Cell Division – An Intro

When cells grow, the run into a problem.  As the cell grows in size, their surface area to volume ratio changes.  As it turns out the higher the volume is in relation to the surface area, the more difficult it becomes to diffuse enough material into the cell.  Think of a city with 1 road.  As the town grows, the main road doesn’t change much.  Sure you may be able to add in a few extra lanes, but the town can grow rapidly in every direction but the road can only grow a little bit.  So when before a cell gets too big to function properly, the cell divides.

In order for both of the daughter cells (the new cells) to be able to survive and work properly, the cell needs to do a little prep work.  In eukaryotes like your venus fly trap, a wild capybara, and even you & me the process of dividing is commonly called mitosis.  More accurately, however, the process is called the M stage of the cell cycle.  In the M stage, two things occur, 1) mitosis, in which the cell’s chromosomes are divided and 2) cytokinesis, in which a cell’s cytoplasm divides in half.  (In prokaryotes, like amoeba, cell division is usually referred to as asexual reproduction, but it is still the same process.)  The actual prep work of division, though, occurs in the rest of the cell cycle.

The Cell Cycle

The cell cycle can be easily broken into two parts: 1) cell division, and 2) interphase.  A great deal happens in both of these parts of the cycle, so we’ll look at them separately.  Today I give you interphase.  Cell division will be in my next post.

Interphase  is made up of 3 parts, which we’ll look at in order.

• First is G1 phase (growth phase), in which cells do most of their growing.  They grow in size as well as make new organelles and proteins.
• Next is S phase (DNA replication phase), in which cells replicate its chromosomes and additional proteins are produced.
• Following that is G2 phase (mitosis preparation phase), in which the cell produces organelles and other molecules necessary for M phase.

You know I’m no artist… well below is my cell cycle diagram.  Yes it took me 3 days despite the fact it looks like a 3-year old drew it.  If you don’t understand it, feel free to ask questions!