organic chemistry and biochemistry lecture text chapter 2
TRANSCRIPT
Organic Molecules
• Molecules containing both carbon and hydrogen
• Carbon– 4 valence electrons in
outer orbital– Needs 8 total for full
complement
Carbon
• Can form 4 covalent bonds
• Can form 1-2 bonds with multiple atoms, including other carbon atoms– Form chains of carbons,
rings, etc.
Reactive Groups
• Hydrocarbon chains may be linked to more reactive elements– E.g., oxygen, nitrogen
Chemical Formulas
• Molecular Formulas– Number of atoms of each element in the
molecule• E.g. water = H2O
• E.g. methane = CH4
• E.g. glucose = C6H12O6
– Does not indicate how atoms bond together
Chemical Formulas
• Structural Formulas– Indicate bonds among atoms within molecules– Single line indicates single covalent bond– Double line indicates double covalent bond– E.g. Acetone (C3H6O)
Chemical Formulas
• Condensed Structural Formulas– Not all bonds drawn– Central atoms shown with atoms bonded to
them
– E.g. Acetone (C3H6O)
(CH3)CO(CH3)
(CH3)2CO
CH3CCH3
Oor or
Chemical Formulas
• Line-Angle Formulas– Bonds represented by lines
– Carbon atoms assumed to be present at the end of any line
– Oxygen and Nitrogen shown, Hydrogen is not
– Each carbon is assumed to have enough hydrogens bonded to it by single bonds to give it four bonds total
Biomolecules• Complex organic molecules used in biological
systems• Polymers
– Made up of repeated subunits
• Major Groups1. Carbohydrates – energy sources, cell communication2. Lipids – energy storage, cell membrane structure,
cushioning, cell communication3. Proteins – structure, cell function (enzymes) , cell
communication4. Nucleic Acids – information storage
Carbohydrates (Sugars)
• molecules that contain H, O and C
• relative amounts of each are the same in all simple carbohydrates– #C atoms = #O atoms– #H atoms = 2x the number of either C or O
• general formula = (CH2O)n
– e.g. glucose – C6H12O6
Carbohydrates (Sugars)• monosaccharide - individual
unit• basic CH2O formula• name possesses the suffix –ose
– e.g. glucose, galactose, fructose, ribose
• Monosaccharides can have the same formula but different arrangements of atoms– Isomers – molecules of same
formula but different structures
Carbohydrates (Sugars)
• Disaccharide– two monosaccharides linked
together • e.g. sucrose
= glucose + fructose
• e.g. maltose = glucose +
glucose
Carbohydrates (Sugars)
• Polysaccharide– Many monosaccharides
linked together
• E.g. glycogen– Polymer of glucose
Carbohydrate Synthesis
• Monosaccharides are linked together by dehydration synthesis– employs specific enzymes– H is removed from one
monosaccharide, an -OH group from the other
– covalent bond (glycosidic bond) formed between the two
– water formed as an end-product
Carbohydrate Digestion
• polysaccharides are broken apart via hydrolysis– a water molecule is split– H+ added to one of the
free monosaccharides– OH group added to the
other
Lipids (Fats, Oils, Waxes)
• very general category• contain compounds
that are not soluble in water (hydrophobic)
• Major classes– Triglycerides– Phospholipids– Steroids
Triglycerides
• fats and oils• formed by dehydration
synthesis• combine glycerol with
three molecules of fatty acid
Triglycerides
• different types of fatty acids• Saturated
– all carbons in chain linked by single bonds
• Unsaturated– one or more carbons in chain
linked by double bonds
• Unsaturated fatty acids tend to be more fluid
Phospholipids
• contain a phosphate group (PO4)
• commonly a combination of a phosphate group to a glycerol molecule attached to two fatty acids– e.g. lecithin
Phospholipids
• possess both polar an nonpolar ends (amphipathic)
• nonpolar ends aggregate together
• form micelles when mixed in water– interact with water – lowers
surface tension of water
Steroids• Consist of 3 six-carbon rings and a
single five-carbon ring interlocked together
• different functional groups attached to basic structure– e.g. sex steroids – produced by
gonads (testosterone, progesterone)– e.g. corticosterones – produced by
adrenal glands– e.g. cholesterol – precursor for
hormones, regulation of cell membrane fluidity
Proteins
• Diverse in structure and function
• Polymers of amino acids• 20 common amino acids
each with:– an amino group
– a carboxyl group
– a functional side-group (differs among a.a.’s)
Peptide Bonds
• Amino acids are joined together by dehydration synthesis
• NH3 group of one joined to the COOH group of another to form a peptide bond– two joined amino acids =
dipeptide– many joined amino acids =
polypeptide
Protein Structure:Primary Structure
• Sequence of amino acids in a polypeptide chain
• From free amino end (N-terminus) to the free carboxyl end (C-terminus)
• May be 1000’s of a.a.’s long
Protein Structure:Secondary Structure
• Formation of helix or sheet shape in a protein chain
• due to hydrogen bonds forming between the amino group of one peptide bond and the carboxyl group from another peptide bond
Protein Structure:Tertiary Structure
• Twisting and folding of a single protein chain
• due to chemical interactions among the different sidechain groups
Protein Structure:Quaternary Structure
• Bonding and interactions of multiple polypeptide chains– e.g. insulin = two
separate chains– e.g. hemoglobin = four
separate chains