Grade 11 Chapter 3 Cellular Respiration PDF

Grade 11 CHAPTER 3 CELLULAR RESPIRATION Grade 11 CHAPTER 3 3-1 GLYCOLYSIS AND FERMATATION 3-2 AEROBIC RESPIRATION Grade 11 HARVESTING CHEMICAL ENERGY All cells br...

Grade 11 CHAPTER 3 CELLULAR RESPIRATION Grade 11 CHAPTER 3 3-1 GLYCOLYSIS AND FERMATATION 3-2 AEROBIC RESPIRATION Grade 11 HARVESTING CHEMICAL ENERGY All cells break down complex organic compounds into simpler molecules. Autotrophs, such as plants, use photosynthesis to convert light energy to chemical energy from sun Into chemical energy ,which is stored in carbohydrates and other organic compounds. Both Autotrophs and heterotrophs depend organic compounds for the energy to power cellular activities. By breaking down these compounds into simpler molecules, cells release energy(ATP). ATP is the main energy currency of cells. Cells make ATP by breaking down organic compounds is known as cellular respiration. Grade 11 HARVESTING CHEMICAL ENERGY Cellular respiration begins with a biochemical pathway called glycolysis, which yields a relatively small amount of ATP Glycolysis can follow either of two main pathways, depending on whether there is oxygen in the cell. If oxygen is absent; product of glycolysis may enter fermentation pathways(Anaerobic pathway) that yield no additional ATP. If oxygen is present; product of glycolysis may enter the aerobic pathway(aerobic respiration) Aerobic respiration produces a much larger amount of ATP than glycolysis. Grade 11 GLYCOLYSI S Glycolysis is a pathway in which one six-carbon molecule of glucose is oxidized to produce two three-carbon molecules of pyruvic acid. Glycolysis consists of a serial of reactions catalyzed by specific enzymes. All of reactions of glycolysis take place in the cytosol of the cell. Glycolysis reactions can be condensed into four main steps. Grade 11 GLYCOLYSI S Four main steps of glycolysis Step1- Two phosphate groups attached to glucose, forming a new six-carbon compound. The phosphate groups are supplied by two molecules of ATP, which are converted into 2 molecules of ADP in the process. Step2- The six-carbon compound formed in Step1 is split into two three-carbon molecules of PGAL. PGAL is also produced by the Calvin cycle in photosynthesis. Steps3- The two PGAL molecules are oxidized ,and each receives a phosphate group. Oxidation of PGAL is accompanied by the reduction of two molecules of NAD to NADH. In this steps two molecules of new three-carbon compound. Steps4- The phosphate groups added in step1 and step3 are removed from the three-carbon compounds formed in step3.This reaction produces two molecules of pyruvic acid. Each phosphate Grade 11 QUESTIONS 1- Which of the following is not formed during the glycolysis? a) CO2 b) NADH c) Pyruvic acid d) ATP 2-The net number of ATP molecules made directly by glycolysis is ………………. a) 2 b) 6 c) 32 d) 38 3- During which metabolic stage is glucose broken down to two pyruvic acids? a) Glycolysis b) The citric acid cycle c) The electron transport chain d) Calvin cycle 4-How many steps are in glycolysis? a) 3 b) 6 c) 4 d) 2 7 Grade 11 FERMENTATION In the absence of oxygen, some cells can convert pyruvic acid into other compounds through additional biochemical pathways that occur in the cytosol. The combination of glycolysis plus these additional pathways is known as fermentation. The additional fer­mentation pathways do not produce ATP. There are many fermentation pathways; Two common fermentation pathways result in the production of lactic acid and ethyl alcohol. Grade 11 Lactic acid fermentation In lactic acid fermentation, an enzyme converts pyruvic acid into another three-carbon compound, called lactic acid. The regeneration of NAD+ in lactic acid fermentation helps to keep glycolysis NET:2ATP operating. 