Mastering Cellular Respiration: Key Concepts & Processes

1. Mrs. Ragsdale Biology SL/HL Chapter 8Topic 8: Cell Respiration and Photosynthesis

2. 8.1 Cell Respiration

3. Lil bit of chemistry review • Oxidation and Reduction reactions • Oxidation – loss of an electron • Reduction – gain of an electron • Typically involve trading H⁺ ions

4. Oxidation vs Reduction Oxidation reactions Reduction reactions Gain of electrons Losing oxygen Gain of hydrogen • Loss of electrons • Gaining oxygen • Loss of hydrogen

5. Major Lingo Used: • Phosphorylation: addition of phosphate groups • Makes reactions that occur in a chain or pathway easier by adding energy • Dephosphorylation: removal of phosphate • Oxidation: loss of hydrogen • Reduction: gain of hydrogen • If compound A is oxidized, then compound B is reduced

6. Cell Respiration: 3 Step Process • Glycolysis – Sugar is converted into pyruvate • Can be aerobic (with oxygen) or anaerobic (without oxygen) • Krebs Cycle – pyruvate is used to charge electron carriers • Link Reaction (happens before Kreb’s Cycle) • Electron Transport Chain – electrons create a hydrogen proton gradient that fuels ATP pumps

7. Cellular Respiration Overview

8. Cytoplasm Glycolysis – Breakdown of glucose into pyruvate

9. Glycolysis – Converting glucose into pyruvate 4 Step Process: • Two phosphate groups added to one molecule of glucose • Phosphorylation – adding a phosphate group • This raises the energy level and powers the rest of the reaction • Hexose biphosphate is split to form two molecules of triose phosphate.

10. Glycolysis continued • Two atoms of hydrogen are removed from each triose phosphate molecule (oxidation). • When hydrogen bonds break, a large amount of energy is released carrying into the next step. • NAD⁺ is converted into NADH • Extra phosphates that were added are then removed  Pyruvate • End result: 2pyruvate + 2NADH + 2H⁺

11. Breakdown of Steps • Add 2 Phosphate to glucose (phosphorylation) • Split this in half and make triose phosphate • Remove 2 hydrogen (oxidation) and make glycerate 3-phosphate • Remove extra phosphates • Net: 2 ATP and 2 NADH + 2H⁺

13. Glycolysis Summary • One glucose molecule (C₆H₁₂O₆) • Breaks down into two pyruvate molecules • Two ATP molecules are used per glucose but 4 are produced => net yield of 2 ATP • Two NAD⁺ molecules converted into NADH + H⁺ • http://www.youtube.com/watch?v=mmACA_eVLTE

14. Aerobic vs Anaerobic Respiration • At the end of glycosis a choice must be made! • Oxygen present = pyruvate proceeds to the mitochondria • Oxygen absent = pyruvate is turned into some form of waste • 2 ATP is all the energy created

15. Pyruvate’s FateWITHOUT Oxygen Anaerobic respiration – when no oxygen is present. • Occurs In the cytoplasm • After glycolysis, pyruvate is converted to a waste product • NO ENERGY IS OBTAINED OR USED • Waste in humans is Lactate (Lactic Acid) • Waste in Yeast is Ethanol and Carbon dioxide

16. Pyruvate’s FateWITH Oxygen Aerobic Respiration- when oxygen is present • Occurs in mitochondria • After glycolysis, pyruvate is broken down in the mitochondria • LARGE yield of energy (34 ATP) • Waste products are CO2 and H2O

17. The Mitochondria Link Reaction, Kreb’s Cycle and Electron Transport Chain

18. Draw and Label: Electron micrograph of Mitochnodria • Outer mitochondrial membrane • Inner mitochondrial membrane • Space between inner and outer membrane • Matrix • 70s ribosomes • Cristae

19. Link Reaction: Beginning of the Kreb’s Cycle • Pyruvate is decarboxylated once (CO2 is removed) and oxidized once (H⁺ is removed) • Forms an acetyl group

20. Kreb’s Cycle • Involves 2 additional decarboxylations and four more oxidations • Product gained: high energy electron carrier = NADH and FADH₂

21. Types of Reactions in Kreb’s Cycle • Decarboxylation – carbon dioxide is removed • Remember, CO₂ is a waste product! • Oxidation – hydrogen removed • NAD⁺ becomes NADH • FAD⁺ becomes FADH₂ • Both of these reactions release/store energy • Substrate-level phosphorylation • Requires the addition of ATP

22. Kreb’s Cycle

23. Electron Transport Chain • A series of electron carriers located in the inner membrane of the mitochondrion • Oxidative Phosphorylation – the energy released by oxidation turning causing ADP to be phosphorylated into ATP • Chemiosmosis – the coupling of ATP synthesis to electron transport via a concentration gradient of protons

24. Electron Transport Chain – in a nutshell • NADH and FADH₂ donate H⁺ protons along the inner membrane wall creating a high concentration gradient of protons within that small space • An ATP synthase pump works to phosphorylate the ADP into ATP using the H⁺ ions to fuel the pump

27. Oxygen’s Big Star Role • So what happens to the extra H⁺ ions and why is it so important that oxygen be there? • After the ATP synthase “pump” is turned and ATP is created, the H⁺ protons must bond with something • Only if Oxygen is present and available to bind with H⁺ creating H₂O can the additional 30 ATP be made. If no oxygen is present, the extra H⁺ build up will trigger pyruvate to be converted into waste products (lactic acid in humans)

28. Functions of Mitochondrial Structure • Outer mitochondrial membrane – separates the contents of the rest of the cell creating a compartment with ideal conditions for aerobic respiration • Inner mitochondrial membrane – contains electron transport chains and ATP synthase which carry out oxidative phosphorylation • Matrix – fluid inside the mitochondrion containing enzymes for the Kreb’s cycle and the link reaction • 70s ribosomes • Loop of DNA

29. Functions of Mitochondrial Structure • Cristae – Tubular shelf-like projections that increase the surface area of the inner membrane making more space for oxidative phosphorylation • Space between inner and outer membrane – Protons are pumped into this space by the electron transport chain • Small space allows for a high proton gradient for chemiosmosis

30. Oxidative Phosphorylation • ADP is phosphorylated into ATP using energy released by the oxidation of NADH into NAD⁺ • Phosphorylation – a fancy pants science word for adding a phosphate to ADP • Oxidative – basically oxidation (removing Hydrogen) powers something

31. Chemiosmosis • Occurs in the inner mitochondrial membrane • H⁺ protons form a gradient in the intermembrane space of the mitochondria • Protons escape back to the matrix via the ATP pump