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Energy management within cells

Energy management within cells. Lecture 5. Controlled Pathways. The various compartments of the cell ( - what are they?) are populated with a very large number of chemical reagents, products, and enzymes. How does the cell control them all?. Reagents > Enzymes > Products.

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Energy management within cells

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  1. Energy management within cells Lecture 5

  2. Controlled Pathways • The various compartments of the cell (- what are they?) are populated with a very large number of chemical reagents, products, and enzymes. • How does the cell control them all? Reagents > Enzymes > Products

  3. Each step in this pathway is regulated by specific enzymes - this is one mechanism which allows multiple reactions to occur in a common environment. Pathways A complex pathway can further be regulated by a number of different feedback mechanisms - both up regulation and down regulation, feedback inhibition and feedback initiation, and other more complex interactions.

  4. -Watch Multimedia- • Biochemical Pathways • FileName: Bio10.swf

  5. The biosynthetic pathway for the two amino acids E and H is shown schematically below. You are able to show that E inhibits enzyme V, and H inhibits enzyme X. Enzyme T is most likely to be subject to feedback inhibition by __________________ alone. • (a) A • (b) B • (c) C • (d) E • (e) H

  6. An average cell has both general reactions which it needs to perform to sustain life, as well as specialized ones that make that cell type unique, i.e. pancreatic cell. • The general reactions are called housekeeping reactions • These can be many in number and their interactions are pretty complex…

  7. Anabolic & Catabolic • Regardless of the complexity they are of two types - • ANABOLIC • CATABOLIC • …

  8. Enzymes • Vast majority are P’s (however, some RNA) • Increase the rate of virtually ALL chemical reactions - fact: A reaction that takes just milliseconds in the presence of an enzyme would take millions of years without (some increase the rate by as much as 1 x 1018 fold!!!) • Enzyme pool selectively determines which reactions shall take place inside a cell & when

  9. Enzymes… • Catalysts - Biological Catalysts • 2 Main Properties • 1. Increase rate without change to enzyme • 2. Do not alter chemical equilibrium • Just speed things along by bringing molecules together and reducing the activation energy of the reactions too.

  10. Random Motion • The meeting of substrates and substrates and enzymes is random. • The meeting is driven by the thermal energy of the molecules at these temperatures • Quicktime movie (rmotion.mov) .…

  11. Activation Energy • An important concept that you have to learn

  12. Enzymes mechanisms • Enzymes are specific • AA’s from different parts of the P’ come together to form the active site (binding pocket) • ‘Lock-and-key’ model - exact fit • Induced fit model - alteration of the substrate by the binding process

  13. Enzyme kinetics • Initial binding is ionic • Subsequent interactions may involve covalent exchanges • Atomic distances involved • Prosthetic groups - small molecules that participate in catalysis - metal ions • Coenzymes - small molecules that enhance rates - organic molecules - Biotin

  14. Enzyme regulation • Activity can be modulated - controlled to suit the needs of the cell • Feedback inhibition - product inhibits more product formation • Allosteric regulation - ‘other - site’ - molecules which bind to the enzymes to alter its physical properties • Phosphorylation - adding of phosphate groups to P’ to regulate activity - serine, threonine, or tyrosine AA’s - : + or -

  15. Metabolic Energy • Cells need energy to function, grow and multiply • A large portion of the cells resources are spent on obtaining energy • Most reactions utilize energy • Gibbs FREE ENERGY = ∆G - release of energy is -∆G • ATP = ∆G of @ -12kcal/mol- releases energy on hydrolysis

  16. Glycolysis(covered in greater detail later in this course) • Breakdown of glucose for energy to Pyruvate • ∆G = -686 kcal/mol • Nearly every cell performs glycolysis • No oxygen required - anaerobic reaction • Location - cytoplasm • Does this same reaction occur in bacteria? • Where does this same reaction occur in bacteria?

  17. Acetyl CoA(covered in greater detail later in this course) • Acetyl coenzyme A • Intermediary in metabolism • Forms when Coenzyme A reacts with pyruvate • Eukaryotes - mitrochondria

  18. Citric acid cycle(covered in greater detail later in this course) • Krebs cycle • Oxidative metabolism • Mitrochondria

  19. Photosynthesis(covered in greater detail later in this course) • Sunlight is the ultimate source of energy • Plants and bacteria produce carbohydrates through photosynthesis • Chlorophylls - photosynthetic pigments

  20. Stay Current Please • Read chapter 2 fully & visit the website.

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