Cellular Respiration Overview By Sarah Lanoie; 12/5/08

Cellular Respiration Formulas Word Equation: Glucose + Oxygen → Energy + Carbon Dioxide + Water Symbol Equation: C6H12O6 + 6O2 → Energy (ATP) + 6CO2 + 6H2O

Cellular Respiration Step-wise release of energy from food Allows for efficient energy use Removal and transfer of electrons from simple food molecules to carriers to release energy for ATP synthesis

Redox Reactions Involve the transfer of electrons from one reactant to another Oxidation = loss of electrons from a substance Reduction = addition of electrons to a substance (reducing the positive charge) Electron donor = reducing agent Electron accepter = oxidizing agent

A Quick Overview of the main Stages 1. Glycolysis In cytosol Glucose is split into pyruvate Creates ATP and NADH

2. Krebs Cycle / Citric Acid cycle In mitochondrial matrix Pyruvate is broken down Creates ATP, NADH, and FADH2 Releases CO2

3. Oxidative Phosphorylation (Electron Transport Chain) In inner mitochondrial membrane NADH and FADH2 release hydrogen (results: NAD+ and FAD) Creates lots of ATP Releases H₂O

Summary

Phosphorylation of ATP Substrate level- when an enzyme transfers a phosphate from a substrate (organic molecule) to ADP Oxidative phosphorylation – powered by electron transport chain and results in an inorganic phosphate is added to ADP to make ATP

Glycolysis

The splitting of glucose Energy is harvested by oxidizing glucose to pyruvate Requires an initial input of energy to get energy out

Glycolysis I (energy in) Glucose enters the cell and gains a phosphate from ATP Glucose is rearranged by enzymes and gains another phosphate from ATP molecule (6 carbon sugar biphosphate) Enzymes split 6 carbon sugar biphosphate into two 3- carbon sugar phosphates

Glycolysis II (energy out) 3-carbon sugar phosphates gain 2 phosphates and during the reaction energy is give off to cause 2 NAD+  2NADH One phosphate from each 3 carbon sugar biphosphate is given to 2 ADP  2 ATP Phosphate groups get re-arranged  release 2 H2O Phosphate from 3 carbon sugars given to 2ADP  2ATP Results in 2 molecules of pyruvate Net release of 2NADH and 2ATP

Aerobic Respiration Aerobic = O₂ present If O₂ present pyruvate goes to mitochondria for Krebs cycle Net ATP production = 36

Anaerobic Respiration Anaerobic = no O₂ present Prokaryotes that live in oxygen free environments Electron transport chain present- oxygen is not final electron acceptor

Fermentation No Oxygen or electron transport chain present (can be used by prokaryotes and eukaryotes) Glycolysis products are fermented for energy Lactic Acid Fermentation Pyruvate takes energy from NADH (goes back to NAD+) and is converted to lactate (a 3 carbon acid) Net ATP production = 2