Cellular respiration http://www.ucsf.edu/thoracic/patient-ed_files/lung.gif

Overview: 6O2 + C6H12O6 6H2O + CO2 + energy Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. http://biology.clc.uc.edu/graphics/bio104/cellresp.jpg 6O2 + C6H12O6 6H2O + CO2 + energy

Fermentation: The process of releasing energy in the absence of oxygen www.winedefinitions.com/.../ secondary1632412.jpg

How much energy is in food? One calorie is the amount of energy needed to raise one gram of water by 1 degree Celsius. One Calorie = one kilocalorie (food labels) One gram of sugar yields 3811 calories of heat energy http://www.absolutestockphoto.com/albums/ftp_uploads/acrosthwaite/normal_Absolute_12_348.jpg

Both processes begin with glycolysis (anaerobic) The process in which one molecule of glucose is broken in half, producing 2 molecules of pyruvic acid. (3-C compound) 2 ATPs are needed to start reaction, and 4 are produced, so there is a net gain of 2 ATP. Electrons are passed to NAD+ molecules Takes place in the cytoplasm Both

Glycolysis C6H12O6 + NAD+ 2 pyruvic acids + NADH http://www.sirinet.net/~jgjohnso/glycolysis.jpg

Fermentation When oxygen is not present, fermentation releases energy from food molecules. NADH is converted back to NAD+ by passing high energy electrons to pyruvic acid, allowing glycolysis to continue. www.aberlour.com/ fermentation/

2 paths of fermentation Alchoholic fermentation: Yeasts and other microorganisms use pyruvic acid to form ethyl alchohol and CO2 and NAD+ Lactic Acid Fermentation: In some cells, such as muscle cells, pyruvic acid is converted to lactic acid and NAD+ www.houseofcraig.net/ recipe_whitebread.html library.thinkquest.org/ 5777/mus2.htm

Krebs Cycle (citric acid cycle) Pyruvic Acid is broken down to carbon dioxide in a series (5 steps) of energy-extracting reactions Takes place in the mitochondrial matrix CO2 is the by-product One glucose (2 turns of cycle)  6 NADH + 2 FADH2 + 2 ATP + 4 CO2

ELECTRON TRANSPORT CHAIN Takes place in cristae (inner mitochondrial membrane) 32 ATP produced in most eukaryotes; prokaryotes 34 High-energy electrons (from NADH and FADH2 ) are passed along a series of carrier proteins (ETC) until the end where there is an enzyme that bonds the e-’s to hydrogen ions and oxygen  water. The energy passed along the ETC is used to move H+ ions into the intermembrane space. ATP synthase provides channels for H+ ions to pass through. Each time it “rotates” an ADP and a P are attached. Aerobic respiration is about 40% efficient. The rest of the energy is lost as heat.

Energy and exercise Muscle cells normally contain small amounts of ATP, enough for a few seconds of intense activity Muscles use lactic acid fermentation (about 90 sec) Extra oxygen is needed to break it down. Glycogen is used for about 20 minutes. Then, stored molecules must be broken down