2 Vocabulary Pretest Section 1 Cellular RespirationPyruvic AcidNADHAnaerobicAerobic RespirationGlycolysisNAD+FermentationLactic Acid FermentationAlcoholic FermentationKilocalorieDoes not require oxygenAnaerobic breakdown of glucoseinto pyruvic acidBreakdown of carbohydratesin the absence of oxygenOccurs in muscle cells duringperiods of strenuous exerciseA unit of energy equal to 1000 caloriesOccurs when yeast breakdown sugarResults in large amounts of ATP(uses oxygen)An electron carrierThe reduced form of NAD+Three carbon compound producedby glycolysisThe process by which cells obtain energyfrom carbohydrates
3 Answer Key Cellular Respiration K Pyruvic Acid J NADH I Anaerobic A Aerobic Respiration GGlycolysis BNAD HFermentation CLactic Acid Fermentation DAlcoholic Fermentation FKilocalorie E
4 Cellular RespirationCellular Respiration —the process by which cells get energy from carbohydrates; oxygen combines with glucose to form water and carbon dioxideC6H12O O CO H2O energy (ATP)
5 The equation is a simple summary of a very complex process. The overall purpose is to convert food into energy by breaking down organic fuel molecules.When oxygen is present during this process it is called aerobic respiration ( which is the most efficient).If no oxygen is present it is called anaerobic respiration (which is much less efficient).Both types (aerobic and anaerobic) start with a process called glycolysis.
6 Glycolysis Glycolysis —first stage of cellular respiration. Glycolysis means “glucose splitting”Occurs in the cytosolNo oxygen is neededGlucose molecules are broken down into two carbon molecules of pyruvic acidPyruvic acid is then used in the Krebs Cycle (which is the second stage of aerobic respiration)Specific enzymes are needed2 molecules of ATP are produced2 molecules of NADH (an electron carrier molecule) are produced
7 4 stages of Glycolysis1. 2 phosphates are added to glucose. They are released from 2 molecules of ATP (changing it to ADP).
8 2. The glucose molecule (with its 2 phosphates) is then split into 2 molecules of G3P (glyceraldehyde 3-phosphate)2 G3P moleculesG3PG3P
9 3. Each G3P gets oxidized by adding another phosphate group 3. Each G3P gets oxidized by adding another phosphate group. Also, electrons and hydrogen atoms are removed from the 3C molecule. They are added to 2 molecules of NAD+ (nicotinamide adenine dinucleotide) to create 2 NADH and 2 H+. These will go to the electron transport chain later on.
10 4. The phosphate groups are now removed from each molecule creating 2 molecules of pyruvic acid (3C). The phosphates are added to 4 molecules of ADP producing 4 ATP molecules.
12 Summary of Glycolysis Basically: One glucose (6C) is broken into two molecules of pyruvic acid (3C)If oxygen is available, the pyruvic acid will move into the mitochondria and aerobic respiration will begin.4 ATP molecules are produced. Two are used to break apart the next glucose molecule and keep glycolysis going.This leaves a net yield of 2 ATP molecules for use by the cell.Two NAD+ are converted into 2 NADH and 2H+. These go to Electron Transport.
13 Efficiency of Glycolysis Measured in kilocalories (kcal)One kilocalorie equals 1,000 calories (cal)Complete oxidation of glucose releases 686 kcalProduction of ATP absorbs 7 kcal2ATP are produced from every glucose molecule broken down by glycolysisThe efficiency is therefore calculated by the following formula:Efficiency of Energy required to make ATPglycolysis = Energy released by oxidation of glucose= x 7 kcal x % = 2%686 kcal
14 Section 2 Vocabulary Pretest Mitochondrial matrixAcetyl CoAKrebs CycleOxaloacetic AcidCitric AcidFADBiochemical pathway that generates ATP6 carbon compound used in the Krebs cycleElectron acceptor: Flavin adenine dinucleotideThe space inside the inner membrane of a mitochondrion2 carbon compound made from pyruvic acid4 carbon compound used in the Krebs cycle
15 Answer Key Mitochondrial matrix D Acetyl CoA E Krebs Cycle A Oxaloacetic Acid FCitric Acid BFAD C
16 Aerobic RespirationIn most cells, the pyruvic acid produced in glycolysis enters the pathway of aerobic respiration.This pathway produces nearly 20 times as much ATP as is produced by glycolysis alone and is therefore the most efficient.Oxygen must be available for this to happen.There are two major stages: The Krebs Cycle and the Electron Transport Chain
17 Intermediate StepAerobic Respiration takes place in the mitochondria of the cell.Before the Krebs Cycle can begin, each of the two pyruvic acid molecules must be converted.The pyruvic acid enters the mitochondrial matrix (space inside the inner membrane of the mitochondria)It reacts with a molecule called coenzyme A to form Acetyl Coenzyme A (acetyl CoA)
18 Notice that acetyl CoA only has 2 carbon atoms. The lost carbon atom is released in a molecule of CO2Also, this reaction reduces a molecule of NAD+ to NADH + H+This happens to both molecules of pyruvic acidTherefore, the end result is:2 molecules of Acetyl CoA for the Krebs cycle2 molecules of CO2 to be released2 molecules of NADH for electron transport.
19 The Krebs CycleThe Krebs Cycle (named for Hans Krebs) is a biochemical pathway that breaks down acetyl CoA.Two turns of the Krebs Cycle produce:2 ATP molecules4 CO2 molecules6 NADH molecule2 FADH2 molecules
20 5 Steps of the Krebs Cycle 1. Acetyl CoA (2 carbon compound) combines with Oxaloacetic acid (4 carbon compound) to produce Citric Acid (6 carbon compound). This regenerates and releases CoA.
