What are the starting molecules of every cycle of respiration and the end products?

Question

I know glycolysis occurs in the cell membrane and may take place with or without oxygen it initially takes place in the cell membrane and continues into the cytoplasm. The result is the gain of two atp and the end product pyruvate.

The krebs cycle occurs in the mitochondria it produces the most enery

is this correct? I'm confused about:
What are the starting molecules of every cycle of respiration and the end products?

Answer 1

you are correct in what you have said.
every cycle of respiration starts with a molecule of glucose which after several steps converts into pyruvate.(2 molecules)
if then ,O2 is present, krebs cycle will occur, otherwise, fermentation takes place. end product of fermentation is a molecule of CO2 and either ethanol(plants) or lactic acid(animals). krebs cycle produces energy molecules (NADH AND FADH2 + ATP) NADH and FADH2 undergo electron transport system to yield 11 molecules of each pyruvate. thus, a total of 24(22 +1+1) ATP's are formed in kreb's cycle.CO2 is also released.
4NAD+ +FAD +2H2O +ADP +Pi +pyruvate = ATP +3CO2 +4NADH+FADH2+4H+ = 3CO2 +24 ATP (IN KREB'S CYCLE)
at the end of whole process of respiration, however, 36 ATP's are gained net (including ATP gain in other processes as well)

Answer 2

The fermentations involve the partial breakdown of glucose without using oxygen. Many prokaryotes have a variety of fermentation pathways, using a number of different fuel molecules. By definition, the end product for the
fermentations is an organic molecule. In aerobic cellular respiration, the final electron acceptor is oxygen, hence, the emphasis on oxygen in aerobic cell respiration. Some prokaryotes use anaerobic electron transfer respiration
pathways in which their final electron acceptor is an inorganic molecule such as sulfate, iron, or nitrogen compounds.

Answer 3

yes glycolysis does occur and make 2 ATP, 2NADH(conveted to FADH2), 2 Pyruvate
Krebs makes 2ATP, 6NADH, 2FADH2
Pyruvate oxidation maks 2 NADH
Then there is ETC which makes most of the ATP since FADH2 makes 2 ATP and NADH makes 3 ATP so you end up with 36 ATP
SO ETC makes the most ATP