Releasing the Energy: Respiration (Reversal of photosynthesis) Respiration as reverse of photosynthesis: 6 CO 2 + 12 H 2 O C 6 H 12 O 6 + 6 H 2 O + 6 O 2 (photosynthesis) C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + 686 Kcal (cellular respiration) These are net reactions and do not show separate e – and H + coming from water during photosynthesis or going to form water during respiration. Remember that hydrogens were put on the carbon in photosynthesis by using light energy. In respiration, the same hydrogens are stripped off from carbon releasing energy. Hydrogens go back to form water with oxygen and carbon goes back to carbon dioxide
Where does respiration occur? Normal respiration has two phases: 1. Glycolysis: Occurs in the cytoplasm. Glucose (6 C and 12 H) is partially oxidized (4 H are removed) to form 2 molecules of pyruvate each with 3C and 4 H). The end-products of glycolysis are 2ATP, 2 NADH and 2 pyruvate. 2. Krebs Cycle (or Tricarboxylic Acid Cycle or Citric Acid Cycle) : Occurs in mitochondria. Pyruvate enters mitochondria where it is fully oxidized to CO 2, electrons are used to reduce O 2 to form water, protons are used to create PMF to drive ATP synthesis. Whereas Krebs Cycle occurs in the mitochondrial matrix, electron transport occurs on the folds called cristae of the mitochondrial inner membrane.
Invest energy (2 ATP) Recover investment “with interest” (2 x 2ATP)
Stage 1: Glucose F-1,6-BP “traps” glucose in cell “Pacemaker” enzyme Can be converted to two 3C- phospho compounds
The Electron Transport Chain (lesson 08) NADH Succinate ½ O 2 H20H20 I II III IV Q
Notice that electron transport carriers are grouped into 4 complexes. Electrons go from NADH to complex I, II, III and IV, and the last one passes electrons to O 2 to form water. Notice also the release of protons in the inter- membrane space (IMS) where proton motive force is built up. Protons push through the ATP synthase (on the right) providing torque energy for ATP synthesis.
Mobile electron carriers Proton pumping complexes
DO NOT PANIC!! You are not responsible for knowing EVERY name presented in the pathways! Only the ones emphasized in class! A list will be provided!