Anaerobic Respiration and Alternative Pathways for fuel

Cellular Energy Animal (and fungi and protist) cells need to access the energy stored by photosynthesis. They release the energy stored in sugars in a process that is the reverse of photosynthesis C6H12O6 + 6O2 -------- 6H2O + 6CO2

Different Pathways after Glycolysis There are two main pathways to release energy from glucose The amount of oxygen available controls the pathway Plenty of Oxygen = Cellular Respiration Not much Oxygen = Fermentation

Two types of Fermentation Lactic Acid Fermentation: Our muscles carry this out when they run low on oxygen, producing ATP and Lactic Acid Alcoholic Fermentation: Yeast cells carry this out, producing ATP and Alcohol.

Picture of Pathway Glycolysis Lots of Oxygen Not enough Oxygen Cellular Respiration Alcoholic Fermentation Lactic Acid Fermentation

Cellular Respiration Oxygen is required Takes place in the mitochondria Produces 32-34 ATP and releases CO2 and H2O as byproducts Muscles will do this as long as they don’t run out of oxygen

Lactic Acid Fermentation Takes place when there’s not enough oxygen for cellular respiration Produces ATP, but also Lactic Acid Also regenerates the NAD+ required to continue with glycolysis. Muscles do this when they run low on oxygen Lactic Acid causes the burning sensation

Alcoholic Fermentation Occurs in organisms that do not carry out cellular respiration or lactic acid fermentation Produces ATP, but also ethanol and CO2 as byproducts. Yeast cells do this—we use them to make beer, wine, and bread.

Our Cells Will either do: Cellular respiration: During slow, steady exercise Lactic Acid Fermentation: During strenuous exercise like sprinting, or lifting heavy weights. Do not carry out alcoholic fermentation—it would kill your cells

Related Pathways to Energy Production

Carbohydrates broken into monosaccharide, then broken down for energy avg. yield of 16 kJ/g of energy Proteins broken down into amino acids to be used to produce cell’s proteins amino groups removed in deamination and converted into ammonia (wastes) rest of a.a. continue through glycolysis or Kreb’s cycle (depending on composition)

Lipids triglycerides broken into glycerol and fatty acids glycerol can be converted to glucose (by gluconeogenesis) or to DHAP or G3P (which enter glycolysis). fatty acids go to the matrix of mitochandria and undergo β-oxidation – 2 carbons at a time are chopped off into acetyl groups which combine with co-enzyme A to produce acteyl-coA (used in Kreb’s cycle) much more ATP formed than from carbs. ex lauric acid (12 C fatty acid) – produces 92 ATP average yield is 38kJ/g of energy