Presentation on theme: "AP Biology Exam Review (2002-2003) Molecules and Cells – 25%"— Presentation transcript:
AP Biology Exam Review (2002-2003) Molecules and Cells – 25%
Chemistry of Life – 7% Water Organic molecules in organisms Free energy changes Enzymes
Polar water molecule Polar covalent bonds polarity Polarity hydrogen bonding and various water properties
Water properties Ex: How do the unique chemical and physical properties of water make life on earth possible? Cohesion: transpiration, blood Adhesion: transpiration Ideal solvent: xylem and phloem sap, oceans, blood, hemolymph Density: maintaining marine life High specific heat: maintaining stability (homeostasis)
pH H 2 O + H 2 O H 3 O - + OH - Water dissociation = H 2 O H + + OH - 1/554 million water molecules dissociates in pure water. pH = 7 when [H + ] and [OH - ] equal to 10 -7
Acids and Bases Acids: pH < 7 Ex: stomach acid, increasing H + gradient Bases: pH > 7 Neutral: pH=7 Ex: blood, urine, body fluids Buffers required to maintain neutrality. (homeostasis)
Buffers H 2 CO 3 + OH - HCO 3 - + H 2 O HCO 3 - + H + H 2 CO 3 Ex: Human red blood cells Carbonic acid (H 2 CO 3 ) and Bicarbonate (HCO 3 - ) buffers to maintain blood cell pH. How can blood cell pH be raised or lowered?
pH Make sure you know the general pH of some biologically important aqueous solutions: blood, gastric guices, urine, seawater, etc.
Dehydration synthesis Aka condensation reaction To break up polymers = hydrolysis Hydrolytic enzymes (fungus, insect saliva) capable of hydrolyzing polymers.
Organic molecules Macromolecules: carbohydrates, proteins, lipids, nucleic acids, vitamins Carbohydrates: energy storage (starch in plants, glycogen in animals); structural support (cellulose, chitin); energy (reactant in cellular respiration) Ex: glucose, fructose, lactose (-ose) Human insulin and glucagon lowers and raises blood glucose levels. (homeostasis)
Storage vs. Structure Starch, Glycogen Cellulose
Organic molecules Proteins: structural support (microtubules, microfilaments, intermediate filaments that make up muscle fibers), enzymes, regulatory proteins Four folding levels: primary (peptide bonds between amino acids); secondary (hydrogen bonds); tertiary (R-group interactions); quaternary (multiple peptide interactions)
General enzyme characteristics Effective in small amounts Unchanged in a reaction (only substrate changes) Doesnt affect equilibrium in chemical reaction (speeds up process in either direction) Specific to act on substrate molecules Cofactors (inorganic metals) or coenzymes (vitamins NAD and FAD) assist Inhibitors able to affect activity
Competitive inhibition Example: oxygen binding to rubisco instead of carbon dioxide photorespiration
Allosteric site Commonly called regulatory site Example: lac and trp operons
Regulatory pathways Negative feedback enables feedback mechanisms Ex: body temperature regulation