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Week 6 Notes

by: Rebecca Sharp
Rebecca Sharp

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These notes cover what we went over in class
Principles Of Biology I
Stevan Marcus
Class Notes
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This 3 page Class Notes was uploaded by Rebecca Sharp on Tuesday March 1, 2016. The Class Notes belongs to BSC 114 at University of Alabama - Tuscaloosa taught by Stevan Marcus in Winter 2016. Since its upload, it has received 34 views. For similar materials see Principles Of Biology I in Biological Sciences at University of Alabama - Tuscaloosa.

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Date Created: 03/01/16
Cell Metabolism  Cell Metabolism is defined as the totality of chemical reactions in a living organism  A starting molecule begins the process, and it ends with a product  Each step is catalyzed by an enzyme, like the hydrolyzation of sucrase o A catalyst is something that helps the reaction to happen easier, ie using less energy, without being used up in the actual reaction itself  Metabolic Pathways can be either Catabolic (release energy) or Anabolic (sonsume energy) o Catabolic breaks down more complex molecules into simple ones o Anabolic builds up complex molecules from simple ones Energy And Its Various Incarnations as it Relates to the Cell  Energy is defined as the ability to do work  Kinetic Energy is the energy of speed, this is the kind of energy a roller coaster has just after screaming down the first hill.  Thermal Energy is the energy of heat, for biological purposes it’s caught up with and concerned with the random movement of atoms and assorted molecules  Potential Energy is officially defined as energy an object has by virtue of its location or structure. This is the kind of energy the roller coaster has at the top of that first hill looking down.  Chemical Energy is the Potential Energy that’s available for release in the chemical reaction Entropy  All living things are ‘open systems’ which means energy and matter can be transferred between us and our surroundings  This means we lose a LOT of heat energy, life as a biological process is really incredibly inefficient  Entropy is the name for the tendency of things to disproportionately lean towards chaos. This trend has been gradually increasing since the beginning of the universe. It’s represented by an ‘S’  Heat increases entropy. So the existence of life is just hastening the end of the universe because the thing about heat energy is that it just dissipates. Lots of other energies are translated into other forms of energy as they’re used up, for example potential energy can become kinetic, or chemical energy can become electric, but heat energy just vanished off into the universe and cools. So what’s coming is eventually all the energy in the universe will become heat energy and dissipate into nothing. Free Energy  Free Energy is the amount of energy available for use when temperature and pressure are uniform in a cell. Represented by ‘G’. It’s a measure of the instability of the system.  Energy used in a cell can be expressed as “Delta G = G final-G initial”  When free energy decreases in a system, the system is more stable  Max stability happens at equilibrium. The only time a cell can do work is when it’s moving towards that equilibrium. So, since work has to be done, nothing is at equilibrium ever.  Processes with a negative change in free energy release energy that can be used for work  The change in energy (Delta G) can be found by the formula; “Delta G=Delta H – T Delta S”, which, in words, means ‘the change in free energy equals the change in heat energy minus the combined amount of the temperature in kelvins times the change in entropy’  When the change in G is positive, the reaction is called Endergonic, and the reaction absorbs free energy  When the change in G is negative, the reaction is called Exergonic, and the reaction releases free energy How Work Works  There’s 3 major types of work  Chemical, like the synthesis of macromolecules  Mechanical, like moving chromosomes around during cell division  Transport, like motor proteins moving vesicles alone the cytoskeleton  ATP powers most of the thing done in a cell, it balences reactions between endergonic and exergonic to help the cell get the energy balance it needs to get things done.  ATP can be broken down into ADP, a much more stable molecule, in an exergonic reaction. Water breaks off a phosphate group in hydrolysis.  This exergonic reaction triggers an endergonic reaction. They work in pairs that way, like yin and yang.  This is reversible, you can stick that phosphate right back on ADP to make ATP again, which allows the ATP to work both ways, to trigger both kinds of reactions. Anatomy of an Enzyme  The enzyme’s reactant that it acts on is called its substrate  When the enzyme binds to its substrate, it’s called an enzyme- substrate complex  The place the substrate binds is called the active site o Things other than substrates can bind to active sites, for example competitive inhibiters which prevent the enzyme from actually getting any work done. Competitive enzymes are the Netflix tab; the enemy of productivity. o Noncompetitive inhibiters also bind to enzymes, but don’t directly interfere with an enzyme’s ability to bind substrates, but do lower the enzyme’s ability to catalyze reactions  When an enzyme changes its shape to accommodate its substrate, it’s called an induced fit  One enzyme can influence thousands of substrate molecules per second o I.e. catalase can convert millions of hydrogen peroxides to water molecules per second. Things that Effect Enzymes  Temperature; each enzyme has a specific temperature it functions best at, human enzymes function best around 35-40 degrees Celcius, while more heat resistant bacteria have enzymes that function best around 75-80 degrees Celcuis.  PH; each enzyme has a specific PH it functions best at. They’re all over the map, some function best on the basic side of the scale (trypsin, 8) and some function best at the acidic end of the scale (pepsin, 2)  Chemicals that specifically affect the enzymes in question Cell Communication  Important to unicellular lifeforms but of paramount importance to multicellular life forms  Examples of uses; response to inner and outer cellular enviorements, repair of cellular damage, growth regulation, and neurological function  The signals are relayed via special signal transduction pathways Signal Transduction Pathways  Defined as the series of steps by which a cellular response is generated by a stimulus on a cell’s surface  Done by biochemical reactions, catalyzed by enzymes, which are activated by other enzymes Stages of Cell Signaling  Reception; a reception molecule ‘receives’ and binds to a signal molecule o The signal receptor is now activated  Transduction; the activated signal receptor signals to other molecules down the chain what is going on  Response; molecules toward the end of the line actually take action and either activate or inhibit their targets to initiate a cellular response to the initial signal


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