Cell Metabolism Part 2


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  • Fits nicely into a 90 min lecture including showing the 15 min movie clip on Protein Synthesis from the Prentice Hall Anatomy and Physiology video.
  • Cell Metabolism Part 2

    1. 1. Ch 4: Cellular Metabolism - P art 2 <ul><li>Energy as it relates to Biology </li></ul><ul><li>Enzymes </li></ul><ul><li>Metabolism </li></ul><ul><ul><li>Catabolism (ATP production) </li></ul></ul><ul><ul><ul><li>Glycolysis and the TCA Cycle </li></ul></ul></ul><ul><ul><li>Anabolism (Synthetic pathways) </li></ul></ul><ul><ul><ul><li>Protein Synthesis </li></ul></ul></ul>
    2. 2. Metabolism <ul><li>Definition = “All chemical reactions that take place within an organism.” </li></ul><ul><li>Metabolic pathways = network of linked reactions </li></ul><ul><li>Basic feature: coupling of exergonic </li></ul><ul><li>rxs with endergonic rxs. (direct vs. indirect coupling) </li></ul>
    3. 3. Review: <ul><li>Energy = capacity to do work </li></ul><ul><ul><li>Usually from ATP </li></ul></ul><ul><li>Enzymes = biological catalyst </li></ul><ul><ul><li>Lower activation energy </li></ul></ul><ul><ul><li>Return to original state </li></ul></ul><ul><ul><li>Opportunity for control </li></ul></ul>
    4. 4. Metabolism p 101 Anabolism  Synthesis Energy transferred commonly measured in calories: 1 cal =  1 g of H 2 O by 1 ° C 1 Kcal =  temp. of 1L H 2 O by 1 o C. = Calorie (capital C) Energy released in catabolic reactions is trapped in 1) Phosphate bonds 2) Electrons Catabolism  Energy
    5. 5. Metabolic pathways: Network of interconnected chemical reactions Linear pathway Circular pathway Branched pathway Intermediates
    6. 6. Control of Metabolic Pathways <ul><li>Enzyme concentration (already covered) </li></ul><ul><li>Enzyme modulators </li></ul><ul><ul><li>- Feedback- or end product inhibition </li></ul></ul><ul><ul><li>- Hormones </li></ul></ul><ul><ul><li>- Other signaling molecules </li></ul></ul><ul><li>Different enzymes for reversible reactions </li></ul><ul><li>Enzyme isolation </li></ul><ul><li>Energy availability (ratio of ADP to ATP) </li></ul>(Chapter 6)
    7. 7. Catabolic Pathways: ATP -Regeneration <ul><li>Amount of ATP produced reflects on usefulness of metabolic pathways: </li></ul><ul><ul><li>Aerobic pathways </li></ul></ul><ul><ul><li>Anaerobic pathways </li></ul></ul>Different biomolecules enter pathway at different points
    8. 8. ATP = Energy Carrier of Cell (not very useful for energy storage) ATP : ADP ratio determines status of ATP synthesis reactions ATP Cycle
    9. 9. Glycolysis <ul><li>From 1 glucose (6 carbons) to 2 pyruvate (3 carbons) molecules </li></ul><ul><li>Main catabolic pathway of cytoplasm </li></ul><ul><li>Does not require O 2  common for (an)aerobic catabolism </li></ul><ul><li>Starts with phosphorylation of Glucose to Glucose 6-P </li></ul><ul><ul><li>(“Before doubling your money you first have to invest!”) </li></ul></ul>
    10. 10. The Steps of Glycolysis Net gain?
