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Cellular Respiration

Cellular Respiration. Pulling some things together…. What did the previous slide represent? Notice that during each energy transformation, heat is lost! What is this called?. Combustion Reactions.

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Cellular Respiration

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  1. Cellular Respiration

  2. Pulling some things together… • What did the previous slide represent? • Notice that during each energy transformation, heat is lost! • What is this called?

  3. Combustion Reactions • A chemical reaction that involves a hydrocarbon and oxygen. It produces energy (heat) so rapidly that a flame results. • The products of this reaction include carbon dioxide and water. • C(x)H(x)+O2→H2O(g)+CO2(g) • Combustion is commonly called burning. • It is an exothermic reaction.

  4. Cells and Energy Glycolysis and respiration as source of energy for the cell How do cells make ATP? Phosphorylation! Chapter 6

  5. Substrate level phosphorylation Uses enzymes Transfers phosphate group from an organic substrate to ADP. X-P + ADP + enzyme X + ATP Cells need to generate ATP!

  6. Needs a membrane. Uses the potential energy to create a concentration gradient of H+ (hydrogen ions) across a membrane. Uses special enzymes, ATP synthases. Chemiosmotic Phosphorylationa.k.a. Chemiosmosis

  7. Things to keep in mind... (we are going to go over this…) Respiration = C6H12O6 + 6O2 6CO2 + 6H2O • Exergonic or endergonic? • What is oxidized? • What is reduced? • In what form is energy released? • What is the importance of CO2 in the atmosphere? • What is the source of oxygen in the atmosphere?

  8. Endergonic reactions: have a net absorption of E Exergonic reactions: have a net release of E. These reactions are “coupled,” one does not occur without the other! While cellular respiration, in total, is an exergonic reaction, it is made up of a series of reactions which involve both types! C6H12O6 + 6O2  6CO2 + 6H2O + ENERGY RELEASED (ATP) Reminder:

  9. Redox Reactions • The movement of electrons from one molecule to another is an oxidation-reduction reaction. • Loss of electrons is oxidation • Gain of electrons is reduction • LEO the lion goes GER • ex. C4H6O5 + NAD+ C4H4O5 + NADH + H+ oxidized reduced

  10. The “master” formula…

  11. There are 2 types of cellular respiration • With oxygen: aerobic cellular respiration (What are aerobic exercises?) • Without oxygen: anaerobic cellular respiration a.k.a. fermentation

  12. Eukaryote vs Prokaryote Glycolytic pathways

  13. Overview of Cellular Respiration A. Glycolysis (anaerobic) Without oxygen With oxygen B. Fermentation B. Aerobic Respiration 1. Citric Acid Cycle 2. Electron Transport Chain (anaerobic respiration)

  14. Would you like that with or without oxygen? • Aerobic - environments with oxygen • Anaerobic - environments without oxygen • Most organisms need O2 but there are some that can live in either environment and a few that must live in the absence of O2! Saccharomyces cerevisiae (yeast) images provided by Peter Hollenhorst and Catherine Fox

  15. Obligate Anaerobes • Clostridium botulinum - Gram-positive, endospore-forming, rod prokaryote. Vegetative and spore stages. Note the flagella. • Causes botulism.Magnification*: x2,000Type: SEM • Clostridium tetani - Gram-positive, rod prokaryote; vegetative and spore stages. Note the flagella. • Causes tetanus. SEM |Magnification*: x1,750Type: SEM

  16. Review of Mitochondria • Eukaryotic organisms carry out cellular respiration in the mitochondria (power house of the cell) http://www.sci.sdsu.edu/TFrey/MitoMovies/CrisMitoMovie.htm

  17. Reminder: Possible evolution of mitochondria-endosymbiont

  18. The Mitochondria • Double membrane • Has it’s own DNA!! • Can reproduce in cell…! • Endosymbiont?? • Possible evolution? http://hybridmedicalanimation.com/anim_mitosis_wmVideo.html

  19. Introduction to Cellular Respiration • The process by which food molecules (glucose) are broken down to release energy (ATP) • C6H12O6 + 6O2 6CO2 + 6H2O + Energy • In eukaryotic organisms, this process takes place in the mitochondria. In prokaryotic organisms, this process takes place in the cell membrane.

  20. Overview: Respiration occurs in 4 (5) main stages • Glycolysis • Exergonic • Occurs in the cytoplasm • Splits glucose into 2 molecules of pyruvic acid • Pyruvic acid is modified into Acetyl CoA as it diffuses into the mitochondria. • Each pyruvic acid loses a carbon to CO2 • This is a high energy fuel molecule for the next stage

  21. Krebs Cycle Exergonic Occurs in the matrix of the mitochondria Produces CO2 as a waste product ** Main function of first 2 stages: supply 3rd stage with electrons! Electron Transport Chain and Chemiosmotic Phosphorylation Occurs on the cristae of the mitochondria Uses oxygen Produces the most ATP

  22. 1 2 3 4 Formation of acetyl coenzyme A Glycolysis Citric acid cycle Electron transport and chemiosmosis Glucose Pyruvate 2 ATP Overview of Aerobic Cellular Respiration Define the four stages of respiration and their location in the cell

