Agenda Curriculum Expectations Overview of cellular respiration Glycolysis Pyruvate Oxidation Kreb’s Cycle Chemiosmosis and Electron Transport Chain Activity
Curriculum Expectations C2.1: use appropriate terminology related to metabolism, including, but not limited to: energy carriers, glycolysis, Krebs cycle, electron transport chain, ATP synthase, oxidative phosphorylation, chemiosmosis, proton pump, photolysis, Calvin cycle, light and dark reactions, and cyclic and noncyclic phosphorylation C3.1explain the chemical changes and energy conversions associated with the processes of aerobic and anaerobic cellular respiration c3.3 use the laws of thermodynamics to explain energy transfer in the cell during the processes of cellular respiration and photosynthesis c3.4 describe, compare, and illustrate (e.g., using flow charts) the matter and energy transformations that occur during the processes of cellular respiration (aerobic and anaerobic) and photosynthesis, including the roles of oxygen and organelles such as mitochondria and chloroplasts
Aerobic Cellular Respiration Occurs in the presence of oxygen An exothermic reaction (∆G= -2870 kJ/mol) The cell only captures 34% of the available free energy in the form of ATP3 goals:1. To break the bonds between the 6-C atoms of glucose, resulting in 6 carbon dioxide molecules2. To move hydrogen atom electrons from glucose to oxygen , forming 6 water molecules3. To trap as much of the free energy released in the process as possible in the form of ATP.
ATP: Adenosine Triphosphate • Contains a nitrogenous base (adenine), a ribose sugar and 3 phosphate group • High energy bond between the 2nd and 3rd phosphate group • When that bond is broken, an abundance of energy is released
Energy Transfer 2 ways in which available free energy is captured into the form of ATP 1. Substrate-Level Phosphorylation • ATP is formed directly in an enzyme-catalyzed reaction.
Energy Transfer2. Oxidative Phosphorylation• ATP is formed indirectly through a series of enzyme- catalyzed redox reactions involving oxygen as the final electron acceptor. NAD+ to NADH: NAD+ removes 2 hydrogen atoms (2 protons, 2 electrons) from glucose forming NADH using a dehydrogenase enzyme FAD to FADH2: LEO the lion goes GER FAD is reduced by 2 - Lose electrons, oxidization hydrogen atoms from - Gain electrons, reduction glucose
Glucose: 6- carbon monosaccharide Primary source of energy for plants and animals
Glycolysis 10 step process that occurs in the cytoplasm under anaerobic conditions A process that evolved in prokaryotes prior to the emergence of organelles, notably the mitochondria 1. Glucose is phosphorylated to G6P (Investment phase) 2. Glucose is rearranged to F6P 3. Glucose is phosphorylated to F1,6- BP (investment phase)
Glycolysis (cont’d) 4&5. F 1, 6-BP is split into DHAP and G3P, then DHAP is converted into G3P, resulting in two G3P molecules 6. Two G3P are converted to two BPG. Hydrogen atoms reduce NAD+ to NADH. 7. BPG is converted to 3PG. A high energy phosphate group on BPG phosphorylates ADP to AT 8. 3PG is rearranged to 2PG
Glycolysis 9. 2PG is converted to PEP by removal of a water molecule 10. PEP is converted to pyruvate. A high energy phosphate group on PEP phosphorylates ADP to ATP Invested 2 ATP Gained 2 NADH 4 ATP Net: 2 NADH and 2 ATP
Mitochondria The power house of the cell, specialized organelles that generate ATP Only eukaryotic cells contain mitochondria Double membrane, inner membrane is highly specialized
Pyruvate Oxidation1. Carboxyl group is removed as CO2 (by pyruvate decarboxylase)2. Pyruvate is oxidized while NAD+ is reduced3. CoenzymeA (CoA) is attached to the acetyl group. Gained: 1 NADH (X2 for each pyruvate)
Kreb’s CycleGained:1 ATP3 NADH1 FADH2(X2 for eachacetyl-CoA)
From here.. Bythe end of the Kreb’s cycle the original glucose molecule has been consumed as the carbon atoms exited as waste in the form of CO2 We have created 4 ATP molecules via substrate level phosphorylation, 10 NADH and 2 FADH2
Electron Transport andChemiosmosis NADH and FADH2 eventually transfer the hydrogen atom electrons they carry to a series of proteins in the inner mitochondrial membrane, called the ETC Each component is alternately reduced from the component before it and oxidized by the component after it. Electrons from NADH and FADH2 are shuttled from one component to the next like a baton in a relay race. Oxygen is one of the most electronegative components, which is needed to oxidize the last component of the ETC
ETC• Components of ETC are arranged in order of increasing electronegativity (The ability of an atom in a molecule to attract a shared electron pair to itself)• Ubiquinone and cytochrome C are mobile electron carriers that shuttle the electrons from one complex to the next.• Many folds of the inner membrane increase surface area and allow many copies of the ETC
ETC cont’d• NADH passes its electrons on to the first protein complex, and FADH2 transfers its electrons to Q• Therefore FADH2 pumps 2 protons into the inter membrane space while NADH pumps 3.• Cytosolic NADH created in glycolysis cannot pass through the inner membrane into the matrix• Glycerol-phosphate shuttle oxidizes NADH to reduce FAD in the matrix into FADH2 so that it can be used.
Chemiosmosis An electrochemical gradient is created with the H+ ions built up in the inter membrane space, storing free energy. The inner mitochondrial membrane is impermeable to protons, forcing them to pass through special proton channels associated with ATP synthase • As protons move through the ATP synthase complex, the free energy of the gradient is reduced • This causes the synthesis of ATP from ADP and inorganic phosphate in the matrix
What if there was no O2? Without oxygen, we wouldn’t be able to free up the last protein (cytochrome oxidase) and the chain would be clogged with stationary electrons. Then H+ ions would not be pumped into the inter membrane space to create the electrochemical gradient.