What is a cell and what makes it cancerous? Part 1

As a cancer researcher I often get questions like, “how does a healthy cell become cancerous?” and “why are cancer cells bad for us?” These are valid questions that I would like to address. But before I try to answer these questions, I would like to give you a brief introduction to the human cell.

Just like the atom is the basic unit of matter, the cell is the basic unit of life and living organisms. As the smallest unit of life, cells can either work individually such as red blood cells transporting oxygen to our tissues/organs or work together to form tissues, organs and organ systems that are required for a functional organism (see figure 1). Structurally, a cell is comparable to a house. Just like a house, a cell has walls called the cell membrane. The cell membrane separates the cells interior from its external environment and consists of phospholipids (fat-derived molecules) and proteins. Proteins embedded in the cell membrane form channels across the cell membrane to allow ions and molecules to enter/exit the cell. These channels are equivalent to the door of a house.

Levels of organization

Internally, cells have compartments called organelles, which are equivalent to the rooms in a house. Just like each room in a house has a specific purpose, each organelle in the cell has a specific purpose.

Major organelles in a human cell includes the cell nucleus, which harbors our genetic material, DNA (deoxyribonucleic acid). The DNA contains all the information (genes) that is required to generate a living organism. The DNA molecule itself consists of four different molecules (guanine, adenine, thymine and cytosine) that are attached to each other to form long strands. Each strand is paired with another strand to form the double stranded DNA molecule. If one would stretch out and add up the length of all the 46 DNA molecules in a single cell, it would reach over 2 meters.

Schematic overview of the DNA molecule. G=guanine, C=cytosine, A=adenine, T=thymine

The endoplasmic reticulum (ER) is the organelle where many of the newly synthesized proteins first end up before they are transported to their final destination. In contrast to the DNA, which is the molecule that contains information that is needed to produce a protein and thus a functional cell, proteins are the molecules that do most of the physical work in the cell. Proteins are referred to as “the molecules of life”. In order for the proteins to function properly, they need to have the correct structure. It is in the ER where proteins are folded into their proper 3D structure.

Most proteins in the ER are then transported to the Golgi apparatus. The Golgi apparatus is the sorting facility of the cell. Different proteins are needed at different places in the cell. It is in the Golgi apparatus where the proteins are sorted and shipped to their final destination.

The last major organelle in a human cell is the mitochondria. Mitochondria are known as the power stations of the cell. They break down nutrients that the cells have taken up to generate energy molecules. Different types of cells have different amount of mitochondria. Muscle cells, which require a lot of energy, can have up to thousands of mitochondria while mature red blood cells lacks mitochondria.

Overview of the cell interior
Overview of the cell interior

Though a human cell is much more complex than I’ve described it, I will not go into further detail. In the next post I will discuss how a normal cell becomes cancerous and why they are bad for us.


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