Glycolysis and Fermentation. Chapter 8

Transcription

1 Glycolysis and Fermentation Chapter 8

2 Cellular Respiration and Photosynthesis 0 Things to know in these chapters 0 Names and order of the processes 0 Reactants and products of each process 0 How do they relate to the overall equations? 0 What environmental factors are needed to run the process? 0 Where will these processes occur? (organisms and organelles) 0 The occasional important step within the process

3 Cellular Respiration 0 Cellular respiration is the process of breaking down sugars to provide cells with energy 0 Cellular Respiration Equation: 0 C 6 H 12 O O 2 6 CO H 2 O + Energy 0 Cellular respiration allows for a molecule of glucose to be broken down as slowly as possible 0 If glucose was broken down quickly, much of the energy it holds would be lost as heat 0 Cellular respiration is able to harness 39% of the energy available in a glucose molecule 0 Photosynthesis is 55% efficient 0 The average gasoline automobile is 25% efficient

4 Cellular Respiration 0 Cellular respiration is 3 separate processes that combine to maximize the energy output in various conditions 0 1. Glycolysis. 0 Slowly convert glucose into pyruvic acid. 0 Obtain small quantity of energy; very little wasted though 0 Designed to maximize energy production later 0 2. Aerobic Respiration 0 Takes place when cell has access to oxygen 0 Citric Acid Cycle and Electron Transport Chain 0 Large amounts of ATP produced 0 3. Anaerobic Respiration (Fermentation) 0 Takes place when cell has no access to oxygen 0 Alcohol or lactic acid produced 0 Maintains life temporarily until oxygen can be maintained

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6 Glycolysis Summary 0 Each process in photosynthesis and respiration is a machine. 0 The machine takes a reactant and, throughout a series of steps, builds products. 0 Like man-made machines, each of these steps creates waste material 0 Unlike man-made machines, the waste materials just happen to be molecules the cell needs 0 Sometimes, the products also are needed. Sometimes they aren t. 0 As long as the cell keeps these machines working, the machines will keep churning out these waste products

7 Glycolysis Summary 0 Glycolysis takes place in the cytoplasm 0 Glycolysis is ten steps long 0 Glycolysis requires an input of energy 0 Glyco = glucose; lysis = to split 0 For the processes in these chapters, I will provide all the information so you know what is happening. The essential info for memorizing will be underlined

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9 0 Step 1 Glycolysis 0 Begins with a molecule of glucose 0 Energy from an ATP is consumed 0 At this point, the cell has used energy and hasn t harnessed any. It s in debt. 0 By spending energy now, it can invest the energy and get MUCH more energy later. 0 The cell forms a molecule of glucose-6-phosphate

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11 0 Step 2 Glycolysis 0 Glucose-6-phosphate is rearranged to form a molecule of fructose-6-phosphate

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13 0 Step 3 Glycolysis 0 Another input of ATP is required 0 At this point the cell has spent two high-energy molecules and has made none. 0 The cell is even more in debt now. 0 Fructose-6-Phosphate is rearranged to form Fructose- 1,6-Bisphosphate

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15 0 Step 4 and Step 5 Glycolysis 0 The glucose molecule is split from one 6-carbon molecule into two 3-carbon molecules 0 The amount of carbon, hydrogen, oxygen and phosphorus hasn t changed. But now there s two molecules instead of one. 0 One molecule immediately forms a glyceraldehyde-3-phosphate (PGAL, or G3P) 0 The other forms a different molecule temporarily, then immediately forms a second PGAL 0 From this point on, there are two identical molecules that enter each step of cell respiration, which means we will double the products we make from here on out. 0 Without the input of energy at the beginning, we couldn t have done this.

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17 0 Step 6 Glycolysis 0 The PGAL is phosphorylated (a free-floating phosphate is attached) 0 This phosphate will eventually be attached to an ADP to form an ATP 0 PGAL also donates a Hydrogen to an NAD + to become an NADH 0 NADH is a waste product in glycolysis, but NADH will be used later in the electron transport chain as a reactant 0 The PGAL rearranges to form a molecule of 1,3- bisphosphoglycerate (PGAP)

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19 0 Step 7 Glycolysis 0 The PGAP donates one of it s phosphates to an ADP to form ATP 0 The ATP is a waste product in glycolysis but the cell can use it somewhere else 0 *Remember: we ve actually made TWO ATP s (one for each PGAL we made earlier) 0 PGAP is rearranged to form a 3-phosphoglycerate (PGA)

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21 0 Step 8 Glycolysis 0 PGA is rearranged to form a 2-phosphoglycerate

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23 0 Step 9 Glycolysis 0 2-phosphoglycerate loses a water molecule 0 2-phosphoglycerate is rearranged to form Phosphoenolpyruvate (PEP)

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25 Glycolysis 0 Step 10 0 PEP donates a phosphate to form an ATP 0 The final molecule of glycolysis is a 3-carbon pyruvate.

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27 0 Inputs 0 1 glucose molecule 0 2 ATP 0 Outputs Glycolysis Summary 0 2 pyruvate molecules 0 2 NADH 0 4 ATP 0 Net Gain 0 2 pyruvate molecules 0 2 NADH 0 2 ATP

28 Fermentation 0 After glycolysis, the pyruvic acid will enter either aerobic or anaerobic respiration 0 Aerobic respiration: if oxygen is available 0 Anaerobic respiration: if oxygen is not available 0 Anaerobic respiration, or fermentation, comes in two forms 0 Alcoholic fermentation: Yeasts and other microorganisms 0 Pyruvic acid + NADH Alcohol + CO2 + NAD + 0 Lactic Acid fermentation: muscle cells 0 Pyruvic acid + NADH Lactic Acid + NAD +

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32 Fermentation 0 Fermentation for humans is not ideal at all. It s a life-support system. 0 Without oxygen, the only process for cells to obtain energy from is glycolysis. 0 In order for glycolysis to occur, it needs three reactants 0 Glucose, which is obtained from food. This is not a problem 0 ADP, to form ATP. This is not a problem 0 NAD + to form NADH. NADH is consumed and transformed back to NAD + during aerobic respiration 0 But we can t go through aerobic respiration right now. So we can t turn the NADH back to NAD +. So we don t have any NAD + to use in glycolysis. So we can t run glycolysis. 0 THIS is the problem.

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34 Fermentation 0 The sole purpose of fermentation is to remove the H off of the NADH and turn it back to NAD +. 0 The NAD + can then re-enter glycolysis, and the cell can get another net gain of 2 ATP. 0 2 ATP is pathetic, but it is something. So why do we do it? 0 Fermentation gives the organism a few extra precious minutes to find some oxygen again 0 Without it, organisms would die the instant their cells are without oxygen.

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36 Cell Respiration Summary 0C 6 H 12 O O 2 6 CO H 2 O + Energy 0 C 6 H 12 O 6 : For glycolysis 0 6 O 2 : To collect the electron in the ETC 0 6 CO 2 : Given off in intermediate step and Citric Acid Cycle 0 6 H 2 O : Given off in the ETC 0 Energy : In the form of ATP