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Cellular Respiration Honors Biology What is Cellular Respiration? The process of converting food energy into ATP energy C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP Why are both Photosynthesis and Cell Respiration important to Ecosystems? Light is the ultimate source of energy for all ecosystems Chemicals cycle and Energy flows Photosynthesis and cellular respiration are opposite reactions Why do plants need both chloroplasts and mitochondria? Chloroplasts use energy from the sun to make glucose Mitochondria convert glucose to ATP—the energy currency of the cell Why use ATP energy and not energy from glucose? Breaking down glucose yields too much energy for cellular reactions and most of the energy would be wasted as heat. 1 Glucose = 686 kcal 1 ATP = 7.3 kcal 1 Glucose → 36 ATP How efficient are cells at converting glucose into ATP? – 38% of the energy from glucose yields ATP, therefore 62% wasted as heat. Cellular Respiration is a Redox Reaction (Oxidation) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O (Reduction) Oxidation is the loss of electrons or H+ Reduction is the gain of electrons or H+ Cellular Respiration is a Redox Reaction Glucose is oxidized when electrons and H+ are passed to coenzymes NAD+ and FAD before reducing or passing them to oxygen. Glucose is oxidized by a series of smaller steps so that smaller packets of energy are released to make ATP, rather than one large explosion of energy. Cell Respiration can be divided into 3 Parts: 1) Glycolysis 2) The Krebs Cycle 3) The Electron Transport Chain Where do the 3 parts of Cellular Respiration take place? Glycolysis: – Cytosol The Krebs Cycle: – Matrix Electron Transport Chain and Cheimiosmotic Phosphorylation: – Cristae Parts of the Mitochondria Anaerobic Respiration (no oxygen required, cytoplasm) Glycolysis (substrate level) Glucose 2 ATP 4 ATP (Net 2 ATP) 2 NADH 2 Pyruvate Aerobic Respiration (oxygen required, mitochondria) Oxidation Of Pyruvate 2 Pyruvate 2 CO2 2 NADH 2 Acetyl CoA Krebs Cycle (substrate level) 2 Acetyl CoA 4 CO2 2 ATP 6 NADH 2 FADH2 Electron Transport Chain (chemiosmotic) 10 NADH 2 FADH2 6 O2 32 ATP 6 H 2O Total ATP Production in Cellular Respiration: 36 ATP produced Glycolysis Glucose 2 ATP 2 NAD+ 2 Pyruvate 4 ATP (Net 2 ATP) 2 NADH Glucose (C6) is split to make 2 Pyruvates (C3) – 1st: ATP energy used to phosphorylate glucose (stored energy) – 2nd: phosphorylated glucose broken down into two C3 sugar phosphates – 3rd: the sugar phosphates are oxidized to yield electrons and H+ ions which are donated to 2NAD+ → 2NADH – 4th: The energy from oxidation is used to make 4 ATP molecules (net 2 ATP) Glycolysis Glucose 2 ATP 2 NAD+ 2 Pyruvate 4 ATP (Net 2 ATP) 2 NADH Glucose (C6) is split to make 2 Pyruvates (C3) An enzyme transfers phosphate to ADP making ATP Glycolysis produces very little ATP energy, most energy is still stored in Pyruvate molecules. Oxidation of Pyruvate /Transition Reaction (After glycolysis, before the Krebs Cycle) 2 Pyruvate 2 NAD+ 2 CO2 2 NADH 2 Acetyl CoA When Oxygen is present, 2 Pyruvates go to the matrix where they are converted into 2 Acetyl CoA (C2). 2CO2 are released while the 2 pyruvate get converted 2 NADH’s carry electrons and hydrogens to the Electron Transport Chain Coenzyme A assists the process of creating Acetyl CoA The Krebs Cycle / Citric Acid Cycle 2 2 6 2 Acetyl CoA ADP NAD+ FAD 4 CO2 2 ATP 6 NADH 2 FADH2 Overview - Two Turns of the Krebs Cycle are required to break down both Acetyl Coenzyme A molecules. - Break down and oxidize each Acetyl Co (2-C’s) to release 2 CO2 and yield electrons and H+ ions to - 3 NAD+ + 1 FAD → 3NADH + 1FADH2. This yields energy to produce 1 ATP (in each turn of the cycle) The Krebs Cycle / Citric Acid Cycle 2 2 6 2 Acetyl CoA ADP NAD+ FAD 4 CO2 2 ATP 6 NADH 2 FADH2 Steps in Matrix of Mitochondria - Oxaloacetate (4C) combines with Acetyl CoA (2C) to form Citric Acid (6C) - NAD+ and FAD molecules are reduced as they pick up electrons and hydrogens - An enzyme combines a phosphate group with ADP to form ATP - After CO2, NADH, FADH2, and ATP is released, Oxaloacetate is recycled back into the cycle to combine with another Acetyl CoA - **Remember the cycle occurs twice! (once for each Acetyl CoA molecule) ** Produces some chemical