When we’re learning about cells at GCSE level, diagrams tend to only look like this:
When you get to university level, they look like this:
That’s a big difference in only a few years! If you look at the second diagram, you can see lots of labels, and you might wonder what they all are, well here’s a quick guide to the different parts of your cells.
First of all – we are made up of animal cells, this means that unlike plant cells, there are no cell walls and no chloroplasts (if there were there might be a bit more of a greenish hue to us).
All the tiny parts of a cells are called organelles, it’s easy to remember each cell as its own little body, and each organelle with its unique functions acts like a tiny organ.
At the heart of the cell is the nucleus. This contains our genetic information and is the control centre for building new proteins. Most cells only have one nucleus, but some, such as liver cells, have multiple nuclei. The only cells within our bodies that don’t have nuclei are red blood cells because of the extra space required within them to carry oxygen around the body, but because of the lack of nucleus, a red blood cell only has a limited lifespan of 3-4 months.
The nucleus is bound by the nuclear envelope, which is a double membrane barrier. The inner layer acts as a scaffold for organising DNA within the nucleus, whilst the outer layer is studded with ribosomes and is continuous with the endoplasmic reticulum (read on to find out what these are). Together, the nuclear envelope has a series of nuclear pores, which allow molecular travel inside and out of the nucleus.
This type of organelle is the power house of a cell, generating the energy necessary to carry out its functions. As you can see in the picture above, a mitochondria has two membranes, the outer, which is smooth and the inner, which folds inwards, creating cristae. It’s here in the inner membrane that energy is made in the electron transport chain:
The oddest thing about mitochondria is that they are very similar to a type of bacteria. Many believe that this is because mitochondria were originally from bacterial cells, which subsequently invaded plant and animal cells and gave use the power houses that we have today.
Mitochondria also contain their own DNA, RNA and ribosomes, and mitochondrial DNA is only passed down through the female line. This means that relatives can be tested for using mitochondrial DNA samples.
These tiny granules are made of ribosomal RNA (ribonucleic acid), and are the centre of protein synthesis. They’re actually made of two parts, which “fit together like the body and cap of an acorn”.
Some ribosomes float freely within the cell cytoplasm, whilst others attach themselves to membranes, such as the endoplasmic reticulum.
Endoplasmic reticulum (rough and smooth)
Endoplasmic reticulum are a series of connected tubes and membranes, surrounding cisternae, which are fluid filled cavities.
The rough variety is covered in ribosomes, which as previously mentioned are involved in protein synthesis. These newly made proteins head into the cisternae before being transported to the golgi apparatus (coming up in part 2..) for further processing.
The smooth endoplasmic reticulum doesn’t play any role in protein synthesis. Instead, enzymes contained within it work in areas such as cholesterol synthesis, hormone synthesis and drug detoxification.
That’s the end of part 1 guys! Stay tuned for part 2…