2ADP 2ATP Glucose 2 Pyruvic acid 2 Lactic acid cccccc ccc ccc ccc ccc 2NAD 2NADH 2 NADH 2NAD ( LACTICACIDFERMENTATION ) Grade 11 Lactic acid fermentation Lactic acid fermentation by microorganisms (some bacteria) plays an essential role in the manufacture of food products such as yogurt and cheese. Lactic acid fermentation also occurs in your muscle cells during very strenuous exercise, such as sprinting at top speed. During this kind of exercise, muscle cells use up oxygen more rapidly than it can be delivered to them. As oxygen becomes depleted, the muscle cells begin to switch from aerobic respiration to lactic acid fermentation. Lactic acid accumulates in the muscle cells, making the cells' cytosol more acidic. The increased acidity may reduce the capacity of the cells to contract, resulting in muscle fatigue, pain, and even cramps. Eventually, the lactic acid diffuses into the blood and is trans­ported to the liver, where it is converted back into pyruvic acid when oxygen becomes available. Grade 11 Alcoholic fermentation Some plant cells and unicellular organisms, such as yeast, use a process called alcoholic fermentation to convert pyruvic acid into ethyl alcohol. Bread making depends on alcoholic fermentation performed by yeast cells. In this case, the CO2 that is produced by fermentation makes the bread rise by forming bubbles inside the dough, and the ethyl alcohol evaporates during 2ADP baking. NET:2ATP 2ATP Glucose 2 Pyruvic acid 2 molecules2-carbon compound 2 Ethyl alcohol cccccc ccc ccc cc cc cc cc 2NAD 2NADH 2 CO2 2NADH 2 NAD ( ALCOHOLIC FERMENTATION ) Grade 11 QUESTIO NS Q1-What are the three similarities between Lactic Acid and Alcoholic Fermentation? 1- THEY ARE TYPES OF FERMENTATION (ANAEROBIC RESPIRATION). 2- THEY DO NOT REQUIRE OXYGEN. 3- THEY TAKE PLACE IN THE CYTOSOL OF THE CELL. Q2-What are the three differences between Lactic Acid and Alcoholic Fermentation? Lactic acid Fermentation Alcoholic fermentation 1-Takes place in some bacteria and muscle cells. 1- Takes place in some plant cells ,some bacteria and yeast. 2-Produce 2 Lactic acid. 2- Produce 2 ethyl alcohol and 2 carbon dioxide 3-Used industry to produce yogurt and cheese. 3-Used industry to produce bread , Grade 11 QUESTIO NSbreaks down in ethyl alcohol Q3- When one molecule of glucose fermentation: I. Amount of net ATP II. Amount of CO2 released III. Amount of ATP Used In which of the following is the amount of the molecules above given correctly? I II III a) 2ATP 4CO2 4ATP b) 2ATP 2CO2 4ATP c) 4ATP 2CO2 2ATP Q4- d) 2ATP 2CO2 2ATP Glucose Glucose Glucose Pyruvic acid Ethyl alcohol Lactic acid I II III Which of the above reactions occurs in all organisms? a) I-II b) I-III c) I Grade 11 CHAPTE R3 3-2 AEROBIC RESPIRATION Grade 11 Aerobic respiration Most cells, the pyruvic acid that is produced in glycolysis does not undergo fermentation. Instead, if oxygen is available, pyruvic acid enters the pathways of aerobic respiration. Aerobic respiration produces nearly 20 times as much ATP as is produced by OVERVIEW OF AEROBIC glycolysis alone. RESPIRATION Aerobic respiration has two major stages: the Krebs cycle and the electron transport chain(ETC). The reactions of the Krebs cycle and the electron transport chain occur only if oxygen is present in the cell. Grade 11 OVERVIEW OF AEROBIC RESPIRATION In prokaryotes, the reactions of the Krebs cycle take place in the cytosol of cell ,the electron transport chain take place the cell membrane. In eukaryotic cells, however, these reactions take place inside mitochondria rather than in the cytosol. The pyruvic acid that is produced in gly­colysis diffuses across the double membrane of a mitochondrion and enters the mitochondrial matrix. The mitochondrial matrix is the space inside the inner membrane of a mitochondrion. The mitochondrial matrix contains the enzymes needed to catalyze the Aerobic respiration reactions of the Krebs cycle. Glycolysis Krebs cycle ETC Prokaryotes Cytoplasm Cytoplasm of cell of cell cell membrane Eukaryotes Cytoplasm Mitochondrial Inner of cell matrix membrane of mitochondrio n Grade 11 OVERVIEW OF AEROBIC RESPIRATION When pyruvic acid enters the mitochondrial matrix, it reacts with a molecule called coenzyme A to form acetyl coenzyme A, abbreviated acetyl CoA. The acetyl part of acetyl CoA contains two carbon atoms, but as you learned earlier, pyruvic acid is a three-carbon compound. The carbon atom that is lost in the conversion of pyruvic acid to acetyl CoA is released in a molecule of CO2 , this reaction reduces a molecule of NAD+ to NADH. Note: This reaction between glycolysis to Krebs cycle. This reaction called formation of Acetyl CoA. X2 