When blood supplies oxygen and food to a cell surface and these molecules diffuse across, we might expect some "resting time." H
owever, if we inspected most cell membranes in a living human body, we would find a nearly continuous flow of substances back-and-forth across the plasma membrane. Which of the following is not a reason why? a) Cell metabolism is constantly using up oxygen and raw materials; this lowers their concentration so more will diffuse into the cell. b) Cell metabolism is constantly producing waste molecules; this increases their concentration so more will diffuse out of the cell. c) Cells produce useful secretions; this increases their concentration and more will diffuse out of the cell. d) Cell metabolism constantly produces carbon dioxide in respiration; this increases its concentration so more will diffuse out of the cell. e) Cells are living entities and in order to live can never "rest".
Blood is the main connective tissue of the body. Blood helps in the transport of oxygen, nutrients and the excretory product of the body. Blood also provides immunity as it contains white blood cells.
The resting time is expected during the diffusion process. But the substance continuous back and forth in the body. This is because cells are the main living entity of the organism. The cells are never at rest in order to live and their resting time is not possible.
Pangaea or Pangea ( /pænˈdʒiːə/) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from earlier continental units approximately 335 million years ago, and began to break apart about 175 million years ago.
