A lysosome is round organelle which is surrounded by a membrane. With no clear internal structure it can be quite difficult to distinguish. The best way to look out for them is to identify other surrounding organelles, then look to see if you can see a grainy texture inside. This texture is the digestive enzymes. The purpose for lysosomes is to digest invading cells (such as pathogens) or to break down worn out components of the cell (for example during apoptosis.) It is important for these digestive enzymes to be kept within a cell, as if they were free to float within the cytoplasm, they would digest vital organelles needed for cell functioning.
Ribosomes are perhaps one of my favourite organelles but rather small. And here we have an organelle that is not surrounded by a membrane! They are the site where proteins are made. They can either be free floating in the cytoplasm or attached to the rough endoplasmic reticulum (another organelle which will later be explained.) Ribosomes are composed of proteins and RNA (ribonucleic acid). So, how do you spot them in a diagram? Depending on the magnification and resolution will determine how easily distinguishable they are. They may sometimes not be visible at all, may sometimes appear as dots, or if you look very closely there are two subunits (the large and the small subunits.) But, the small subunit really isn’t that small in comparison. Its purpose is to allow the flow of information during protein synthesis. The large subunit contains the site where new bonds called peptide bonds are made when creating proteins.
The Rough Endoplasmic Reticulum (RER) is not one to forget, it may be a mouthful at first but you’ll get used to it! The first thing you should note is that you must capitalise all the words. The RER are a system of membranes enclosing on a fluid-filled space. When looking at a diagram you will see lots of dots surrounding the surface, these are ribosomes. The ribosomes on the RER are called membrane bound. So after the proteins have been synthesised at the ribosomes, the RER folds and processes them. The Smooth Endoplasmic Reticulum (SER) is similar to the RER, just with no ribosomes, thus has a smooth texture. Its role is to synthesise and process lipids, carbohydrates and steroids. Depending on the cell will determine the amount of RER or SER. If a cell is specialised to produce proteins then it will tend to have more RER. Then if a cell is specialised in producing lipids and steroid hormones then a larger amount of SER.
Lastly we have a centriole, a small hollow cylinder made of microtubules which are tiny protein cylinders. Centrioles are found in all animal cells and only some plant cells. This is because their purpose is to allow the separation of chromosomes in cell division. They are found in pairs but during anaphase (a stage in cell division) they separate and move towards opposite poles (ends) of the nucleus. Fun fact, if you would like a way to remember them, picture the Spanish churro, that is their shape.
0 Comment:
Be the first one to comment on this article.