Bisc 160 Chapter 8 9 23 15 The same signals can result in completely different responses Receptor intermediate second messenger Second messengers amplify signals Receptor and effector o Direct Indirect o o o o Signal cascades Rapid amplification Examples Cyclic AMP cAMP Diacylglycerol Inositol triphosphate Calcium ions Nitric Acid Variety of second messengers cAMP nucleotide They can turn on the opening of ion channels calcium ions Can do stuff with enzymes Triggers reactions o o o o o Nitric oxide activates chemicals within a cell Gets turned on by signal transduction but then leaves cell as a gas and goes to other cell to do stuff Signal transduction is regulated o Regulation Regulating enzymes and second messengers Turning on and turning off of signal transduction process Enzymes can deactivate things o o Enzyme synthesis breakdown Enzyme activation or inhibition by other molecules Signal transduction alters cellular activities o Open ion channels Neuron activity uses ion channels a lot to get messages to brain o Alter enzyme activities Start DNA transcription o Cells can communicate directly o Gap junctions Small pores between two different cells Only in animals o Plasmodesmata Only in plants Energy is the capacity for change o Biology energy Same thing as gap but bigger than gap junctions can move things through like glucose o o o o o o o o o o o o o Chemical reactions Breaking bonds making bonds use ATP convert stuff from outside to make ATP Storage of energy with carbohydrates glycogen starch Energy stored in chemical bonds Capacity for change change in bonds and molecule properties Physics definition of energy is different Energy can be stored converted into movement Stored energy potential energy Potential energy stored energy kinetic energy when actually doing work Chemical energy stored energy mechanical energy when actually doing work Metabolism is the sum of all chemical reactions o Anabolic reactions Kinetic to potential Building molecules o Catabolic reactions Potential to kinetic Break apart molecules ATP is a catabolic reaction Energy is neither created nor destroyed 1st law of thermodynamics free energy Chemical bonds carbs lipids ATP mechanical or biochemical work Potential energy kinetic energy Just switching energy around Not making or destroying it o o Use free energy to do work o Every time you do a chemical reaction you lose some free energy Let off little molecules that move around Lose some heat Energy unavailable for work Entropy Figure 8 2 Entropy disorder increases with the number of reactions 2nd law of thermodynamics Total energy includes usable and unusable energy o H G TS G H TS Enthalpy H Free energy G Entropy S Temperature T Free energy can be used or released o G reactants H reactants TS reactants Same equation for products o Change or delta G G products G reactants Positive DelG energy consumed Negative DelG energy released Free energy depends on DelH and DelS o G H TS o DelG DelH T DelS Building complex organisms generates disorder 10 kg of organized molecules Building takes energy generates disorder o o o Maintenance