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Inside Your Cells



You are a squishy robot. You consist of approximately 30 trillion cells working like little factories producing proteins, using and creating energy, keeping you alive. Your cells will look different depending on their function, but here is an explanation of some of the “Standard” organelles in eukaryotic cells.

The Nucleus

The nucleus is like the brain of the cell. It is found in almost all of your cells except for red blood cells. The nucleus contains DNA (which is packaged into chromosomes) and some proteins, all within its nuclear membrane. This membrane keeps the contents of the nucleus separated from the rest of the cell, while still allowing proteins and RNA to travel in and out through pores. 

The Nucleolus

The nucleolus is a structure found within the nucleus that is responsible for the production of ribosomes. 


Protein synthesis is the ribosome's job. They act like tiny protein machines, reading messenger RNA (mRNA) and creating a chain of amino acids according to the mRNA instructions. mRNA is made up of a chain of bases, and each group of 3 bases corresponds to one amino acid. Amino acids are brought to the ribosomes by tRNA, which binds to the mRNA. The ribosome links the amino acids together, once the chain is finished it can be released, then will go on to fold into a functional shape and go through any necessary post-translational modifications.

The Endoplasmic reticulum

This organelle is made up of two subunits, the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER). In diagrams, it’ll be fairly easy to tell the difference between the two since they're named after how they look, with the rough endoplasmic reticulum looking bumpy thanks to the ribosomes that cover it, and the smooth endoplasmic reticulum looking, well, smooth. While both are made of a continuous membrane the structure of the smooth endoplasmic reticulum is more tube-like whereas the rough endoplasmic reticulum membrane forms flatter sacs.  Proteins and other molecules can move around within the endoplasmic reticulum, some will stay there whereas others will be sent to different destinations in vesicles. 

The endoplasmic reticulum is involved in the production, processing, and transport of proteins. The rough endoplasmic reticulum is the section in charge of making the proteins, and therefore news help from ribosomes that attach to it build a chain of amino acids. The chain can then go on to fold into its correct shapes inside the RER. The smooth endoplasmic reticulum helps synthesise other materials that the cell may need, such as steroid hormones, carbohydrates and lipids (like cholesterol or the phospholipids needed to form membranes). 

The Mitochondria

Mitochondria! The powerhouse of the cell! What does that mean? This membrane-bound organelle generates most of the ATP (energy source) that the cell needs. They produce this ATP through a chain of chemical reactions called the citric acid cycle (also known as the Krebs cycle or tricarboxylic acid cycle). 


Lysosomes are membrane-bound organelles that contain digestive enzymes. They are able to break down waste material from the cell, destroy foreign bodies like bacteria and viruses and well as help maintain the cell’s plasma membrane. 

The Golgi Apparatus

The Golgi apparatus (also known as the Golgi body or Golgi complex) is, like the RER, a membrane-bound organelle made up of flattened sacs called cisternae. It is involved in the modification and transport of proteins, as well as packaging them into small membrane-bound sacs (vesicles) to be sent to their correct destination. 

The Centrioles

These cylinder-shaped organelles are found in a pair in the cytoplasm near the nuclear envelope. They play an important part in cell division, moving to opposite sides of the nucleus and helping with the formation of mitotic spindles during mitosis. 


Microfilaments are part of the cell's cytoskeleton. The cytoskeleton is what keeps the cell in the right shape, keeping it strong and supported. Made of a network of protein filaments and microtubules, the cytoskeleton is located in the cytoplasm and is crucial to cell division, the internal organisation of the cell, and cell movement. 

and the rest?

Cells with different jobs may have different organelles or organelles performing different roles, this article is just an overview of the standard stuff you'll see in animal cells. If you're interested in organelles with more specific jobs or the inner workings of other types of cells, leave a comment.


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