They come from the atmosphere, since plants use carbon dioxide to produce carbohydrates :)
Plasma membrane is a part of the cell made of a lipid bilayer and an embedded protein layer. It protects the cell from the surroundings and also controls the materials leaving or entering the cell. The membrane is semipermeable and therefore allows certain materials to enter or leave the cell. In this case, the plasma membrane may prevent unlimited flow of water into or out of the cell.
The main difference between aerobic respiration and anaerobic respiration is that aerobic using oxygen in the reaction, while anaerobic does not.
Even though both aerobic and anaerobic respiration releases energy, but their reactants and other products are completely different.
For example in human, in aerobic respiration, oxygen and glucose reacts to give out carbon dioxide and water; while in anaerobic respiration, which usually happens during exercise when oxygen is not enough, the muscle cells uses only glucose to produce energy and lactic acid.
Therefore, the main difference is where aerobic uses oxygen, and anaerobic don’t.
Some unicellular organisms are similar to animals because they have the ability to move.
Third option
