People with HIV are unable to fight off these rare diseases because they have a weakened immune system.
It would be the nuclear membrane
What ecosystem are you talking about ?
Cellular respiration is the metabolic process by which a cell produces usable energy in the form of ATP. In order to accomplish this cells require Glucose and Oxygen to form the reaction which produces ATP and the byproducts of Water and CO2.
In reality its a complex topic however this is the basic form.
