BSCI105 Exam 2 Study guide
BSCI105 Exam 2 Study guide BSCI105
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This 8 page Study Guide was uploaded by Cathryn Tsu on Monday March 7, 2016. The Study Guide belongs to BSCI105 at University of Maryland taught by Norma Allewell in Spring 2016. Since its upload, it has received 170 views. For similar materials see Principles of Biology in Biological Sciences at University of Maryland.
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Date Created: 03/07/16
03/07/2016 BSCI105 EXAM 2 (Chapters 710) STUDY GUIDE Date of exam: Friday, 03/11/16 Chapter 7: Membrane Structure & Function Selective Permeabilit when the plasma membrane permits specific substances to cross it more easily than others ❖ Constant movement across the membrane ❖ Nonpolar molecules (hydrophobic) dissolve in the bilayer and cross w/ ease ❖ Polar molecules (sugars)/ water → hydrophilic so pass slowly ❖ Transport Proteins ➢ Channel proteins essentially a hydrophilic passage for molecules & ions to use to pass through the membrane ■ Aquaporins channel proteins that assists in the passage of H2 O molecules ➢ Carrier proteins carry their molecules/ions & as a result, changes the shape to push them across the membrane taken from pg. 133 Lipids (most abundant →hospholipids), proteins, and sometimes carbohydrates are the membrane’s fundamental components Phospholipids aremphipatic have both a hydrophilic head and a hydrophobic region Fluid Mosaic Model Phospholipid bilay separates the 2 sides of the membra (hydrophobic tails are “shielded” from water; hydrophilic heads are exposed to the membrane’s extracellulr and cytoplasmic sides) ❖ Extracellular Side Extracellular Matrix (ECM) ➢ Fibers of the ECM attach to membrane proteins (i.e integral protei to add to the membrane’s framework 03/07/2016 ➢ Contains extracellular fluid, collagen, & fibronectin Glycoproteins ➢ When membrane carbohydrates (short branched chains of <15 sugar units) covalently bond to proteins Glycolipids ➢ When the membrane carbohydrates covalently bond to lipids ❖ Cytoplasmic Side Cholesterol ➢ Steroid inserted b/t the phospholipid molecules ★ Two prominent protein populations: Peripheral Proteins (look like eggs) ➢ Not lodged in the lipid bilayer ➢ Attachments are loosely connected to the surface of the membrane exposed to integral proteins Integral Proteins (look like brontosauruses) ➢ Penetrates the lipid bilayer’s hydrophobic inside ➢ Most are transmembrane proteins that surround the membrane ➢ Structure (basically): Nterminus α helices (nonpolar amino acids) Cterminus ★ Both glycoproteins & glycolipids play an integral role in m embrane synthesis pg. 129) Membrane fluidity (affects permeability and protein movement) ❖ Held together by hydrophobic interactions (weaker than covalent bonds) ❖ Lipids & some proteins shift laterally @ rapid speed (sometimes, although rare, flip across membrane and phospholipid layers) ❖ Proteins →immobile b/c of their attachment to the cytoskeleton/ECM ❖ Membrane stays fluid as temp. decreases until phospholipids settle closely packed & solidify ❖ Depends on: 03/07/2016 ➢ Cholesterol (animal cells) “fluidity buffer” that reduces phospholipid movement making the membrane viscous @ high temps. & lowers the temp. needed to solidify the membrane (disrupts phospholipid packing) ➢ Unsaturated vs. Saturated Kinked C tails prevent packing packed close together More fluid Less fluid (more viscous) ★ Variations w/in cell membranes depend on different types of environments Membrane protein functions (pg. 1: ❖ Transport ❖ Enzyme activity ❖ Signal transduction ★ ❖ Cell → cell recognition ❖ Intercellular joining ❖ Cytoskeleton & ECM attachment Passive Transport (doesn’t require energy) ❖ Diffusion the movement of particles into all possible available space ➢ Individual movement = random, population movement = directional ➢ More concentration → less concentration ➢ One solute vs.two solutes (pg. 131) ➢ Substances diffuse down their individualoncentration gradients (the area where the density ↑or ↓) ■ represents potential energy & fuels diffusion Water balance ❖ Cells w/o cell walls ➢ Tonicity the ability of a solution to cause a cell to gain/lose water ■ Isotonic ideal; the environment is the same to the cell’s and there is no net movement of water ■ Hypotonic lower solute concentration; water enters quicker than it exists and so the cell bursts ■ Hypertonic higher solute concentration; the cell loses too much water and so shrinks and could possibly die ❖ Cells w/ cell walls ➢ Cell wall will expand only so much until it reaches a point where it urgor t pressure ■ Hypotonic →turgid (ideal) ■ Isotonic → limp ■ Hypertonic →pulls away from membrane @ multiple points Plasmolysis) ❖ Osmosis diffusion of water across a membrane 03/07/2016 ❖ Osmoregulation the control of solute concentration & water balance Facilitated diffusion (passive transport assisted by transport proteins) ❖ Ion channels, usually thought of as gated channels that open/close for different stimuli Active transport (needs energy, solute concentration against the gradient) ❖ Transport proteins: carrier proteins ❖ lets cells maintain differing internal concentrations ❖ Uses ATP for energy ➢ Terminal phosphate group →carrier protein + + ➢ NaK Pump trades Na for K across membrane ( ★ animal cells) Pg. 135 ❖ Ion pumps maintain m embrane potential (voltage across a membrane; ranges from approx. 