My youngest daughter just turned 5 a few days ago and drew the following picture today. She has not suffered through any of my biology lectures thus far. However, she somehow has learned a great deal of biology from somewhere. Here is the drawing I found from her. I asked her to talk about each of the elements and I was blown away. Let me endeavor to tell you what she drew.
Macropinocytosis (A & B)
Part A and B – Macropinocytosis. My daughter told me how important it is to describe the cell drinking habits of a cell. Cells do this to sample their external environments. This is very much a real behavior. She told me that there are 3 main different ways to get cargo into a cell. There is clathrin-mediated, caveolae-mediated endocytosis which are both receptor-mediated and macropinocytosis which involves the uptake of fluid and its dissolved entities. She said she only wanted to talk about macropinocytosis. Here is another image from wikipedia:
Golgi Apparatus (C and G)
Benjamin Franklin did some great things for the nearly bankrupt U.S. Post Office (USPS). If the USPS functioned like a golgi apparatus, they’d be stellar. The golgi apparatus is a professional shipper of proteins. Have you ever wondered how a cell knows where to put all of the proteins? Some proteins need to be in very specific places within the cell. For example, an enzyme called hydrolases which are enzymes responsible for hydrolyzing (breaks ester bonds) need to go to lysosomes. The golgi apparatus can ship it there. There are vesicles (G) that are destined to be sent outside the cell and can even reside inside the cell until signaled to leave. The golgi apparatus is a kay player in this. The golgi apparatus can also put proteins in the wall of the cell itself. Not only that, the golgi apparatus can even control which side of the cell wall the protein is facing. Proteins have amino acid sequences within themselves that have tags to tell the golgi where to take it. This information is in our DNA itself. We have tags for sending proteins to the mitochondria (which we will get to in a little bit).
Cytoskeleton (D-F & K-L)
My daughter wanted me to mention the two different types of cytoskeleton filaments, as indicated by the orange and pink in her inspiring drawing. There are actin-based filaments and microtubulin-based filaments. Do you think, we as humans, could walk around without a skeleton. Our cells need a skeleton to do the same (K; depicting the forefront of the cell in terms of its motility). Our cells need the skeleton to create physical posts whereby they can create force to do something such as macropinocytosis or cell division (see video directly below). It is beautiful. You will see tubes assembling in the Inner Life of A Cell video (the last video posted within this article). That is exactly that. You will also see something walking on the actin. Our bodies use myosin to walk on actin. Our cells use this actin and myosin walking mechanism to transport something along a route that it wants it to take. Our muscles even use actin and myosin as a contraction mechanism. Ready to be freaked out? Viruses can hijack these filaments as a roadway to where they would like to go within our cells. This article discuses 5 virus types (F and L) which can do this. Please note how happy my daughter drew the viruses because they were hijacking the cytoskeleton. Viruses are such jerks!
Nucleus, Nucleolus and Heterochromatin (H-J)
My daughter wanted me to discuss the nucleus (H), the nucleolus (J) and heterochromatin (I). The nucleus is a special, extra safe, place for our code of life – our DNA. Our DNA creates a copy of itself (transcription) in the form of something slightly different and more temporary called messenger RNA (mRNA) via ribosomes and sends it outside the nucleus. This is where the mRNA is translated into proteins (thank you Watson and Crick for the code!). This code instructs our bodies to function. A lot of our DNA that used to be called junk actually has amazing functionality that we were unaware of such as the ability to actually fold and sense a molecule! DNA -> mRNA -> Protein! and the protein amount can be controlled by telling DNA to make something, by mRNA to be degraded, and sending the protein to be destroyed in yet another process. Our bodies can control how much of a protein is made in a beautiful way. Our bodies can even control when protein is made according to time and light.
Ribosomes congregate within a structure called the nucleolus (J). She said not to belabor that but wanted it there because it was the most prominent feature within the nucleus.
Heterochromatin is something fascinating. Our bodies have all of the DNA it needs in every one of our cells… in fact we have about 1 trillion cells per kilogram and the average person is about 70 kg. That means the average person has 70 trillion cells. Each cell has DNA that can be stretched one meter. What! Imagine… how far all of your DNA can stretch in your body? How far!? Well it can go to the sun and back 500 times!!!!!!!!!!!!!!!!!!!!!!!!!!!!
There are about 300 different cell types. The cells know what cell type they are based on what is called a methylation pattern. The methylation pattern will dictate how tightly bound the DNA is. The tightly unused DNA is packed to the side of the nucleus and is called heterochromatin. The used part of the DNA is referred to as the euchromatin. Fascinatingly, women have 2 X chromosomes and so they will randomly choose an X to put on the side of a cell that is not used. This means that genetically they can be thought of as expressing proteins in a mosaic fashion in a sense. This is what leads to different genes being expressed in different parts of a female.
This is actually an amazingly cool thing and can have very interesting outcomes in a variety of tissues!
Next Nobel Price (M)
I believe that my daughter here has described something novel as indicated by the M. She has yet to be awarded the Nobel Prize. Sweden, here we come!
Mitochondria (N)
Mitochondria are fascinating. Imagine a bacteria-esque entity living within you that has plasmid DNA like bacteria and replicates on its own that is living in a symbiotic relationship but also is being held hostage by your cells. That is what the mitochondria’s relationship is like within your cells. It cannot leave because our bodies over time has taken a ton of its genes and so the mitochondria is dependent on our genome but also has it’s own genome. Our cells provide it with everything it needs and also we take from it the currency of energy… ATP. ATP when used gets converted to ADP and inorganic phosphate. How is ATP replenished? Holy cow… if you want to know something fascinating learn about this. There are proton pumps that ram protons into the intermembrane space of the mitochondria… it is creating a reservoir which it then allows protons to come back through a pore in the membrane that actually physically spins and basically takes ADP and inorganic phosphate and smashes it back together to get ATP… it literally is a machine in every sense. Besides this, there is another real cool story here. I am not going to get into the details of Cytochrome C and what it is doing in the mitochondria other than acting as an electron acceptor and passing electrons in a chain… which is also really cool… but when the cell is told to die via apoptosis, it will do so by having Cytochrome C leave the mitochondria… again, it loves electrons… it goes into the nucleus and rips apart the DNA. This is an inflammation-free process. A lot of people pronounce apoptosis with the “pop” in the middle… There is no “pop”. It is “A-poh-toe-sis”. It means leaves falling off of a tree and is describing the blebbing process.
Inner Life of a Cell
This next and final video I am posting here… I am not going to lie… I have shed a tear or two… It is called the Inner Life of a Cell. It is absolutely gorgeous and shows the inner workings of our cells. It is absolutely gorgeous.