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Understanding Cellular Respiration in Biology

Learn about cellular respiration, the process in which cells break down organic compounds to make ATP, the energy currency of cells. Explore the different stages including glycolysis, Krebs cycle, and electron transport chain, and understand how organisms obtain energy. Discover the significance of aerobic and anaerobic respiration, and the energy yield from each process.

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Understanding Cellular Respiration in Biology

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  1. Cellular Respiration Honors Biology 2012

  2. Comprehension Check What types of organisms need energy? What types of organisms can make their own energy?

  3. Cellular Respiration: • DEFINITION: Complex process in which cells break down organic compounds to make ATP (ADP +  ATP) • We feel hungry because food provides us energy, the biochemical pathway that allows us to get energy from our food is cellular respiration. Equation for Cellular Respiration: • FACT: A working muscle cell converts ADP to ATP at a rate of 10 million molecules per second. 602 + C6H1206 6CO2 +6H2O +Energy

  4. Main Reactions in Cellular Respiration (depending on presence of O2)

  5. Overview of Glycolysis Glycolysis: Biochemical pathway which begins both types of cellular respiration. • Occurs in cytosol of cell • Breaks down one glucose into two 3-carbon molecules of pyruvic acid (pyruvate) ** Note: 2 ATP’s were used in step 1, but 4 ATP’s were made in step 4. This is called a NET GAIN of 2 ATP Glycolysis Animation

  6. ANAEROBIC RESPIRATION • Glycolysis • Fermentation: absence of oxygen, some organisms can convert pyruvic acid into another 3-carbon compound, but NO ADDITIONAL ATP ARE FORMED Energy released from anaerobic respiration: • 2 ATP molecules released by glycolysis • 0 ATP result because of fermentation • TOTAL ENERGY GAIN = 2 ATP • This is only 3.5% of all the energy stored in a single glucose molecule • Much of energy originally contained in glucose is still held in the bonds that make up pyruvic acid

  7. Alcoholic Fermentation • Process where yeast and bacteria convert pyruvic acid into ethyl alcohol and CO2 • No ATP are gained (regenerates NAD+ for glycolysis) • Basis of the wine, beer, and baking industries

  8. Lactic Acid Fermentation • Enzyme reactions convert pyruvic acid into another 3-carbon compound, lactic acid • No ATP are gained • LAF occurs in your muscle cells • Once oxygen is available, the body converts lactic acid back to pyruvic acid in our liver

  9. AEROBIC RESPIRATION Stage 1: GLYCOLYSIS Stage 2: KREBS CYCLE / CITRIC ACID CYCLE Stage 3: Electron Transport Chain • Requires oxygen to be present • Produces 20 times more ATP than Glycolysis alone! • Prokaryotes can do it, but it occurs in the cytosol • Eukaryotes have mitochondria (matrix and cristae) for this specific purpose

  10. AEROBIC RESPIRATION Krebs Cycle/Citric Acid Cycle -Pyruvic acid produced by glycolysis enters mitochondrion -Krebs Cycle occurs in mitochondrial matrix -2 pyruvic acid  2 acetyl CoA  Citric Acid -The cycle begins and ends with citric acid -Krebs Cycle produces NADH, FADH2, and ATP Steps to the Krebs Cycle • Acetyl CoA combines with Oxaloacetic Acid to form 6-carbon Citric Acid • Citric Acid releases CO2 and H to form a 5-carbon compound • 5-carbon compound releases another CO2 and H to form a 4-carbon compound • 4-carbon compound releases H to regenerate oxaloacetic Acid • Krebs Cycle runs 2x (1x for each acetyl CoA) • There is a net gain of 2 ATP http://people.unt.edu/~hds0006/tca/index.htm Citric Acid Oxaloacetic Acid

  11. Electron Transport Chain • Electrons pass through molecules in cristae towards a lower energy level to final electron acceptor, oxygen • NADH and FADH2 supply protons (H+) which make ATP through chemiosmosis • In matrix, H+ combines with oxygen to form water and use the extra H+ floating around • 34 ATP are gained

  12. Aerobic Respiration Energy Yield • 38 ATP from a single glucose molecule • 2 ATP in glycolysis (made 4, but used 2) • 2 ATP in Krebs cycle • 34 ATP in ETC • This total varies from cell to cell, and is usually only 36 ATP per glucose molecule • Plant and animal cells spend 2 ATP in moving products though membranes and only net 36 ATP per 1 molecule of glucose • 66% efficient at releasing the energy in the molecule • 20X more efficient than anaerobic respiration

  13. Energy and Exercise ATP comes from: Cellular Respiration (long term) Lactic Acid Fermentation (short term) Muscle storage (short term) Why are you “out of breath” after strenuous exercise?

  14. Comprehension Check Anaerobic Respiration STAGES # of ATP Gained 1. ___________ _____ 2. ___________ _____ TOTAL: _____ Aerobic Respiration STAGES # of ATP Gained 1. _____________ _____ 2. _____________ _____ 3. _____________ _____ TOTAL: _____

  15. SUMMARY Anaerobic Respiration STAGES # of ATP Gained 1. GLYCOLYSIS2 2. FERMENTATION0 TOTAL: 2 Aerobic Respiration STAGES # of ATP Gained 1. GLYCOLYSIS2 2. KREBS CYCLE2 3. ELECTRON TRANSPORT CHAIN 34 TOTAL: 38

  16. Review Animations • Overall Review: http://www.qcc.cuny.edu/BiologicalSciences/Faculty/DMeyer/respiration.html • Glycolysis: http://instruct1.cit.cornell.edu/Courses/biomi290/MOVIES/GLYCOLYSIS.HTML • Overview of Photosynthesis and Cellular Respiration http://highered.mcgraw-hill.com/sites/dl/free/0078617022/164155/00053412.html

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