1 / 24

Energy management within cells

Energy management within cells. Lecture 6. 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.

Jimmy
Télécharger la présentation

Energy management within cells

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. Energy management within cells Lecture 6

  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.

More Related