Cellular Respiration. Cellular Respiration. C 6 H 12 O 6 + 6O > 6CO 2 + 6H energy. Heat + ATP. You need to know this!

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1 Cellular Respiration LISA Biology Cellular Respiration C 6 H 12 O 6 + 6O > 6CO 2 + 6H energy You need to know this! Heat + ATP 1

2 Did that equation look familiar? * The equation for cellular respiration is the EXACT OPPOSITE of the one for photosynthesis! Adenosine Triphosphate (ATP) * ATP = Energy carrying molecule used by cells to fuel their cellular processes * ATP is composed of an adenine base, ribose sugar, & 3 phosphate (PO 4 ) groups 2

3 ATP * The PO 4 (phosphate) bonds are high- energy bonds that require energy to be made & release energy when broken ATP * Phosphorylation refers to the chemical reactions that make ATP by adding P i (phosphate) to ADP * Adenosine diphosphate + 1 phosphate = adenosine triphosphate 3

4 Overview * Cellular respiration is a set of catabolic reactions in the cell that convert biochemical energy from molecules into ATP * Catabolic reaction: breakdown of molecules into smaller units to release energy * In this case, glucose is going to broken down to form CO 2, H 2 O, and energy * Remember: C 6 H 12 O 6 + 6O > 6CO 2 + 6H energy 4

5 Sites of Cell Respiration * 3 steps of cellular respiration occur in different places within the cell * Cell cytoplasm * Also known as the cytosol * Mitochondria * Inner membrane space * Membrane of the folded cristae Mitochondria Structure Review * Has smooth outer membrane & folded inner membrane * Folds are called cristae * Space inside cristae is called the matrix & contains DNA & ribosomes * Site of aerobic respiration 5

6 Process Overview * Involves a series of 3 reactions * Glycolysis * Krebs Cycle * Oxidative Phosphorylation 6

7 Glycolysis * Needed to break down glucose and other organic molecules into smaller monomers * Occurs in the cytoplasm outside the mitochondria * Glycolysis means splitting of sugar Steps * 1. Two phosphate molecules from 2 ATP are added to glucose * This makes glucose more chemically reactive * 2. The unstable glucose then splits into two 3- carbon molecules of PGAL * Remember: we saw PGAL during photosynthesis as well! * 3. Another phosphate from ATP is again added to each PGAL 7

8 * 4. Each PGAL is oxidized by NAD to yield NADH, which releases energy * Oxidation = loses electrons * 5. The phosphates on PGAL molecules are then removed and added to ADP to produce ATP * The addition of phosphate is what makes adenosine Diphosphate (ADP) into adenosine TRIphosphate (ATP) * This final product is called a pyruvate 8

9 Glycolysis 9

10 Kreb s Cycle * The pyruvate molecules are small enough to enter the mitochondria by active transport * Before the Kreb s cycle can begin, the pyruvate is converted into a compound called acetyl coenzyme A * AKA acetyl CoA Steps * Kreb s Cycle occurs in the mitochondria matrix * 1 ATP is generated for every acetyl CoA molecule * How many acetyl CoA molecules did we start with? * 2! We had 2 pyruvates. * CO 2 is also produced * Products: 4 NADH, 2 ATP, and 2 FADH 2 * The energy (ATP) and electrons are then used during oxidative phosphorylation 10

11 11

12 Oxidative Phosphorylation * Uses NADH and FADH 2 formed during the Kreb s Cycle as electron donors for an electron transport chain (ETC) found in the inner membrane of the mitochondria * The folded cristae of the inner membrane increases the surface area to allow for more ETCs * The cell uses energy released by the ETC to power ATP synthesis * Synthesis means to make Oxidative Phosphorylation: Electron Transport * NADH and FADH 2 are the electron donors for the ETC * The electron transport chain consists of a series of proteins * Just like in photosynthesis! * The final electron acceptor is oxygen 12

13 Say whaaaat * Let me repeat * THE FINAL ELECTRON ACCEPTOR IS OXYGEN * That is WHY we cannot live without oxygen!!!! * No oxygen = no electron transport chain = no Kreb s = no cellular respiration = NO ENERGY!!!! * The movement of electrons down the ETC forces the movement of protons across the membrane and into the matrix of the mitochondria * Forms a concentration gradient * Used to make ATP from ATP Synthase through a process called chemiosmosis 13

14 Oxidative Phosphorylation: Chemiosmosis * Uses a proton concentration gradient and ATP Synthase to make ATP * ATP Synthase: enzyme that makes ATP from ADP and inorganic phosphate * We also saw this guy in photosynthesis at the end of the electron transport chain in the light reactions Summary * Glucose goes into glycolysis and comes out as pyruvate * Pyruvate converted to Acetyl CoA and goes into the Krebs Cycle * CO2 produced by glycolysis & Krebs cycle * O2 goes into the ETC and comes out as H2O * Most cells produce ATP per glucose 14

15 Fermentation * Enables for the production of ATP without the use of oxygen as the final electron acceptor at the end of the ETC * Remember: * Aerobic: with oxygen * Anaerobic: without oxygen * Both cellular respiration and fermentation have glycolysis as the first step * Humans CANNOT do this to survive without oxygen; we MUST have oxygen Alcohol Fermentation * Used by bacteria and yeast (a fungus) * Remember that pyruvate was the final product of glycolysis * This pyruvate is converted into ethanol * This is an anaerobic process so oxygen is not needed! 15

16 Lactic Acid Fermentation * The pyruvate is converted into lactate (lactic acid) * Occurs in human muscle cells during strenuous exercise when oxygen becomes scare * Accumulation of lactic acid may cause muscle fatigue and pain. * Again, oxygen is not used so this is also anaerobic process 16