Skip to 0 minutes and 14 seconds An individual, who has been diagnosed with cancer often has many questions about what caused the cancer, whether it could’ve been caught at an earlier stage, and what treatment is available for them. But before we go on to consider some of the really exciting current developments in cancer biology and research, we’re going to spend some time making sure we have a thorough understanding of how cells work.
Skip to 0 minutes and 38 seconds In the same way that most of us wouldn’t know how to fix the engine of a car that has broken down because we don’t understand the normal workings of a car, neither can we really even begin to start knowing how to fix a cancer cell unless we understand what is supposed to be happening in a normal cell. So with that in mind, let’s have a look in a bit more depth about what the human body is made up from. Starting at a higher level of organisation, we can see that the human body contains many organs that we’re all familiar with, such the brain, lungs, kidney, or intestines.
Skip to 1 minute and 14 seconds Organs themselves are composed of groups of tissues organised in such a way that they perform a specific function. For example, we can look at the heart and see that there are three mains tissue types present– myocardium, endocardium, and pericardium. Tissues are made up of group of cells, which have a common purpose and function. If we were to use a microscope to look more closely, we would be able to see that tissue is made up of cells. Cells, such as those we can see here are the basic building blocks of life.
Skip to 1 minute and 50 seconds Although in this course we’re focusing on humans, cells of one type or another are fundamental to all organisms, whether they’re composed of only one cell or of trillions of cells. We can’t see them without a microscope, but recent research suggests that there may be around 37 trillion cells in the human body. By using a more powerful microscope to examine an individual cell, scientists have been able to determine that a cell is actually made up of many different components. Looking at the basic cell structure, we can see that it is bound by a membrane, which defines the extra- and intracellular environments. This also regulates what comes in and out of the cell, and the rate at which this transfer occurs.
Skip to 2 minutes and 37 seconds Within the cell is the cytoplasm, which is a thick liquid holding the components of the cell. The different components or subcellular compartments we can see within the cell are called organelles. This is the way in which the cell organises the different functions that it has to undertake. Some of the organelles we can see here are mitochondria, which are involved in energy production; lysosomes, which help the cell dispose of waste products; and the Golgi body, which is responsible for packaging and transport of molecules.
Skip to 3 minutes and 13 seconds Next, we’ll take a closer look at this membrane-bound structure within the cell, called the nucleus. Within the nucleus are the chromosomes. In humans, 23 pairs– 22 pairs of autosomes and two sex chromosomes. Each of our cells carries two copies of our genome. One copy of each chromosome inherited from our mother and one copy from our father. Chromosomes are composed of DNA, or deoxyribonucleic acid. DNA is a double-stranded molecule composed of a sugar phosphate backbone linked to bases, 3 billion of them. These form the rungs of the ladder that you can see. DNA is the hereditary material that is passed down from parent to child, and the sum total of our DNA is called our genome.
Skip to 4 minutes and 3 seconds Every cell in the body carries the same DNA, and an important property of DNA is that it can copy itself exactly to pass on when it divides to form new cells. Here we’re looking at just one such chromosome pair. You can see that the bases in the DNA strand are named adenine, A, guanine, G, cytosine, C, and thymine, T. These are the letters, which allow the message of our DNA to be written in a similar way that the alphabet is the code, which is used to form words. You’ll also probably also notice that the two strands contain pairs of bases. A always pairs with T and G always pairs with C.
Skip to 4 minutes and 41 seconds Genes are made up of a specific number and order of these bases, which tell the cells which proteins they should make. On closer examination, each chromosome contains a number of genes. In humans, there are around 30,000 of these. Moving down another level again, we’re now seeing the structure of an individual gene. If you look at the structure of the gene, you’ll see that it is made up of coding sections, exons, which are surrounded by non-coding sections, introns. There are also number of regulatory sequences in the gene, particularly at the start and the end. As well as genes which code for protein, there is also a large amount of DNA, in fact the vast majority, which is not protein coding.
Skip to 5 minutes and 33 seconds Some of this non-coding sequence plays a regulatory role, but for other parts, the function has not yet been determined. We’ll be looking in this course at the role genes play in cancer so for now we’ll look a bit more at how genes help to determine what goes on in the rest of the cell. Essentially, there are two main steps by which the gene that we’ve looked at becomes a protein. The first step is called transcription. During this step, the DNA is transcribed still in the nucleus into a similar molecule called RNA. Once the RNA molecule is complete, it is processed and taken into the cytoplasm.
Skip to 6 minutes and 13 seconds Here the message is decoded and translated into a protein, which can perform specific functions within the cell. For example, here we see the haemoglobin protein, which is made up of two different protein chains encoded by genes on chromosomes 11 and 16. It helps carry oxygen round the body in red blood cells. There are also proteins, which regulates processes, such as cell proliferation and cell death, some of which are important in cancer development. So here’s a summary of what you have learned from this video. Take a moment to review the important points that we’ve covered.
Skip to 6 minutes and 56 seconds Now, that we have a good overall view of the cell, we can move on in the next video to learn about how cells grow and divide, another very important building block on our way to understanding cancer.
Before cancer: the normal cell
This video will help answer the question ‘what is a cell?’ and give you a better understanding of how the information contained in our genes is actually used in the everyday workings of a cell.
© Leah Marks, University of Glasgow