ch.2 moleculesm water and organic compounds

how to find mass number

count number of protons and electrons

how to find molecualr weight

count number of atoms in a molecule for each element and multiply it by the atomic mass (number found on peridoic table) then add everything up

what is valence

atoms bond capacity based by its number of upaired electrons

valence of C

4

valence of N

3

valence of H

1

what is the octet rule

a chemical principle stating that atoms tend to gain, lose, or share electrons to achieve a stable electron configuration with eight electrons in their outermost shell

what is electronegativity

refers to the relative ability of an atom to attract electrons when it is combined with another atom; the stronger the electronegativity of an atom, the greater its affinity for the electrons from other atoms.

what does electronegativity depend on

number of valence electrons and the size of the atom.

what type of bond does hghy electrongetive elemts form

an ionic bond

what is the strongest bond in bio?

covalent bond

what is a covalent bond

when atoms share a pair of electrons

what bond is present in all compounds and molecules?

covalent bonds

exampels of covlent bonds:

glycosidic bonds of carbohydrates, ester bonds of lipids, peptide bonds of proteins, and phosphodiester bonds of DNA/RNA

how does a nonpolar covalent bond happen

when two atoms, with same or similar electronegativity, and the atoms in these molecules share electrons equally. E

how does a polar covalent bond happen

when two atoms share electrons unequally, one has a higher EN or unpaired electrons

what is an ionic bond

Ionic bonding is the complete transfer of valence electron(s) between atoms because the EN of one atom is greater than another

example of an ionic bond

NaCl, NaF, NaHCO₃

in aqueous solutions which bond is stronger- covalent or ionic?

covalent

where are ionic bonds found ?

neyween protiens and positively and negatively charged amino acids

what is hydrogen bonding

The hydrogen covalently attached to one electronegative atom is attracted to another electronegative atom.

hydrophilic bonds are normally

polar, charged molecues, and soluable in water

hydrophobic bonds are normally

nonpolar, lipid solubale molecules, exlcuded from aqueous solutions by hydrogen bonding among polar molecules

what does A pair with in DNA and RNA

T/U

What does C pair with in DNA/RNA

G

what are van der waals interactons

When the atoms in a closely packed molecules interact, there are pockets of constantly changing positive and negative charges due to the changing distribution of electron clouds.

example of van der waals

lipids in biological membranes and cellulose in plant cell walls.

example of hydrophib/hydophilic interactions

phospholipid bilayer

what are the biolgical, chemical, and physical properties of water in supporting life

cohesivness, high specfic heat, High Hvap, freezing and expansion, versatile solvent, medium and ingredient for many chemical reactions

cohesivness in water

water has cohensionbc of the constant forming and breaking of H-bonds. constant forming and breaking of H-bonds. also have good adhseiveness

high specfic heat in water

water can bsorb and relseass heat to stablze the temp in the surrounding area to make it habitable

freezing and expansion

the h bonds in water keep it fruther apart in ice then liquid form. since ice is lighter than it water it keeps the water beneath it warm, making it good for aquatic life in cold conditions

versatile solvent

beause of its polarity and charded molecules it makes an excellent solvent

medium and ingredint for many biochemical reactions

all biochemical reactions in a cell occur in aqeuos soltions, many reactions need water to happen and other produce water as a byproduct. (95% of a living cell is watrer)

major properties of aqueous solutions

solute concentration and H+ ion concentration

what is the amount of H+ and OH- in pure water

they are at equilibrium [H+] = [OH-]

what is pH

a numerical scale from 0 to 14 that indicates how acidic or basic it is

what is Kw

water constant that refers to the product of H+ and OH-

Kw = [H+] X [OH-]

in pure water this is 10^-7 M X 10^-7 M = 10^-14 M.

as PH increases…

H+ increases or OH- changes 10 fold

what is an acid

a chemical that dissociates in a solution and increases the [H+]. can be cosnidered a proton donor

what is a base

a chemical that is either a proton acceptor or hydroxide donor that can decrease [H+] or increase [OH-] in a solution,

a ph from 1-7 is

acidic

a pH from 7-14 is

basic

what is a buffer

a substance that minimizes the pH change by accepting excess H s, when pH decreases or by donating H , when pH increases. Most buffers are weak acids or weak bases.

what is pK

the pH at which the ratio of an acid form to the base form is one to one

what is an isomer

a molecule that has the same chemical formula (the same types and numbers of atoms) as another molecule but has a different arrangement of those atoms

hydroxyl group function (-OH) polar or nonpolar? acid/base?

very polar and soluable in water. almost all carbohydrates, proteins, and nucleic acids contain it

carboNYL group polar or nonpolar? acid/base?

polar. found in propanol, and acetone

what is a ketone

an acid your body produces when it burns fat for energy because it can't get enough glucose from carbohydrates

when carbonyl is in the middle of the molecule it is

a ketone

what is a carboxyl polar or nonpolar? acid/base?

acidic. can ionize to form conjugate base COO- and relases H+

amino group polar or nonpolar? acid/base?

act as a base by accepting protons

sulfhydrl group polar or nonpolar? acid/base?

a reactive group. present in amino acid, cysteine.

what is a disulfide bridge (-S-S-)

a covalent bond formed between the sulfur atoms of two cysteine amino acid residues in a protein, creating a strong link that helps stabilize the protein's three-dimensional structure

Phospahte group polar or nonpolar? acid/base?

conjugate base of phosphoric acid. an acidic and reactive group

methyl group-polar or nonpolar? acid/base?

nonpolar group. affects slubity of compund in aqueous or organic solutions.