energy in the form of ATP but most of the chemical energy is in the form of NADH and FADH2 which then go on to the Electron Transport Chain. The Electron Transport Chain 10 NADH 2 FADH2 Oxygen 32 ATP H2O NADH and FADH2 (carrying hydrogens and electrons) go to the Electron Transport Chain. NADH and FADH2 release electrons to carriers/proteins embedded in the membrane of the cristae. As the electrons are transferred, H+ ions are pumped from the matrix to the intermembrane space up the concentration gradient. http://vcell.ndsu.nodak.edu/animations/etc/movie.htm The Electron Transport Chain 10 NADH 2 FADH2 Oxygen 32 ATP H2O Electrons are passed along a series of 9 carriers until they are ultimately donated to an Oxygen molecule. ½ O2 + 2 electrons + 2 H+ (from NADH and FADH2) → H2O. The high H+ concentration in the inner membrane space creates a gradient and is used to produce ATP http://vcell.ndsu.nodak.edu/animations/etc/movie.htm ATP Synthase – The H+ in the intermembrane space have a high concentration – So they move back across the inner mitochondrial membrane and into the matrix through a molecule called ATP Synthase – As ATP Synthase turns and H+ ions pass through, it changes shape and the enzyme makes ATP Review ATP Production: 1) Glycolysis → 2 ATP 2) Oxidation of Pyruvate → No ATP 3) The Krebs Cycle → 2 ATP 4) The Electron Transport Chain - Each NADH produces 2-3 ATP so 10 NADH → 28 ATP - Each FADH2 produces 2 ATP so 2 FADH2 → 4 ATP Total = 36 ATP Review ATP Production: 1 Glucose = 686 kcal 1 ATP = 7.3 kcal 1 Glucose → 36 ATP How efficient are cells at converting glucose into ATP? – 38% of the energy from glucose yields ATP, therefore 62% wasted as heat (used to maintain body temperature or is dissipated) – Ex. Most efficient Cars: only 25% of the energy from gasoline is used to move the car, 75% heat. All Types of Molecules can be used to form ATP by Cell Respiration: Proteins, Carbohydrates, and Lipids must first be broken down into their monomers and absorbed in the small intestine. Monomers may be further broken down into intermediate molecules before entering different parts of Cell respiration to ultimately form ATP. Anaerobic Respiration: Fermentation If there is NO oxygen, then cells can make ATP by Fermentation Without oxygen, The Krebs Cycle and the Electron Transport Chain do not operate, but glycolysis still occurs. Glucose → Pyruvate NAD+ Glycolysis 2 NADH 2 ATP → Reduction Rxn Lactate or Alcohol + CO2 Anaerobic Respiration: Fermentation Fermentation yields a net gain of 2 ATP for every 1 Glucose. (Inefficient) Two Forms of Fermentation: Lactic Acid Fermentation (animals) Alcohol Fermentation (yeast and some bacteria) WITHOUT O2 PYRUVIC ACID ___________ OXYGEN ANAEROBIC 2 kinds of fermentation Alcoholic & Lactic acid ALCOHOLIC FERMENTATION PYRUVIC ACID + + ALCOHOL CO NAD → + 2+ Happens when yeast makes bread dough rise air spaces in bread CO2 bubbles make _____________ evaporates Alcohol _______________ during cooking http://www.deliciousdelicious.com/archives/herb%20bread%201.jpg ALCOHOLIC FERMENTATION PYRUVIC ACID + →ALCOHOL + CO2 + NAD+ Happens when beer yeast ___________ make _______ or bacteria wine ____________ make ______ http://www.firstpath.com/images/alcohol.jpg LACTIC ACID FERMENTATION PYRUVIC ACID + → LACTIC ACID + NAD+ muscles Happens in _____________ during ____________when body exercise can’t get oxygen to tissues fast enough. Lactic acid builds up in muscles causing soreness http://www.miranda.com/library.en/Images/Pictures/girls-runners.jpg LACTIC ACID FERMENTATION PYRUVIC ACID + → LACTIC ACID Happens when bacteria are used to make foods and beverages like: __________________________ yogurt, cheese, buttermilk, __________________________ & sour cream, pickles, __________________________ saurkraut, and kimchi + NAD+ http://chronicle.augusta.com/images/headlines/032200/DANNON_YOGURT.jpg http://www.reillydairy.com/natural_cheese.html WHY DO FERMENTATION? WHY NOT JUST KEEP MAKING ATP USING GLYCOLYSIS? WITHOUT OXYGEN, PYRUVIC ACID builds up ___________ and all the NAD+ carriers get full. _______ Eventually glycolysis will NAD+ PYRUVIC ACID + →ALCOHOL + CO2 LACTIC ACID + NAD+ NAD+ ______ You get the NAD+ carriers back FERMENTATION HAPPENS so cells + REGENERATE the NAD can ____________________ needed to keep glycolysis going