Cellular Respiration (9.1 and 9.2)

Chemical Energy and Food calorie Measure of the energy stored in food 1 calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 °C The Calorie = 1000 calories There is energy in each type of macromolecule Carbohydrates 4 calories/gram Proteins 4 calories/gram Lipids 9 calories/gram

Cells Break down food molecules gradually Capturing a little bit of energy in key steps Energy is stored in chemical bonds Use the energy to make molecules such as ATP that directly power the activities of the cell

What is Cellular Respiration? The process that releases energy from food in the presence of oxygen Represented by the equation: C6H12O6 + 6O2 ------> 6CO2 + 6H2O + ATP glucose oxygen carbon dioxide water energy An aerobic process because oxygen in required A living cell has to control the release of this energy

Stages of Cellular Respiration Glycolysis Krebs cycle Electron Transport Chain

1. Glycolysis Only a small amount of energy is captured to produce energy from glucose in this stage 90% of the available energy locked in a molecule called pyruvic acid 6C glucose is broken down into 2 molecules of pyruvic acid, each with 3 carbons Produces 2 ATP molecules

2. Krebs Cycle Pyruvic acid from glycolysis reacts to form acetyl-CoA which enters this stage of the reaction Citric acid is produced from the reaction A little more energy is produced Carbon dioxide and 2 more ATP molecules are produced

3. Electron Transport Chain The most energy is produced in this part of the reaction Requires reactants from the other two stages 32 ATP molecules produced along with water (H2O)

Energy Totals Stage of Cellular Respiration # of ATP Molecules Produced Glycolysis 2 Krebs Cycle Electron Transport Chain 32 TOTAL 36 ATP Molecules

Oxygen and Energy Oxygen is not required for the first stage of cellular respiration Anaerobic – in the absence of oxygen Glycolysis does not require oxygen Oxygen is required for the last two stages of cellular respiration Aerobic process – requiring oxygen Oxygen is required for the Krebs Cycle and the electron transport chain

Cellular Locations Cytoplasm Site of glycolysis Mitochondria Krebs cycle Electron transport chain

Fermentation (9.3) In the absence of oxygen, fermentation releases energy from food molecules by producing ATP

2 Types of Fermentation Alcoholic Lactic Acid Produces ethyl alcohol and CO2 Used in beer , wine and bread-making Lactic Acid Converts pyruvic acid to lactic acid Does not give off CO2 Humans produce lactic acid during exercise Certain prokaryotes/bacteria undergo this process Used widely in food production: cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut, kimchi

Energy and Exercise Only enough ATP energy in cells for a few seconds of intense activity After energy used up, muscle cells produce ATP through lactic acid fermentation Fermentation produces lactic acid as a byproduct Heavy breathing pays the oxygen debt created by exercise and rids the body of lactic acid