chapter 1-2: biochem Flashcards
electrons: charge and mass
-1 charge; negligible
proton: charge and mass
+1 charge; 1 au
neutron: charge and mass
0 charge; 1 au
isotopes
same amount of electrons and protons, different neutrons = different mass #
ion
charged atom
types of molecular bonds
covalent, ionic, polar, hydrogen, van der waals
what type of bond results from a small difference in electronegativity?
Non polar covalent
what type of bond results from a large difference in electronegativity?
ionic
what is a higher value of electronegativity indicative of?
more pull on electrons
what type of bond is the complete transfer of electrons
ionic
what type of bond is sharing electrons?
covalent
nonpolar covalent bonds
electros are shared equally bc atoms have the same electronegativity or molecular geometry negates polarity
polar covalent bonds
electrons are not shared equally - more electronegative atom hogs electrons
result of polar covalent bonds
partial charges on the molecule - more electronegative atom will be more negatively charged and the other will be more positively charged - called dipoles
hydrogen bonds
attraction between oppositely charged regions of polar molecules - also called dipole-dipole interactions - only between H & N, O, F
van der waals interactions
attractions between oppositely charged atoms in nonpolar molecules - movement of electrons results in small temporary dipoles; very weak but many interactions can amount to a significant force; often seen in liquids
how many hydrogen bonds can water form with other polar or charged molecules?
four
is water polar or nonpolar?
polar
what underlies water’s central role in living systems?
polarity and ability to form hydrogen bonds with other water molecules
qualities of water? (5)
1) water is sticky (cohesion and adhesion)
2) liquid water has high surface tension
3) high specific heat
4) solid water is less dense than liquid water
5) universal solvent
cohesion vs adhesion
cohesion: water molecules stick together
adhesion: stick to other things (like xylem of a plant)
water molecules can form hydrogen bonds with other molecules and polar surfaces
high surface tension of water
water prefers to bond to itself, forming a “skin” on the surface bc air is nonpolar
high specific heat of water
energy breaks down hydrogen bonds but new ones form almost immediately, so temperature doesn’t increase by much unless you add a lot of energy
why is ice less dense than water?
as water freezes, more hydrogen bonds are formed between water molecules which creates a very organized structure because of repelling forces between molecules
