Energy

Lecture 5 AQUIRE/USE ENERGY Cellular respiration is the breakdown of glucose. The energy stored in glucose when it was formed in photosynthesis is then released and captured. This energy is then stored in ATP, a molecule which can be used to supply the stored energy for use in cell metabolism. ATP ? Adenosine TriPhosphate REVIEW OF ADP/ATP cycle 1. ADP + Phosphate + Energy ATP 2. ATP ADP + Phosphate + energy GENERAL CELLULAR RESPIRATION A. Molecules used from outside the body 1. glucose [A molecule with 6 carbon atoms] a. Plants make glucose from Carbon dioxide, oxygen and water. b. It takes 6CO2 to make glucose and lots of energy. It is glucose that animals use. The energy is transferred to the bonds between Carbons in the newly formed glucose. This energy is released when the bonds between the glucose carbons are broken and used to MAKE ATP in animals. So sunlight goes though ATP and glucose (plants) and back to ATP when animals need energy 2. NADH and FADH2 a. They starts as NAD+ and FAD b. Both NAD+ and FAD can accept 2 high energy electrons from various molecules, all of which are derived from the cellular breakdown of glucose. Reaction: NAD+ + 2 electrons ? NADH FAD + 2 electrons ? FADH2 SO, the process of cellular respiration is to extract energy from glucose and stored in the molecules ATP, NADH and FADH2. In ATP, the energy is stored in a phosphate bond. In NADH and FADH2, the energy is stored in high energy electrons. Cellular respiration uses three different paths, in sequence, to extract the energy from glucose. They are (in order) glycolysis, Krebs cycle and oxidative phosphorylation. NOTE: DO NOT MEMORIZE THE GLYCOLYTIC PATHWAY NAMES. YOU SHOULD KNOW THE OVERALL FUNCTION AND THE TYPES OF ENERGY RICH MOLECULES USED OR FORMED. GLYCOLYSIS Performed in the cytoplasm A. Glucose (6 carbon molecule) as starting point 1. First, glucose must be activated, energy is added from ATP 2. Two ATP are used to give energy to glucose. This energy is added and is used to drive all other reactions of glycolysis B. Second, glucose is split into 2 x 3 carbon molecules (pyruvate) C. Third, pyruvate is produced (2 x 3 carbons) gain energy D. Four ATP are produced, but we owe 2 molecules of ATP that we used in order to start glycolysis - end up with 2 ATP net production. - NADH is produced (2 molecules per glucose molecule) when glucose is broken down from 6C to 2 x 3C - Pyruvate is produced (2 molecules per glucose molecule) ATP KREBS CYCLE performed dissolved in mitochondria liquid A. Overview Cycle in which the remainder of glucose is completely broken down to give carbon dioxide + energy B. Preparatory Step 1. Pyruvate is changed from a 3 carbon molecule into 2 carbons 2. In this step, 1 NADH and 1 CO2 carbon dioxide molecules are produced per pyruvate molecule 3. Add the 2 carbon molecule from preparatory step to a pre- existing 4 carbon molecule = 6 carbon molecule C. Krebs Cycle 1. Remove one carbon = leaves a 5 carbon molecule 6 CARBONS 5 CARBONS 1 glucose 2 NADH + 2 CO2 1 pyruvate 1 CO2 + 1 NADH 2. Remove another carbon - leaves a 4 carbon molecule 5 CARBONS 4 CARBONS 1 glucose 2 NADH + 2 CO2 3C pyruvate 2C pyruvate + CO2 +4C random 6C break the bond, turn into separate carbons = ATP and NADH 5C 4C which goes back to wait for 2C more pyruvate - two cycles of the Krebs cycle are needed for one glucose molecule 4. Rearrange the 4 carbon molecule to get back to the original 4 carbon molecule to complete the cycle. 4 CARBONS OXALOACETATE 4 CARBONS In this rearrangment, 0 carbon dioxide + 2 NADH + 2 FADH2 + 2 ATP are produced per glucose molecule DON'T GET CONFUSED: BECAUSE GLUCOSE IS SPLIT INTO 2 PARTS, ONE GETS FROM EACH HALF OF GLUCOSE FROM THE START OF GLYCOLYSIS TO THE END OF THE KREBS CYCLE. 1 Pyruvate makes: 3 ATP 4 NADH 1 FADH2 3 CO2 In the Krebs cycle proper + preparatory reaction: 8 NADH, 2 FADH2, 2 ATP, 6 Carbon dioxide (as waste) per glucose molecule Now Notice: For every CO2 which is released from glucose, you always get an NADH molecule. The electrons given to NADH come about because the bonds between Carbon molecules of glucose are broken. FORMATION OF ATP is performed in Complexes found embedded in the mitochondrial membrane A. Mitochondrial electron transport chain 1. Found in mitochondrial membrane 2. Three large protein complexes for the complete chain B. Complex I 1. NADH and FADH2 give electrons to a protein in complex I a. Now, the two molecules NAD+ and FAD have no electrons so they can move away and get more electrons. 2. Electrons are passed down a series of proteins within Complex I. 3. Energy is released at each transfer of electrons 4. Energy released at Complex I (from electrons donated by NADH and FADH2) is used to move H+ C. Complex II 1. Electrons from Complex I are passed to Complex II 2. Series of transfers occurs again 3. Energy released in Complex II is used to move H+. D. Complex III 1. Electrons from Complex II are passed to Complex III 2. Series of transfers occurs again 3. Energy released in Complex III is used to move H+ E. Final disposal of electrons [NOW WE USE OXYGEN!!!] 1. After Complex III the electrons have no more energy 2. The electrons are given to oxygen and water is formed 3. Reaction: 2 electrons + 2 H+ + Oxygen à H2O 4. Water is removed as waste from the lungs during breathing H+ is forced into the outer compartment using energy given off in transfer of electrons, diffusion pushes it back in as fast as it can to make new ATP ATP SYNTHASE: H+ flows THROUGH this protein and the energy from the flow of H+ is used to form ATP from ADP + P.