Cellular Respiration and Fermentation

Section 9.1 Cellular Respiration: An Overview Essential Question: How do organisms obtain energy? Guiding Question: Why do most organisms undergo the process of cellular respiration? Objectives: Explain where organisms get the energy they need for life processes Define cellular respiration Compare photosynthesis and cellular respiration

Chemical Energy and Food Organisms get the energy they need from breaking of chemical bonds in food Autotrophs (plants) – can make food using energy from sunlight Heterotrophs (animals/fungus) – must consume other organisms as food to obtain energy

Calorie – unit of energy stored in food – amount of energy needed to raise temperature of 1g of water 1 o C Cells can use carbohydrates, proteins, fats as food Amount of calories varies b/c chemical structures vary (variations in energy-storing bonds) 1g glucose = 3811 calories 1g beef fat = 8893 calories Carbs/proteins = 4000 calories

Overview of Cellular Respiration Cellular respiration - process that releases energy from food in presence of oxygen Involves dozens of reactions Must release explosive chemical energy in food a little bit at a time Overall equation: Oxygen + glucose  carbon dioxide + water + Energy

Stages of Cellular Respiration Captures energy from food in 3 stages – 1.Glycolysis 2.Krebs Cycle 3.Electron Transport Chain

Glycolysis Glucose enters & small amount of ATP generated  pyruvic acid remains

Kreb’s Cycle Pyruvic acid enters & small amount of ATP generated

Electron Transport Chain uses OXYGEN & products of previous stages & generates bulk of energy (ADP  ATP)

Oxygen and Energy Oxygen required at very end of ETC Respiration = breathing  need oxygen Cellular respiration = energy-releasing pathways within cell Aerobic – “in air” – pathways of cellular respiration that require oxygen Krebs cycle – indirectly requires oxygen ETC – directly requires oxygen Anaerobic – “without air” – Glycolysis – does not directly or indirectly require oxygen

Mitochondria – structures in the cell that convert chemical energy stored in food to usable energy for the cell If oxygen is PRESENT  cellular respiration occurs Glycolysis – occurs in cytoplasm Krebs cycle – occurs in mitochondrion Electron Transport Chain – occurs in inner mitochondrion membrane

If oxygen is NOT PRESENT  fermentation occurs in place of cellular respiration Makes it possible for glycolysis to continue  generates ATP  allows cellular activities to continue

Comparing Photosynthesis and Cellular Respiration Why don’t we run out of oxygen? Where does all the carbon dioxide waste go?

Cellular respiration is balanced out by photosynthesis Energy flows in opposite directions Photosynthesis “deposits” energy (carbohydrates) Cellular respiration “withdraws” energy from carbohydrates 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.

Section 9.2 The Process of Cellular Respiration Essential Question: How do organisms obtain energy? Guiding Question: How do cells release energy from food in the presence of oxygen? Objectives: Describe what happens during glycolysis Describe what happens during the Krebs cycle Explain how high-energy electrons are used by the electron transport chain Identify how much ATP cellular respiration generates

Glycolysis Glycolysis = “sugar breaking” 1 molecule of glucose (6 carbons) is transformed into 2 molecules of pyruvic acid (3 carbons each)

ATP Production 2 ATP molecules used to start reaction Glycolysis produces 4 ATP molecules Net gain = 2 ATP for each glucose molecule

NADH Production Glycolysis removes high- energy electrons & passes them to NAD+ (electron carrier) NAD+ + 2 electrons = NADH NADH holds electrons to pass to other molecules 4 ATP molecules made

Advantages of Glycolysis Net gain = 2 ATP 1. Fast process Can produce 1000s of ATP in few milliseconds 2. Does NOT require oxygen Can quickly supply energy to cells when no oxygen is available When oxygen is available  pyruvic acid and NADH used by other processes in cellular respiration

Draw the Process of Glycolysis

The Krebs Cycle AKA = citric acid cycle Citric acid is 1 st compound formed If oxygen is PRESENT: Pyruvic acid from glycolysis is broken down into carbon dioxide in a series of energy-extracting reactions

Citric Acid Production Pyruvic acid passes through 2 mitochondrion membranes into matrix 1 carbon from pyruvic acid added to carbon dioxide  released into air 2 carbons from pyruvic acid move on as acetic acid and attach to coenzyme A = acetyl-CoA Acetyl-CoA adds acetyl group to 4-carbon molecule in cycle = Citric Acid (6 carbons)

