Aresearch group has discovered an organism with cells that contain a previously undescribed organelle. they do some tests on the isolated organelle to see if it is involved in any major metabolic reactions. to do this, they incubate these organelles for a period of time and determine changes in the amount of various substances in the suspending solution. the results follow.

glucose: none
co2: increase
o2: none
atp: increase
nadh: increase

based on this analysis, which part of cellular respiration do you conclude is taking place in this organelle?

a) pyruvate oxidation
b) citric acid cycle
c) glycolysis
d) electron transport chain/oxidative phosphorylation
e) glycolysis and the citric acid cycle

B) citric acid cycle

Explanation:

Citric acid cycle or Krebs cycle is a part of cellular respiration and occurs in mitochondria in eukaryotes. In this process oxidation of acetyl-coA ( which comes from carbohydrates, fats and proteins) takes place and energy is released.

Along with acetyl-coA, water is also used and in the end NAD+ is reduced to NADH, ATP is produced and by product CO2 is generated. ATP is used as a source of energy. NADH also enters electron transport chain in next stage for production of more ATP.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!