Module 4 Cellular Respiration PDF

BIOL 103 Module 4 Cellular Respiration B. Cameron 1 Recall: All Metabolic Reactions Require Energy Chemical reactions constantly take place in the cell Catabolic AND anabolic reactions BOTH require activation energy Enzymes can reduce the amount of ener...

BIOL 103 Module 4 Cellular Respiration B. Cameron 1 Recall: All Metabolic Reactions Require Energy Chemical reactions constantly take place in the cell Catabolic AND anabolic reactions BOTH require activation energy Enzymes can reduce the amount of energy needed Some STILL need more energy ATP is a molecule that can store and release energy needed for countless chemical and cellular processes (used in ALL cells) 2 Energy is Stored Between Phosphates of ATP ATP (adenosine triphosphate) molecules are: 1 adenine (nitrogenous base) 1 ribose sugar 3 phosphates A large amount of energy can be stored between the second and third phosphate (high energy bond) Hydrolysis releases this energy, great for cellular work! 3 ATP is Like a Rechargeable Battery ATP releases energy by having its third phosphate removed ATP then becomes ADP (adenosine diphosphate) To be used again, ADP will need to have a third phosphate re-added so energy can be restored as ATP Cellular respiration is the process in which cells reconvert ADP to ATP 4 Cellular Respiration: Forming ATP from Glucose Glucose has a large amount of energy stored within its covalent bonds Cellular respiration is the process of harvesting energy from glucose and transferring this energy into ATP molecules This is done by harvesting high energy electrons and using THEM to build ATP A single molecule of glucose can yield 32-34 ATP via cellular respiration 5 NAD+ and FAD are Electron Acceptors NAD+ and FAD are co-enzymes that can accept high energy electrons and transport them within the cell When they receive the electrons, they also combine with H+ to become NADH and FADH2 Without NAD+ and FAD, electrons can't be harvested 6 Cellular Respiration Is a Three Step Process 1. Glucose is broken in half in the cytoplasm and some electrons are harvested (glycolysis) 2. The remaining pieces are brought into the mitochondrion to continue the electron harvesting process (Citric acid cycle) 3. The harvested electrons are used to eventually build ATP molecules within the mitochondrion (electron transport chain and chemiosmosis) C6H12O6 6 O2 6 CO2 6 H2O ATP Glucose Oxygen Carbon Water Energy dioxide 7 7  Visual Overview of Cellular Respiration Cytoplasm Mitochondrion – – – – – – 6 NADH 2 NADH 2 NADH – – 2 FADH2 Glycolysis 2 Acetyl Citric Electron Glucose Pyruvates CoA Acid Transport Cycle Maximum per glucose: 2 2 About About ATP ATP 28 ATP 32 ATP by direct by direct by ATP synthesis synthesis synthase 8 1st Step: Glycolysis (Breaking Glucose) In glycolysis, a glucose molecule is split in half Two pyruvate molecules are the products This step takes places in the cytoplasm of the cell No mitochondria needed No oxygen needed 9 Glycolysis Results in a Net Gain of 2 ATP Glycolysis requires 2 ATP, but eventually synthesizes 4 ATP Thus, there is a net gain of 2 ATP So, cells without mitochondria or without oxygen can still create a small amount of ATP! 10 Glycolysis Creates 2 NADH Molecules In addition to 2 ATP, 2 NAD+ molecules harvest high energy electrons, forming 2 NADH molecules These molecules will shuttle the electrons into the mitochondrion for the third step 11 Glycolysis Overview: Breaking Glucose One glucose molecule gets broken down and the net gain is 2 ATP, 2 NADH and 2 pyruvates 12 Cytoplasm Mitochondrion – – – – – – 6 NADH 2 NADH 2 NADH – – 2 FADH2 Glycolysis 2 Acetyl Citric Electron Glucose Pyruvates CoA Acid Transport Cycle Maximum per glucose: 2 2 About About ATP ATP 28 ATP 32 ATP by direct by direct by ATP synthesis synthesis synthase 13 Fermentation If no oxygen is available, pyruvate enters fermentation after glycolysis instead of the rest of the cellular respiration stages (which require oxygen) (Audesirk et al., 2017) Fermentation: Anaerobic Respiration The main purpose of fermentation is to revert NADH back to NAD+ for