Grade 11 THE KREBS CYCLE The Krebs cycle takes place in the mitochondrial matrix and involves five main steps. Step 1: Acetyl CoA combines with oxaloacetic acid to produce citric acid. Step 2: Citric acid releases a CO2molecule to form a five- carbon compound. Step 3: The five-carbon compound releases a CO2 molecule to form a four-carbon compound. Step 4: The four-carbon compound is converted into a new four-carbon compound. Step 5: The new four-carbon compound is converted back into oxaloacetic acid. Two turns produce six NADH, two FADH2, two ATP, and four CO2 molecules. The CO2 is a waste product that diffuses out of the cells. X Grade 11 Glycolysis produces two NADH molecules and that the conversion of pyruvic acid to acetyl CoA produces two more. Adding the six NADH molecules from the Krebs cycle gives a total of 10 NADH molecules. These 10 NADH molecules and the two FADH2 molecules from the Krebs cycle drive NOTE: the next stage of aerobic respiration(ETC). ATP NADH CO2 FADH2 Glycolysis 2 ATP 2 NADH --------- --------- Formation of Acetyl ------- 2 NADH 2 CO2 ---------- CoA Krebs Cycle 2 ATP 6 NADH 4 CO2 2 FADH2 Grade 11 QUESTIONS 1- How many molecules of NADH are produced during the 2 turns Krebs cycle? a)1 b) 2 c) 3 d) 6 2-Which is a product of Krebs Cycle? a) Carbon dioxide b) NADH c) FADH2 d) All of them 3- How many molecules of ATP are produced during the 2 turns Krebs cycle? a) 2 b) 38 c) 4 d) 34 4-Before the Krebs cycle can proceed, pyruvic acid must be converted into a) Citric acid b) Glucose c) Acetyl CoA d) NADH 20 Grade 11 ELECTRON TRANSPORT SYSTEM The electron transport chain constitutes the second stage of aerobic respiration. In eukaryotic cells, the electron transport chain lines the inner membrane of the mitochondrion. The inner membrane has many long folds called cristae. In prokaryotes, the electron transport chain lines the cell membrane. ATP is produced by the electron transport chain when NADH and FADH2 release hydrogen atoms, regenerating NAD and FAD. Grade 11 ELECTRON TRANSPORT SYSTEM FIGURE 3-8 NADH and FADH2 supply electrons and protons to the electron transport chain. The electrons are passed along the chain from molecule to molecule. The protons are pumped out of the mitochondrial matrix. As the protons return to the mitochondrial matrix through ATP synthase, they release energy, driving the synthesis of ATP. The final acceptor of electrons is oxygen, which also accepts protons in a reaction that forms water. By combining with both electrons and protons, oxygen forms water, as shown in the following equation: O2 + 4e- + 4H+ 2H2O Grade 11 ENERGY YIELD How many ATP molecules are made in aerobic respiration? Glycolysis and the Krebs cycle each produce 2 ATP molecules. Each NADH molecule that supplies the electron transport chain can generate three ATP molecules, and each FADH2 molecule can generate two ATP molecules. Thus, the 10 NADH and two FADH2 molecules made through aerobic respiration can produce up to 34 ATP molecules by the electron transport chain. Adding the four ATP molecules from glycolysis and the Krebs cycle gives a maximum yield of 38 ATP molecules per molecule of glucose. Grade 11 CELLULAR RESPIRATION VS PHOTOSYNTHESIS The products of photosynthesis are reactants in aerobic respiration, and the products of aerobic respiration are reac­tants in photosynthesis. Cellular respiration provides the ATP that all cells need to support the activities of life. Grade 11 QUESTIONS Q1- By accepting electrons and protons, the oxygen used in aerobic respiration turns into a) CO2 b) H20 c) C6H1206 d) ATP Q2- Some events related to cellular respiration are given below: I. Formation of pyruvic acid II. Lactic acid fermentation III. Ethyl alcohol fermentation IV. Krebs cycle reactions In which of the above is CO2 produced? a) I and II b) I, II and III c) II and III d) III and Q3- IV Most of the ATP synthesized in aerobic respiration is made a) During glycolysis b) Through fermentation c) In the cytosol d) Through chemiosmosis (ETC) 25  CONCEPT MAPPING USE THE FOLLOWING TERMS AND PHRASES TO COMPLETE THE CONCEPT MAP BELOW. ANAEROBIC PROCESS- OXYGEN - ELECTRON TRANSPORT CHAIN - PYRUVIC ACID – GLUCOSE – GLYCOLYSIS – KREBS CYCLE 26 27