Cellular Respiration

1. Cellular Respiration Chapter 6

2. Autotrophs • Autotrophs are organisms that can use basic energy sources (i.e. sunlight) to make energy containing organic molecules from inorganic raw materials. • 2 Types • Photosynthetic autotrophs • Chemosynthetic autotrophs

3. Chemosynthesis • Chemosynthesis is a process used by prokaryotic organisms to use inorganic chemical reactions as a source of energy to make larger organic molecules.

4. Heterotrophs • Heterotrophs require organic molecules as food. • They get their energy from the chemical bonds in food molecules such as carbohydrates, fats, and proteins.

5. Prokaryotic Cells

6. Prokaryotic Cells • Prokaryotic cells have no nuclei. • Prokaryotic cells lack mitochondria and chloroplasts. • They carry out photosynthesis and cellular respiration within the cytoplasm or on the inner surfaces of the membranes.

7. Eukaryotic Cells

8. Eukaryotic Cells • Eukaryotic cells contain nuclei, mitochondria, and in the case of plant cells chloroplasts. • Plant cells, animal cells, fungi and protists are all eukaryotic.

9. Cellular Respiration • Cellular respiration is the controlled release of chemical-bond energy from large, organic molecules. • This energy is utilized for many activities to sustain life. • Both autotrophs and heterotrophs carry out cellular respiration.

10. Aerobic Vs. Anaerobic • Aerobic respiration requires oxygen. • Anaerobic respiration does not require oxygen.

11. Aerobic Respiration • Aerobic cellular respiration is a specific series of enzyme controlled chemical reactions in which oxygen is involved in the breakdown of glucose into carbon-dioxide and water. • The chemical-bond energy is released in the form of ATP. • Sugar + Oxygen  carbon dioxide + water + energy (ATP)

12. Aerobic Respiration • Simplified Reaction: • C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l) ΔHc -2880 kJ • Covalent bonds in glucose contain large amounts of chemical potential energy. • The potential energy is released and utilized to create ATP.

13. Glycolysis • Glycolysis is a series of enzyme controlled anaerobic reactions that result in the breakdown of glucose and the formation of ATP. • A 6-carbon sugar glucose molecule is split into two smaller 3-carbon molecules which are further broken down into pyruvic acid or pyruvate. • 2 ATP molecules are created during glycolysis and electrons are released during the process.

14. Krebs Cycle • The Krebs cycle is a series of enzyme-controlled reactions that take place inside the mitochondrion. • Pyruvic acid formed during glycolysis is broken down further. • Carbon dioxide, electrons, and 2 molecules of ATP are produced in this reaction.

15. Electron Transport System • The electrons released from glycolysis and the Krebs cycle are carried to the electron-transport system (ETS) by NADH and FADH2. • The electrons are transferred through a series of oxidation-reduction reactions until they are ultimately accepted by oxygen atoms forming oxygen ions. • 32 molecules of ATP are produced.

16. Aerobic Respiration Summary • Glucose enters glycolysis. • Broken down into pyruvic acid. • Pyruvic acid enters the Krebs cycle. • Pyruvic acid is further broken down and carbon-dioxide is released. • Electrons and hydrogen ions from glycolysis and the Krebs cycle are transferred by NADH and FADH2 to the ETS. • Electrons are transferred to oxygen to form oxygen ions. • Hydrogen ions and oxygen ions combine to form water.

17. Anaerobic Cellular Respiration • Anaerobic respiration does not require oxygen as the final electron acceptor. • Some organisms do not have the necessary enzymes to carry out the Krebs cycle and ETS. • Many prokaryotic organisms fall into this category. • Yeast is a eukaryotic organism that performs anaerobic respiration.

18. Fermentation • Fermentation describes anaerobic pathways that oxidize glucose to produce ATP. • An organic molecule is the ultimate electron acceptor as opposed to oxygen. • Fermentation often begins with glycolysis to produce pyruvic acid.

19. Alcoholic Fermentation • Alcoholic fermentation is the anaerobic pathway followed by yeast cells when oxygen is not present • Pyruvic acid is converted to ethanol and carbon-dioxide. • 4 ATPS are generated from this process, but glycolysis costs 2 ATPs yielding a net gain of 2 ATPs.

20. Lactic Acid Fermentation • In Lactic acid fermentation, the pyruvic acid from glycolysis is converted to lactic acid. • The entire process yields a net gain of 2 ATP molecules per glucose molecule. • The lactic acid waste products from these types of anaerobic bacteria are used to make fermented dairy products such as yogurt, sour cream, and cheese.

21. Lactic Acid Fermentation • Lactic acid fermentation occurs in the human body in RBCs and muscle cells. • Muscle cells will function aerobically as long as oxygen is available, but will function anaerobically once the oxygen runs out. • Nerve cells always require oxygen for respiration. • RBCs lack a nucleus and mitochondria and therefore must always perform anaerobic, lactic acid fermentation.

22. Fat Respiration • A triglyceride (neutral fat) consists of a glycerol molecule with 3 fatty acids attached to it. • A molecule of fat stores several times the amount of energy as a molecule of glucose. • Fat is an excellent long-term energy storage material. • Other molecules such as glucose can be converted to fat for storage.

23. Protein Respiration • Protein molecules must first be broken down into amino acids. • The amino acids must then have their amino group (-NH2) removed (deamination). • The amino group is then converted to ammonia. In the human body ammonia is converted to urea or uric acid which can then be excreted.