Cellular Respiration Glycolysis Recap and Fermentation Processes

1. Cellular RespirationGlycolysis Recap and Fermentation Processes IB HL Biology 1 Adapted from L. Ferguson and S. Frander

2. Cell Respiration- controlled release of energy from organic compounds in cells to form ATP Aerobic Cellular Respirationa metabolic pathway with over 20 reactions, using 20 enzymes

3. Why cell respiration? • Cells require a constant source of energy to perform various tasks • Movement • Transport • Division

4. Summary Equation • The summary equation for cellular respiration is: C6H12O6 + O2 CO2 + H2O + Glucose + oxygen  carbon dioxide + water + ATP ATP

5. Key players in this process • Glucose: source of fuel • NAD+: electron carrier • Enzymes: mediate entire process • Mitochondria: site of aerobic respiration • ATP: principal end product • Protons/Electrons: sources of potential energy • Oxygen: final electron acceptor

6. Redox Reactions • Reduction: reducing overall positive charge by gaining electrons • Oxidation: loss of electrons • OIL RIG • Oxidation Is Loss of e- and addition of oxygen • Reduction Is Gain of e- and loss of oxygen • Redox reactions produce energy change • Reduction absorbs energy (endergonic) • Oxidation releases energy (exergonic)

7. Three stages of cell respiration • Stage 1: Glycolysis (energy investment) • Some ATP is made, some is used • Stage 2: Krebs Cycle (oxidation of pyruvate) • Generation of CO2 • Stage 3: Oxidative Phosphorylation -ETC • Generation of most ATP

8. Three stages of respiration

9. Summary of Glycolysis Glucose, present in the cytoplasm, is partially broken down to pyruvate, a three carbon molecule. These series of enzymatic reactions produce two NADH and four ATP. Two ATP are invested to activate the glucose, so a net of two ATP are formed. Image from http://kvhs.nbed.nb.ca/gallant/biology/glycolysis.html

10. Glycolysis Animations • McGraw Hill animation • Glycoysismovie • Glycolysis animation shown in class Wed, Feb 22

11. General Outline • Glucose Glycolysis No Oxygen Anaerobic Oxygen Aerobic Pyruvic Acid Transition Reaction Fermentation Krebs Cycle ETS 2ATP 36-38 ATP

12. But what if there’s no oxygen? Remember, the first living organisms lived in an anaerobic environment…

13. Without oxygen… • NADH cannot be oxidized back to NAD+ • In order for aerobic respiration to occur, NADH must be oxidized and some intermediate compound must be reduced

14. Anaerobic Cell Respiration • If no oxygen is available, the pyruvate remains in the cytoplasm and is converted into a waste product that can be removed from the cell • No ATP is produced in these reactions • In humans, the waste product is lactate (lactic acid) • In yeast the products are ethanol and carbon dioxide

15. Fermentation enables some cells to produce ATP without the use of oxygen • Krebs cycle and oxidative phophorylation require O2 to produce ATP • Glycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions) and is beginning stage of fermentation • Also side reactions occur that allow NADH to be oxidized back to NAD+ by donating electrons and H atoms to intermediate products to form ethanol and lactate

16. Alcoholic Fermentation • Glycolysis happens • Pyruvate is then converted to acetaldehyde, CO2 is released • Acetaldehyde is reduced by NADH to ethanol • No additional ATP is made • Occurs in yeasts, some bacteria

17. Lactic acid fermentation • Glycolysis happens • Pyruvate is reduced by NADH and forms lactate (lactic acid) • No CO2 is released • No additional ATP is formed • Done by bacteria, muscle cells of humans

18. 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) Explain means to give a detailed account of causes, reasons or mechanisms. Anaerobic respiration is the oxidation of organic compounds without oxygen. It is less efficient than aerobic respiration (with oxygen). There are different types of anaerobic respiration. Here we will compare anaerobic respiration in yeast and humans.

19. ethanol and CO2 from yeast

20. lactate (lactic acid) in humans (ex: muscle fatigue) • bacteria can also do this

21. Other molecules can be used in respiration • Proteins: must be deaminated, then converted to pyruvate • Fats: undergo beta-oxidation • Cells prefer carbs

22. Mitochondrion • Mitochondria are membrane-bound organelles • The outer membrane is fairly smooth. But the inner membrane is highly convoluted, forming folds called cristae. • The cristae greatly increase the inner membrane's surface area. On these cristae organic molecules are combined with oxygen to produce ATP - the primary energy source for the cell.

23. 8.1.3 Structure of the mitochondria. • Location of aerobic respiration • Pyruvate, the product of glycolysis can be further oxidized here to release more energy. • Mitochondria are only found in eukaryotic cells. • Cells that need a lot of energy will have many mitochondria ( liver cell) or can develop them under training (muscles cells). • There is a double membrane. • The inner membrane is folded to form 'cristae'. • There is a space between the two membranes which is important for creating a place to concentrate H+ (see 8.1.6 ) • The inner space is called the matrix. • Mitochondria contain some of their own DNA (mDNA). 8.1.6 Relationship between the structure and function of the mitochondria. 1. Cristae folds increase the surface area for electron transfer system. 2. The double membrane creates a small space into which the H+ can be concentrated. 3. Matrix creates an isolated space in which the Krebs cycle can occur.

24. DRAW AND LABEL A DIAGRAM SHOWING THE STRUCTURE OF A MITOCHONDRION AS SEEN IN ELECTRON MICROGRAPHS.