  23. Stage 1: Glycolysis glyco- : sugar (glucose) -lysis: to split

  24. A. Glycolysis (Overview) • A molecule of glucose (6 carbon compound) is broken apart making 2 pyruvic acid compounds (3 carbons each) • 2 ATP and 2 NADH molecules produced

  25. Glycolysis • STEP 1 - 2 phosphates are attached to glucose, forming a new 6-C compound. The phosphate groups come from 2 ATP, which are converted to ADP. (Glucose is phosphorylated!) • STEP 2 - The 6-C compound formed in Step 1 is split into 2 3-C molecules of PGAL. • STEP 3 - The 2 PGAL molecules are oxidized (LEO), and each receives a phosphate group forming 2 new 3-C compounds. The phosphate groups are provided by 2 molecules of NAD+ forming NADH.

  26. STEP 4 - The phosphate groups added in Step 1 and Step 3 are removed from the 3-C compounds. • This reaction produces 2 molecules of Pyruvic Acid. • Each phosphate group combines with a molecule of ADP to make a molecule of ATP. • Because a total of 4 phosphate groups were added, FOUR MOLECULES OF ATP ARE PRODUCED.

  27. Substrate-level phosphorylation • Enzymes in the cytoplasm pass a high energy phosphate to ADP to make ATP. • Not very efficient… • FYI: The high energy phosphates came from the oxidation of BPG, in the presence of an enzyme, forming PGAL (a.k.a. G3P) and ATP.

  28. Keep up with totals:

  29. Summary of glycolysis:

  30. Don’t panic… you do not need to memorize this, but it will give you a greater appreciation for what really is happening to get from glucose to pyruvate! How many different enzymes are involved?

  31. Question 1 How much ATP is needed to activate glycolysis? Glucose Energy investment phase and splitting of glucose 2 ATP 3 steps 2 ADP Fructose-1,6-bisphosphate P P 2 X Glyceraldehyde phosphate (G3P) P P (see next slide)

  32. Question 2 How much ATP/net & ATP is produced in glycolysis? 2 X Glyceraldehyde phosphate (G3P) Energy capture phase P P (G3P) (G3P) NAD+ NAD+ NADH NADH 5 steps 2 ADP 2 ADP 2 ATP 2 ATP Net yield per glucose:? ATPs and ? NADH Pyruvate Pyruvate

  33. Question 3 Identify the exergonic and endergonic reactions in the following exergonic coupled enzyme steps in glycolysis: • Energy investment phase: • Glucose + ATP Glucose-6-phosphate + ADP • Energy capture phase: • Phosphoenolpyruvate + ADP  Pyruvate + ATP

  34. In summary…. • 2 ATP molecules were used in Step 1, but 4 are produced in Step 4. Therefore, glycolysis has a NET YIELD of 2 ATP molecules for every molecule of glucose that is converted into Pyruvic Acid http://biology.clc.uc.edu/courses/bio104/atp.htm

  35. 2 pyruvic acid molecules Glucose + 4 H+ + energy stored in 2 ATP molecules

  36. Glycolysis Facts: • Glycolysis is the universal E-harvesting process of life. • Because glycolysis occurs universally, it is thought to be an ancient metabolic system. • The net gain of two ATP molecules represents only 5% of the E that a cell can harvest from a glucose molecule.

  37. If O2 is not available Fermentation alcoholic lactic acid many types of fermentation! If O2 is available Kreb cycle Pyruvic Acid’s 2 Possible Pathways

  38. Glycolysis Glucose (C6) 2 NAD+ 2 NADH 2 ATP 2 Pyruvate (C3) CO2 2 Ethyl alcohol (C2) 2 Possible Paths if no O2 present Why must pyruvate be converted to either ethyl alcohol or lactate in the absence of oxygen? Glycolysis Glucose 2 NAD+ 2 NADH 2 ATP 2 Pyruvate 2 Lactate (C3)

  39. Stage 2: The Preparatory Reaction Acetyl CoA Production

  40. B.O.P. (Breakdown of Pyruvate) • 1. The 2 pyruvic acid compounds (3C) are changed into 2 2-carbon compounds and 2 molecules of CO2 • 2. Occurs in the space between the membranes of the mitochondria

  41. Takes place as pyruvate moves into the matrix of the mitochondria

  42. Production of Acetyl CoA • When pyruvic acid enters the mitochondrial matrix, it reacts with a molecule called coenzyme A to form Acetyl Coenzyme A, abbreviated acetyl CoA. CO2, NADH, and H+ are produced in this reaction. • Remember: There are 2 pyruvic acids formed from 1 glucose!

  43. Question 1 How many of the six carbons of glucose are lost in this way? Pyruvate (C3) + CoA + NAD+  Acetyl(C2)CoA + CO2 +NADH

  44. Question 2 Considering the transition reaction and the first reaction of the Krebs cycle below, how would you describe the role of Coenzyme A? Transition reaction: Pyruvate (C3) + CoA  Acetyl(C2)CoA + CO2 Krebs cycle first reaction: Oxaloacetate (C4)+ AcetylCoA  Citrate (C6) + CoA

  45. Stage 3 Krebs Cycle a.k.a. Critic Acid Cycle

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