1AP Biology Exam Review (2002-2003) Molecules and Cells – 25%
2Chemistry of Life – 7% Water Organic molecules in organisms Free energy changesEnzymes
3Polar water molecule Polar covalent bonds polarity Polarity hydrogen bonding and various water properties
4Water propertiesEx: How do the unique chemical and physical properties of water make life on earth possible?Cohesion: transpiration, bloodAdhesion: transpirationIdeal solvent: xylem and phloem sap, oceans, blood, hemolymphDensity: maintaining marine lifeHigh specific heat: maintaining stability (homeostasis)
5pH H2O + H2O H3O- + OH- Water dissociation = H2O H+ + OH- 1/554 million water molecules dissociates in pure water.pH = 7 when [H+] and [OH-] equal to 10-7
6Acids and Bases Acids: pH < 7 Ex: stomach acid, increasing H+ gradientBases: pH > 7Neutral: pH=7Ex: blood, urine, body fluidsBuffers required to maintain neutrality. (homeostasis)
7Buffers H2CO3 + OH- HCO3- + H2O HCO3- + H+ H2CO3 Ex: Human red blood cellsCarbonic acid (H2CO3) and Bicarbonate (HCO3-) buffers to maintain blood cell pH.How can blood cell pH be raised or lowered?
8pHMake sure you know the general pH of some biologically important aqueous solutions: blood, gastric guices, urine, seawater, etc.
9Dehydration synthesis Aka “condensation reaction”To break up polymers = hydrolysisHydrolytic enzymes (fungus, insect saliva) capable of hydrolyzing polymers.
10Organic moleculesMacromolecules: carbohydrates, proteins, lipids, nucleic acids, vitaminsCarbohydrates: 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)
19Organic moleculesLipids: membrane structure, long term energy storage, brain insulationSmooth endoplasmic reticulum product; stored in adipose tissue (made of fat cells)Steroid rings: sex hormones, cholesterol (animals only)Phospholipid: membrane
20Organic molecules Nucleic acids: ATP, GTP, nucleotides DNA remains within nucleus of eukaryotes.Circular DNA in prokaryotes with plasmids
21Free energy changesGoverned by two laws of thermodynamics
22First law of thermodynamics Conservation of energyEx: coupled reactions, nutrient cyclingCoupled reactions happen in the electron transport chain.ATPADP + PGTPGDP + P
23Second law of thermodynamics EntropyEx: 10% energy loss in environment, proton gradient, diffusion, higher to lower concentration (countercurrent exchange), depolarization
24Exergonic vs. Endergonic reactions What are some of these processes that occur in biological systems?
27General enzyme characteristics Effective in small amountsUnchanged in a reaction (only substrate changes)Doesn’t affect equilibrium in chemical reaction (speeds up process in either direction)Specific to act on substrate moleculesCofactors (inorganic metals) or coenzymes (vitamins NAD and FAD) assistInhibitors able to affect activity
28Competitive inhibition Example: oxygen binding to rubisco instead of carbon dioxide photorespiration
29Allosteric site Commonly called “regulatory site” Example: lac and trp operons
30Regulatory pathways Negative feedback enables feedback mechanisms Ex: body temperature regulation