21 2. Citric acid releases a CO2 molecule and is oxidized by losing a hydrogen atom. This forms a new 5 carbon compound. The hydrogen atom is transferred to NAD+, reducing it to NADH.
22 3. The 5 carbon compound now releases a CO2 molecule and a hydrogen atom. This creates a 4 carbon compound and the hydrogen atom is again added to NAD+, reducing it to NADH. A molecule of ATP is also synthesized from ADP.
23 4. The 4 carbon compound releases a hydrogen atom which is used to reduce FAD (Flavin Adenine Dinucleotide) to FADH2. (FAD, like NAD+ also accepts electrons during redox reactions.
24 5. The 4 carbon compound now releases a hydrogen atom to regenerate oxaloacetic acid, which can be used to start the Krebs cycle over again. The hydrogen atom released again reduces NAD+ to NADH.
26 Review of the Gylcolysis and the Krebs Cycle In Glycolysis, one glucose molecule produces two pyruvic acid molecules, which can then form two molecules of Acetyl CoA.Both of the Acetyl CoA molecules enter the Krebs Cycle creating two turns of the cycle.This produces 6 NADH, 2 FADH2, 2 ATP and 4 CO2 molecules (waste product that diffuses out of the cell).The 6 NADH and 2 FADH2 molecules drive the next stage of aerobic respiration—the Electron Transport Chain.
27 Electron Transport Chain The Electron Transport Chain, linked with chemiosmosis makes up the second stage of aerobic respiration.Electrons are transferred from one molecule to another by several electron carrying molecules located in the membrane of the mitochondria.All steps occur in the cristae (inner membrane)Follow the steps in the diagram:
28 H+ are pumped back in by ATP synthase embedded in the membrane. ATP is produced when NADH and FADH2 release hydrogen atoms (this regenrates NAD+ and FAD, which return to the Krebs Cycle to be reused) Each hydrogen atom gives up electrons and hydrogen ions (H+)The electrons released are at a high energy level and move down the chain. They lose energy as they move from molecule to molecule.The lost energy is used to pump the hydrogen ions from the matrix to the other side of the membrane.A concentration gradient of hydrogen ions across the membrane is created.H+ are pumped back in by ATP synthase embedded in the membrane.ATP is made from ADP and phosphates.Oxygen is the final electron acceptor and also accepts H+ ions to make water.
29 Efficiency of Cellular Respiration Through Aerobic Cellular Respiration, a maximum of 38 ATP molecules can be produced from one glucose molecule.2 from Glycolysis2 from Krebs cyclefrom the Electron Transport Chain
30 To see how we get 38, follow along…. 2 ATPs directly from glycolysis 2ATPs directly from Krebs cycleEach NADH can generate 3ATPs from electron transport (30 total)Each FADH2 can generate 2ATPs from electron transport (4 total)
31 The actual number of ATP molecules generated through Aerobic Respiration varies from cell to cell. (36-38)Most eukaryotic cells produce only 36 molecules per glucose molecule because the active transport of NADH through a cell membrane uses up some ATP.When 38 ATP molecules are generated the efficiency is calculated as follows:Efficiency of Energy required to make ATPCellular Respiration = Energy released by oxidation of glucose= x kcal x 100% = 39%686 kcalThis is 20 times more efficient than glycolysis alone !!
32 Anaerobic Respiration If no oxygen is present, the Krebs Cycle and Electron Transport Chain are not utilized.The cell must have a way to keep glycolysis going.Glycolysis would stop without a cellular process that recycles NAD+ and NADH.Without such a process, glycolysis would quickly use up all the NAD+ in the cell.Glycolysis and ATP production would stop and the cell would die.Fermentation to the rescue
33 FermentationFermentation is the chemical pathway that recycles NAD+ in the absence of oxygen. It keeps glycolysis going. No additional ATP is made. Therefore, you still have the 2% efficiency rate for energy release.Two types of fermentation:Lactic Acid FermentationAlcoholic Fermentation
34 Lactic Acid Fermentation Pyruvic acid is converted by a specific enzyme into lactic acid.Two hydrogen atoms from NADH and H+ are transferred to pyruvic acid to form the lactic acid molecule.NADH is oxidized to NAD+ and reused to keep glycolysis going.
35 Occurs mostly in muscle cells during hard exercise. Lactic acid fermentation occurs in foods such as yogurt and cheese as well as certain animal cells.Occurs mostly in muscle cells during hard exercise.Muscle cells use up oxygen too fast and switch from aerobic to anaerobic respiration.Lactic acid builds up reducing the cells ability to contract. This causes fatigue, pain and cramps.Slow down!!! Allow the lacticacid time to diffuse back into theblood stream and to the liverwhere it is converted back intopyruvic acid.
36 Alcoholic Fermentation Converts pyruvic acid to carbon dioxide and ethyl alcohol.NAD+ is recycled in the same manner as before.
37 Bakers use the alcoholic fermentation of yeast to make bread. CO2 is produced and trapped in the dough, causing it to rise.When the dough is baked, yeast cells die and the alcohol evaporates.You can’t get drunk from eatingbread !!!
38 COMPARING PHOTOSYNTHESIS AND CELLULAR RESPIRATION Click to revealCOMPARING PHOTOSYNTHESIS AND CELLULAR RESPIRATIONPHOTOSYNTHESISRESPIRATIONFUNCTION Production of Glucose Oxidation of GlucoseLOCATION chloroplasts mitochondriaREACTANTS 6CO2 + 6H2O C6H12O O2PRODUCTS C6H12O O2 6CO H2OEQUATION light6CO2 + 6H2O C6H12O O2 C6H12O O CO2 + 6H2O +ATP