A mighty fortress is our God, A bulwark never failing.”
A Mighty Fortress is Our God, Martin Luther
Inside of each of those different types of cells, you will find even smaller parts that work together so the cell can do its job. In many ways, cells are like the castles of old, with many people striving together to build a good life and to protect themselves and their families. When you think of a castle, you might first think of the soaring towers and grand windows, but if you were to walk up to one, the first thing you would notice is the walls. Tall and imposing, these walls protect those within, but have gates that can let people and goods in and out. The castle walls are like a cell’s membrane – a thin layer that keeps a cell together and allows food and water to enter and exit the cell. In plants, they have another layer around their cell: the cell wall which provides strength and structure to help trees reach the sky.
Once you enter a castle, you would find the open space of the bailey – the courtyard inside the walls. Busy workers move to and fro through the castle, moving among the horses, the blacksmith shop, the carpenter’s, and so forth. In cells, the bailey is like the cytoplasm [sy-toe-plaz-um], a substance similar to Jell-o which gently holds all the other parts of the cell in place (although some parts can move through it). Within the cytoplasm, you will find organelles, small structures that have a specific job to do, just like the stables, forge, and, of course, the keep of the castle
What is a keep, you say (unless, of course, you just finished rocking medieval history)? It is the tower part of the castle – the part that, if you were looking at, you would likely call the castle. It is where the lord of the castle and his family live, directing all of the workers and knights in their tasks. This is like the nucleus of the cell – the part that holds the information that makes the creature the way that it is; this information is known as DNA (that stands for deoxyribonucleic acid [dee-ox-ee-rye-boe-new-clay-ick]– the scientific name for the molecule itself). These instructions are wrapped up tightly inside the nucleus and tell other parts of the cell how to function and how to make things for the creature, much like the lord gives instructions to his subjects about the crops to grow and the defenses to build.
Inside the keep, you would often find the kitchens, the place where food is made to feed everyone at the castle to give them the energy that they need in order to do their jobs. In your body, thesemitochondria([my-toe-con-dree-uh] pill-shaped organelles, often pictured with a little squiggle down the middle) take the food that you eat and turn it into a type of energy that the other parts of the cell can use. Plant cells have an additional source of energy – the chloroplasts [klor-oh-plasts] – other little pill-shaped features that have an amazing power. They can take the energy from the sun and turn it into sugar which the plant can then use to power its cells. Plants can store excess sugar in vacuoles, a blobby, sometimes kidney-shaped organelle like a castle’s storehouse. Animal cells also have vacuoles, but usually they are smaller and spherical, where they store the food and water that you eat before it goes to the mitochondria (think of the vacuoles like the root cellar that holds the apples before the kitchen mitochondria turns it into an apple pie that the people in the castle can eat).
Just like in a castle where many artisans (weapon makers, tailors, blacksmiths, and so forth) create things for the lord and the wider world, one of the main jobs of many cells is to make protein. Proteins, for those who don’t know, make muscles, send messages, and do many other jobs in your body. Proteins are made by ribosomes [rye-boe-zomes] in your cells – small balls (even by cell standards) that are found throughout the cell, but especially on the endoplasmic reticulum [en-doe-plaz-mic ruh-tick-you-lum]. The rough endoplasmic reticulum is attached to the nucleus and looks kind of like a maze with bumps all over it; the smooth endoplasmic reticulum (which lacks ribosomes) looks like sea sponges. All of these parts work together to make your cells work which allow you to stay healthy and strong, just like a medieval kingdom.
Note: There are other parts to the cell that we didn’t talk about here. Some we will visit in part 2 but others we won’t. We will learn about the most important part of the cells, but there is always more to discover in this world made by an infinite Creator.