50 to 200 mV since a cell’s interior is () ) ❖ Cotransport a transport protein that can combine a downwards diffusion w/an additional substance transport upwards against its gradient ★ Ions diffuse downboth heir concentration gradientnd lectrochemical gradient ❖ Electrogenic pump a transport protein creates voltage across a membrane + ➢ Proton pump moves protons (H ) out of the cell & transfers a (+) charge from cytoplasm → extracellular solution Exocytosis Endocytosis ➔ When a cell secretes molecules ➔ When a cell absorbs molecules & through the combination of separates matter by generating vesicles & the membrane new vesicles from the membrane ◆ Transport vesicles (golgi) → ➔ Types microtubules → lasma ◆ Phagocytosis : cell absorbs a particle through extending membrane →b ilayer pseudopedia & packing it in a molecules get rearranged food vacuole (fusion) →ecrete ◆ Pinocytosis: cell consistently molecules takes in EC fluid into small vesicles ◆ Receptormediated : a particular form of pinocytosis that lets a cell gain huge amounts of substances Chapter 8: Intro to Metabolism Metabolism the entirety of an organism’s chemical reactions 03/07/2016 ❖ Metabolic pathway when a molecule is transformed through a series of steps that are each catalyzed by a different enzyme ( ★ an enzyme acts as a regulator to balance metabolism) ➢ Anabolic pathways (absorb energy); build complex molecules from simple ones ➢ Catabolic pathways (release energy); breakdown of complex molecules into simpler ones Energy ❖ 1st Law of Thermodynamics energy can neither be created nor destroyed, just transferred and transformed ❖ 2nd Law of Thermodynamics every energy transfer/transformation increases the entropy (disorder) of the universe ❖ Spontaneous process when/if a process individually leads to an increase in entropy, it can continue w/o energy input ❖ Free energy of a system: predicts if a reaction is spontaneous ΔG = ΔH − TΔS ΔG = change in free energy ΔH = change in enthalpy T = temp. (K) ΔS = change in entropy Exergonic reaction Endergonic reaction Releases free energy Absorbs free energy Spontaneous Nonspontaneous −ΔG +ΔG The energy of reactants is > than products The energy of products is > reactants 03/07/2016 Activation enethe energy needed to break bonds (twisting the molecules) ★ Enzymes lower the activation energy barrier to accelerate the reactions ❖ Energy coupling the use of an exergonic reaction to power an endergonic one (ATP is important) ➢ ATP’s phosphate group bonds can be broken by h ydrolysisexergonic reaction) but the released energy comes from change to lower energy level ➢ Phosphorylated Intermediate the receiving molecule that is covalently bonded to the phosphate groups (less stable) which contributes to the changing shape of proteins & motor proteins Enzymes ❖ Substrate the reactant an enzyme acts on ❖ Substrate ⇒Substrateenzyme complex (enzyme bonded to substrate) ⇒Enzyme & product ❖ Active site the only region that binds to the substrate because of its complementary shape ➢ Induced fit when the active site closes up and creates an ideal environment for the substrate (Pg. 154) ❖ Cofactors nonproteins that assist in catalytic activity ❖ Enzyme inhibitors (enzyme reverts back to normal when these inhibitors are removed) ➢ Stabilizes inactive shape ➢ ATP ➢ Competitive vs. Noncompetitive Molecule directly binds to the active Molecule binds to thllosteric site site, blocking the substrate & changes the active site’s shape ★ Michaelis & Menten equation ★ Chapter 9: Cellular Respiration & Fermentation Redox reactions (transfer of 1 or more electrons from 1 reactant to another) ❖ Releases stored energy used to make ATP 03/07/2016 ❖ Oxidation loss of electrons ➢ Reducing agent the substance that accepts the electrons ❖ Reduction addition of electrons ➢ Oxidizing agent the substance that loses the electrons + − Ex. Na + Cl → Na + Cl Na ⇒oxidized & is the reducing agent Cl ⇒ reduced & is the oxidizing agent Cellular/Aerobic respiration (exergonic) C 6H 12 6 6O 2→ 6CO + 62 O + A2P oxidized reduced Glycolysis Pyruvate Oxidation Citric acid cycle Oxidative phosphorylation ● Glucose → 2 ● Pyruvate is ● Oxidizes the ● The electron pyruvate oxidized into organic fuel from transport chain ● Loses 2 ATP acetyl CoA pyruvate absorbs ● Gains 4 ATP ● Reduces NAD + electrons from ● Reduces NAD + to NADH the breakdown products of the to NADH ● R leases CO 2 previous steps ● Electron transport chain: electron carriers alternate b/t oxidized & reduced states as they gain/lose electrons ● Chemiosmosis : process that stores energy as 03/07/2016 a hydrogen ion gradient (ATP synthase*) 2 ATP + 2 NADH + 2 2 acetyl CoA + 2 NADH + 6 NADH + 2 FADH + 2 About 26/28 ATP; pyruvate 2 CO 2 ATP + 4 CO 2 everyt+ing reduced +o NAD and FADH Fermentation (breakdown of organic fuels w/o oxygen ❖ Alcohol fermentation ❖ Lactic acid fermentation Chapter 10: Photosynthesis ★ For this test, it’s just important to know the fundamentals of photosynthesis (the process’ complexities will be tested later on in Exam 3 and the final according to Prof. Allewell) Light reactions (dependent on light) ❖ Photosystem II (functions 1st) ❖ Photosystem I ❖ Electron Transport chain Dark reactions (don’t need light) ❖ Calvin cycle
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