Text the terms biotechnology refers to the use of living organisms to modify human health and the environment throughout history we have learned a great deal about the different organisms better ancestors used so effectively increased technology has helped biologists study the organisms cell structure and function and they have found ways to use these organisms even more effectively than our ancestors however biologists must have a basic understanding themselves and their many functions before manipulating their gene expression for our benefit understanding what makes up a cell and how to cell works is fundamental to all the biological sciences. A cell is the smallest unit of life and the building block above all living organisms appreciating the similarities and differences between cell types within and among organisms is particularly important to the fields of cell biology and molecular biology. Molecular biology can be confusing because it is a subject that focuses on things so small you can’t even see them so let’s begin with big organisms and work down to the molecular level organisms such as a little girl are made above organ systems such as the digestive system pictured here each of these organ systems are comprised of individual organ as shown in the diagram organs such as the liver the stomach and the small and large intestines are part of the digestive system all of these organs are made up of tissues. Tissues our group of similar cells that perform the same functions such as epithelia tissue and the smooth muscle tissue pictured here. Tissues are made up of cells and a cell is the smallest unit of life finally cells contain organelles and molecules such as DNA let’s examine it sell more closely there to general classifications cells pro carry out excels and you carry out excels pro carry out its are single-celled organisms and bacteria and some alchy on the other hand you carry out excels make up more complex organisms like plants and animals prokaryotic cells lack a membrane-bound nucleus so the DNA which is usually a single circular molecule float in the cytoplasm love the cell you chaotic cells contain a membrane-bound nucleus that holds all the DNA in one part to sell as well as many other organelles now let’s look at the function %uh each organelle in a you carry