Beyond Glucose & Control of Respiration

1. Beyond Glucose & Control of Respiration Phosphofructokinase (active v. inactive form)

2. Big Questions 1. How are the processes of cellular respiration controlled in the cell? 2. How do control mechanisms operate in the cell to respond to energy constraints of the environment?

3. Cellular respiration

4. polysaccharides    glucose other 6C sugars    glucose hydrolysis modified Beyond glucose: Other carbohydrates • Glycolysis accepts a wide range of carbohydrates fuels • ex. starch, glycogen • ex. galactose, fructose

5. proteins    amino acids H | —C— | H | —C— | H H hydrolysis C—OH C—OH N N waste glycolysis Krebs cycle H H R R O O || || Beyond glucose: Proteins 2C sugar = carbon skeleton = enters glycolysis or Krebs cycleat different stages amino group = waste product excreted as ammonia, urea, or uric acid

6. fats    glycerol + fatty acids hydrolysis glycerol (3C)  G3P  glycolysis fatty acids 2C acetyl acetyl Krebs groups coA cycle 2C fatty acids 3C glycerol enters glycolysis as G3P enter Krebs cycle as acetyl CoA Beyond glucose: Fats

7. fat carbohydrate Carbohydrates vs. Fats • Fat generates 2x ATP vs. carbohydrate • more C in gram of fat • more energy releasing bonds • more O in gram of carbohydrate • so it’s already partly oxidized • less energy to release That’s whyit takes so muchto lose a pound a fat!

8. Metabolism • Coordination of chemical processes across whole organism • digestion • catabolism when organism needs energy or needs raw materials • synthesis • anabolism when organism has enough energy & a supply of raw materials • by regulating enzymes • feedback mechanisms • raw materials stimulate production • products inhibit further production CO2

9. Metabolism • Digestion • digestion of carbohydrates, fats & proteins • all catabolized through same pathways • enter at different points • cell extracts energy from every source Cells areversatile & selfish! CO2

10. pyruvate glucose Krebs cycleintermediaries amino acids   acetyl CoA  fatty acids Metabolism • Synthesis • enough energy? build stuff! • cell uses points in glycolysis & Krebs cycle as links to pathways for synthesis • run pathways “backwards” • have extra fuel, build fat! Cells areversatile & thrifty!

11. Central Role of Acetyl CoA Glycolysis Glucose Pyruvate Glycolysis CO2 • Acetyl CoA is central to both energy production & biomolecule synthesis • Depending on organism’s need • build ATP • immediate use • build fat • stored energy Pyruvate oxidation NAD+ NADH Krebs cycle Protein ETC Lipid Acetyl coA coenzyme A acetyl group Fat ATP

12. Control of Respiration Feedback Control

13.       enzyme 1 enzyme 2 enzyme 3 enzyme 4 enzyme 5 enzyme 6 Feedback Inhibition • Regulation & coordination of production • final product is inhibitor of earlier step • allosteric inhibitor of earlier enzyme • no unnecessary accumulation of product • production is self-limiting A B C D E F G X allosteric inhibitor of enzyme 1

14. Respond to cell’s needs • Key point of control • phosphofructokinase • allosteric regulation of enzyme • why here? “can’t turn back” step before splitting glucose • AMP & ADP stimulate • ATP & citrate Why is this regulation important? Balancing act: availability of raw materials vs. energy demands vs. synthesis

15. A Metabolic economy • Basic principles of supply & demand regulate metabolic economy • balance the supply of raw materials with the products produced • these molecules become feedback regulators • they control enzymes at strategic points in glycolysis & Krebs cycle • levels of AMP, ADP, ATP • regulation by final products & raw materials • levels of intermediates compounds in pathways • regulation of earlier steps in pathways • levels of other biomolecules in body • regulates rate of siphoning off to synthesis pathways

16. It’s a Balancing Act Glycolysis Glucose Pyruvate Glycolysis • Balancing synthesiswith availability of both energy & raw materials is essential for survival! • do it well & you survive longer • you survive longer &you have more offspring • you have more offspring & you get to “take over the world” Pyruvate oxidation Krebs cycle Protein ETC Lipid Fat ATP

17. Got the energy… Ask Questions!!

18. Review Questions

19. Glycolysis does not continue if: • There is no oxygen present • NADH is not oxidized • FADH is not reduced • There is excess glucose • There is excess CO2

20. 2. All of the following can serve as the starting material for respiration EXCEPT: • Glucose • Amino Acids • Tri-glycerides • Starch • ATP

21. You are researching starvation. Which of the following do you hypothesize to be the most likely order of digestion of classes of macromolecules in starving animals? • Carbohydrates ->proteins ->lipids • Lipids ->carbohydrates ->proteins • Carbohydrates ->lipids ->proteins • Proteins ->lipids ->carbohydrates Explain your reasoning.