Getting things into the cell: Mediated Transport

There are different methods of getting things into and out of cells. The method of movement depends on the chemical structure, size, and polarity of the molecule. 

In order to best understand this, lets first take a look at the structure of a plasma membrane. 

The plasma membrane can best be described by the Fluid Mosaic Model. The plasma membrane or cellular membrane is a double-layered membrane that serves to protect the cell from its external environment. It is mostly composed of phospholipids, which have polar head groups facing the outside (since they are hydrophilic or water-loving) and non-polar hydrophobic (water-hating) tails made up of Fatty Acids. 

Now in order for a molecule to get into or out of the cell, it needs to cross this plasma membrane. There are several different methods to accomplish this:

1. Simple Diffusion: this allows you to cross the membrane by simply diffusing through it. In order to do this however, the molecule must be small enough and it cannot be polar. 
2. Protein Channels: this are areas in the lipid bilayer membrane that allow small polar molecules to cross the membrane. 
3. If the molecule is too polar and/or large and is unable to enter the cell via simple diffusion, then  a carrier is needed. Carriers are used to literally move the molecule from one side of the cell to the other. 

Most molecules will require a carrier to enter the cell. This is called Mediated Transport and there are different versions of this movement. It can be active or passive depending on the factors and conditions. Active Mediated Transport moves a molecule against its concentration gradient into the cell using the power of ATP (Adenosine Triphosphate). Passive Mediated Transport is... passive. 

The take home message in all of this is that if a molecule is polar then it can only cross the membrane by either a channel or a pump. A great way to learn through books, blogs, and tons of apps is through the new Kindle Fire. Shop Amazon - All - New Kindle Paperwhite  

What cells look like under a microscope:

This cell is undergoing Mitosis. Specifically Metaphase

The Eukaryotic Cell: Essentials Everyone Should Know

We begin our journey through the body by taking a look at one of the most fundamental topics in Biology, the cell. We will take a closer look at what a cell is made up of in order to fully appreciate the functionality and purpose of them. The cell is made up of many different things that we call organelles. These organelles are inside the cell and contain different functions. 

What are cells? 

Eukaryotic cells are found in mammals like yourself. Cells are the basic structures that combine to form specific tissues in the body, and these tissues will eventually form organs.

Functions of cells:

Cells are important in every process that takes place in your body- metabolism, communication, cell signaling, energy production, protection from harmful invaders, the list is endless. The important thing to understand is that cells specialize in certain functions depending on where in the body they are located. The cells making up your skin for example are made up of many epithelial cells. Other epithelial cells can line an organ that has contact with an outside environment.

Parts of cells:

All eukaryotic cells contain a nucleus that is enclosed by a nuclear membrane or envelope. The nucleus is the most important part of a cell because it contains all of your DNA and RNA, and other important genetic information. The nuclear membrane encloses the nucleus in order to protect all of that important information located inside of it by choosing what goes in and what goes out, this is called selective permeability.

Also located inside the cell is the Mitochondria, this is the powerhouse of the cell and functions to make energy in the form of ATP for various metabolic processes. An interesting fact about the Mitochondria is that you get EVERY mitochondrion in your body from your mother! How special of a gift!

The Golgi Apparatus is the packing and distributing center of your cell, think of this one as the warehouse for UPS, it sorts and packages everything that is about to get kicked out into the world. It does this by using secretory vesicles.

The Endoplasmic Reticulum or E.R.  can be smooth or rough. Rough E.R. functions to make proteins using the Ribosome studs that are located on the surface. Smooth E.R. functions in the metabolism of carbohydrates and lipids, among other things.

Centrioles are important for structure,  and they are made up of microtubules. Microfilaments are another important cytoskeletal component that help in cellular specializations like muscle movement.

Other organelles are lysosomes, glycogen particles and polyribosomes. Lysosomes are important because they function in programmed cell death by lysing and releasing all the chemicals inside. This process is called Apoptosis.

So there you have it! These are the fundamentals that everyone should know!

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