Title: Cellular waste product
Content:  When in the presence of oxygen, cells use aerobic respiration to obtain energy from glucose molecules. Simplified Theoretical Reaction: C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O(l) + ~ 30ATP Cells undergoing aerobic respiration produce 6 molecules of carbon dioxide, 6 molecules of water, and up to 30 molecules of ATP (adenosine triphosphate), which is directly used to produce energy, from each molecule of glucose in the presence of surplus oxygen. In aerobic respiration, oxygen serves as the recipient of electrons from the electron transport chain. Aerobic respiration is thus very efficient because oxygen is a strong oxidant. Aerobic respiration proceeds in a series of steps, which also increases efficiency - since glucose 
Title: Dioxygen in biological reactions
Content: + 6 → 6 + 6 + 2880 kJ/mol Molecular oxygen, O2, is essential for cellular respiration in all aerobic organisms, providing most of the chemical energy released. Oxygen is used as an electron acceptor in mitochondria to generate chemical energy in the form of adenosine triphosphate (ATP) during oxidative phosphorylation. The reaction for the aerobic respiration is essentially the reverse of photosynthesis, except that now there is a large release of the chemical energy of O2, which is stored in ATP molecules (up to 38 ATP molecules are formed from one molecule of glucose). The simplified version of this reaction is:
Title: Cellular respiration
Content:  This is also called the Krebs cycle or the tricarboxylic acid cycle. When oxygen is present, acetyl-CoA is produced from the pyruvate molecules created from glycolysis. Once acetyl-CoA is formed, aerobic or anaerobic respiration can occur. When oxygen is present, the mitochondria will undergo aerobic respiration which leads to the Krebs cycle. However, if oxygen is not present, fermentation of the pyruvate molecule will occur. In the presence of oxygen, when acetyl-CoA is produced, the molecule then enters the citric acid cycle (Krebs cycle) inside the mitochondrial matrix, and is oxidized to CO2 while at the same time reducing NAD to NADH. NADH can be used by the electron transport chain to create further ATP as part of oxidative phosphorylation. To fully oxidize the equivalent of one 
Title: Cellular respiration
Content:  molecule, two acetyl-CoA must be metabolized by the Krebs cycle. Two low-energy waste products, H2O and CO2, are created during this cycle. The citric acid cycle is an 8-step process involving 18 different enzymes and co-enzymes. During the cycle, acetyl-CoA (2 carbons) + oxaloacetate (4 carbons) yields citrate (6 carbons), which is rearranged to a more reactive form called isocitrate (6 carbons). Isocitrate is modified to become α-ketoglutarate (5 carbons), succinyl-CoA, succinate, fumarate, malate, and, finally, oxaloacetate. The net gain from one cycle is 3 NADH and 1 FADH2 as hydrogen- (proton plus electron)-carrying compounds and 1 high-energy GTP, which may subsequently be used to produce ATP. Thus, the total yield from 1 glucose molecule (2 pyruvate molecules) is 6 NADH, 2 FADH2, and 2 ATP.
Title: Cellular respiration
Content:  of the ATP produced by aerobic cellular respiration is made by oxidative phosphorylation. The energy of O2 released is used to create a chemiosmotic potential by pumping protons across a membrane. This potential is then used to drive ATP synthase and produce ATP from ADP and a phosphate group. Biology textbooks often state that 38 ATP molecules can be made per oxidized glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system). However, this maximum yield is never quite reached because of losses due to leaky membranes as well as the cost of moving pyruvate and ADP into the mitochondrial matrix, and current estimates range around 29 to 30 ATP 
Title: Biochemistry
Content:  In aerobic cells with sufficient oxygen, as in most human cells, the pyruvate is further metabolized. It is irreversibly converted to acetyl-CoA, giving off one carbon atom as the waste product carbon dioxide, generating another reducing equivalent as NADH. The two molecules acetyl-CoA (from one molecule of glucose) then enter the citric acid cycle, producing two molecules of ATP, six more NADH molecules and two reduced (ubi)quinones (via FADH2 as enzyme-bound cofactor), and releasing the remaining carbon atoms as carbon dioxide. The produced NADH and quinol molecules then feed into the enzyme complexes of the respiratory chain, an electron transport system transferring the electrons ultimately to oxygen and conserving the released energy in the form of a proton gradient over a membrane (inner mitochondrial membrane in eukaryotes). Thus, oxygen is reduced 
Title: Soil respiration
Content:  The tricarboxylic acid (TCA) cycle – or citric acid cycle – is an important step in cellular respiration. In the TCA cycle, a six carbon sugar is oxidized. This oxidation produces the CO2 and H2O from the sugar. Plants, fungi, animals and bacteria all use this cycle to convert organic compounds to energy. This is how the majority of soil respiration occurs at its most basic level. Since the process relies on oxygen to occur, this is referred to as aerobic respiration.
Title: Carbon dioxide
Content:  Yeast metabolizes sugar to produce CO2 and ethanol, also known as alcohol, as follows: All aerobic organisms produce CO2 when they oxidize carbohydrates, fatty acids, and proteins. The large number of reactions involved are exceedingly complex and not described easily. Refer to (cellular respiration, anaerobic respiration and photosynthesis). The equation for the respiration of glucose and other monosaccharides is: Anaerobic organisms decompose organic material producing methane and carbon dioxide together with traces of other compounds. Regardless of the type of organic material, the production of gases follows well defined kinetic pattern. Carbon dioxide comprises about 40–45% of the gas that emanates from decomposition in landfills (termed "landfill gas"). Most of the remaining 50–55% is methane.
Title: Aerobic organism
Content: C6H12O6 + 6 O2 + 38 ADP + 38 phosphate → 6 CO2 + 44 H2O + 38 ATP A good example is the oxidation of glucose (a monosaccharide) in aerobic respiration:  where glucose releases the chemical energy stored in the relative weak double bond of oxygen. This equation is a summary of what happens in three series of biochemical reactions: glycolysis, the Krebs cycle, and oxidative phosphorylation.
Title: Citric acid cycle
Content:  Products of the first turn of the cycle are one GTP (or ATP), three NADH, one FADH2 and two CO2. Because two acetyl-CoA molecules are produced from each glucose molecule, two cycles are required per glucose molecule. Therefore, at the end of two cycles, the products are: two GTP, six NADH, two FADH2, and four CO2. The above reactions are balanced if Pi represents the H2PO4− ion, ADP and GDP the ADP2− and GDP2− ions, respectively, and ATP and GTP the ATP3− and GTP3− ions, respectively. The total number of ATP molecules obtained after complete oxidation of one glucose in glycolysis, citric acid cycle, and oxidative phosphorylation is estimated to be between 30 and 38.

Question: how many co2 molecules are produced in aerobic respiration?
Answer: 6.