Nucleic Acids• Informational polymers• Made of C,H,O,N and P• No general formula• Examples: DNA and RNA
Nucleic Acids• Polymers of nucleotides• Nucleotides have three parts:• nitrogenous base• pentose sugar• phosphate
Nitrogenous Bases• Rings of C and N• The N atoms tend to take up H+ • Make it basic
• Two types:• Pyrimidines (single ring)• Purines (double rings)
Pentose Sugar• 5-C sugar• Ribose - RNA• Deoxyribose – DNA• RNA and DNA differ in a –OH group on the 2nd carbon.
RNA• Ribonucleic Acid.• Structure and protein synthesis.• Genetic information for a few viruses only.
Proteins
•The molecular tools of the cell.•Polypeptide chains of Amino Acids
monomer linked by peptide bonds.•Made of C,H,O,N, and sometimes S.•No general formula.•Has Amino group NH3
Amino Acids
• All have a Carbon with four attachments:• -COOH (acid)• -NH2 (amine)• -H• -R (some other side group)
R groups
• The properties of the R groups determine the properties of the protein.•20 different kinds:• Nonpolar - 9 AA• Polar - 6 AA• Electrically Charged• Acidic - 2 AA• Basic - 3 AA
Polypeptide Chains
• Formed by dehydration synthesis between the carboxyl group of one AA and the amino group of the second AA.
• Produce an backbone of: (N-C-C)X
Levels Of Protein Structure
• Organizing the polypeptide into its 3-D functional shape.• Primary• Secondary• Tertiary• Quaternary
Primary
• Sequence of amino acids in the polypeptide chain.
• Many different sequences are possible with 20 AAs.
Secondary
•3-D structure formed by hydrogen bonding between parts of the peptide backbone.• Two main secondary
structures:• a helix• pleated sheets
Tertiary
• Bonding between the R groups.• Examples:• hydrophobic interactions• ionic bonding• Disulfide bridges (covalent bond)
Denaturing Of A Protein
• Events that cause a protein to lose structure (and function).• Example:• pH shifts• salt concentrations• heat
Enzymes
• Activation Energy• Energy needed to reach
the transition state• Needed to start reaction
Activation Energy
Potential Energy
Enzymes• Biological catalysts made of protein.• Cause the rate of a chemical reaction to increase.• Usually specific to one substrate. • Each chemical reaction in a cell requires its own enzyme.
Reactions
• Enzymes lower the activation energy for a chemical reaction to take place.
• Makes it faster/easier to reach transition state
Active Site• The area of an enzyme that
binds to the substrate.• Structure is designed to fit the
molecular shape of the substrate.
• Therefore, each enzyme is substrate specific.
Example• Lactose• A disaccharide
• Enzyme breaks into 2 monosacharides• Lactase
• Is added to milk to break the sugar so the body doesn’t have to• This makes lactose-free milk • Many people of African/Asian descent are lactose intolerant. • Only areas where cattle were raised developed the ability to digest lactose
Factors that affect Enzymes
• Environment• pH, temp, salt
• Cofactors• Non-organic helpers to enzymes. Ex. Fe, Zn, Cu
• Coenzymes• Organic helpers to enzymes. Ex. vitamins
• Inhibitors• Competitive - mimic the substrate and bind to the active
site.• Noncompetitive - bind to some other part of the enzyme.
• Allosteric Sites
Metabolic Control• Feedback Inhibition• When a metabolic pathway is switched off by its end-product.• End-product usually inhibits an enzyme earlier in the pathway.
• Structural Order• Separation of enzymes and metabolic pathways in time or space
by the cell's organization.• Example: enzymes of respiration