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With your neighbor: Identify 3 things that you already know about cellular respiration.

With your neighbor: Identify 3 things that you already know about cellular respiration. Identify a question that you have about cellular respiration. Cellular Respiration —Breaking down glucose to provide energy for the cell. C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O.

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With your neighbor: Identify 3 things that you already know about cellular respiration.

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  1. With your neighbor: • Identify 3 things that you already know about cellular respiration. • Identify a question that you have about cellular respiration.

  2. Cellular Respiration—Breaking down glucose to provide energy for the cell C6H12O6 + 6O2 6CO2 + 6H2O In eukaryotes, the bulk of cell respiration occurs in the mitochondria. In prokaryotes, where does cell respiration occur?

  3. C6H12O6 + 6O2 6CO2 + 6H2O DG = -686 kcal/mole = VERY EXERGONIC enzyme ATP + + ADP P protein This energy is stored as ATP, which then can help the cell do work.

  4. REDOX REACTIONS • Reduction = • Gaining electrons • Gaining H • Losing O • Oxidation = • Losing electrons • Losing H • Gaining O Energy is released when electrons move closer to electronegative atoms. Hydrocarbons have lots of potential energy.

  5. Fill in which arrow in the cellular respiration reaction shows oxidation and which shows reduction. Give one reason for each that justifies your labeling. C6H12O6 + 6O2 6CO2 + 6H2O

  6. Glucose loses electrons (and hydrogen atoms slowly and doesn’t give them directly to O2. The messenger used is NAD+.

  7. Mitochondrial matrix contains enzymes, coenzymes, water, & phosphates • Inner membraneis made of 80% proteins, 20% lipids. In contrast, red blood cell membranes are 30% lipids. What can you infer about the inner membrane from its composition?

  8. Overview of Cellular Respiration

  9. ATP can be made by substrate-level phosphorylation(in glycolysis and the citric acid cycle) or by oxidative phosphorylation(in the electron transport chain)

  10. Step 1: Glycolysis (in cytosol)—sugar splitting Overall Reaction: Glucose  2 Pyruvate + 2 ATP + 2NADH for use in the cell to the ETC in the inner mitochondrial membrane 6C 3C to the citric acid cycle in the mitochondrial matrix

  11. Even though cell respiration is exergonic, some energy (activation energy) needs to be expended before energy production begins.

  12. There are 10 steps in glycolysis Step 1: glucose  glucose-6-P (uses ATP) Step 2: glucose-6-P  fructose-6-P Step 3: fructose-6-P  fructose-1,6-bP (uses ATP) This is the first irreversible step—catalyzed by PHOSPHOFRUCTOKINASE Step 4: splits into 2 3C compounds

  13. Step 6: 2 NADH produced Step 7: 2 ATP made Step 10: 2 ATP made, pyruvate formed From 1 glucose, we get: Net: 2 pyruvate 2 ATP 2 NADH

  14. Step 2: PyruvateDehydrogenase Complex In the mitochondrial matrix, pyruvate must be converted into acetyl-CoA to enter the citric acid cycle. 2 pyruvate + 2 NAD+ + 2 Coenzyme A  2 acetyl CoA + 2 NADH + 2 CO2 Net: 2 NADH

  15. Step 3: Krebs cycle (in the mitochondrial matrix)—also known as the citric acidcycle, TCA cycle The Krebs cycle dismantles the acetyl CoA to get its electrons. First, acetyl CoA (2C) adds to oxaloacetate(4C) to make citrate (6C). 2 CO2 molecules are lost overall in order to return to the 4C oxaloacetate

  16. From 1 pyruvate, • we get: • 1 ATP • 3 NADH • 1 FADH2 Which means… FADH2 is an electron carrier similar to NADH From 1 glucose, we get: Net: 2 ATP 6 NADH 2 FADH2

  17. So far we’ve got: We haven’t made too much ATP yet, and it’s all been from substrate-level phosphorylation.

  18. Step 4: Electron Transport Chain/Oxidative Phosphorylation(in the inner membrane of the mitochondria) Remember that the inner membrane of the mitochondria is impermeable to most molecules, including H+. Electrons are transferred along the proteins that make up the inner mitochondrial membrane. When electrons are added to a protein, is it oxidized or reduced? When electrons are removed, is the protein oxidized or reduced?

  19. NADH gives its e-s to the first protein in the chain, and NAD+ is regenerated. O2 is the final electron acceptor. Lower affinity for e- Higher affinity for e-

  20. As e-s are passed from one protein to another, they release energy. That energy is used to pump H+ across the inner mitochondrial membrane from the matrix to the intermembrane space.

  21. The H+ flows back to the matrix through a channel called ATP synthase. It acts as a rotor that can use mechanical energy to join ADP and P to make ATP.

  22. Because this is dependent on O2 as the final electron acceptor, the production of ATP from the gradient produced by the ETC is called oxidative phosphorylation. This is an example of chemiosmotic coupling. • Osmotic—H+ gradient is established across • the inner mitochondrial membrane • (solute concentration gradient) • 2. Chemi—potential energy stored in the gradient • is released and captured to form ATP from ADP and P (chemical process)

  23. Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. In a few sentences, compare the production of ATP by the electron transport chain and oxidative phosphorylationto the production of hydroelectric power.

  24. Each NADH causes 3 ATPs to be generated. Each FADH2 causes 2 ATPs to be generated. 2 ATP + 2 ATP + 34 ATP = 38 ATP max per glucose

  25. Let’s take one more look at the overall picture.

  26. Do we really get 38 ATPs for each glucose? • Probably not! Because… • Energy is used to transport NADH into mitochondria (in eukaryotes only) • NADH yields between 2 and 3 ATPs • FADH2 yields between 1 and 2 ATPs • So it’s anywhere from 32-36 ATPs/glucose

  27. For oxidative phosphorylation to occur, we must have oxygen. When O2 accepts e-s, it becomes H2O and leaves. Another O2 arrives to accept more e-s. e- O2 If no electrons can be transferred, no H+ can be pumped! That means no ATP can be made through oxidative phosphorylation.

  28. For glycolysis to occur, all we need is NAD+ to accept electrons (be reduced). Pyruvate serves as an electron acceptor. Instead of taking e-s to the ETC, NADH gives them to pyruvate. Fermentation—regeneration of NAD+ so that glycolysis can keep going How many ATP are made in anaerobic respiration for each molecule of glucose? Since there’s no oxidative phosphorylation, aerobic respiration yields up to 19 times more ATP than anaerobic respiration does!

  29. Alcohol fermentation occurs in yeast. Lactic acid fermentation occurs in bacteria, fungi, and human muscle cells.

  30. Proteins and fats are broken down and enter the process of cell respiration at various steps. Breakdown of carbohydrates provides more ATP than breakdown of proteins and lipids since they complete the whole process.

  31. Regulation of Cellular Respiration Lots of ATP made, little consumed  Respiration slows down Little ATP made, lots consumed  Respiration speeds up Phosphofructokinaseis inhibited ALLOSTERICALLY by ATP and citrate. AMP stimulates phosphofructokinase.

  32. What is the purpose of cellular respiration? • Identify the 4 steps of cellular respiration and where each step occurs. • For each step, what goes in and what comes out? • When ATP is made, is it made by substrate-level or oxidative phosphorylation? • Which step(s) of cellular respiration can happen in anaerobic conditions? • What is the purpose of fermentation?

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