Cell Respiration

1. Cell Respiration Mrs: Jackie

2. Respiration defined • Respiration- series of chemical reactions that occur inside a living cell. • Involves breakdown of large substances into smaller substances • Substance most commonly used is glucose

3. Stages of respiration • 1. Glycolysis • Occurs in the cytosol (semifluid part of the cytoplasm) • Involves the phosphorylation of glucose into glucose-6-phosphate • Follow by many reactions resulting in the splitting of glucose in half to form 2 pyruvic acid molecules ( each with 3 Carbons) • Other important products 2NADH + H+ and 2 ATP

4. Glycolisis continues • 1.Glucose 6-phosphate is formed when the 6th carbon on the glucose molecule is phosphorylated by an ATP molecule. • 2. Glucose 6-phosphate is converted into a 5-carbon ring isomer, fructose 6-phosphate. • 3. Fructose 6-phosphate is phosphorylated by another ATP to form fructose 1, 6-diphosphate. • 4. Fructose 1, 6-diphosphate is processed by an enzyme into two glyceraldehyde 3-phosphate molecules. • 5. Two molecules of glyceraldehyde 3-phosphate are oxidized, losing hydrogen atoms and gaining phosphate groups to form 1, 3-diphosphoglycerate. Two molecules of NAD+ are converted into NADH2+ in the process.

5. Glycolysis continues 6. Two 1,3-diphosphoglycerate molecules phosphorylate ADP (adenine diphosphate) to yield two molecules of 3-phosphoglycerate and two ATPs are produced. 7. The phosphate groups on 3-phosphoglycerate move to the 2nd carbon, forming 2-phosphoglycerate. 8. The two 2-phosphoglycerate molecules are dehydrated and forms two high-energy phosphoenolpyruvate molecules. 9. The two phospoenolpyruvate phosphorylates two ADPs and produces two more ATPs and two molecules of pyruvate.

6. Glycolysis summary In the next sequence of reactions 4 molecules of ATP are produced and the total energy harvest of ATP can be calculated as shown on the table

7. Glycolysis • NAD+ is a coenzyme • Hydrogen carrier • NADH + H formed by removing hydrogen from glucose (oxidation of glucose), and giving this H to NAD+ (reduction) • NAD+ +2H NADH+ H+ • Glucose is reduced (removal of H) and NADH is oxidized

8. Glycolysis • NAD+  NADH + H+ Glucose oxidation pyruvate • Pyruvic acid made in glycolysis can now enter into aerobic or anaerobic pathways of respiration

9. Anaerobic respiration • If respiration is anaerobic • Pyruvate is reduced into either lactic acid releasing NAD+ or • Alcohol is produced with the release of NAD+ and carbon dioxide • The reduction of pyruvate into lactic acid or ethanol does not release energy. • Only serves in the release of NAD+

10. Anaerobic respiration • These NADs can be used again in glycolysis • This step produced ethanol or lactic acid which is less toxic as a waste product in the surroundings of these organisms

11. Anaerobic respiration • Occurs in mostly small animals which do not need much energy for the way of life • The two ATP formed are enough for providing energy to these simple organisms such as bacteria and yeast • Also occurs during strenuous exercise in mammals

12. Anaerobic respiration Glycolysis Phosphorilation Oxidation Lysis 2 pyruvate + 2 ATP +2NADH + H+ Fermentation

13. Fermentation 2 pyruvate either 2NADH + H 2NADH + H 2NAD 2NAD + CO2 LACTIC ACID Ethanol

14. Oxidation and reduction • Oxidation involves the loss of electrons from an element • Reduction involves a gain of electron • Phosphorylation is a process in which ATP is made.

15. Industrial uses of anaerobic respiration • Alcoholic fermentation • Manufacture of alcoholic drinks • Wine – make by incubating crushed grapes in a sealed container at a temperature of 40 degrees celsius. • Need the correct bacterias and yeast that carry out anaerobic respiration and breakdown of sugar in grapes into ethanol and CO2

16. Industrial uses of anaerobic respiration • Manufacture of Yogurt • Milk is incubated over night with bacteria at around 40 degrees • Lactic acid makes the milk to clot into yogurt

17. Aerobic respiration • After glycolysis the pyruvic acid enters into the mitochondria • In the matrix of the mitochondria, pyruvate is decarboxylated (CO2 mol is removed) • Decarboxylase remove CO2 • Dehydrogenase oxidised (hydrogen removed)

18. Aerobic respiration • Resulting molecule is called acetyl group (2 carbons) • Results from the removal of Carbon dioxide and combination with coenzyme A= Acetyl Co A • This reactions are called link reactions since they link pyruvate with the Krebs cycle • This compound Acetyl Co A then enters into the matrix of the mitochondria.

19. The Krebs Cycle • Starting molecule is 2 carbon compound called oxaloacetic acid • It reacts with acetyl CoA and forms a 6 carbon compound called Citric acid

20. The Krebs Cycle • Coenzyme A comes out unaffected • Citric acid loses CO2 and becomes a 5 carbon compound • A different stages in the cycle compounds loses Hydrogen which comes out in the form of NADH+H and FADH2

21. The Krebs Cycle • Final output • 2ATP, • 4CO2, • 6NADH +H • and 2FADH2

22. Chemiosmotic oxidative phosphorylation and the electron transport chain

23. Chemiosmotic oxidative phosphorylation and the electron transport chain • NADH + H and FADH2 coming out of all the reaction of respiration are processed in the mitochondria to produce ATP • This is carry out by electron carriers that are situated in the inner membrane of the mitochondria and cristae

24. Electron transport chain • NADH +H gives its electron to the first electron carrier in the ETC, thus NADH +H becomes NAD+, in other terms NADH+H is oxidized and the first carrier in the chain is reduce • The first carrier passes the electron to the next carrier and so on • electrons are passed from one carrier to the next in the electron transport chain • As the electrons are passed from one carrier to the next they go down to a lower and lower energy level.

25. Electron transport chain • These electrons are finally taken by oxygen to form water. • Oxygen is the final recipient of the electrons passing down the electron transport chain. In this process oxygen becomes reduced into water. • Going down the energy gradient, the electrons released energy

26. Electron transport chain • The energy released from the electrons is used to pump protons (H+) from the matrix to the intermembranal space. • Due to the small volume of this space, it become highly concentrated with protons very quickly

27. Electron transport chain • This created two compartments in the mitochondria with different proton concentrations. The matrix with a low concentration and the intermembranal space with a high concentration. • This results in the protons moving down their concentration gradient from the intermembranal space to the matrix. • However the only path they can pass is through channels provided by the enzyme ATP synthetase.

28. Electron transport chain • Protons diffuse quickly through the ATPase channels, thus activating this enzyme. • When ATPase becomes active, it catalyses the phosphorilation of ADP into ATP, and so ATP is formed in this way from NADH+H • All the above steps are called oxidative phosphorilation.

29. Products • NAD+ and FAD take hydrogen stripped off the glucose molecule into the ETC where they are processed into ATP. • Carbons of the glucose are released in the form of CO2.