Basic Lessons in Biology: Cells

Giant cells

I’ve had the opportunity to spend time with my family in the past couple of months, and every time I talk about my research (aka my life) with my family, I realize how much jargon and scientific mumbo-jumbo clouds peoples’ understanding of the most basic biological processes. So I’m going to start writing some descriptions of biological things and try to make them as jargon-free as possible.

First up: Cells

Every cell is like a factory. Within it, there’s the nucleus, where the DNA is located, and in the factory analogy, that’s where the manager is with the blueprints for the product. There are assembly lines (ribosomes, endoplasmic reticulum, golgi apparatus) that take the instructions from the DNA and turn them into a product (proteins). The process of translating DNA into proteins is one that I’ll be talking much more about in future posts. There are vehicles (vesicles) that transport the products to other parts of the cell and to the world outside of the factory. There are generators that provide the energy needed for all of the functions of the factory (mitochondria). Each cell is a somewhat specific factory: cells in the heart are making different products than the cells in your stomach. Cells in different organs have very different jobs, and so have to make very different products. However, every cell has the same DNA, which is why in crime TV shows they can take pretty much any biological evidence (hair, skin, blood, semen, etc.) and be able to compare that to the DNA of the suspects. So how can the same DNA result in such different cells, so that some cells create the eye and others create skin?

Animal Cell Diagram

Animal Cell Diagram

Think about how a car company might manufacture cars. The executives of the company know how many of each type of car they want to produce, and they give that information to the people in charge of making each type of car. Each type of car has to have its parts produced by a factory and then assembled. So the main office of each factory has the information from the executives regarding the overall plan of the company (how many of each car type to make), and each factory has their specific job to execute to achieve the company’s goal. Together, the factories create entire cars, which together make up an entire fleet. In this example, the instructions from the executives are like the DNA. The managers of each type of car are the organs, and the factories that produce parts for specific types of cars are the cells within each organ. Putting everything together, the cells make up the organs, and the organs make up the entire organism, just as the car parts make the cars, and all of the types of cars together make up the fleet that the company has produced.

If the car analogy is not intuitive, you could also think about it like how a fashion runway outfit might come together. A fashion designer has a vision for what the final outfit will look like, including clothing, accessories, makeup, and hairstyle. However, the fashion designer has people working to on each part of the overall look, so that there’s a makeup specialist, and someone sewing the clothes. These people also rely on the manufacturers of the things they use (cloth, makeup, etc.). Based on the overall plan from the fashion designer, each group completes its task (e.g. making the clothes, applying the makeup, styling the hair) and accomplishes one part of the plan. Together, all of the pieces come together to make the whole ensemble. In this example, the DNA is the fashion designer’s plan, the organs are the people working to execute each component of the overall plan, and the cells are the people, objects, and manufacturers that allow the components to come together.

That is an explanation of how the same DNA can lead to cells having very different functions, but I also must describe the mechanism behind how cells differentiate to have specific functions, as well as how those many cells are organized into complex tissues, organs, and organisms. Cells send and receive signals, often in the form of chemicals or proteins. Commonly known examples of these types of signals are hormones (long-distance signals that communicate with cells throughout the body), neurotransmitters (short-distance signals between individuals cells in the brain), and immune response protein receptors (short-distance proteins on a cell that receive information from other cells and affect their own cell). These types of signals help communicate to a cell where it is in the body, and tells it to use the particular parts of the DNA that need to be used. Cells of similar types are organized into tissues. Muscle is a really good example of a type of tissue. Tissues are combined together to make an organ, which in turn make up organ systems, which make up an entire organism.

Cells -> Tissues -> Organs -> Organ Systems -> Organism

Cells -> Tissues -> Organs -> Organ Systems -> Organism

So, to summarize: cells are like little factories, and cells receive signals from the outside world telling them what their jobs are. Cells performing similar jobs are grouped together into tissues, and those tissues combine to make organs. An entire organism is composed of organs all working together to keep the organism alive.

Next lesson: DNA transcription & translation (turning DNA into proteins)

Please let me know what you think of this first lesson! I’d love feedback to improve, and if there’s a particular topic you’re interested in, please let me know. Put it in the comments!

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