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Chapter 9: Cellular Respiration and Fermentation

Chapter 9: Cellular Respiration and Fermentation. p.248-265. Voc Terms. Cellular respiration Aerobic Anaerobic Glycolysis NAD+ Krebs cycle Matrix Fermentation. Chapter 9: Big Idea. Cellular Basis of life- How do organisms obtain Energy

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Chapter 9: Cellular Respiration and Fermentation

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  1. Chapter 9: Cellular Respiration and Fermentation p.248-265 Cellular Respiration 2009

  2. Voc Terms • Cellular respiration • Aerobic • Anaerobic • Glycolysis • NAD+ • Krebs cycle • Matrix • Fermentation Cellular Respiration 2009

  3. Chapter 9: Big Idea Cellular Basis of life- How do organisms obtain Energy 9.1- Why do most organisms undergo the process of cellular respiration? 9.2- How do cell release energy from food in the presence of oxygen? 9.3- How do cells release energy from food without oxygen? Cellular Respiration 2009

  4. THINK ABOUT IT • You feel weak when you are hungry because food serves as a source of energy. How does the food you eat get converted into a usable form of energy for your cells? Cellular Respiration 2009

  5. Harvesting Chemical Energy • Cellular respiration- complex process in which cells make ATP by breaking down organic cpds. • What are Autotrophs? use photosynthesis to convert light energy from the sun into chemical energy, stored organic cpds Both auto and heterotrophs undergo cellular respiration to break organic cpds into simpler molecules to release energy (ATP and work) chapter 7 biology notes

  6. Chemical Energy and Food • Where do organisms get energy? • Organisms get the energy they need from food. Cellular Respiration 2009

  7. Chemical Energy and Food • Food provides living things with the chemical building blocks they need to grow and reproduce. • Food molecules contain chemical energy that is released when its chemical bonds are broken. Cellular Respiration 2009

  8. Chemical Energy and Food • Energy stored in food is expressed in units of calories. A Calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. 1000 calories = 1 kilocalorie, or Calorie. • Cells use all sorts of molecules for food, including fats, proteins, and carbohydrates. The energy stored in each of these molecules varies because their chemical structures, and therefore their energy-storing bonds, differ. • Cells break down food molecules gradually and use the energy stored in the chemical bonds to produce compounds such as ATP that power the activities of the cell. Cellular Respiration 2009

  9. Overview of Cellular Respiration What is cellular respiration? • Cellular respiration is the process that releases energy from food in the presence of oxygen. Cellular Respiration 2009

  10. Glycolysis • Is a biochemical pathway in which one 6C molecule of glucose is oxidized to produce two 3C molecule Terms: • Pyruvic acid- 3 carbon molecule • NADH/FADH2- electron carrier molecule • Anaerobic- does not require the presence of oxygen • Aerobic- requires oxygen chapter 7 biology notes

  11. Overview of Cellular Respiration • If oxygen is available, organisms can obtain energy from food by a process called cellular respiration. The summary of cellular respiration is presented below. • In symbols: 6 O2 + C6H12O6  6 CO2 + 6 H2O + Energy • In words: • Oxygen + Glucose  Carbon dioxide + Water + Energy • The cell has to release the chemical energy in food molecules (like glucose) gradually, otherwise most of the energy would be lost in the form of heat and light. Cellular Respiration 2009

  12. Stages of Cellular Respiration The three main stages of cellular respiration: 1. Glycolysis 2. Krebs cycle 3. Electron transport chain. Cellular Respiration 2009

  13. Stages of Cellular Respiration Glycolysis produces only a small amount of energy. Most of glucose’s energy (90%) remains locked in the chemical bonds of pyruvic acid at the end of glycolysis. (2 net ATP) Cellular Respiration 2009

  14. Stages of Cellular Respiration • During the Krebs cycle, a little more energy is generated from pyruvic acid. • (2 Net ATP) Cellular Respiration 2009

  15. Stages of Cellular Respiration The electron transport chain produces the bulk of the energy in cellular respiration by using oxygen, a powerful electron acceptor. (34- 36 Net ATP) Cellular Respiration 2009

  16. Oxygen and Energy • Pathways of cellular respiration that require oxygen are called aerobic. The Krebs cycle and electron transport chain are both aerobic processes. Both processes take place inside the mitochondria. Cellular Respiration 2009

