Little
Cell, Little Cell, Let Me Come In!
By
Matt Nicholas, Exeter-Milligan Science Instructor
All living things are made
of cells that are too small to see without a microscope. They are very complex
collections of DNA, organelles, and a soup of nutrients called cytoplasm, but
all of those parts are held inside the cell by the cell membrane. This membrane
is the exterior of the cell, but it is also the bouncer or gate keeper. How then
do gases, nutrients, hormones, and other chemicals get into and out of our
cells? Well, it turns out that there are many ways to get into a cell depending
on what is knocking at the door.
The EM Biology class has been hard at work studying all methods of
membrane transport from Passive(zero energy) methods like diffusion and
osmosis, to Active(non-zero energy) methods like the Sodium-Potassium pump. On
Monday however, the class had to do a bit of acting. They got to be their best
phospholipids and act out endocytosis and exocytosis. Too keep it short,
endocytosis is when substances enter the cell by caving in and pinching off a
“bubble” of the membrane around the substance, and exocytosis is when a
“bubble” from inside the cell joins with the membrane and empties its contents
into the surroundings.
As seen in the picture, several students are linked together to
make the plasma membrane, and Selah Petersen is the substance trying to get
into the cell(top left). The students making up the membrane cave in to make
space for Selah(top right), she enters the space(bottom left), and then the
students close in on themselves making a vesicle, the bubble from earlier,
around her(bottom right). She is now inside the cell and free to do whatever
function is needed. This is the endocytosis process. If run in reverse, it
would be exocytosis.
As these processes play out on scales smaller than the hair on my
chinny chin-chin, it can be hard to comprehend, but don’t huff and puff! If you
are looking for an expert on the “in’s and out’s” of cells, just ask one of
your favorite EM Biology students!