Lesson 4: From Eating to Energy - BIOL 1441

Lesson 4: From Eating to Energy BIOL 1441 Cell & Molecular Biology  Learning Objectives (a.k.a. Study Guide) By the end of this lesson, students will 7. Describe the relationship between be able to: catabolic, anabolic, endergonic, and...

Lesson 4: From Eating to Energy BIOL 1441 Cell & Molecular Biology  Learning Objectives (a.k.a. Study Guide) By the end of this lesson, students will 7. Describe the relationship between be able to: catabolic, anabolic, endergonic, and exergonic reactions. 1. Explain why the human body needs to eat. 8. Explain how ATP & ADP are related. 2. Define the term “metabolism” 9. Explain what happens during redox 3. Describe the function of chemical bonds. reactions. 4. Explain how the structure of ATP makes it 10.Write the overall chemical equation for good for storing & releasing energy. cellular respiration. 5. Explain what happens in catabolic & 11.Identify the location where each step of anabolic reactions. cellular respiration occurs in the cell. 6. Explain what happens in endergonic & exergonic reactions.  Learning Objectives (a.k.a. Study Guide) By the end of this lesson, students will 16. Explain how electrons are used to build a be able to: proton gradient across the inner mitochondrial membrane. 12. Differentiate between substrate-level phosphorylation & chemiosmosis. 17. Explain how the movement of protons is used to build ATP. 13. List the number of carbons found in glucose & pyruvate. 18. Describe the role of oxygen in the process of cellular respiration. 14. Identify the starting materials & products created by each of these processes: 19. Describe the purpose of fermentation. glycolysis, pyruvate oxidation, the Citric 20. Explain how alcohol & lactic acid Acid Cycle (a.k.a. Krebs Cycle), and the fermentation occur, including types of Electron Transport Chain (and oxidative organisms using each pathway phosphorylation). 21. Explain the role of feedback inhibition in 15. Explain the function of electron carriers regulating cellular respiration. in cellular respiration.  Your cells In cellular respiration the have taken energy is transferred to the bonds between the up glucose. phosphate groups ATP. Now what? ATP can be used by cells as a source of energy by breaking the high energy phosphate bonds. The energy in glucose is stored in the chemical bonds between the atoms. It is not directly available for your cells to use.  From Eating to Energy On the most basic level, you need to eat to get the energy required to survive Energy is required for building macromolecules (like proteins & nucleic acids) Energy is required for life-sustaining processes like active transport Foods store energy in their chemical bonds By breaking those chemical bonds, that energy is released into your cells Your cells can use that energy immediately or store it by forming new chemical bonds Enzyme Metabolism is the sum of all the chemical reactions that occur in your cells to keep you alive  Refresher: Metabolism Terminology The chemical reactions of metabolism can be classified as catabolic or anabolic Catabolic reactions break large polymers into smaller monomers These reactions release energy Anabolic reactions build large polymers from smaller monomers These reactions require energy Catabolic & anabolic reactions are paired The monomers made in catabolic reactions are used to build polymers in anabolic reactions  Metabolism Terminology The chemical reactions of metabolism can Products also be classified as exergonic or Reactants endergonic Exergonic reactions release energy This is because the products of the reactions have LESS energy than the reactants Endergonic reactions require energy Reactants This is because the products of the reactions have MORE energy than the reactants Products Exergonic & endergonic reactions are paired The energy released in exergonic reactions is used to power endergonic reactions  Enzymes Speed up the rate of chemical reactions Without enzymes, reactions would occur much too slowly for organism functioning Enzymes facilitate both anabolic and catabolic reactions Enzymes act on substrates (in this example, lactose) to make products (in this case glucose and galactose)  Anabolic reactions Endergonic reactions RELEASE / REQUIRE RELEASE / REQUIRE energy. Let’s energy. Practice! Catabolic reactions Exergonic reactions RELEASE / REQUIRE RELEASE / REQUIRE energy. energy. Based on energy requirements, Based on energy requirements, anabolic reactions are the same as catabolic reactions are the same as _____________ reactions. _____________ reactions.  