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Laws of thermodynamics Energy is never created or destroyed, only transformed Entropy (disorder) increases Transforming energy Convert energy source to ATP: usable cellular energy light food ATP ATP: Energy Currency for the cell Phosphate bonds are highly unstable. DG = -7.3 kcal/mol H2 O Pi ATP powers many reactions in cells ATP powers many reactions in cells Active transport Specific transport protein required Energy required! Any kind of molecules Either direction Can move against gradient Can transport all molecules No equilibrium Simple active transport Energy from ATP Simple active transport Energy from ATP Directional transport One kind of molecule Simple active transport PMCA transporter removes Ca2+ from cytoplasm Very low [Ca2+] required for signaling Ca2+ ATP ADP How do we get ATP from Glucose? Transfer energy stored in glucose to a storage molecule ATP NADH Glycolysis- Oxidizing glucose to pyruvate Citric Acid Cycle – Oxidizing pyruvate to CO2 Election Transport – Collecting electrons from NADH and transferring this energy towards making ATP. Carbohydrates H-C-OH units Often used for energy by cells Glucose is a simple 6C sugar Carbohydrates Polymer: polysaccharides (complex carbohydrates) starch cellulose glycogen chitin peptidoglycan Oxidation Gain of electrons Increased number of bonds to O O pulls e– from C – – – H–C–H H–C–H H–C–H – O – OH – H H H most reduced O – – H – C – OH O=C=O most oxidized Oxidation reactions When one molecule is oxidized, another is reduced Electron carriers (“coenzymes”): NAD+, FAD – oxidation H–C–H – H–C–H – – O OH H 2 e– NAD+ reduction oxidation NADH “Burning” sugars Glucose → CO2 is highly exergonic Same reaction as burning paper or wood Oxidation glucose free energy (G) CO2 reaction progress → “Burning” sugars Glucose → CO2 is highly exergonic Same reaction as burning paper or wood Oxidation O=C=O “Burning” sugars Glucose → CO2 is highly exergonic Same reaction as burning paper or wood Oxidation glucose free energy (G) CO2 reaction progress → “Burning” sugars Glucose → CO2 is highly exergonic Same reaction as burning paper or wood Oxidation glucose free energy (G) CO2 reaction progress → “Burning” sugars Biochemical pathway Enzymes catalyze steps Energy captured in ATP glucose free energy (G) CO2 reaction progress → “Burning” sugars Oxidized molecules have less chemical energy Energetic electrons transferred to carriers – H–C–H oxidation – – O OH H–C–H lower energy – higher energy H 2 e– glucose NAD+ free energy (G) CO2 reaction progress → reduction NADH Aerobic cell respiration Complete oxidation of glucose glucose 4 stages: Glycolysis Citric acid cycle Electron transport Chemiosmosis oxidation 6 CO2 1. Glycolysis Partial oxidation of glucose in cytosol glucose Yum! oxidation 2 pyruvate 2 ATP, 2 NADH gluT 1. Glycolysis First step: phosphorylation catalyzed by hexokinase Energy invested Allows facilitated transport glucose hexokinase ATP ADP P glucose 6-phosphate 1. Glycolysis Another phosphorylation step 6C molecule split into two 3C molecules glucose 6-phosphate glucose hexokinase ATP ADP P P PFK ATP P ADP P P 1. Glycolysis Oxidation Energy stored as high-energy e– on NADH NAD+ glucose 6-phosphate glucose hexokinase ATP ADP P PFK ATP NADH P P P P P P P ADP P NAD+ NADH 1. Glycolysis 2 ATP synthesis steps Net gain of 2 ATP per glucose 6C glucose → 2 3C pyruvates NAD+ glucose 6-phosphate glucose hexokinase ATP ADP P P PFK ATP NADH P ADP ATP P ADP P P ADP ATP pyruvate P P NAD+ P NADH P P ADP ATP ADP ATP 2. Citric Acid Cycle (CAC) AKA tricarboxylic acid cycle (TCA), AKA Krebs cycle Occurs in matrix of mitochondria (or cytosol in prokaryotes) 2. Citric Acid Cycle (CAC) “Transition step” Transport into matrix Connects glycolysis to CAC pyruvate o.m. i.m. Coenzyme A NADH NAD+ cytosol matrix CO2 acetyl CoA 2. Citric Acid Cycle (CAC) “Transition step” Large protein complex spans o.m. and i.m. Transporter and enzyme Oxidation of one carbon to CO2 pyruvate Attachment of coenzyme A o.m. i.m. Coenzyme A NADH NAD+ cytosol matrix CO2 acetyl CoA 2. Citric Acid Cycle (CAC) 2C acetyl CoA + 4C = 6C citric acid acetyl CoA CoA citric acid 2. Citric Acid Cycle (CAC) 2 oxidation reactions complete the oxidation of glucose acetyl CoA CoA citric acid NADH CO2 NAD+ NADH CO2 NAD+ 2. Citric Acid Cycle (CAC) One GTP synthesized and converted to ATP acetyl CoA CoA citric acid NADH CO2 NAD+ NADH CO2 NAD+ GDP GTP ADP ATP 2. Citric Acid Cycle (CAC) Two more oxidation steps regenerate original 4C molecule acetyl CoA CoA citric acid NADH CO2 FADH2 NAD+ FAD NADH CO2 NAD+ GDP NADH NAD+ GTP ADP ATP 2. Citric Acid Cycle (CAC) Where’s the carbon from glucose? 2. Citric Acid Cycle (CAC) Where’s the carbon from glucose? 6 CO2 Where’s the energy from glucose? 2. Citric Acid Cycle (CAC) Where’s the carbon from glucose? 6 CO2 Where’s the energy from glucose? 4 net ATP (2 from glycolysis, 2 for each pyruvate in CAC) 2. Citric Acid Cycle (CAC) Where’s the carbon from glucose? 6 CO2 Where’s the energy from glucose? 4 net ATP (2 from glycolysis, 2 for each pyruvate in CAC) 10 NADH (2 glycolysis, 2 transition, 6 CAC) 2. Citric Acid Cycle (CAC) Where’s the carbon from glucose? 6 CO2 Where’s the energy from glucose? 4 net ATP (2 from glycolysis, 2 for each pyruvate in CAC) 10 NADH (2 glycolysis, 2 transition, 6 CAC) 2 FADH2 (CAC)