Review • Cellular respiration requires O2 to produce ATP • Glycolysis can produce ATP with or without O2 What happens if oxygen is not available? In the absence of O2 glycolysis couples with fermentation to produce ATP Fermentation and Cellular Respiration Compared… • Both use glycolysis to break down glucose to pyruvic acid • Cellular respiration produces much more ATP!! Fermentation • Enables some cells to produce ATP without the use of oxygen • Produces a limited amount of ATP from glucose without an ETC (electron transport chain) • Produces ethyl alcohol or lactic acid Two common types: 1. Alcoholic fermentation 2. Lactic acid fermentation Alcohol Fermentation • Pyruvic acid is converted to ethanol in two steps, releasing CO2 • Example: - yeast used in brewing, winemaking and baking Lactic Acid Fermentation • Pyruvic acid is reduced to NADH forming lactate as an end product with no release of CO2 • Examples: - used by some fungi and bacteria to make cheese and yogurt -human muscle when O2 is scarce Fermentation in Human Muscle Cells • Human muscle cells can make ATP with and without oxygen – They have enough ATP to support activities such as quick sprinting for about 5 seconds – A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds • (That’s why some power athletes consume large quantities of creatine) – To keep running, your muscles must generate ATP by the anaerobic process of fermentation FEELING THE “BURN” When you exercise: – Muscles need energy in order to perform work – Your cells use oxygen to release energy from glucose – If you exercise too hard, your muscles shut down from a lack of oxygen FEELING THE “BURN” (2) – Without enough oxygen, muscle cells break down glucose to produce lactic acid – Lactic acid causes the “burn” associated with heavy exercise – Lactic acid is toxic. So if too much lactic acid builds up, the body lets you know through pain – the “burn” Conditioning: • Physical conditioning allows your body to adapt to increased activity • The body can increase its ability to deliver oxygen to muscles • Lactic acid starts to accumulate in the muscles once you start operating above your anaerobic threshold. This is normally somewhere between 80% and 90% of your maximum heart rate (MHR) in trained athletes. Runners: • Runners need to complete long runs to develop the aerobic capacity • This happens by means of capillarisation (formation of more small blood vessels, thus enhancing oxygen transport to the muscles) • This creates greater efficiency in the heart and lungs. • If the aerobic capacity is greater, it means there will be more oxygen available to the working muscles and this should delay the onset of lactic acid at a given work intensity.