Metabolism: An Overview These are the reactions that These are the happen when you reactions that eat food & break it are necessary down in your body. for organism functioning. This is how energy from your food is stored.  ATP & ADP Energy-rich chemical bonds ATP & ADP are the main forms of chemical energy in a cell Energy is stored in the energy-rich chemical bonds between their phosphate groups ATP = adenosine triphosphate ATP has 3 phosphate groups, so it has A LOT of energy ATP is made when the cell has extra energy ADP = adenosine diphosphate ADP has 2 phosphate groups, so it has some energy ADP is made when the cell uses the energy in ATP (by removing one of its phosphate groups)  This energy comes from catabolic (exergonic) chemical reactions. Example: digesting food This energy goes into anabolic (endergonic) chemical reactions. Example: building new proteins Let’s Practice! Is this catabolic or anabolic? Is this endergonic or exergonic? How can you tell? Is this catabolic or anabolic? Is this endergonic or exergonic? How can you tell?  Oxidation & Reduction In metabolism, chemical bonds are broken & built Chemical bonds are made of electrons When a molecule loses electrons, it becomes oxidized Often, this loss is seen as the breaking of a chemical bond Oxidation can also generate a positively-charged ion When a molecule gains electrons, it becomes reduced Often, this is seen as a the building of a new chemical bond Reduction can also generate a negatively-charged ion  Let’s Practice: NAD & NADH + The oxidized The reduced form of this form of this molecule is molecule is NAD+. NADH. Has the oxidized Has the reduced form gained or lost form gained or electrons? lost electrons?  Cellular Respiration Cellular respiration is the process your cells use to generate energy from glucose When glucose is oxidized, the energy stored in its chemical bonds is released This energy is then captured in the chemical bonds of newly- formed ATP molecules Ultimately, energy-poor electrons are given to oxygen This means oxygen is reduced  In reality, cellular respiration requires This version of the chemical several different processes that occur in equation for cellular respiration multiple locations in the cell and involves makes it look very simple. many enzyme-mediated steps (not pictured). How Do You Make ATP Step 1: glycolysis from Glucose? Split the glucose into pyruvate molecules Cellular Step 2: pyruvate oxidation Respiration Move the pyruvates into the mitochondria & process them Step 3: the Citric Acid (Krebs) Cycle Remove energy-rich electrons from the processed pyruvates Step 4: oxidative phosphorylation Use the energy from those high- energy electrons to build ATP  Building ATP ATP is built by phosphorylating ADP This means a new chemical bond is built between ADP & a phosphate group +  The energy of ATP is stored in that chemical bond ADP ATP In glycolysis & the Citric Acid Cycle, ATP synthesis occurs using substrate- level phosphorylation A phosphate group is removed from one molecule (the substrate) It is then directly attached to ADP  Building ATP ATP can also be made using oxidative phosphorylation Oxidative phosphorylation uses the Electron Transport Chain (ETC) & Chemiosmosis First, the ETC creates a proton (H+) concentration gradient across the inner mitochondrial membrane Then, ATP synthase uses the energy of that gradient to build ATP in a process called The Electron Transport Chain Chemiosmosis chemiosmosis (ETC)  Electron Carriers The Electron Transport Chain (ETC) uses energy from electron carriers to Ready to receive Transporting Electrons have been create the H+ concentration gradient electrons electrons released Electron carriers “capture” the energy from one chemical reaction & transport it to a different part of the cell to be used Electron carriers like the Uber for electrons In cellular respiration, the primary electron carriers are NAD+ / NADH & FAD / FADH2  Cellular Respiration: The Big Picture C6H12O6 + 6 O2  6 CO2 + 6 H2O + ~36 ATP Energy-rich glucose (C6H12O6) is broken into energy-poor carbon dioxide (CO2) Two forms of energy are created: ATP & energized electron carriers (NADH & FADH2) Ultimately, the energy of electron carriers is also transformed into ATP using the Electron Transport Chain Note: Krebs Cycle and Citric Acid Cycle are the same thing. For each process, know these things: What does it start with? What does it end with? Where does it occur? Does it build ATP? Does it build energized electron carriers?  