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Transcript
Starter: What is the equation for cellular respiration? Glucose energy (ATP) + O2 CO2 + water + Starter: What are the energy carriers in cellular respiration? How many net ATP come out of glycolysis? Cellular Respiration: Harvesting Chemical Energy Metabolism There are chemical reactions going on in all living organisms that are essential for the growth and repair of the body and for nutrition and release of energy in a useable form. These processes are both breakingdown(catabolism)and building-up (anabolism)processes, and combined, they are called the metabolism of the body. The Metabolic Pathway of Cellular Respiration Cellular respiration is an example of a metabolic pathway It is a complex energy release process, controlled by enzymes, that breaks down the complex molecules one step at a time, releasing energy in small controlled amounts All of the reactions involved in cellular respiration can be grouped into three main stages: 1. Glycolysis 2. The Krebs cycle 3. Electron transport This is what happens in the process of burning: fire fuel + + air energy wastes (wood) in the form heat and water vapour light and CO2 The complex food molecules contain so much energy that the cell would be unable to handle it if it was all released at once, as in burning. Firstly, let's get to know the players.... Energy Carriers 1. ATP - Adenosine Triphosphate 2. NADH - Nicotinomide Adenine Dinucleotide 3. FADH2- Flavin Adenine Dinucleotide ATP W is the nitrogenous base (adenosine) X is the ribose sugar, together W and X make up Adenosine. Y is a phosphate group, and Z is the high energy bond between the phosphate groups. When Z is hydrolyzed, energy is released that can be used by the cell. ATP consists of a base, in this case adenine (red), a ribose (magenta) and a phosphate chain (blue). A Road Map for Cellular Respiration Cytosol/ Cytoplasm Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Glycolysis Glucose 2 Pyruvate Krebs Cycle Electron Transport Figure 6.7 Stage 1: Glycolysis A molecule of glucose is split into two molecules of pyruvate These molecules then donate high energy electrons to NAD+, forming NADH Glycolysis makes some ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP 2 Pyruvate Glucose Figure 6.8 Stage 2: The Krebs Cycle The Krebs cycle completes the breakdown of sugar In the Krebs cycle, Pyruvate from glycolysis is first “prepped” into a usable form, Acetyl-CoA Acetic acid Pyruvate CO2 Coenzyme 1 A 2 The Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2 The cycle uses some of this energy to make ATP The cycle also forms NADH and FADH2 Kreb's Cycle 1 Output Input 2 Acetic acid 2 CO2 Kreb's Cycle ADP 3 NAD+ FAD 3 4 5 6 The Kreb's Cycle Animation Stage 3: Electron Transport/Respiratory Chain transport releases the energy Electron your cells need to make the most of their ATP The molecules of electron transport chains are built into the inner membranes of mitochondria The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane These ions store potential energy When the hydrogen ions flow back through the membrane, they release energy The ions flow through ATP synthase ATP synthase takes the energy from this flow and synthesises ATP Electron Transport Animation Protein complex Electron carrier Electron flow Inner mitochondrial membrane Electron transport chain ATP synthase Figure 6.12 Adding Up the ATP from Cellular Respiration Cytosol Mitochondrion Glycolysis Glucose 2 Pyruvate 2 AcetylCoA Krebs Cycle Electron Transport Maximum per glucose: by direct synthesis by direct synthesis by ATP synthase Figure 6.14 The Versatility of Cellular Respiration Cellular respiration can “burn” other kind of molecules besides glucose Diverse types of carbohydrates Fats Proteins Food Polysaccharides Sugars Glycerol Fats Fatty acids Proteins Where Carbs, Protein and Fat enter... Amino acids Amino groups Glycolysis AcetylCoA Krebs Cycle Electron Transport Figure 6.13 FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY Some of your cells can actually work for short periods without oxygen For example, muscle cells can produce ATP under anaerobic conditions Fermentation - the anaerobic harvest of food energy Fermentation in Human Muscle Cells Human muscle cells can make ATP with and without oxygen They have enough ATP to support activities such as quick sprinting for about 5 seconds A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds To keep running, your muscles must generate ATP by the anaerobic process of fermentation Glycolysis is the metabolic pathway that provides ATP during fermentation Pyruvate is reduced by NADH, producing NAD+, which keeps glycolysis going In human muscle cells, lactic acid is a byproduct Fermentation 2 ADP+ 2 2 ADP+ 2 Glycolysis 2 NAD+ Glucose (a) Lactic acid fermentation 2 Pyruvate + 2 H+ 2 NAD+ 2 Lactic acid Fermentation in Microorganisms Various types of microorganisms perform fermentation Yeast cells carry out a slightly different type of fermentation pathway This pathway produces CO2 and ethyl alcohol The food industry uses yeast to produce various food products Figure 6.16 Activity: Using Limewater complete an experiment to test one of the products from anaerobic respiration