Cellular Respiration Chapter 6

Energy Flow and Chemical Cycling in the Biosphere  Fuel molecules in food represent solar energy traced back to the sun  Animals depend on plants: to convert solar energy to chemical energy In form of sugars and other organic molecules

Producers and Consumers  Autotrophs Producers Make own organic matter from inorganic nutrients Photosynthesis  Heterotrophs Consumers Cannot make organic molecules from inorganic ones Cellular respiration

Chemical Cycling between Photosynthesis and Cellular Respiration  The ingredients for photosynthesis: CO 2 obtained from the air H 2 O obtained from the damp soil  Chloroplasts rearrange the atoms of these ingredients produce sugars (glucose) and other organic molecules Oxygen gas a by-product of photosynthesis

Cellular Respiration  Release of energy from molecules accompanied by the use of this energy to synthesize ATP molecules  Metabolic pathway  Main method that chemical energy is harvested from food and converted to ATP  Aerobic Requires oxygen and gives off carbon dioxide  Oxidation – reduction reaction Glucose oxidized Oxygen reduced

Redox Reaction (O-R)  Chemical reaction that transfers electrons from one substance to another  Oxidation Loss of electrons  Reduction Acceptance of electrons Oxidation Reduction

ATP  Adenosine triphosphate (ATP) Nucleotide with the base adenine and the sugar ribose Main energy carrier in cells Formed during reactions that breakdown organic compounds to CO 2 and water  Requires ample oxygen  Occurs within the mitochondrion Hydrolyzes phosphates to release energy  form adenosine diphosphate (ADP)

Cellular respiration  Cellular respiration and breathing are closely related Cellular respiration requires a cell to exchange gases with its surroundings Breathing exchanges these gases between blood and outside air

Where Is the Energy in Food?  The process of aerobic respiration requires oxygen and carbohydrates C 6 H 12 O O 2  6 CO H 2 O + energy  The products are carbon dioxide, water, and energy (heat or ATP)

The Players….  Glucose  NAD  FAD

Where Is the Energy in Food?  Cellular respiration takes place in three stages: 1. Glycolysis 2. Citric Acid Cycle 3. Electron transport

1. Glycolysis  Occurs in the cytoplasm  Glucose split into 2 molecules Pyruvate  Does not require oxygen to generate ATP  Then, enters aerobic or anaerobic reactions

2. Citric Acid Cycle  “Krebs Cycle”  occurs within the mitochondrion  Converts pyruvic acid – acetic acid – Acetyl CoA  electrons passed to an electron transport chain in order to power the production of ATP

3. Electron transport chain  Uses electrons to make ATP  NAD & FAD Carry electrons from the cytoplasm or the mitochondrial matrix and carry them to the mitochondria NADH and FADH 2 transfer their electrons to a series of membrane-associated molecules

Fermentation  Occurs when O 2 is not available  Animal cells convert pyruvate to lactate  Other organisms convert pyruvate to alcohol and CO 2