Step 1: Glycolysis Glycolysis is the initial glucose-breaking process Many chemical reactions break its chemical bonds, rearrange its elements, and harvest some of its energy Starting materials: glucose (C6H12O6) + 2 ATP + 2 NAD+ *Oxygen (O2) is NOT required for this process!* Ending materials: 2 pyruvate (C3H4O3) + 2 (net) ATP + 2 NADH Technically, 4 ATP are made, but 2 ATP are required, so the cell only gains 2 ATP This ATP is made through substrate-level phosphorylation Location: the cytoplasm  Glycolysis: Glucose has A Closer Look 6 carbons. Remember! Glycolysis generates two forms of energy: ATP & NADH Each pyruvate By making two pyruvate, the has 3 carbons. number of carbons does not change.  Step 2: Pyruvate Oxidation Each 3-carbon pyruvate still has A LOT of energy The pyruvates are transported into the mitochondria so that energy can be harvested Starting materials: 2 pyruvate + 2 NAD+ + 2 Coenzyme A complexes Ending materials: 2 acetyl coenzyme A (acetyl CoA) + 2 CO2 + 2 NADH Location: the mitochondrial matrix (a.k.a. its center)  Mitochondrial Structures The outer mitochondrial membrane divides it from the cytoplasm The inner membrane is the location of the Electron Transport Chain (ETC) The intermembrane space (between the membranes) is where the ETC pumps H+ ions into The matrix is the central fluid-filled As H+ re-enter the matrix through the area of the mitochondria ATP Synthase enzyme, ATP is built It is the site of the Citric Acid (Krebs) Cycle Step 3: The Citric Acid (Krebs) Cycle The Citric Acid Cycle harvests all the remaining energy in Acetyl Coenzyme A (Acetyl CoA) REMEMBER: one glucose molecule makes two acetyl CoA’s! Starting materials: 2 acetyl CoA + 6 NAD+ + 2 FAD (+ oxaloacetate ) Ending materials: oxaloacetate + 4 CO2 + 2 ATP + 6 NADH + 2 FADH2 Location: the mitochondrial matrix (a.k.a. its center)  *This process happens The Citric Acid Cycle: TWICE since there are two acetyl CoA’s.* A Closer Look The Citric Acid Cycle begins with a 4- carbon molecule (oxaloacetate). 2 carbons are added when acetyl- CoA enters the cycle. Those 2 carbons leave the cycle as CO2 molecules, generating NADH. As the remaining 4 carbons rearrange their structure, ATP & more energized electron carriers are made.  Glucose So, Where’s the Glycolysis Glucose? Pyruvate Pyruvate Released Released as CO2 Pyruvate as CO2 Glucose has 6 carbons Oxidation Acetyl Coenzyme A Acetyl Coenzyme A CoA CoA By the end of the Citric Acid Cycle, all 6 carbons have been separated from one another & released as Released Citric Acid Citric Acid Released CO2 (carbon dioxide) as CO2 Cycle Cycle as CO2  And Where’s the Energy? At the end of the Citric Acid Cycle, only 4 ATP have been made 2 (net) ATP from glycolysis 2 ATP from the Citric Acid Cycle The rest of the energy is stored in electron carriers 10 NADH (from glycolysis, pyruvate oxidation, & the Citric Acid Cycle) 2 FADH2 (from the Citric Acid Cycle) Oxidative phosphorylation transforms the energy in those electron carriers into ATP  Oxidative Phosphorylation Oxidative phosphorylation builds most of the ATP generated through cellular respiration. First, the Electron Transport Chain (ETC) creates an H+ concentration gradient across the inner mitochondrial membrane. Then, during chemiosmosis, ATP synthase uses that gradient to build ATP. #1 #2  The Electron Transport Chain (ETC) Electrons (from NADH & FADH2) travel through each of the ETC protein complexes. Their energy is used by the proteins to pump H+ ions (a.k.a. protons) into the intermembrane space. By the end of the ETC, the electrons no longer store any energy & are combined with O2.  