Introduction to Cells

The world of biology revolves around cells! The cell is the basic unit of the body and every function that the pertains to the body. It is the smallest living subdivision we have in our bodies and is diverse in structure and function.Cells make up our tissues, organs,d and systems. Since this blog is about the physiology and not anatomy I will not go too deep into cells but I will go over the basics of cells that is important to know about. Some of the topics I will go into deeper detail but in a later blog.

Cells have tiny organs-like parts in them called organelles. Organelles provide structures and compartments in the cell. They also proide isolation of chemical reactions. An importing thing to remember about organelles are that each one performs a specific function.

The cell is made of three regions: the cell membrane, the cytoplasm, and the nucleus. The first I will go over is the cell membrane; also known as the plasma membrane.

Plasma Membrane
The plasma membrane is like the "shell" of the cell. It allows isolation and privacy and has its own cellular homeostasis pattern (refer to my homeostasis section on the main page). It seperates the intercellular environment from the extracellular environment. The plasma membrane is semipermeable, which means ot is in charge of maintaining everything that goes in and out of the cell.
The plasma membrane is made out of three structural components :lipids, proteins, and carbohydrates.
I do not own any rights to this picture!!

The segment with the orange balls with the little strings is called the phospholipid bilayer. The phosholipid bilayer is considered to be ampipathic, which means it loves water and hates it. The part that loves water is polar and the part that hates water is nonpolar. The orange balls are the polar regions that float in the intra/extracellular environment. The nonpolar region is the area with the little strings. These can also be refered to as nonpolar tails. The large various shaped beings that are protruding from the cell are proteins which I will go more into detail in another blog. The phospholipid bilayer is like the skin of the cell. Its what gives the cell its body. A cell without its phospholipid bilayer is like us without skin; we would be a bunch of organs walking around exposed to the elements.

Cytoplasm

The cytoplasm is basically everything inside the cell. It consists of cytosol, organelles, and the cytoskeleton. First, I will go over the cytosol. The cytosol is the jelly-like substance inside the cell. The aqueous substance is the location for many metabolic reactions and is also responsible for the storage of fat, glycogen, and secretory vessicles. It is the medium for diffusion and is the spot where protein synthesis occurs. It hold all the organelles and the cytoskeleton.
Next I will go over the cytoskeleton. The cytoskeleton is a network of protein fibers called microfilaments and microtubles located in the cytosol. it gives the cell structural support and shape. It also gives the cell external movement. Cells use cilia and flagella for movement. Sometimes cells can even have an amoeboid type movement that will be later discussed in another blog. Think of the cytoskeleton as being like our own skeleton! Our skeleton provides support, structure, movement, and protection for our bodies!
Now I shall go over the organelles! I will only go over a few that will be important. Remember: organelles are "organs".
Lysosome: It is a membrane bound organelle containing digestive enzymes. It can breakdown large molecules for nutrient purposes and destroy bacteria and old organelles. Think of the lysosome as the stomach of the cell. Since the lysosome contains all those digestive enzymes, breaking it would be bad. The enzymes would start digesting everything including the cell itself. This can be a good thing or a bad thing.
Mitochondria: It is a double membrane bound organelle with folds on the inside. Inner fold is called is called the cristae which surrounds the matrix, the space withing the cristae.

The mitochondria is the "powerhouse" of the cell. It is in charge of making the fuel for the cell called ATP (ATP  is very very very important so you gotta remember this!!!!) ATP is created by using the energy released from the breakdown of food. I will go more into detail about this process later. Mitochondria are unique because they posess their own DNA! All of the mitochondria in a person's body came from the mother's egg cell. Mitochondria is STRICTLY mother to child.
Ribosomes: Ribosomes free float of are attatched to the RER(rough endoplasmic reticulum). There is a large protein-RNA complex with ribosomes. Think of ribosomes as being a "protein factory". They synthesize proteins based on triplets of codons on a mRNA(dont worry I will have a blog specifically on this topic).
Rough Endoplasmic Reticulum (RER): The RER is coated with ribosomes which is what gives it that rough surface. This is just another work station for protein synthesis only any proteins created in the ribosomes are further modified in the golgi complex. It synthesizes proteins for the cell membrane (which are inserted into the membrane via vessicle), lysosomes, or to be exported outside of the cell.
Golgi Complex/Apparatus: They look like a flatten stack of pancakes! This folds that create the stacks are called cisternae. The Golgi Complex takes those those proteins made in the RER and completes them by modifying (posttransitional modifications), sorting them in a vessicle, then directing the finished products to their destinations.
Vessicle: Think of a vessicle being like mail.  It is a small membrane bound pod that it used to transport materials within the cell. It can carry proteins or nutrients to different parts of the cell. A vessicle can either fuse with the plasma membrane to secret wastes or bind with another organelle like a lysosome.
Smooth Endoplasmic Reticulum (SER): The SER contains no ribosomes and has a smooth surface. In it in charge of lipid synthesis, Calcuim storage, metabolizing various molecules, and the breakdown of carbohydrates.
Whew thats most of the important organelles! If there is a specific organelle you would like to know about that I didnt mention here just let me know.

Nucleus
The nucleus is like the brain of the cell; the control center. It contains information about protein synthesis. The nucleus is double membrane bound and along its surface are nuclear pores. An important thing to remember about the nucleus is that it contains chromotin. Inside the nucleus is another pod called the nucleolus! Inside the nucleolus is where RNA is synthesized.


Well thats basically the basics of cells. These notes were based off of actual notes from myself while I was in the class and further research outside the class. I also used the notes from my AWESOME professors who kindly handed them down to me and contributed extra information about this section. This information was also checked and clarified from various physiology books. For the pictures, I do not own any rights to them! If you have any questions feel free to ask on my blogspot or email me!