KREB’S CYCLE

THE MITOCHONDRIA A mitochondrion is a specialized site of aerobic respiration. It is another example of endosymbiosis. Like chloroplasts, mitochondria also have their own DNA and ribosomes. They also have a large organization of membranes that provides surface area for reactions. Unlike chloroplasts, it is the inner membrane that provides this surface area, through many folds called cristae. uROUjK4

FROM CYTOPLASM TO MITOCHONDRIA Products from glycolysis (2 pyruvate and 2 NADH - what about ATP?) are first transported from the cytoplasm into the mitochondria through active transport. The pyruvate undergoes a reaction called Pyruvate Oxidation, under which the pyruvate is oxidized (and 2 more NAD + are reduced to NADH). It loses a CO 2 in the process and the remaining 2- Carbon molecule is attached to Coenzyme A to produce a molecule called Acetyl CoA. Note this is the first time CO 2 has been given off. (As this happens for each of the two pyruvates, this is 2 of the original 6 carbons found in glucose.)

THE KREB’S CYCLE Also known as the citric acid cycle, this is a cycle that occurs in the mitochondrial matrix and incorporates Acetyl CoA in order to break it down and capture its biochemical energy. It is an 8 step pathway, and it occurs twice for every molecule of glucose (2 acetyl CoA molecules that result from it).

IMPORTANT STEPS IN KREBS Important steps: 4C oxaloacetate reacts with 2C acetyl-CoA to produce 6C citrate Energy is harvested in steps 3, 4, 5, 6, and 8 For each acetyl CoA: 3 NADH, 1 GTP/ATP, and 1 FADH 2 is produced. After step 8, the oxaloacetate has been recycled, and can be used again.

FOLLOW THE CARBON By the end of Krebs cycle, all six carbon atoms of the original glucose molecule have been lost as CO 2 (which will be released as waste). All that is left of the original glucose molecule is some free energy in ATP, NADH and FADH 2. XEhB9wFk3n4r4k9KC2

FOLLOW THE ENERGY In your groups, determine all the energy products that arise from the breakdown of glucose. What is our net energy production at this point?