Aerobic Respiration: Glycolysis, Pyruvate Oxidation & the Citric Acid Cycle Image of glucose powder from: http://www.starchdextrinadhesives.com/glucose-powder.htm

Glycolysis found in almost all living organisms occurs in the cytoplasm does not require oxygen first stage of aerobic cellular respiration

Reactions of Glycolysis 10 enzyme-catalyzed reactions 6-carbon glucose is split into two 3-carbon pyruvate molecules net energy gain of 2 ATP 2 NAD+ are reduced to NADH occurs in three stages

What does the term phosphorylation mean? What does isomerization mean?

Investment (#1-3) glucose undergoes two phosphorylations & an isomerization 2 ATP are invested Phosphorylation: glucose --> glucose-6-phosphate Isomerization: G6P --> fructose 6-phosphate Phosphorylation F6P --> fructose 1,6-biphosphate Image from: http://www.angelfire.com/sc3/toxchick/biolchem/biolchem06.html

Cleavage (#4-5) splits into two 3-carbon molecules: G3P & DHAP DHAP isomerizes into G3P Image from: http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/part2/glyc olysis.htm

Energy pay-off (#6-10) 4 ATP are made (net 2 ATP) some electrons & protons are released & stored for ETC (2 NADH) Final result: 3-carbon pyruvate (x2) Image from: http://cnx.org/content/m44432/latest/?collection=col11448/1.1

2 pyruvate + 2 NADH + 2 H+ + 2 ATP Energy Yield 2 NADH per glucose molecule 2 molecules of ATP are used 4 molecules of ATP are produced overall net yield of 2 ATP per glucose molecule Net Equation glucose + 2 NAD+ + 2 ADP + 2 Pi -----> 2 pyruvate + 2 NADH + 2 H+ + 2 ATP

Aerobic Respiration: Glycolysis, Pyruvate Oxidation & the Citric Acid Cycle

The Transition Reaction -Pyruvate Oxidation Before pyruvate enters the Krebs Cycle, it is oxidised in the transition step. Pyruvate molecules are actively transported into the mitochondrial matrix.

The Transition Reaction -Pyruvate Oxidation Carbon dioxide is removed from the pyruvate Hydrogen atoms are removed and transferred to NAD+. reactions are carried out by enzymes A 2-carbon compound called an acetyl group is formed & is attached to coenzyme A. The resulting acetyl CoA can enter the Citric Acid Cycle.

If no ATP is created in the pyruvate oxidation stage, does that mean no energy is harvested?

Aerobic Respiration: Glycolysis, Pyruvate Oxidation & the Citric Acid Cycle

The Citric Acid Cycle (Krebs)

The Citric Acid (Krebs) Cycle Acetyl CoA from the transition step is combined with a 4C compound called oxaloacetate, forming 6C citrate. Citrate undergoes a series of decarboxylation and dehydrogenation reactions which result in the regeneration of oxaloacetate.

The Krebs Cycle

Products of the Krebs Cycle Each turn of the Krebs Cycle produces: 4 molecules of reduced NAD+ (1 from Pyr Ox) 1 molecule of reduced FAD 1 molecule of ATP 3 molecules of CO2 (1 from Pyr.Ox.) The Krebs Cycle turns twice for every glucose molecule broken down; per glucose molecule the yield is doubled: 8 NAD+; 2 FAD; 2ATP and 6 CO2

What is left of the glucose molecule at the end of the citric acid cycle? How many ATP have been produced so far?