Cellular Respiration Energy Conversion

Why? Convert energy to forms usable by cells – Chemical bond energy  ATP energy – ATP via chemiosmosis; NADH via redox reaction – Electron transport – Electrochemical proton concentration gradient Have store of ATP & NADH molecules available Drive cellular processes – Transportation of metabolites, organelles, etc… – Locomotion of cell – Synthesizing complex molecules

ATP = adenosine triphosphate Adenosine – Adenine = nitrogenous purine base – Ribose = a cyclic 5-carbon sugar Triphosphate – Phosphate is negatively charged polyatomic ion – Placing phosphates near each other requires work – Energy of electrostatic repulsion is stored in bond – Broken bond releases energy for doing work

Who? Aerobic bacteria All aerobic eukaryotic organisms – 1000 to 2000 mitochondria in each liver cell – Mitochondria associated with microtubules – May move in cytoplasm or be fixed in location Concentrated in areas of high energy demands Form long chains with each other Wrapped around flagellum Packed between cardiac myofibrils

Where? Mitochondrion is site of oxidative respiration Mitochondria have double membranes – Inner vs. outer membrane Outer membrane has transport proteins & large pores Inner membrane is selectively permeable; forms cristae Membranes create 2 internal compartments – Matrix is inside organelle Enzyme-rich mixture, mDNA, ribosomes, tRNA, etc… – Intermembrane space is between membranes. Site of ATP synthesis

When? Begins when large amounts of acetyl coenzyme A (acetyl CoA)are produced in the matrix space Major fuel is acetyl CoA from pyruvate usually Stores of fatty acids & glycogen fuel process – Fats are stored in adipose tissue (fuel for 1 month) – Glycogen/ glucose is stored in liver (fuel for 1 day) – Glucose via glycolysis yields pyruvate

When else? Fats can be broken down into fatty acids and glycerol – Glycerol broken down in glycolysis to pyruvate – Fatty acids broken down into 2-C fragment Proteins can be broken down into amino acids – Certain amino acids can lose NH 3 to form pyruvate – Some amino acids minus NH 3 form 2-C fragment Pyruvate/2-C fragment (acetyl CoA) enters mitochondria for citric acid cycle

How? Glycolysis – Sugar is broken down into pyruvic acid + 2 ATP Citric acid cycle (Kreb’s cycle) – Acetyl CoA from pyruvate enters cycle – H 2 O supplies extra O 2 & H + – 2 CO NADH + FADH GTP exit Electron transport chain – Electrons from NADH move down chain – 26 ATP formed via ATP synthase

Anaerobic: Step 1 Glycolysis  C 6 H 12 O 6  2 C 3 H 3 O ATP + 2 NADH (net)  Glucose via 9 steps is broken down into 2 pyruvates 3-C Pyruvate  2-C acetyl CoA + CO 2

Citric Acid Cycle: Step 2 Citric acid cycle (Kreb’s cycle) in matrix  Pyruvate  Acetyl CoA + CO 2 + NADH  Acetyl CoA enters Kreb’s cycle  Kreb’s has 8 enzymatic reactions that harvest electrons  NAD + accepts electrons  NADH carries electrons  CO 2 + electrons (NADH + FADH 2 ) + 2 ATP & H + movement are end products

Electron Transport Chain Oxidative phosphorylation – In inner mitochondrial membrane – Electrons are delivered by NADH – Electrons move down chain of proteins – H + build up in mitochondrial intermembrane space due to movement of electrons  ATP synthase is powered by H + movement across membrane  26 ATP are produced  ½ O H +  H 2 O {oxygen is final electron acceptor)

Final Count Glucose + oxygen  carbon dioxide + water + 38 ATP