  17. Oxygen and Energy • Gylcolysis is an anaerobic process. It does not directly require oxygen, nor does it rely on an oxygen-requiring process to run. However, it is still considered part of cellular respiration. Glycolysis takes place in the cytoplasm of a cell. Cellular Respiration 2009

  18. Comparing Photosynthesis and Cellular Respiration • What is the relationship between photosynthesis and cellular respiration? • Photosynthesis removes carbon dioxide from the atmosphere, and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere, and cellular respiration uses that oxygen to release energy from food. Cellular Respiration 2009

  19. Comparing Photosynthesis and Cellular Respiration • Photosynthesis and cellular respiration are opposite processes. • The energy flows in opposite directions. Photosynthesis “deposits” energy, and cellular respiration “withdraws” energy. • The reactants of cellular respiration are the products of photosynthesis and vice versa. Cellular Respiration 2009

  20. Comparing Photosynthesis and Cellular Respiration • The release of energy by cellular respiration takes place in plants, animals, fungi, protists, and most bacteria. • Energy capture by photosynthesis occurs only in plants, algae, and some bacteria. Cellular Respiration 2009

  21. THINK ABOUT IT • Food burns! How does a living cell extract the energy stored in food without setting a fire or blowing things up? Cellular Respiration 2009

  22. Glycolysis What happens during the process of glycolysis? • During glycolysis, 1 molecule of glucose, a 6-carbon compound, is transformed into 2 molecules of pyruvic acid, a 3-carbon compound. Cellular Respiration 2009

  23. Glycolysis Glycolysis is the first stage of cellular respiration. • During glycolysis, glucose is broken down into 2 molecules of the 3-carbon molecule pyruvic acid. Pyruvic acid is a reactant in the Krebs cycle. • ATP and NADH are produced as part of the process. Cellular Respiration 2009

  24. The Advantages of Glycolysis • Glycolysis produces ATP very fast, which is an advantage when the energy demands of the cell suddenly increase. • Glycolysis does not require oxygen, so it can quickly supply energy to cells when oxygen is unavailable. Cellular Respiration 2009

  25. The Krebs Cycle What happens during the Krebs cycle? • During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. Cellular Respiration 2009

  26. Krebs Cycle • Biochemical pathway that breaks down acetyl Co A, producing CO2, hydrogen atoms, and ATP • Hans Krebs (1900-1981), German biochemist Five main steps that occur in the mitochondrial matrix, aerobic process that oxidizes pyruvates to CO2 ** this process yields 2 ATP same as glycolysis, but it does give 10NADH molecules and 2 FADH2 molecules which will drive the next stage ETC , where most energy is transferred from glucose to ATP chapter 7 biology notes

  27. The Krebs Cycle • During the Krebs cycle, the second stage of cellular respiration, pyruvic acid produced in glycolysis is broken down into carbon dioxide in a series of energy-extracting reactions. • The Krebs cycle is also known as the citric acid cycle because citric acid is the first compound formed in this series of reactions. Cellular Respiration 2009

  28. chapter 7 biology notes

  29. Energy Extraction • Remember! Each molecule of glucose results in 2 molecules of pyruvic acid, which enter the Krebs cycle. So each molecule of glucose results in two complete “turns” of the Krebs cycle. • Therefore, for each glucose molecule, 6 CO2 molecules, 2 ATP molecules, 8 NADH molecules, and 2 FADH2 molecules are produced. Cellular Respiration 2009

  30. Electron Transport and ATP Synthesis How does the electron transport chain use high-energy electrons from glycolysis and the Krebs cycle? • The electron transport chain uses the high-energy electrons from glycolysis and the Krebs cycle to convert ADP into ATP. Cellular Respiration 2009

  31. chapter 7 biology notes

  32. Electron Transport • NADH and FADH2 pass their high-energy electrons to electron carrier proteins in the electron transport chain. Cellular Respiration 2009

  33. Importance of oxygen • ATP can be synthesized by chemiosmosis only if electrons continue to move from molecule to molecule in the ETC. • The last molecule in the ETC must pass e- on to a final electron acceptor. If not it will stop!! • The oxygen allows for additional electron to pass along the chain, ATP can continue to be made through chemiosmosis chapter 7 biology notes

