Cellular Respiration

1. Cellular Respiration Pp 78-83

2. 3.7 Cell respiration • 3.7.1 Define cell respiration. • 3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP. • 3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. • 3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

3. Syllabus Definition • Cell respiration is the controlled release of energy from organic compounds in cells to form ATP • Metabolize/breakdown/ “slow oxidation”

4. Oxidation • Oxidation involves the loss of electrons from an element, whereas reduction involves the gain of electrons and that oxidation frequently involves gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen. • “Biology” definition of “oxidation”

5. cell respiration • Takes place in cytoplasm (glycolysis) and the mitochondria (Krebbs and Electron Tranport Chain) • Glucose is the major substrate for respiration • Adenosine triphosphates (ATP) is the product and the molecule which directly fuels the majority of biological reactions.

6. Why cell respiration? • Cells require a constant source of energy (renewed daily) to perform various tasks e.g. • Metabolism, Synthesis, Active Transport, Locomotion, Cell Structure, Cell Communication, DNA/RNA Synthesis, tRNA Protein Synthesis

7. Types of Respiration (i) Anaerobic Respiration (ii) Aerobic Respiration Occurs in the absence of Oxygen Occurs in presence of Oxygen Occurs in the cells’ cytoplasm Occurs in the cells’ mitochondria Yields small amount of ATP (2 molecules) per molecule of glucose Yields large amount of ATP (38 molecules) per molecule of glucose Involves fermentation of pyruvate to lactate in muscles/CO2 & ethanol in plant & yeast Does not involve fermentation

8. Comparison between Aerobic & Anaerobic Respiration -Animals

9. Adenosine triphosphate (ATP): • ATP is the chemical molecule which directly fuels the majority of biological reactions • About 1025 ATP molecules are hydrolysed to ADP and inorganic phosphate (Pi) daily • ADP is reduced back to ATP using the free energy from the oxidation of organic molecules

10. ATP Cycle

11. Anaerobic Cell Respiration • anaerobic cell respiration occursin the absence of oxygen • during glycolysis glucose is broken breakdown in the cytoplasm • leading to the production of pyruvate, • production of small amount of energy (2 ATP molecules per molecule of glucose) • in muscles, pyruvate is converted into lactic acid during lactic acid fermentation • anaerobic respiration occurs in animals during intense muscular activity • in yeast & plant cells, pyruvate is converted into alcohol (ethanol) & CO2 during alcoholic fermentation • no additional APT is produced during fermentation

12. “Three stages” of aerobic respiration • Stage 1: 2 ATP • Glycolysis (energy investment) • 4 ATP is made, 2 is used – • Stage 2 (and 3): 38 ATP • Krebs Cycle (oxidation of pyruvate) • Lots of energy carriers - Generation of CO2 • Oxidative Phosphorylation • Generation of most ATP

13. Outline the process of aerobic respiration • during glycolysis glucose is partially oxidized in the cytoplasm • small amount ATP produced during glycolysis • two pyruvate molecules are formed by glycolysis • pyruvate absorbed into mitochondrion • pyruvate is broken down in the mitochondrion in the presence of oxygen • to produce carbon dioxide & water • large amount of energy in form of ATP is produced per glucose molecule

14. Stage 1: Glycolysis • Where • Cell’s cytoplasm • Why • To break glucose down into pyruvate, which feeds into the Krebs Cycle • To regenerate NAD, an electron carrier

15. Krebs Cycle

16. Structure of a mitochondrion • the electron micrograph on the left shows the structure of a mitochondrion as seen under the electron microscope • draw a labelled diagram to show the structure of a mitochondrion • explain the relationship between the structure of the mitochondrion and its function

17. Structural adaptation of mitochondrion to its function • large inner surface area of cristae for respiratory complexes such as electron transport chains • matrix contains DNA and ribosomes for protein (enzyme) synthesis • it also contains Krebs cycle enzymes • double membrane(s) isolates metabolic processes from the rest of the cytoplasm • small intermembrane space between inner and outer membranes allows accumulation of protons for chemiosmosis

18. Aerobic respiration

19. Three stages of respiration

20. Summary