Energy Extraction Citric acid release 2 carbons (1 at a time)  released as carbon dioxide = 4 carbon molecule Recycled to be used at beginning of cycle again Electrons transferred to electron carriers 5 different places 2 different electron carriers NAD+  NADH FAD  FADH 2 Each turn of cycle = 1ADP  1ATP (1 glucose = 2 turns) ATP  cell for activities CO 2  exhaled as waste Electron carriers  ETC to generate lots of ATP

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Do Now Where does the Kreb’s cycle take place? Why are there 2 total ATP produced instead of 1? What happens to the NADH and FADH2 produced? If 6 FADH2 are produced in the Kreb’s cycle, how many glucose molecules did you start with?

Electron Transport and ATP Synthesis Electron Transport Chain uses high-energy electrons from glycolysis and Krebs cycle to convert ADP to ATP. NADH and FADH2 pass high-energy electrons to Electron Transport Chain

Electron Transport Chain 1.NADH and FADH2 release electrons, converted into NAD+ and FAD (H+ released into the mitochondrial matrix). 2.H+ ions are pumped across inner mitochondrial membrane as electrons move along membrane (with the help of proteins).

Electron Transport Chain (continued) 3. Oxygen is final electron acceptor (protons and electrons combine with oxygen to form water). 4. H+ ions then diffuse back into matrix through ATP synthase (chemiosmosis), producing 32 ATP. Total ATP produced for one molecule of glucose = 32 ATP molecules

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Soooo… Where does the electron transport chain take place? How many ATP are produced? How many total molecules of ATP are produced for one molecule of glucose? chapter25/animation__electron_transport_system_and_atp_synthesi s__quiz_1_.html chapter25/animation__electron_transport_system_and_atp_synthesi s__quiz_1_.html

The Totals Glycolysis & Krebs cycle & ETC release about 36 ATP molecules per 1 glucose molecule. Glycolysis – 2 ATP Kreb’s Cycle – 2 ATP Electron Transport Chain – 32 ATP Cell can use carbs, fats, proteins as fuel Efficiency < 100% 36 ATP molecules = 36% of total energy of glucose 64% = lost as heat to environment

Section 9.3 Fermentation Essential Question: How do organisms obtain energy? Guiding Question: How do cells release energy from food without oxygen? Objectives: Explain how organisms get energy in the absence of oxygen Identify the pathways the body uses to release energy during exercise

Stand up! Move your arms up and down for three minutes! Do not stop until the time is up! What is happening in your arms?

Anaerobic Respiration Making ATP without oxygen (fermentation) Problems: Only 2 net ATP per glucose molecule Limited amount of NAD+ Yeast, People, Bacteria, Fungus Used to make beer, wine, and bread

2 Main Types of Fermentation 1. Lactic Acid Fermentation Pyruvate from glycolysis converted to lactic acid Lactic acid is associated with the “burn” associated with heavy exercise If too much lactic acid builds up, your muscles feel sore and may give out

Lactic Acid Fermentation Inputs: Glucose, 2ADP, 1 NAD+ Outputs: 2ATP, 1 NADH, 2 lactic acid Ex: Bacteria that help in making yogurt, cheese and sour cream. Human muscle cells when out of oxygen.

Lactic Acid Fermentation  Physical conditioning allows your body to adapt to increased activity:  The body can increase its ability to deliver oxygen to muscles  Long-distance runners wait until the final sprint to exceed their aerobic capacity

2 Main Types of Fermentation 2. Alcohol Fermentation In yeast and some bacteria Pyruvate is converted to ethyl alcohol and carbon dioxide Ex: yeast used for baking bread and making wine/beer w09QKf9GU w09QKf9GU

Alcohol Fermentation Inputs: Glucose, 2ADP Outputs: 2ATP, 2 ethanol, 2 CO 2 NAD+ gets regenerated

Aerobic vs. Anaerobic Respiration Lactic acid or CO2/ethanol Cytoplasm

Quick Energy ATP in muscles only last a couple seconds of intense activity (50 meters) ATP from lactic acid fermenation lasts about 90 seconds (200–300 meter sprint) Causes oxygen debt that is repayed by heavy breathing for 2-3 minutes

Long-Term Energy For exercise longer than about 90 seconds, cellular respiration is the only way to continue generating a supply of ATP Cellular respiration: Releases energy more slowly than fermentation Uses stores of glycogen (carbohydrate) in muscles for minutes After 20 mins  breaks down other stored molecules (fats)