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Chromosome Terminology

Chromosome Terminology. Chromosome = 2 replicated DNA strands. Centromere = place where sister chromatids remain attached and kinetochore forms. Kinetochore = proteinaceous structure where microtubules attach. Chromatid = one DNA strand. Chromatid (sister).

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Chromosome Terminology

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  1. Chromosome Terminology Chromosome = 2 replicated DNA strands Centromere = place where sister chromatids remain attached and kinetochore forms Kinetochore = proteinaceous structure where microtubules attach Chromatid = one DNA strand Chromatid (sister)

  2. Nuclear envelope breakdown occurs thru’ fragmentation Interphase Nuclear envelope Lamina (pink) Lamin phosphor- ylation at prophase NE vesicles Lamin dephosph at anaphase-telophase

  3. Cell Cycle Checkpoints G1 to S: Is cell big enough? If no, stop. Is there DNA damage? If yes, stop Metaphase to anaphase: G2 to M: Is DNA fully replicated? If no, stop Is there DNA damage? If yes, stop Are all sister chromatids attached to opposite poles? If no, stop.

  4. Enzymes are proteins designed to fit a specific substrate(s) Enzyme Substrates Enzyme/Sub- strate Complex Enzyme & Products

  5. (ES) S + E (EP) E + P Diffusion & Affinity Catalysis Product release • Speed up thermodynamically favorable reactions (catalysts). • Specific to substrates or reaction. • Used over & over. • Conformation designed to match substrate.

  6. Induced fit model for enzymes

  7. Enzymes decrease the activation energy in reactions Transition state or hi NRG intermediate W/o enzyme Reactants + enzyme G free NRG Products Progress of rxn

  8. Analogies for NRG barriers

  9. Michaelis-Menten Kinetics Vmax Km

  10. Enzymes use common mechanisms to catalyze rxns Hold substrates correctly.  Reduces diffusion limits. Manipulate charges (electrons).  Increases reactivity of groups. + + - - Physically or chemically stress bonds

  11. Control of Enzyme Activity • Alter enzyme synthesis (expression) • Alter transcription • Alter translation • Regulate degradation rate • Zymogens • Chymotrypsinogen to chymotrypsin • Cofactors (calmodulin, Mg2+, Ca2+) • Phosphorylation • Inhibitors & Activators • Allosteric - not at active site • Competitive inhibition bind at active site Conformational changes

  12. Competitive Inhibition • Inhibitor binds at active site, competing with the substrate • Inhibitor is a chemical analog of the substrate. • Best competitive inhibitors mimic the transition state. substrates E inhibitor

  13. Competitive inhibitors can be overcome by increasing [S] Substrates bind & reaction proceeds

  14. Binding of allosteric effectors causes conformational changes at the active site Allosteric inhibitor binds Allosteric binding site Distorted active site is nonfunctional Active site functional Enzyme Active Enzyme Inactive

  15. Enzyme Summary • Hi Km = low affinity • Vmax = the maximal velocity that an enzyme can catalyze a rxn. Competitive inhibitors • Bind at active site • raise the Km, but do not affect Vmax Noncompetitive inhibitors • Bind at an allosteric site • Lower Vmax, but do not affect Km

  16. Feedback Inhibition E-1 A E-2 E-3 B D C F final product Active Inactive

  17. Biological Oxidations • Removal of electrons and replacement of C-H or C-C bonds w/ C-O bonds • CH3 CH2OH CHO COOH • CO2 Hi NRG Low NRG

  18. Lactic Acid or Ethanol +CO2 2 NADH OR O2 NADH Krebs Cycle e¯ Transport ATP Synthase 32 ATP CO2 Glycolysis is required for both anaerobic and aerobic metabolism Glucose 2 ADP 2 NAD+ 2 ATP 2 NADH Pyruvate

  19. Catabolizing NRG from glucose 2 Lactic acid (3C) or 2 Ethanol (2C) + 2CO2 Fermentation = anaerobic metabolism Electron transport OR glycolysis (6C) TCA cycle ATP synthase 34 ATP 2 ATP 6CO2 Aerobic metabolism mitochondrion

  20. Glycolysis Summary 2ADP + 2NAD+ 2ATP + 2NADH

  21. Glycolysis in Detail

  22. Glycolysis Overview NRG investment 1st 3 steps Committed to glycolysis NRG extraction 2 molecules of pyruvate are final products

  23. Hexokinase Kinases phosphorylate

  24. Phosphofructokinase Enzyme names relate to substrate names ATP  AMP 

  25. Pyruvate kinase Or in glycolysis sometimes to product names

  26. Isomerases move atoms around Phosphoglucose isomerase

  27. Dehydrogenases remove H

  28. Krebs cycle

  29. Pyruvate enters the Krebs cycle via Coenzyme A 2 C from pyruvate break off & bond w/ CoA to form acetyl CoA The 2C then leave acetyl CoA to form citrate 4 C 6 C

  30. Krebs or citric acid cycle 2C 6C 4C NADH + H+ NADH + H+ CO2 5C NADH + H+ 4C CO2 FADH2 GTP

  31. Oxidative phosphorylation Outer Membrane Intermembranous space pH  7 ATP synthase F0 = stalk IV III I F1 = ball -200 mV pH  8 Inner Membrane Matrix Electron transport system

  32. 3H+ 2H+ 4H+ 2H+ O2 2H+ 4H+ H2O ATP 2H+ ADP + Pi 2e- 3H+ Oxidative phosphorylation ATP synthase IV III I NADH + H+ -200 mV pH  8 Inner Membrane Electron transport system

  33. ETS & Oxidative Phosphorylation • NRG released during transport of e- is used to pump H+ from matrix to IM space • Creates a [H+] gradient which serves as an energy source (electrochemical potential) • H+ can only re-enter matrix through ATP synthase. • Movement of H+ changes conformation of ATP synthase which allows ATP to be made from ADP

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