reuse in glycolysis Then the cell can continue with glycolysis and make a bit of ATP (which is better than nothing!) In fermentation, the pyruvates from glycolysis are converted into either lactate or ethanol These are by-products and must be removed by the cell 15 Pyruvates Transfer to Mitochondria If oxygen is available in the cell, the pyruvates are transferred into the mitochondria Before entering the Citric Acid Cycle, more high energy electrons will be harvested in a preparatory step 16 Pyruvates Break to form more NADH When the pyruvates enter the mitochondrion, a carbon is removed to form CO2, leaving acetic acid A molecule called Coenzyme A joins the acetic acid to form acetyl-coA In this process, two electrons are donated to an NAD + molecule to form more NADH 17 2nd Step: The Citric Acid Cycle In the 2nd step of cellular respiration, the citric acid cycle, acetyl-CoA molecules are fully broken down into 2 CO2 molecules More electrons are harvested and stored in NADH and FADH2 molecules 1 ATP is created Note: for one glucose molecule, this would happen twice 18 Citric Acid Cycle Overview: Breaking Acetyl Groups An acetic acid (2 carbon) molecule enters the cycle and 2 CO2, 1 ATP, 3 NADH, and 1 FADH2 are formed This occurs twice per glucose molecule 19 Cytoplasm Mitochondrion – – – – – – 6 NADH 2 NADH 2 NADH – – 2 FADH2 Glycolysis 2 Acetyl Citric Electron Glucose Pyruvates CoA Acid Transport Cycle Maximum per glucose: 2 2 About About ATP ATP 28 ATP 32 ATP by direct by direct by ATP synthesis synthesis synthase 20 Recall: Mitochondria have Two Membranes Mitochondria have an outer membrane and an inner membrane The space between these membranes is called the intermembrane space The space beneath the inner membrane is called the mitochondrial matrix 21 Final Step: Electron Transport Chain NADH and FADH2 will drop off their electrons to specialized protein channels in the inner mitochondrial membrane As these proteins pass the electrons down the chain (hence, electron transport chain), they use this energy to form a concentration gradient for H+ 22 Electron Transport Chain: Actively Transporting H+ As the electrons get passed, they lose energy This energy is used to actively transport H+ from the mitochondrial matrix into the intermembrane space This transport causes a concentration gradient to form 23 Oxygen Accepts Electrons at end of ETC Eventually, electron energy is so low, only oxygen would accept it (called the terminal acceptor) Without oxygen pulling at these electrons, this process would stop! The oxygen with its extra electrons combines with two H+ to form water (H2O) 24 ETC Forms Electrochemical Gradient Space between H+ H+ H+ H+ H+ membranes H+ Electron H+ + + carrier H H 3 + H Protein complex Inner mitochondrial membrane FADH2 FAD H+ Electron 2 H+ 1 flow O2 2 H2O 2 4 NADH NAD+ 1 H+ H+ H+ H+ Matrix Electron transport chain 25 ETC Forms Electrochemical Gradient Once enough H + have been pumped into the intermembrane space, there is a strong gradient: High [H +] in the intermembrane space Low [H +] in the mitochondrial matrix The H+ will now passively move back, if given the right channel... 26 Chemiosmosis forms ATP via ATP Synthase ATP synthase is a protein channel that will allow H+ to travel back into the mitochondrial matrix ATP synthase is ALSO an enzyme: for every H+ that travel into matrix (chemiosmosis), it synthesizes 1 ATP! ATP synthesis via chemiosmosis is how 90% of ATP is made (~28 ATP)! 27  ETC and ATP Synthase Audesirk et al., 2017 ETC & ATP Synthase Overview: Making ATP Electrons from NADH and FADH2 are donated to ETC, which use this energy to pump H+ into intermembrane space and create a gradient O2 eventually combines with these electrons and two H+ to form H2O The resulting gradient causes H+ to travel back to matrix through ATP synthase, which makes ATP! 29 Cytoplasm Mitochondrion – – – – – – 6 NADH 2 NADH 2 NADH – – 2 FADH2 Glycolysis 2 Acetyl Citric Electron Glucose Pyruvates CoA Acid Transport Cycle Maximum per glucose: 2 2 About About ATP ATP 28 ATP 32 ATP by direct by direct by ATP synthesis synthesis synthase 30