Cellular Respiration

How do living things get the energy they need to survive? From the food they eat! Remember the gummy bear?!?

Chemical Energy and Food One gram of glucose (C6H12O6), when burned in the presence of O2, releases 3811 calories of heat E. A calorie is a measure of energy. In respiration, Cells release the energy from glucose, which is stored in chemical bonds, beginning with GLYCOLYSIS!

Overview of Cellular Respiration Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. Equation: 6O2 + C6H12O6 → 6CO2 + 6H2O + energy oxygen + glucose → carbon dioxide + water + energy MEMORIZE THIS! (Psst - Look familiar?!)

Photosynthesis and Respiration make a cycle called the Carbon cycle. YES! The equation for cellular respiration is the exact opposite of that of photosynthesis! Photosynthesis: 6CO2 + 6H2O + energy → 6O2 + C6H12O6 Respiration: 6O2 + C6H12O6 → 6CO2 + 6H2O + energy Photosynthesis and Respiration make a cycle called the Carbon cycle.

Overview of Cellular Respiration

Overview of Cellular Respiration Two main stages: 1. glycolysis (in the cytoplasm) 2. Aerobic Respiration (in the mitochondria)

The First Step: Glycolysis Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of ATP

The First Step: Glycolysis cells have to put in (use) 2 ATP’s to get glycolysis started, but 4 ATP’s are produced at the end of glycolysis, for a net gain of 2 ATP’s

The First Step: Glycolysis this process is so fast that thousands of ATPs can be produced in a few milliseconds! Glycolysis does NOT require oxygen!

The First Step: Glycolysis ATP goes off to the other parts of the cell to do work The other products of glycolysis are sent off to the mitochondria to be further broken down to produce much more energy rich ATP!

What if oxygen is NOT present? if there is no oxygen present, glycolysis is followed by another pathway, Anaerobic Fermentation. (Anareobic means “no air”)

Two types of fermentation 1. Alcoholic Fermentation 2. Lactic Acid Fermentation

Alcoholic Fermentation used by yeasts (& other microorganisms) equation: pyruvic acid + NADH  alcohol + CO2 + NAD+ Creates CO2 and alcohol

Lactic Acid Fermentation equation: pyruvic acid + NADH  lactic acid + NAD+ LAF is a back up fermentation for your cells when they don’t get enough Oxygen. This is why your muscles burn when you work out. lactic acid is also a waste product for some organisms to make food and beverages such as cheese, yogurt, buttermilk, and sour cream

What if there is Oxygen?… If there IS oxygen present, Aerobic Respiration follows Glycolysis.

The Krebs Cycle The second part of respiration occurs in the mitochondria It can produce a LOT more ATP than glycolysis.

The Totals Glycolysis only produces 2 ATP molecules per one glucose With O2, glycolysis and Aerobic Respiration produce 36 ATP molecules per one glucose!

Energy and Exercise At the start of a race, your body has access to 3 ATP sources: 1. stored ATP already in muscles 2. new ATP made by lactic acid fermentation 3. new ATP made by cellular respiration

Energy and Exercise: Quick Energy stored ATP can provide E for a few seconds (50 meters) new ATP made by lactic acid fermentation provides energy for about 90 sec (200-300 meters) lactic acid fermentation produces lactic acid, which can only be rid of with extra oxygen – where does this come from? heavy breathing after the race!

Energy and Exercise: Long-Term Energy your body uses ATP from cellular respiration for endurance races cellular respiration releases energy more slowly than fermentation, which is why athletes have to pace themselves after 15-20 min of activity, your body uses energy from other stored molecules (such as fats) for energy, which is why aerobic forms of exercise are good for weight loss

Comparing Photosynthesis & Cellular Respiration function energy capture energy releases location chloroplasts mitochondria reactants CO2 and H2O C6H12O6 and O2 products equation 6CO2 + 6H2O → C6H12O6 + 6O2 C6H12O6 + 6O2 → 6CO2 + 6H2O energy energy