introduction to organic molecules

bio 2 lecture 1

pH scale

used to describe whether a solution is acidic or basic

pH of an acidic solution

less than 7

pH of a basic solution

greater than 7

range of pH of most biological fluids

6 to 8

acid

substance that increases the H⁺ concentration of a solution

base

substance that reduces the H⁺ concentration of a solution

formula for pH

pH = -log[H⁺]

weak acid

acid that does not dissociate significantly in water

conjugate base

what’s left of an acid after it donates a proton

formula for dissociation constant

K_a = [H⁺][A-]/[HA]

Henderson-Hasselbalch equation

pH = pK_a + log([A-]/[HA])

buffer

substance that minimizes changes in concentrations of H⁺ and OH^- in a solution

organic molecules

chemical compounds that contain carbon, excluding simple oxides, carbonates, cyanides, and allotropes

what are the ways in which a carbon skeleton can vary?

• length

• branching

• double bonds

• rings

isomers

compounds with the same molecular formula but different structures and properties

structural isomers

isomers with different covalent arrangements

stereoisomers

isomers with the same sequence of bonded atoms, but that differ in 3D orientation of atoms in space

cis-trans isomers

isomers with the same covalent bonds but differ in in spatial arrangements

enantiomers

isomers that are mirror images of each other

functional groups

components of organic molecules involved in chemical reactions

what are the seven most important functional groups?

• hydroxyl

• carbonyl

• carboxyl

• amino

• sulfhydryl

• phosphate

• methyl

hydroxyl group

-OH

carbonyl group

C=O

carboxyl group

-COOH

amino group

-NH₂

sulfhydryl group

-SH

phosphate group

-OPO₃^2-

methyl group

-CH₃