Cellular Respiration

Where do organisms get energy? Organisms get energy from food molecules which contain energy that is released when their chemical bonds are broken.

What is a calorie? The amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. The Calorie (capital C) that is used on food labels is a kilocalorie, or 1000 calories.

Calories The energy stored in each of the macromolecules varies because of their chemical structures, therefore their energy-storing bonds, differ.

Calories Cells don’t burn food and release energy as heat. They break down food molecules gradually, capturing a little bit of chemical energy at key steps to produce ATP. Remember: ATP is cell energy

Oxygen Requirements Aerobic- require oxygen Anaerobic- does not require oxygen

What is cellular respiration? The process that releases energy from food in the presence of oxygen 6 O2+C6H12O66 CO2+ 6 H2O+ Energy Oxygen+Glucose Carbon Dioxide+Water+Energy

Cellular Respiration Involves a series of controlled reactions that slowly release energy. If the energy were to be released too suddenly, most of it would be lost in the forms of light and heat

The Steps of Cellular Respiration

Glycolysis During glycolysis, one molecule of glucose is transformed into two molecules of pyruvic acid and energy is released

Glycolysis In the process of glycolysis, 2 ATP molecules are used and 4 are made, for a net increase of 2 molecules. Although the energy yield is small, the process is so fast that cells can produce thousands of ATP molecules in just a few milliseconds

Glycolysis Glycolysis does not require oxygen. This means that it can quickly supply chemical energy to cells when oxygen is not available.

The Krebs cycle During the Krebs cycle, pyruvic acid is broken down into carbon dioxide (requires oxygen) The Krebs cycle begins when pyruvic acid passes through the two membranes of the mitochondria and into the matrix (the innermost compartment of the mitochondria)

The Krebs cycle The Krebs cycle results in 1 ATP molecule for every 1 molecule of pyruvic acid. The carbon dioxide that is produced is expelled in every exhalation.

The Electron Transport Chain The electron transport chain uses high- energy electrons from glycolysis and the Krebs cycle to create ATP (requires oxygen) For every 1 molecule of glucose, 32 molecules of ATP are created.

Cellular Respiration Totals Together, glycolysis, the Krebs cycle, and the electron transport chain release about 36 molecules of ATP per molecule of glucose. Aerobic conditions enable the cell to produce 18 times as much energy than anaerobic alone. The 36 ATP molecules generated represent about 36% of the total energy of glucose. The remaining 64% is released as heat.

Cellular Respiration vs. Photosynthesis Photosynthesis removes carbon dioxide from the atmosphere, and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere, and cellular respiration uses that oxygen to release energy from food.

What is fermentation? An anaerobic process that occurs in the cytoplasm of cells that releases ATP from food molecules. Takes place after glycolysis

Alcoholic Fermentation Produces alcohol and carbon dioxide from pyruvic acid Performed by yeasts and other microorganisms Used to make alcoholic beverages and causes bread to rise

Lactic Acid Fermentation Produces lactic acid from pyruvic acid Performed by most organisms, including us Prokaryotes are used to make cheese, yogurt, buttermilk, and sour cream