In ‘What’s In a Cell? Part 1‘ I explained the nucleus, mitochondria, ribosomes and the endoplasmic reticulum. Let’s crack on with the rest!
The golgi apparatus
Sometimes known as the golgi body, this organelle is made of membranous sacs and tiny membrane vesicles. Newly made proteins are modified and directed inside the golgi apparatus. Transport vesicles that have budded off the rough endoplasmic reticulum containing the proteins fuse with the receiving side of the golgi apparatus, the cis face, once the protein is inside it’s modified and packaged into another vesicle which buds off from the trans face of the organelle before travelling to its destination.
These little organelles contain digestive enzymes, and are found in large numbers within phagocytes, the bacteria that destroy and clean up invading bacteria. Lysosomes can digest almost all kinds of biological material, and not only digest bacteria, but also break down worn out organelles and non-functional tissues (such as breaking down the webs between fingers and toes whilst we’re all in the womb) as well as breaking down bone to release calcium.
Lysosomes have strong membranes, but they’re not unbreakable. If a cell is injured, deprived of oxygen even if there’s too much vitamin A present, a lysosome can rupture, leading to a cell digesting itself.
These barrel-shaped organelles are responsible for making microtubules and organising mitotic spindle for cell division. Centrioles are often paired together at right angles (see below) and are made of microtubules as well, which are arranged into pinwheel of nine microtubule triplets.
Last, but by no means least, we have the cytoplasm. Unlike the others, this isn’t an organelle, but is the cellular material found within the cell membrane, including the organelles themselves. A popular image of cytoplasm is a structureless, inert gel, but it is in fact the area where a lot of cellular activity takes place. It’s made from three different components, the cytosol, a semitransparent fluid in which everything is suspended, containing water, salts, sugars, proteins and other nutrients.
As previously mentioned, it also contains the organelles with their specific functions and the third component is inclusions, chemical substances that vary depending on particular cell types. For example, a fat cell will contain many lipid droplets as an inclusion, whereas skin and hair cells will contain the pigment melanin.