The cell membrane acts as a barrier between the cell and its environment. which best describes the type of barrier that the cell membrane forms? a. impermeable, like a brick wall.
b. permeable but selective, like a wall with gates.
c. very permeable, like a fishing net.
d. permeable only to water, like a very fine net.

not only is it colder, it also becomes darker, less salty, and more dense.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.