Cellular Respiration

Cellular Respiration Overview

• Transformation of chemical energy in food into chemical energy cells can use: ATP

• These reactions proceed the same way in plants and animals. Process is called cellular respiration

• Overall Reaction:– C6H12O6 + 6O2 → 6CO2 + 6H2O

Obtaining Energy• Photoautotrophs – change light energy into

chemical energy stored in bonds of glucose and polysaccharides (green plants, cyanobacteria)

• Heterotrophs – feed on other organisms for chemical energy

• Chemoautotrophs – microorganisms that can obtain energy from inorganic sources (Fe or S compounds in volcanoes, deep sea vents…)

• Glucose – primary source of energy for most organisms

• Cellular respiration – process by which glucose is broken down and energy stored in bonds is released, can be aerobic or anaerobic– Aerobic – oxygen used as an oxidizing agent

(electron acceptor)– Anaerobic – uses a molecule other than oxygen

as an oxidizing agent

Cellular Respiration Overview

Purpose of Cellular Respiration:

• Trap free energy into forming ATP

• Move H atoms (electrons) from glucose to oxygen creating 6 H2O

• Break bonds between 6C atoms in glucose creating 6 CO2

Formation of ATP

Substrate-level Phosphorylation• ATP formed directly in enzyme

catalyzed reaction• P containing compound

transfers P to ADP making ATP• 4 ATP created this way from 1

molecule glucose

2 Ways ATP is formed during Cellular respiration:

Oxidative Phosphorylation

• ATP formed indirectly in more complex process

• co-enzyme NAD+ (nicotinamide adenine dinucleotide) removes 2 H atoms and is reduced to NADH + H+

• another co-enzyme, FAD (flavin adenine dinucleotide) also reduced by 2 H to become FADH2

• these co-enzymes act as mobile energy carriers in cell, moving energy from one stage of cellular respiration to another where its used to create ATP

4 Stages of Cellular Respiration

Name Details

Stage 1 Glycolysis•10 step process in cytoplasm

Stage 2Pyruvate Oxidation

•1 step process in mitochondria

Stage 3Kreb’s Cycle

• 8 step cycle in mitochondria

Stage 4Electron Transport Chain

• multi-step process in mitochondrial membrane

Glycolysis• A series of reactions which break the 6-carbon glucose

molecule down into two 3-carbon molecules called pyruvate.

• Occurs in the cytoplasm of the cell and is anaerobic.• Process is an ancient one-all organisms from simple

bacteria to humans perform it the same way• Yields 2 ATP molecules for every one glucose molecule

broken down (creates 4 ATP but uses 2)• Yields 2 NADH per glucose molecule (used later to

create more ATP)– cellResp_main