A brief summary of the main parts of cells.
As British Science Week 2018 comes to a close, I thought I would write a blog post about some of the main structures which are found in cells – 10 in fact, one for each day of British Science Week (which is actually 10 days: 9th-18th March).
Nucleus: The nucleus is the part of the cell that everyone could probably remember from school. It’s the ‘control centre’ of the cell, that is to say, the bit where DNA is (mainly) stored and transcribed. The nucleus separates all of this important information from the rest of the cell, keeping it all in one place so that the different RNA sequences needed by the cell to make proteins can all be easily created from the DNA. The nuclear envelope is very good at its job, and for a good reason. If the DNA were to get damaged by either leaking into the rest of the cell, or something harmful from the rest of the cell entering the nucleus, the cell would no longer have the right code to be healthy. Damaged DNA is a huge cause of some serious diseases, including cancer.
Mitochondria/Chloroplasts: I’m sure everyone can recall the phrase “the mitochondria is the powerhouse of the cell!” from school. But what does that mean? Mitochondria are the parts of the cell which produce all the energy which cells (and therefore, we) need to survive. It does this during respiration, where mitochondrial proteins assist in the breakdown of glucose to produce energy. Plants contain chloroplasts, which are a bit like mitochondria. Chloroplasts are responsible for providing energy by using solar energy.
Rough Endoplasmic Reticulum: This is ‘rough’ because it is coated in ribosomes. These are molecules that produce proteins from the RNA sequences which the DNA encodes in the nucleus. The RER is situated right next to the nucleus, a bit like a cloak. Any proteins made by the ribosomes can get sorted in the RER to determine if they are to remain in the nucleus/nuclear envelope or be sorted elsewhere by the Golgi apparatus. Also, the RER has a big role in ensuring that all proteins are correctly folded in the right way to carry out their function. If a protein isn’t the right shape, it is not allowed to leave. It’s a bit like the teacher that would stand at the door and not let you out for dinner until your uniform was perfect. It minimises the risk of diseases linked to misfolded proteins, such as Alzheimer’s.
Smooth Endoplasmic Reticulum: This is not associated with protein synthesis so does not contain lots of ribosomes, hence why it is classed as ‘smooth’. Instead, the SER makes steroids and other lipid (fat) molecules. This allows cells to produce hormones and other fat-based substances. Since the smooth endoplasmic reticulum is not involved in turning the RNA from the nucleus into protein, it is not as tightly associated with the nucleus of the cell.
Golgi: The Golgi apparatus (sometimes called the Golgi body or Golgi complex) is the part of the cell that’s most like the sorting hat in Harry Potter. It receives proteins from the rough endoplasmic reticulum and packages them to be sent to the part of the cell which they belong in. It does this based upon signals and characteristics featured on the proteins which hint at where the particular protein is supposed to function. Once the Golgi has decided, it sends the proteins on their way to the right part of the cell.
Lysosome: The lysosomes are little pockets of waste disposal in the cell. When proteins become faulty, the lysosome breaks them up into smaller pieces, so that all of the useful parts of the protein can be reused to make new proteins in the cell. We could learn a lot from cells and how efficient they are at recycling. Any material which enters the cell is also broken down by lysosomes, so that it can be used to build more useful things, a bit like a biological version of upcycling an old chair into some trendy shelves, or something similar.
Peroxisome: Peroxisomes are like lysosomes – they’re little pockets of waste disposal. However, whilst lysosomes break apart proteins, peroxisomes break apart fats. A bit like having brown and blue bins for your bottle and paper recycling, that’s your lysosomes and peroxisomes. Alongside fatty molecules, peroxisomes are also capable of protecting the cell against reactive oxygen species – molecules which can interact with DNA to cause damage – which are usually found in cigarettes, amongst other things.
Actin Filaments: These are a part of the cytoskeleton alongside microtubules and intermediate filaments. They’re sometimes called microfilaments. These filaments are very important in the movement and contraction of cells – they’re found in the contractile cable which allows the division of cells during the cell cycle, and also in muscle cells. The contraction and relaxation of muscles depends largely upon the actin fibres within the muscle cells.
Intermediate Filaments: These are another part of the cytoskeleton, alongside microtubules and actin filaments. Intermediate filaments are more structural – they help to provide structure to the different parts of the cell. Intermediate filaments also help in the movement of different proteins to new areas of the cell from the Golgi apparatus. You could think of them as a sort of delivery route which the proteins take.
Microtubules: These are part of the cytoskeleton of cells alongside intermediate and actin filaments. They are very important in the process of cell division, as they make up the spindle which pulls the chromosomes apart as the cell splits into two new daughter cells. They’re very strong, and sort of like thick ropes – think of the process of cell division as a sort of tug of war where each new cell wants a chromosome in it.
So there’s a brief tour of a cell for you, folks! I hope that you’ve found it useful, and at least now have a grasp of the basics of cell biology.
As always, feel free to contact me over on twitter if there’s anything you’d like me to write about.