9-1 Chemical Pathways• Food provides living things with the chemical building blocks they need to grow and reproduce• Food serves as a source of raw materials used to synthesize new molecules• Food serves as a source of energyChemical Energy and Foodcalorie - _______________________________________________________________________________________________________________________________________Calorie - _______________________________________Glycolysis - _____________________________________________________________Overview of Cellular RespirationCellular Respiration - ______________________________________________________________________________________________________________________________________________________________________________________________________ • The equation for cellular respiration is… • There are 3 stages that capture the chemical energy available in food molecules and use it to produce ATP
2 Pyruvic acid Glucose To the electron transport chainATP Production • You need to put a little energy in to get going • _____ molecules of ATP are used up to get glycolysis going • _____molecules of ATP are produced at the end of glycolysis • Net gain of _____ATP moleculesNADH Production • One of the reactions of glycolysis removes 4 high energy electrons and passes them to a carrier called NAD+ • NAD+ accepts a pair of high energy electrons and becomes NADH • NADH holds the electrons until they can be transferred to other molecules • Energy yield from glycolysis is small, but the process is fast • Doesn’t require ___________________________Problems with glycolysis • •Fermentation • When O2 is not present, glycolysis is followed by a different pathway • This pathway and glycolysis combined is called… FermentationFermentation - ___________________________________________________________
________________________________________________________________________ • During fermentation, cells convert NADH to NAD+ by passing high energy electrons back to pyruvic acid • Changes NADH back to NAD+ • Allows glycolysis to keep producing ATPAnerobic - ______________________________________________________________There are 2 main types of fermentation1.2.Alcoholic Fermentation • Causes bread to riseLactic Acid Fermentation • Regenerates NAD+ so that glycolysis can continue Glucose Pyruvic acid
• Lactic acid is produced during rapid exercise when the body is low on O2 • You quickly run out of O2 • The buildup of lactic acid causes painful burning sensation (This is why you feel sore)Name _______________________________ Date ______________________ Per _____ 9-1 Section Review 1. Describe the process of cellular respiration. 2. What are the products of glycolysis? 3. Name the two main types of fermentation. 4. What is a calorie? A Calorie? 5. How is the function of NAD+ similar to that of NADP+?
6. How are lactic acid fermentation and alcoholic fermentation similar? How are they different? 9-2 The Krebs Cycle and Electron Transport • At the end of glycolysis, about 90% of the chemical energy that was available in glucose is still unused, locked in high energy electrons of pyruvic acid • To export the rest of that energy, the cell turns to the world’s most powerful electron acceptor… ___________________________Aerobic - ________________________________________________RESPIRATION is not CELLULAR RESPIRATION!2. The Krebs Cycle (The second stage of cellular respiration)
• Pyruvic Acid is broken down into carbon dioxide in a series of energy – extracting reactionElectron Transport • Uses the high – energy electrons from the Krebs cycle to convert ADP into ATP
A: Electron Transport • High – energy electrons from NADH and FADH2 are passed along the electron transport chain • At the end of the electron transport chain is an enzyme that combines these electrons with hydrogen ions and oxygen to form water • _________________________serves as the final electron acceptor of the electron transport chainB: Hydrogen Ion Movement • Every time 2 high-energy electrons transport down the electron transport chain, their energy is used to transport hydrogen ions (H+) across the membrane. • During electron transport, H+ ions build up in the intermembrane space, making it positively charged. • The other side of the membrane, from which those H+ ions have been taken, is now negatively charged.C: ATP Production
• The inner membranes of the mitochondria contain protein spheres called ATP synthases. • As H+ ions escape through channels into these proteins, the ATP synthases spin. Each time it rotates, the enzyme grabs a low-energy ADP and attaches a phosphate, forming high-energy ATP. • On average, each pair of high-energy electrons that moves down the electron transport chain provides enough energy to convert 3 ADP molecules into 3 ATP molecules.The Totals • 18 times as much ATP can be generated from glucose in the presence of oxygen • The final wastes of cellular respiration are o o Q: How efficient is this whole process? A: 38 percent of the total energy of glucose is released. • More efficient at using food than car engines are at burning gasoline Q: What happens to the rest of the energy? A:ATP Production The complete breakdown of glucose throughcellular respiration, including glycolysis, results in the production of36 molecules of ATP.Name ________________________________ Date _____________________ Per _____ 9-2 Section Review
1. What happens to pyruvic acid during the Krebs cycle?2. How does the electron transport chain use the high-energy electrons from the Krebs cycle?3. Why is cellular respiration considered to be much more efficient than glycolysis alone?4. How many molecules of ATP are produced in the entire breakdown of glucose?5. Compare photosynthesis and cellular respiration. How are they similar? How are they different?