  34. The Totals How much energy does cellular respiration generate? • Together, glycolysis, the Krebs cycle, and the electron transport chain release about 36-38 molecules of ATP per molecule of glucose. Cellular Respiration 2009

  35. Energy Totals • In the presence of oxygen, the complete breakdown of glucose through cellular respiration results in the production of 36 ATP molecules. • This represents about 36 percent of the total energy of glucose. The remaining 64 percent is released as heat. Cellular Respiration 2009

  36. Energy Totals • The cell can generate ATP from just about any source, even though we’ve modeled it using only glucose. Complex carbohydrates are broken down into simple sugars like glucose. Lipids and proteins can be broken down into molecules that enter the Krebs cycle or glycolysis at one of several places. Cellular Respiration 2009

  37. Efficiency of cellular respiration • glycolysis and the Krebs cycle give a max yield of 38 ATP molecules per molecule of glucose • It can vary from cell to cell • As a result most euk cells produce only 36 ATP (39% efficiency) (38 x7)/ 686 **Cellular resp is 20x more efficient than glycolysis alone chapter 7 biology notes

  38. chapter 7 biology notes

  39. THINK ABOUT IT • We use oxygen to release chemical energy from the food we eat, but what if oxygen is not around? • Is there a pathway that allows cells to extract energy from food in the absence of oxygen? Cellular Respiration 2009

  40. Fermentation How do organisms generate energy when oxygen is not available? • In the absence of oxygen, fermentation releases energy from food molecules by producing NAD+ to regenerate glycolysis. • Takes place in the cytoplasm of the cell Cellular Respiration 2009

  41. Fermentation • Under anaerobic conditions, fermentation follows glycolysis. During fermentation, cells convert NADH produced by glycolysis back into the electron carrier NAD+, which allows glycolysis to continue producing ATP. Cellular Respiration 2009

  42. Rumen Microbes • The rumen is a special stomach chamber in cows and other large hoofed mammals. It acts as a fermentation vat and has been estimated in some cows to contain as many as 8.2 X 10^15 microbes, including over 200 species of bacteria, protozoa and fungi!! (adaptation for digesting plants) chapter 7 biology notes

  43. Fermentation • When O2 is present CR continues as pyruvic acid enter the pathways of aerobic respiration. • When no O2 is present- anaerobic environment cells must convert pyruvic acid into other cpds through additional biochemical pathways that occur in the cytoplasm • The combination of glycolysis and these pathways that regenerate NAD+ is fermentation chapter 7 biology notes

  44. Fermentation cont: • Additional pathways do not produce ATP • If there were not a cellular process that recycled NAD+ from NADH, glycolysis would quickly use up all the NAD+ in the cell • Glycolysis would STOP! ATP production would STOP!! fermentation pathways allow for the continued production of ATP chapter 7 biology notes

  45. Fermentation cont: • There are many fermentation pathways • They differ in terms of enzymes that are used • They differ in the cpds that are made from pyruvic acid Two common fermentation pathways result in the production of • Lactic acid • Ethyl alcohol chapter 7 biology notes

  46. chapter 7 biology notes

  47. Alcoholic Fermentation • Yeast and a few other microorganisms use alcoholic fermentation that produces ethyl alcohol and carbon dioxide. • This process is used to produce alcoholic beverages and causes bread dough to rise. Chemical equation: Pyruvic acid + NADH  Alcohol + CO2 + NAD Cellular Respiration 2009

  48. Alcoholic Fermentation cont • The ethyl alcohol is the alcohol in alcoholic beverages • To make wines, the CO2 that is generated is allowed to escape • If you make champagne it is retained for the carbonation • Bread making also depends on alcoholic fermentation performed by yeast cells, CO2 produced makes the bread rise because of the bubbles produced the ethyl alcohol evaporates during the baking process chapter 7 biology notes

  49. Lactic Acid Fermentation • Most organisms, including humans, carry out fermentation using a chemical reaction that converts pyruvic acid to lactic acid. Chemical equation: Pyruvic acid + NADH  Lactic acid + NAD+ Cellular Respiration 2009

  50. Lactic Acid Fermentation cont: • Why is this important LA fermentation by microorganisms play an essential role in the manufacture of many dairy products Ex. Fermentation of milk spoiling, if controlled we can use it to make buttermilk, cheese, yogurt, sour cream chapter 7 biology notes

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