Related Pathways of Cellular Respiration AKA… Not the hard part. In fact, if you know the normal path, this should be easy.

Alternate Fuels Carbs are the first choice. What if we don’t eat carbs? Carbs are the first choice. What if we don’t eat carbs?Proteins Proteins are the third choice of energy – after carbs and lipids. Proteins are the third choice of energy – after carbs and lipids. Amino acids undergo deamination in which the amino groups (-NH 2 ) are removed and made into ammonia. Amino acids undergo deamination in which the amino groups (-NH 2 ) are removed and made into ammonia. The remainder of the amino acid is converted into an intermediary of glycolysis or the Kreb’s cycle depending on the identity (R-group) of the amino acid. The remainder of the amino acid is converted into an intermediary of glycolysis or the Kreb’s cycle depending on the identity (R-group) of the amino acid.

Fat Fuel Lipids Lipids are the second choice for the body (despite the fact they hold more energy per unit than any carb). Lipids are the second choice for the body (despite the fact they hold more energy per unit than any carb). Triglycerides are the main fat in food – they are broken down into fatty acids and glycerol. Triglycerides are the main fat in food – they are broken down into fatty acids and glycerol. Glycerol may go through gluconeogenesis and be converted into glucose or enter glycolysis as one of the 3-carbon intermediaries. Glycerol may go through gluconeogenesis and be converted into glucose or enter glycolysis as one of the 3-carbon intermediaries. Fatty acids undergo ß-oxidation in which they are cut into 2-carbon pieces that enter the Kreb’s cycle as Acteyl-CoA’s. (Do the math – its huge!) Fatty acids undergo ß-oxidation in which they are cut into 2-carbon pieces that enter the Kreb’s cycle as Acteyl-CoA’s. (Do the math – its huge!)

Anaerobic Pathways The term “anaerobic” means “in the absence of oxygen”. The term “anaerobic” means “in the absence of oxygen”. There are many methods of anaerobic respiration but eukaryotes mostly use just two methods of anaerobic respiration – ethanol fermentation and lactate (lactic acid) fermentation. Fermentation means the process is anaerobic. There are many methods of anaerobic respiration but eukaryotes mostly use just two methods of anaerobic respiration – ethanol fermentation and lactate (lactic acid) fermentation. Fermentation means the process is anaerobic. Both processes will use glycolysis to start as it does not require oxygen. The difference will be what we do with the pyruvate at the end of glycolysis. Both processes will use glycolysis to start as it does not require oxygen. The difference will be what we do with the pyruvate at the end of glycolysis.

Why Ferment? Glycolysis occurs first and gives a small yield of ATP but in the process you use up some NAD +. Without the ETC being used because it is aerobic, the NADH’s stay as NADH’s and all of the NAD + gets used up and you can't even run glycolysis after a while. Glycolysis occurs first and gives a small yield of ATP but in the process you use up some NAD +. Without the ETC being used because it is aerobic, the NADH’s stay as NADH’s and all of the NAD + gets used up and you can't even run glycolysis after a while. You have to have a way to recycle your NAD + and NADH or you won’t even be able to get the little bit of energy glycolysis offers. That is why things run fermentation. You have to have a way to recycle your NAD + and NADH or you won’t even be able to get the little bit of energy glycolysis offers. That is why things run fermentation. It’s not a lot of energy but it is way better than no energy! It’s not a lot of energy but it is way better than no energy!

Ethanol Fermentation Ethanol fermentation is an anaerobic respiration process carried out by yeast cells – they can run fermentation and survive just fine because yeast cells do not require a lot of energy – they are boring! Ethanol fermentation is an anaerobic respiration process carried out by yeast cells – they can run fermentation and survive just fine because yeast cells do not require a lot of energy – they are boring! So here is what happens… So here is what happens… 1.Glycolysis: Glucose  2 Pyruvate 2.2 Pyruvate  2 Acetaldehyde + 2 CO Acetaldehyde  2 Ethanol During this, we get the recycling of NAD + and NADH. During this, we get the recycling of NAD + and NADH. Ethanol fermentation is used in bread, beer and wine making. Ethanol fermentation is used in bread, beer and wine making.

Ethanol Fermentation

Lactate Fermentation Lactate fermentation occurs in animals like us humans when we exert high physical demands on our body Lactate fermentation occurs in animals like us humans when we exert high physical demands on our body Our cell’s energy needs exceed our body’s ability to supply oxygen – we can’t breathe fast enough so the cells have to use something other than oxygen. Our cell’s energy needs exceed our body’s ability to supply oxygen – we can’t breathe fast enough so the cells have to use something other than oxygen. We use lactate fermentation but can’t do so for long because glycolysis does not give enough ATP to keep us going. We need a lot of ATP! We use lactate fermentation but can’t do so for long because glycolysis does not give enough ATP to keep us going. We need a lot of ATP!

Lactate/Lactic Acid Fermentation So what do we do when we can’t breathe fast enough?... So what do we do when we can’t breathe fast enough?... 1.Glycolysis: Glucose  2 Pyruvate 2.2 Pyruvate  2 Lactate The NAD + and NADH are recycled during this process. The NAD + and NADH are recycled during this process. After the strenuous activity – we still breath hard to repay the oxygen debt. The oxygen goes back in to catabolize the lactate to CO 2 and H 2 O. After the strenuous activity – we still breath hard to repay the oxygen debt. The oxygen goes back in to catabolize the lactate to CO 2 and H 2 O. We use lactic acid fermentation when we want to build muscle – feel the burn! We use lactic acid fermentation when we want to build muscle – feel the burn!

Lactate/Lactic Acid Fermentation

FIN (Yeah, you may have worked hard, but not hard enough to feel the burn.)