Biology lecture #2

Prokaryotic cells

Doesn’t have a membrane-bound nucleus, larger than virusesEu

Eukaryotic cells

cells with a membrane-bound nucleus, larger than prokaryotic cells

Viruses

larger than macromolecules

Macromolecules

Larger than single atoms

Atoms

building blocks of life

Elements

An individual type of atom

Central nucleus

contains most of the atoms mass (contains protons and neutrons)

Electrons

Outside of nucleus, very little mass, found in orbitals

Proton charge

+1

Neutrons charge

0R

Electrons charge

-1

Electrically neutral

same number of protons and electrons

If a macromolecule or atom has a net charge its called

ion

Ionic bonds

oppositly charged molecules/atoms attract (no sharing)

Covalent bonds

occur when atoms share electrons (which bond them)

Polar covalent bonds

where electrons are shared unequally

Nonpolar covalent bonds

electrons are shared equally

Electronegativity

Describes how strongly an atom attracts electrons (EN varies from atom to atom) and determines if a covalent bond will be polar or non polar

if EN of atoms is similar

non polar covalent bond (equal sharing) <0.5

if EN of atoms is different

Polar covalent bond (non-equal sharing ) >=0.5