charge (extra electrons relative to protons)
what is essential to water’s biological function
its polarity
depending on how molecules reacts with water they can be described as:
hydrophilic (form H bonds with water)
or
hydrophobic (do not form H bonds with water)
what happens when salts are placed in water
Na+ and Cl- are pulled apart and become surrounded by water molecules -> salt dissolves in water
bc of partial positive charge on H associates with negative charge on Cl and partial negative charge on O associates with + charge on Na
what are chemical reactions
breaking and forming of chemical bonds
what is the universal solvent?
water -> can dissolve more types of molecules than any other molecule
why is water the medium of life
most abundant molecule in biological organisms
what is a hydrogen bond
weak bonds formed between an electronegative atom and a hydrogen atom that is already covalently linked to another atom
H atoms form H bonds with O and N
pair of shared electrons is closer to the electronegative atom
why is pH important
for cellular function (ex protein structure or enzyme activity)
what is pH
in a solution of water, some of the water molecules exist as protons (H+) and hydroxide ions (OH-)
measurement of concentration of protons (H+) in a solution
ranges from 0-14
pure water -> pH 7
solutions with pH less than 7 -> acidic
solutions with pH higher than 7 -> basic
what are functional groups
change chemical character to carbon chains
chemical properties of their own
a N, O, P, or S in a functional grp is more electronegative -> form polar functional grps
methyl grp -> nonpolar functional grp
typically involved in reactions to combine simpler molecules to form polymers
what are organic molecules
molecules that contain carbon
what is the chemical significance of carbon
can combine with many other elements to forma wide variety of molecules
can form 4 covalent bonds -> combos of single/double bonds
can be linked to form chains/rings
ex. in methane, each of the 4 valence electrons share a molecular orbital with electron of one of the H atoms
what are the 4 types of biological molecules
- proteins: structural support and assist chem rxns by acting as catalysts
- nucleic acids: encode and transmit genetic info
- carbohydrates: structural support for many organisms and source of energy
- lipids: make up cell membranes, store energy, important in cell communication
