They are both sources of energy. They are almost exactly the same however ATP-Adenosine Triphosphate has one more phosphate group than ADP-Adenosine Diphosphate.
The cell membrane is also called selectively permeable membrane for the sole reason being it is selective in nature.
It forms a physical barrier and as a barrier between the cell and the external environment as it allows only selected necessary molecules to pass through it and at the same time prevents entry of unwanted / unnecessary substances.
It also regulates the entry and exit of molecules into and out of the cell.
The cell membrane permits the entry of vital molecules like
<span>water, oxygen, amino acids and glucose into the cell as they are crucial for various life processes and at the same time metabolic waste products are expelled through the cell membrane.</span>
Atmosphere? I am not really sure what you are asking.
