Topic 2: Intro to Biochem and Water Structure and Function

Proton (mass, charge, location)

mass - one atomic unit (AU)

charge - positive

location of subatomic particles - inside the nucleus

Neutron (mass, charge, location)

mass - one atomic unit (AU) (a tiny bit more)

charge - neutral

location of subatomic particles - inside the nucleus

Electron (mass, charge, location)

mass - zero atomic units (AU)

charge - negative

location of subatomic particles - outside the nucleus

atom

smallest piece of an element

isotope

different forms of the same atom that vary only in the # of neutrons they possess

ion

an atom or molecule that has a net electrical charge because it has lost one or more electrons

cation

positively charged ion, formed when an atom loses one or more electrons, has more protons than electrons

anion

negatively charged ion, formed when an atom gains one or more electrons, has more electrons than protons

ionic bonds

chemical bond formed between ions with opposite charges, through the attraction of the opposite charges

non polar covalent bond

form between two atoms of the same element or between elements that share electrons equally, no positive or negative charge

polar covalent bond

two atoms unequally share electrons, giving the atoms with more of the electrons a slight negative change and the atoms with less of the electrons a slight positive charge

label parts of the polar structure of water

oxygen = slightly negative

hydrogen = slightly positive

dashed lines = hydrogen bonds

bonds between hydrogen and oxygen = polar covalent bonds

what is hydrogen bonding

electrostatic attraction between the partially positive hydrogen atom of one water molecule and the partially negative oxygen atom of another

weak bonds - very easily broken

why does hydrogen bonding occur

hydrogen from one water molecule forms bond with oxygen of another molecule of water because of their slight opposite charges

hydrogen bonding - surface tension

water molecules are attracted to each other with hydrogen bonding, which keeps the surface layer together, resisting outside pressure and breakage

hydrogen bonding - density of water

hydrogen bonding makes liquid water denser than solid water because when water freezes the hydrogen bonds remain, while in liquid water the bonds are constantly breaking, so the molecules are closer together

hydrogen bonding - heat capacity

water can absorb heat without changing temperature or changing into a gas because heat energy is first consumed to break hydrogen bonds holding molecules together apart instead of raising the temperature of the molecules themselves

hydrogen bonding - ability to dissolve substances

Water molecules bond with polar molecules and pull ionic compounds apart, forming spheres of hydration around the atoms/ions which keeps them evenly dispersed in solution.

cohesion

attraction between like molecules, in water occurs because partially positive and negative water molecules form hydrogen bonds with each other

adhesion

attraction between unlike molecules, occurs in water because it is polar and can be attracted to oppositely charged surfaces or molecules