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BSCI105 Exam 2 Study guide

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by: Cathryn Tsu

BSCI105 Exam 2 Study guide BSCI105

Marketplace > University of Maryland > Biological Sciences > BSCI105 > BSCI105 Exam 2 Study guide
Cathryn Tsu
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Hey guys, this study guide is for our next exam that covers Chapters 7-10. I tried to add as much info as I could. All info is based off of the textbook. Enjoy and good luck!
Principles of Biology
Norma Allewell
Study Guide
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"Can you just teach this course please? lol :)"
Dr. Samara Sanford

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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 are​mphipatic ​­ 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 e​xtracellulr 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 individual​oncentration 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 down​both heir concentration gradient​nd ​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 th​llosteric 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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