Cellular respiration is performed by the mitochondira; it turns glucose or food to energy that the cell can use. Photosynthesis is performed by chloroplast and is only found in plant cells; it turns the sun's energy to glucose which can be turned into energy for the plant.
The galactic disk is a component of the spiral galaxies and consists of stellar and gaseous components as it forms a random motion with the circular objects that orbit around the galactic center.
The rotational curve in a milky way is similar to that of the rotation of the universal rotating disk and is evident by the dark matter in the galaxies.
