Cellular Respiration Energy Conversion Why Convert energy to

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

Amoeba proteus

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, m. DNA, ribosomes, t. RNA, etc… – Intermembrane space is between membranes. • Site of ATP synthesis

When? • Begins when large amounts of acetyl coenzyme A (acetyl Co. A)are produced in the matrix space • Major fuel is acetyl Co. A 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 Co. A) enters mitochondria for citric acid cycle

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

Anaerobic: Step 1 • Glycolysis ØC 6 H 12 O 6 2 C 3 H 3 O 3 - + 2 ATP + 2 NADH (net) ØGlucose via 9 steps is broken down into 2 pyruvates • 3 -C Pyruvate 2 -C acetyl Co. A + CO 2

Citric Acid Cycle: Step 2 • Citric acid cycle (Kreb’s cycle) in matrix ØPyruvate Acetyl Co. A + CO 2 + NADH ØAcetyl Co. A enters Kreb’s cycle ØKreb’s has 8 enzymatic reactions that harvest electrons ØNAD+ accepts electrons NADH carries electrons ØCO 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 ØATP synthase is powered by H+ movement across membrane Ø 26 ATP are produced ؽ O 2 + 2 H+ H 2 O {oxygen is final electron acceptor)

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