Chemiosmosis INTERMEMBRANE SPACE H+ ATP Synthase is the ATP-generating protein of Stator oxidative phosphorylation Rotor The concentration of H+ (protons) is very high in the intermembrane space & much lower in the matrix ATP synthase – which is embedded in the inner mitochondrial membrane – allows protons to move back into the matrix Internal rod The energy that is released when these protons move back in is called proton motive force Catalytic knob ATP synthase uses the power of proton motive force ADP to create new ATP + Pi It takes the movement of 4 protons (H+) to make 1 ATP molecule of ATP MITOCHONDRIAL MATRIX  The Role of Oxygen Oxidative phosphorylation is the only cellular respiration process that requires oxygen (O2) O2 is the final electron acceptor at the end of the Electron Transport Chain (ETC) Energy-poor electrons are donated to O2, making space for other electrons to continue to move through the ETC If oxygen was not present, electrons would build up in the Electron Transport Chain & electron carriers would remain permanently reduced  Cellular Respiration: A Review Respiration begins with glucose (C6H12O6). The glucose is split into pyruvate in the cytoplasm, then transported into the mitochondria. As the pyruvate is processed further, both ATP & energized electron carriers are made. Ultimately, the most ATP is built through oxidative phosphorylation, the process that harnesses the energy stored in electron carriers.  Respiration Processes & Their Mitochondrial Locations Study Tip: Make sure you know where each cellular respiration process occurs!  Stored Forms of Location Starts with: Ends with: Energy (ATP, NADH, or FADH2) Glycolysis Pyruvate oxidation The Citric Acid Cycle Oxidative Phosphorylation  Oxygen & Cellular Respiration The only part of cellular respiration that directly uses oxygen is the Electron Transport Chain (ETC) O2 removes low-energy electrons from the ETC, allowing new electrons to constantly enter it Electrons in the ETC come from NADH & FADH2 Donating electrons to the ETC oxidizes the carriers to NAD+ & FAD, the form needed for all the other parts of cellular respiration If the electron carriers can’t be oxidized, ALL cellular respiration stops  Fermentation Cells use fermentation when there is no oxygen present The goal of fermentation is to regenerate the oxidized electron carrier NAD+ Without this carrier, glycolysis cannot occur, and… Without glycolysis, a cell has no ways to make ANY ATP  Alcohol Fermentation Alcohol fermentation is used by yeast to regenerate NAD+ The pyruvate (made by glycolysis) is transformed into ethanol This transformation requires electrons, which NADH provides, oxidizing it back into NAD+ Alcohol fermentation is used in brewing & wine-making This process generates a lot of CO2 Fermentation tanks have valves to help relieve the pressure this gas creates  Lactic Acid Fermentation Lactic acid fermentation is used to regenerate NAD+ in bacteria, fungi, & mammals The pyruvate (made by glycolysis) is transformed into lactic acid This transformation requires electrons, which NADH provides, oxidizing it back into NAD+ Lactic acid fermentation is used to make many different foods Examples: yogurt, cheese, sourdough bread Lactic acid leads to a tangy taste in these foods  Summary of Aerobic and Anaerobic Pathways Whether or not O2 is present, glycolysis will ALWAYS be used to make ATP If O2 is NOT present, fermentation is used to regenerate NAD+ (so If O2 IS present, the cell glycolysis can continue) makes A LOT of ATP with the Citric Acid Cycle & oxidative phosphorylation Macromolecules besides carbohydrates can be catabolized using some of the same metabolic pathways as glucose  Regulating Cellular Respiration The steps of cellular respiration are regulated using feedback inhibition This means that the products of the chemical reactions can inhibit the continuation of the chemical reaction Many of the enzymes involved in respiration are sensitive to ATP If A LOT of ATP is present, they are inactive If A LITTLE ATP is present, they are active Other factors (like pH changes due to lactic acid buildup) can also influence enzyme activity  Your cells In cellular respiration the have taken energy is transferred to the bonds between the up glucose. phosphate groups ATP. Now what? ATP can be used by cells as a source of energy by breaking the high energy phosphate bonds. The energy in glucose is stored in the chemical bonds between the atoms. It is not directly available for your cells to use.  To Prepare for Next Class…  Review your class notes Use the eTextbook & Other Helpful Resources to supplement your lecture notes  Complete the homework assignment and use it to direct your studying  Print the slides for Lesson #5- Green Energy