Most animal cell membranes have proteins that pump what ions out of the cell and potassium ions into the cell.
a. calcium
b. carbon
c. magnesium
d. sodium

answer; i believe its echoic memory,it is believed to last three to four seconds; good luck

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.