1 / 51

Cell Cycle

Cell Cycle. G1. S. G2. M. Prophase : Chromosomes condense into visible structures. Nuclear envelope breaks down. Interphase microtubules disassemble. Spindle forms. Prometaphase: Chromosomes make attachments to each pole and align on the spindle equator (metaphase plate).

osanna
Download Presentation

Cell Cycle

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Cell Cycle G1 S G2 M

  2. Prophase: • Chromosomes condense into visible structures. • Nuclear envelope breaks down. • Interphase microtubules disassemble. • Spindle forms. • Prometaphase: • Chromosomes make attachments to each pole and align on the spindle equator (metaphase plate).

  3. Opposing forces & polym slowly move chromosomes to equator

  4. Metaphase: • Chromosomes are aligned on equator. • Within a chromosome, sister chromatids are attached to opposite poles via attachment of kinetochores to microtubules.

  5. N

  6. Microtubules attach to chromatids at kinetochores

  7. Centrioles and centrosomes duplicate during S & G2

  8. Anaphase: • A- Sister chromatids separate. • Sister chromatids (now independent chromosomes) move along kinetochore microtubules to the pole to which they are attached. • B- The poles move apart.

  9. Microtubules Forces at anaphase are exerted at kinetochores and overlap zone Minus end directed motors + - Plus end directed motor

  10. Telophase: • Spindle disassembles. • Chromosomes decondense. • Nucleus reforms (nuclear envelope reassembles). • Interphase microtubule array reforms.

  11. Nuclear envelope breakdown occurs thru’ fragmentation Lamin phosphor- ylation at prophase Lamin dephosph at ana- telophase

  12. Thermodynamics determines whether a reaction CAN go • The change in free NRG (DG) for a reaction determines whether or not it is spontaneous. • The units for DG are cal/mol. • If DG is negative - the reaction is spontaneous and considered thermodynamically favorable. • If DG is positive - the reaction is NOT spontaneous and considered thermodynamically UNfavorable. • The sign AND magnitude of DG matters! • The standard free energy change (DG’) is the free energy change figured under a set of specified conditions, called standard conditions. • Standard conditions: 25C, 1 atm, 1 M concentration for all reactants (except H20 which is at 55.6 M), pH 7 (‘).

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

  14. Induced fit model for enzymes

  15. (ES) S + E (EP) E + P Diffusion & Affinity Catalysis Product release

  16. 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

  17. Analogies for NRG barriers

  18. Michaelis-Menten Kinetics Vmax Km

  19. 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

  20. 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

  21. O ¯O P O¯ O O ¯O P O¯ O Phosphorylation ACTIVATING ADP + kinase ATP + kinase INHIBITING ADP + kinase ATP + kinase

  22. Enzyme inhibitors • Important for cellular regulation of enzyme activity (turn off enzyme), useful for scientists (study transition state), important for pharmaceutical/biotech companies (drugs, antibiotics, pesticides). • Enzyme inhibitors fall into two broad classes: • Irreversible inhibitors - bind tightly, often covalently. • Reversible inhibitors - bind loosely and can be displaced. • Competitive - bind to enzyme’s active site. Can be overcome by high [S]. Raises Km; Vmax same. • Noncompetitive - bind to site on enzyme other than active site.Cannot be overcome by high [S]. Km same; lowers Vmax. • Uncompetitive - binds to and stabilizes ES complex. Lowers Km; lowers Vmax.

  23. Lineweaver-Burk plots of reversible enzyme inhibitors Uninh. Inh. Competitive Noncompetitive Uncompetitive

  24. Competitive Inhibition Can be overcome by increasing [S] substrates inhibitor E

  25. Binding of allosteric effectors& Conformational changes Allosteric binding site Active site

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

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

  28. 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

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

  30. Glycolysis

  31. How Can the Production of ATP Be Thermodynamically Favored? These compounds have a lower affinity for their phosphate group compared to ATP.

  32. Hexokinase Kinases phosphorylate

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

  34. Pyruvate kinase Or in glycolysis sometimes to product names

  35. Isomerases move atoms around Phosphoglucose isomerase

  36. Dehydrogenases remove H

  37. Krebs cycle

  38. Pyruvate enters the Krebs cycle via Coenzyme A

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

  40. 3H+ 2H+ 4H+ 2H+ O2 2H+ 4H+ H2O ATP 2H+ ADP + Pi 2e- 3H+ Oxidative phosphorylation ATP synthase IV III I NADH -200 mV pH  8 Inner Membrane Electron transport system

  41. Viruses come in many flavors • All contain nucleic acid and some protein • DNA or RNA • single-stranded or double-stranded • RNA viruses are positive sense strand, negative sense strand, or retroviruses • reverse transcriptase • Protein Coat protects nucleic acid and mediates binding to host cell. • Viroids have no protein coat

  42. Bacteriophage inject DNA into host

  43. HIV is a retroviral provirus

  44. Virus life histories • Typically host-cell specific, only replicating in a host • Lytic viruses escape by lysing and killing host • Lysogenic viruses live in host for long periods of time, continually releasing more virus • Typically, take over host transcription & translation machinery. • Capsids assembled in cytoplasm or PM

  45. Prokaryotes • No nucleus or organelles • Circular DNA • complex biochemistry • Rods, cocci, spirochete.

  46. More prokaryotes • Typically reproduce by simple fission. • Quite rapid

  47. Prokaryotes can exchange genes thru conjugation Plasmid

  48. Fungi • Multicellular forms make mycelia and hyphae • Cell walls of chitin • Generally haploid throughout most of life cycle

  49. Fungal diversity • Ascomycota: yeasts and mildews • meiosis produces spores held in asci or sacs • Basidiomycota: Club fungi, mushrooms. • haploid hyphae conjugate to form dikaryons • Diploids form in basidia to produce haploid spores • Zygomycota: Molds • hyphae lack septa = multinucleate

More Related