What are three problems that occur when the cell grows to large

1. Diffusion is too slow to provide materials to the interior of a cell that is too large. Likewise, diffusion can't adequately take out all the wastes from a cell that is too large. If diffusion is like passing buckets of water from person to person to put out a fire, this process will work well enough for a fire in a small shed. It goes fast enough to get enough water to the interior. However, if the building is large like a school, the water won't be passed in fast enough to put out the fire.  2. The DNA can't be copied fast enough to handle all the protein synthesis requirements of a cell that is too large. You know that the DNA has the instructions for making protein, and the DNA's instructions have to be copied to mRNA. This is similar to having a science lab in which the teacher has to give each pair of students oral instructions. If there are six students in the class, then the teacher can probably instruct them fast enough for them to all get the lab finished. But if there are forty students, the teacher probably can't give the instructions fast enough to take care of the needs of such a large class.  3. Large cells have a proportionately smaller amount of surface area. This is usually stated as: "Large cells have a smaller surface area to volume ratio." The surface is the plasma membrane which has the job of letting the right materials in and out of the cell. As cells increase in volume, the surface area doesn't increase at the same rate. Imagine the volume as being a room full of people, and the surface area as being the walls of the room. The walls have a door every 2 meters. If a small room is full of people, none of the people are very far from a door, and the number of doors will be adequate to let that many people out in case of an emergency. But if you picture a large room like a gym in a high school, the number of doors will not be enough to handle that many people trying to get out.

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.