Kreb's cycle (1)

20,346 views

Published on

BIOCHEM WK 3

1 Comment
33 Likes
Statistics
Notes
No Downloads
Views
Total views
20,346
On SlideShare
0
From Embeds
0
Number of Embeds
17
Actions
Shares
0
Downloads
1,191
Comments
1
Likes
33
Embeds 0
No embeds

No notes for slide

Kreb's cycle (1)

  1. 1. KREB’S CYCLE (TRICARBOXYLIC ACID (TCA)CYCLE/CITRIC ACID CYCLE) BIOCHEMISTRY LEC WEEK 3
  2. 2. METABOLIC PATHWAYS <ul><li>A series of consecutive biochemical reactions catalyzed by enzymes that produce a specific end product. </li></ul><ul><li>Catabolism- the breakdown of food stuffs to simple organic chemicals. </li></ul><ul><li>Anabolism- the synthesis of biomolecules from simple organic chemicals. </li></ul>
  3. 3. METABOLIC PATHWAYS <ul><li>Very Few metabolites are used to synthesize a large variety of biomolecules : </li></ul><ul><li>Acetyl-Coenzyme A (acetyl-CoA) </li></ul><ul><li>Pyruvate </li></ul><ul><li>Citrate acid cycle intermediates </li></ul>
  4. 4. METABOLIC PATHWAYS <ul><li>Three main pathways for energy production: </li></ul><ul><li>Glycolysis </li></ul><ul><li>Citric acid cycle </li></ul><ul><li>Oxidative-Phosphorylation </li></ul>
  5. 5. METABOLIC PATHWAYS <ul><li>Certain pathways are involved in both breakdown and buildup of molecules these pathways are called amphibolic . The citric acid cycle is an example of this. </li></ul>
  6. 6. OVERALL GOAL/IMPORTANCE <ul><li>Makes ATP </li></ul><ul><li>Makes NADH </li></ul><ul><li>Makes FADH 2 </li></ul><ul><li>A cyclical series of biochemical reactions that is fundamental to the metabolism of aerobic organisms, i.e. animals, plants, and many microorganisms </li></ul>
  7. 7. Geography <ul><li>Krebs in mitochondrial matrix </li></ul><ul><li>Mitochondrion </li></ul><ul><ul><li>Outer membrane very permeable </li></ul></ul><ul><ul><ul><li>Space between membranes called intermembrane space </li></ul></ul></ul><ul><ul><li>Inner membrane (cristae) </li></ul></ul><ul><ul><ul><li>Permeable to pyruvate, </li></ul></ul></ul><ul><ul><ul><li>Impermeable to fatty acids, NAD, etc </li></ul></ul></ul><ul><ul><li>Matrix is inside inner membrane </li></ul></ul>
  8. 8. The citric acid cycle enzymes are found in the matrix of the mitochondria
  9. 9. OVERVIEW <ul><li>Described by Hans Adolf Krebs in 1937 </li></ul><ul><li>A feature of cell chemistry shared by all types of life. </li></ul><ul><li>A complex series of reactions beginning and ending with the compound oxaloacetate. </li></ul><ul><li>The cycle produces carbon dioxide and the energy-rich compound ATP. </li></ul>
  10. 10. OVERVIEW <ul><li>Eight successive reaction steps. </li></ul><ul><li>The six carbon citrate is formed from two carbon acetyl-CoA and four carbon oxaloacetate. </li></ul><ul><li>Oxidation of citrate yields CO2 and regenerates oxaloacetate. </li></ul><ul><li>The energy released is captured in the reduced coenzymes NADH and FADH2. </li></ul>
  11. 11. Conversion of pyruvate to Acetyl CoA <ul><li>2 per glucose (all of Kreb’s) </li></ul><ul><li>Oxidative decarboxylation </li></ul><ul><li>Makes NADH </li></ul>
  12. 12. Fates of Acetyl CoA <ul><li>In the presence of CHO </li></ul><ul><ul><li>Metabolized to CO 2 , NADH, FADH 2 ,GTP and, ultimately, ATP </li></ul></ul><ul><li>If energy not being used (Lots of ATP present) </li></ul><ul><ul><li>Made into fat </li></ul></ul><ul><li>If energy being used, but no CHO present </li></ul><ul><ul><li>Starvation </li></ul></ul><ul><ul><li>Forms ketone bodies (see fat metabolism slides) </li></ul></ul><ul><ul><li>Danger! </li></ul></ul>
  13. 13. Kreb’s Cycle
  14. 14. 1. Citrate Synthase Reaction
  15. 15. 2. Aconitase Reaction <ul><li>Forms isocitrate </li></ul>
  16. 16. 3. Isocitrate Dehydrogenase <ul><li>All dehydrogenase reactions make NADH or FADH 2 </li></ul>
  17. 17. 4. α -ketoglutarate dehydrogenase <ul><li>Same as pyruvate dehydrogenase reaction </li></ul>
  18. 18. 5. Succinyl CoA synthetase <ul><li>Coupled to synthesis of GTP </li></ul><ul><ul><li>GTP very similar to ATP and interconverted later </li></ul></ul>
  19. 19. 6. Succinate dehydrogenase <ul><li>Dehydrogenation </li></ul><ul><li>Uses FAD </li></ul>
  20. 20. 7. Fumarase <ul><li>Addition of water to a double bond </li></ul>
  21. 21. 8. Malate Dehydrogenase <ul><li>Makes NADH </li></ul><ul><li>Regenerates oxaloacetate for another round </li></ul>
  22. 22. Net From Kreb’s <ul><li>Oxidative process </li></ul><ul><ul><li>3 NADH </li></ul></ul><ul><ul><li>FADH 2 </li></ul></ul><ul><ul><li>GTP </li></ul></ul><ul><li>X 2 per glucose </li></ul><ul><ul><li>6 NADH </li></ul></ul><ul><ul><li>2 FADH 2 </li></ul></ul><ul><ul><li>2 GTP </li></ul></ul><ul><li>All ultimately turned into ATP (oxidative phosphorylation) </li></ul>

×