Study guide for Exam 1
Study guide for Exam 1 BIOB 260 - 00
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BIOB 260 - 00
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This 5 page Study Guide was uploaded by Ashley Alexander on Thursday September 24, 2015. The Study Guide belongs to BIOB 260 - 00 at University of Montana taught by Scott Samuels (P), Mark Lindsay Grimes in Fall 2015. Since its upload, it has received 151 views. For similar materials see Cellular and Molecular Biology in Biological Sciences at University of Montana.
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Date Created: 09/24/15
Cell Molec Exam 1 Study Guide These are the answersexplanations that I have found for the study guide that was posted 1 Thermodynamics a b 2 Lipids a b The two thermodynamic components of free energy are Entropy S and Enthalpy H The Keq is the equilibrium constant or the concentration of products over reactants at equilibrium AG specifies free energy at STP AGI speci es free energy at STP and 1 M concentration and neutral pH Enzymes catalyze reactions by lowering the activation energy This is made possible by stabilizing transition states Phospholipid 9 Hydrophilic head Hydrophobic tail Lipids cause water molecules to be more ordered this decreases entropy and makes free energy more positive therefore this is a more energetically unfavorable situation for hydrophobic molecules such as lipids to be exposed to water directly I like to envision water molecules as monkeys swinging through trees They can maintain their kinetic energy by swinging off of each other and other polar molecules by way of polar regions branches When water encounters a hydrophobic molecule it s like encountering a tree with no branches and the water molecule or monkey has to find a new path in order to keep its momentum Thus its much easier if you can put all of the branchless trees or nonpolar molecules in one place to be avoided 3 Lipids with different structures a If lipids had only one fatty acid tail they would form micelles because their molecular shape would resemble more of a conical shape rather than a cylindrical shape which can be stacked b If fatty acid tails were shorter the bilayer would be more uid and weaker just like a sheet of plastic gets weaker and imsier as it gets thinner c If all the hydrocarbons in a bilayer were all saturated the bilayer would lose flexibility because its subunits would be stiffer d If all the lipids were unsaturated the bilayer would be more fleXible and not as strong e The bilayer would probably not change if molecules are specific to being saturated versus unsaturated as long as they were evenly dispersed f If the phospholipids covalently linked to hydrocarbon tails didn t eXist the bilayer could not eXist because there would be nothing to shield the hydrophobic tails from water g If phospholipids had 2 heads meaning the tails would be continuous the lipid bilayer would be unchanged because the chemical properties would be virtually the same 4 Cholesterol stabilizes the phospholipid bilayer 5 Proteins a Transmembrane proteins span entire membrane b Membrane associated proteins Irma hiriawr C All below are membrane associated proteins Lipid Linked Proteins i Numbers 1 3 and 4 are all lipid linked as well d Protein attached membrane proteins i Numbers 5 and 6 are protein attached membrane proteins as well 6 Molecules in order of membrane permeability a Hydrophobic they are pushed toward the hydrophobic molecules inside the bilayer by entropy changes in water Small polar attracted to hydrophilic heads Large polar also attracted to the hydrophilic heads but they diffuse more slowly d Charged water forms a cage like structure around these molecules making their overall structure huge and highly unlikely to diffuse through the membrane 7 Transporters a Symport i Molecules are moved against their concentration gradient by coupling them With another molecule that moves through the same transporter in the same direction b Antiport i Same idea as the symport but molecules move in opposite directions c Uniport i Only a single molecule moves either With its concentration gradient or it must be pumped With the assistance of ATP llnilrl t lr Synpnrt lr Antipmm r 8 Na K ATPase a When a neuron is excited by a sensory signal it must send this signal across the body to the processing organs It does this by allowing a chemical charge imbalance across the membrane of the nerves axon This charge imbalance occurs because the cell maintains high concentrations of K ions inside the cell and high concentrations of Na outside the cell The cell blocks Na from entering the cell by keeping the Na pumps closed but allowing K to leak out through its selective channels A positive charge builds up on the outside of the cell this is the repolarized state When the axon receives enough stimulus it opens the Na channels and sodium across the membrane releasing energy that causes adjacent channels to open this is the depolarized state To keep the signal from owing backward Na pumps are inactivated after they pass the signal on Then once the signal has passed the process repeats itself as the cell begins to pump sodium ions out and potassium ions in restoring the charge this is the resting state 9 A K will have no net movement B K will move out of the vesicles C K will move into the vesicles 10 1 Rising potential sodium channels open 2 Falling potential sodium channels inactivated 3 Afterhyperpolarization sodium channels closed 11 Action potential only travels in one direction because after the membrane is depolarized the pumps become inactivated preventing a backward ow of the signal 12 Excitatory neurons send sodium ion pumps into their open state and thus raise the action potential Inhibitory neurons lower the charge difference and raise the threshold for sodium channels to open
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