Plants, animals, humans, and bacteria all have one thing in common! All though these organisms* are very different, we all have one thing in common; we are made up of cells. To understand cells and their functions in our bodies, we must first recognize the theories associated with them.
*organisms = a living thing
The Cell Theory
There are three parts to the cell theory. This is the widely accepted belief of many scientists:
All living organisms are made up of one or more cells
The cell is the basic unit of structure and organization in organisms
Cells arise from pre-existing cells
In other words, this means that all cells are formed from cells already present (through a process known as mitosis)
Parts of a Cell
You can imagine a cell as a mini factory. In this factory, there are several machines that all have different jobs. These machines work together to help the factory function properly. In scientific terms, the "machines" inside the "factory" are similar to structures known as organelles inside our cells. The picture above represents different organelles located throughout a cell. These organelles help the cell perform duties such as growing, storing DNA, making protein, and more. In the picture below, you can find the names of all the organelles in a cell:
Mitochondria
Plasma Membrane
Microtubule
Centrosome
Microfilament
Lysosome
Smooth and Rough Endoplasmic Reticulum (ER)
Peroxisome
Vacuole
Golgi apparatus
Nucleus
Nucleolus
Ribosomes
(1) The Nucleus
The nucleus is the most important and most secure area of the cell. You can think about the nucleus as a treasure chest, because it contains a very valuable substance known as DNA. DNA contains the information your body requires to grow and function. It is safely stored in the nucleus to prevent damage. The nucleus's number one priority to store DNA, but it also has other jobs such as coordinating cell activities. You can also imagine the nucleus as the cell's control center because it oversees what the cell does, when it does it, and how it does it.
(2) The Plasma Membrane [PM]
The plasma membrane is the outer layer of all cells. Here are three main characteristics about the PM that are important to remember:
It is semi-permeable
This term indicates that the plasma membrane only allows certain compounds to enter the cell. It is like a gate-keeper.
It is made up of hydrophilic heads and hydrophobic tails
"Hydrophilic" means water-loving, which means the top of the PM is attracted to water. "Hydrophobic" means water-fearing, which means the bottom of the PM is repelled by water. The picture below demonstrates the relationship between the heads and tails of the plasma membrane
Its main purpose is to protect the cell
(3) The Ribosome
Ribosomes are the site of protein production in your cells. Ribosomes are present in the cell's cytosol* as well as on top of other organelles. The protein production process involves the following steps:
Inside the nucleus, a form of DNA known as mRNA (messenger RNA) is created through a process called transcription
The mRNA leaves the nucleus to enter the ribosome
The ribosome reads the mRNA like an instruction manual to create proteins
The ribosome assembles the different materials to create the proteins through a process called translation
Once the protein is fully made, it can begin its work in the body
(4) The Mitochondria
The mitochondria is known as the "powerhouse of the cell". It is an organelle that produces a very important compound called ATP. ATP is the body's way of storing energy that can be used later. This organelle is made up of 4 different parts: the cristae, matrix, inner membrane, and outer membrane. These different parts allow it to create ATP in an efficient manner.
Some cells have different amounts of mitochondria; this number depends on how much energy that cell uses. For example, muscle cells use a lot of energy, so they require more mitochondrion to produce larger amounts of ATP. On the other hand, skin cells do not require as much energy, so they have fewer.
Today, we've discussed only the most important organelles of a cell, but to find more information about ALL organelles, visit this site: Cell Organelles
Sources
Cells. (n.d.). Retrieved August 19, 2020, from https://www.mdpi.com/journal/cells
Libretexts. (2020, August 15). 4.1C: Cell Theory. Retrieved August 19, 2020, from https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book:_General_Biology_(Boundless)/4:_Cell_Structure/4.1:_Studying_Cells/4.1C:_Cell_Theory
Mitochondria. (n.d.). Retrieved August 19, 2020, from https://www.genome.gov/genetics-glossary/Mitochondria
Perles, C. (2017, November 21). Describe the Kinds of Molecules That Cannot Easily Diffuse Through Cell Membranes. Retrieved August 19, 2020, from https://education.seattlepi.com/describe-kinds-molecules-cannot-easily-diffuse-through-cell-membranes-4406.html
What is a cell? - Genetics Home Reference - NIH. (n.d.). Retrieved August 19, 2020, from https://ghr.nlm.nih.gov/primer/basics/cell
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