Presentation on theme: "AP Biology Exam Review (2002-2003) Molecules and Cells – 25%"— Presentation transcript:
AP Biology Exam Review ( ) 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 H 2 O HCO 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)
Tertiary Important in the formation of active sites of enzymes
Protein denaturation Chaperonin, heat shock proteins
Organic molecules Lipids: membrane structure, long term energy storage, brain insulation Smooth endoplasmic reticulum product; stored in adipose tissue (made of fat cells) Steroid rings: sex hormones, cholesterol (animals only) Phospholipid: membrane
Organic molecules Nucleic acids: ATP, GTP, nucleotides DNA remains within nucleus of eukaryotes. Circular DNA in prokaryotes with plasmids
Free energy changes Governed by two laws of thermodynamics
First law of thermodynamics Conservation of energy Ex: coupled reactions, nutrient cycling ATPADP + P GTP GDP + P Coupled reactions happen in the electron transport chain.
Second law of thermodynamics Entropy Ex: 10% energy loss in environment, proton gradient, diffusion, higher to lower concentration (countercurrent exchange), depolarization
Exergonic vs. Endergonic reactions What are some of these processes that occur in biological systems?
Effects of enzymes
Lock and key vs. induced fit model
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
Trp operon in bacteria only
Lac operon in bacteria only
Enzymes Enzymes denature with changes in temperature and pH. Example showing Importance of homeostasis
cAMP as secondary messenger Proteins and receptors involved in signal amplification