    11. 11. Pyruvate has 2 Possible Fates: Anaerobic catabolism: Pyruvate Lactate Aerobic catabolism: Pyruvate Citric Acid Cycle
    12. 12. Citric Acid Cycle <ul><li>Other names ? </li></ul><ul><li>Takes place in ? </li></ul><ul><li>Energy Produced: </li></ul><ul><ul><li>1 ATP </li></ul></ul><ul><ul><li>3 NADH </li></ul></ul><ul><ul><li>1 FADH 2 </li></ul></ul><ul><li>Waste – 2 CO 2 </li></ul>Electron transport System
    13. 13. Energy Yield of Krebs Cycle See Fig. 4-24 NADH NADH NADH FADH 2
    14. 14. Final step: Electron Transport System <ul><li>Chemiosmotic theory / oxidative phosphorylation </li></ul><ul><li>Transfers energy from NADH and FADH 2 to ATP (via e - donation and H + transport) </li></ul><ul><li>Mechanism: Energy released by movement of e - through transport system is stored temporarily in H + gradient </li></ul><ul><li>NADH produces a maximum of 2.5 ATP FADH 2 produces a maximum of 1.5 ATP </li></ul><ul><li>1 ATP formed per 3H + shuttled through ATP Synthase </li></ul>Fig 4-25
    15. 16. Cellular Respiration Maximum potential yield for aerobic glucose metabolism: 30-32 ATP synthesized from ADP H 2 O is a byproduct Summary of CHO catabolism
    16. 17. Protein Catabolism?? <ul><li>Proteases </li></ul><ul><li>Peptidases </li></ul><ul><li>Deamination (removal of the NH 3 ) </li></ul><ul><ul><li>NH 3 becomes urea </li></ul></ul><ul><li>Pyruvate, Acetyl CoA, TCA intermediates are left. </li></ul>
    17. 18. Lipid Catabolism?? <ul><li>Lipolysis </li></ul><ul><ul><li>Lipases break lipids into glycerol (3-C) </li></ul></ul><ul><li>Glycerol enters the glycolytic pathway </li></ul><ul><ul><li>Called β -oxidation </li></ul></ul>
    18. 19. Synthetic Pathways Unit molecules Macromolecules Polysaccharides Lipids DNA Protein nutrients & energy required Anabolic reactions synthesize large biomolecules Glucose Amino Acids
    19. 20. Glycogen Synthesis <ul><li>Made from glucose </li></ul><ul><li>Stored in all cells but especially in </li></ul><ul><li>Liver (keeps 4h glycogen reserve for between meals) </li></ul><ul><li>Skeletal Muscle  muscle contraction </li></ul>Gluconeogenesis Glycolysis in reverse From glycerol, aa and lactate All cells can make G-6-P, only liver and Kidney can make glucose
    20. 21. Protein Synthesis Proteins are necessary for cell functions Protein synthesis is under nuclear direction  DNA specifies Proteins DNA mRNA Protein ? ?
    21. 22. How can only 4 bases in DNA encode > 20 different aa in protein? <ul><li>1 letter word: 1 base = 1 aa </li></ul><ul><li>2 letter word: 2 bases = 4 2 = 16 aa </li></ul><ul><li>3 letter word: 3 bases = 4 3 = 64 aa </li></ul><ul><li>3 letter words = base triplets or codons </li></ul>
    22. 23. <ul><li>1 start codon </li></ul><ul><li>3 stop codon </li></ul><ul><li>60 other codons for 19 aa </li></ul>Redundancy of Genetic Code (p 115) A combination of three bases forms a codon
    23. 24. Transcription <ul><li>DNA is transcribed into complementary mRNA </li></ul>by RNA Polymerase + nucleotides + Mg 2+ + ATP Gene = elementary unit of inheritance Compare to Fig. 4-33
    24. 25. mRNA Processing (Fig. 4-33)
    25. 26. Protein synthesis fig 4-27
    26. 27. Translation mRNA is translated into string of aa (= polypeptide) mRNA + ribosomes + tRNA meet in cytoplasm Anticodon pairs with mRNA codon  aa determined Amino acids are linked via peptide bond. 2 important components ??
    27. 28. Fig 4-34 Primary Structure
    28. 29. Protein Sorting <ul><li>No signal sequence  protein stays in cell </li></ul><ul><li>Signal sequence  protein destined for translocation into organelles or for export </li></ul>Post – Translational protein modifications: Folding, cleavage, additions  glyco- , lipo- proteins
    29. 30. <ul><li>Modifications in ER </li></ul><ul><li>Transition vesicles to </li></ul><ul><li>Golgi apparatus for further modifications </li></ul><ul><li>Transport vesicles to cell membrane </li></ul>For “export proteins”: Signal sequence leads growing polypeptide chain across ER membrane into ER lumen
    30. 32. DNA Replication <ul><li>Semi- conservative </li></ul><ul><li>DNA polymerase </li></ul>