Answer:
A cell wall is a structural layer surrounding
of plant cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism
Oxygen and carbon dioxide is exchanged by the millions of alveoli in the lungs and the capillaries that envelop them. we inhale oxygen (which is then exchanged with carbon dioxide in the lungs) and then we exhale the carbon dioxide. although, the air that we breathe usually consists more nitrogen than oxygen.
Endothermic reactions are chemical reactions that absorb more energy than they release.
