13/09/2010 § 1 Comment
To state it very frankly, cells are one-one-hundredth of a millimeter. 1/100. Of a millimeter. The cells that make our bodies, the cells that form every single living organism on this earth are very small and they are puny in size for a reason.
When we say our bodies need nutrients, in reality, the cells need nutrients and the food we consume so that they can turn it into energy. I think that basically, our cells do all the work for us. We as humans in spirit and soul … don’t do much and the cells are the ones who are chemically changing everything we put in our bodies into energy for them to use.
To get these nutrients, however, the cells have to be small so that food and nutrients don’t have a difficult time to get around the surface area of each individual cells and won’t have a hard time entering the cell. In class, we watched an animation of a small cell obtaining the necessary demand of nutrients because it had a large surface area – volume ratio.
Now, if an object has a large surface-area – volume ratio, it means that the surface area is larger than its volume. I think, because I’m not so clear with this part of the lecture, this means that many nutrients have a lot of space and many chances to get inside the cell, but because of the small volume, it’s very easy for them to get to the middle of the cell. I mean, that’s how I think about it in terms of the Peter-in-the-classroom and Peter-in-the-gym analogy. Peter can get into the class through the wide windows, through the many doors and if he wanted, he could break through the floor or the ceiling but because the volume isn’t as large as the gym, the classroom’s surface-area – volume is greater than the gym’s. It’ll be easier for him to get to the middle of the classroom because there isn’t as much space he’ll have to travel.
[It’s like the cube. There are 6 sides on the cube. The surface area for one side is 1, let’s say. This means that (if my math is correct), the total surface area is 6 units. If one side is 1 unit in length, then the volume must be (1 x 1 x 1) 1. The ratio is then (surface area ÷ volume) 6. (6 ÷ 1 = 6). Whereas if the cube is bigger and one face is 4 units in area, then the total surface area is 24 units. Then, the volume (lwh) is 4³ = 64. So, the ratio is (24 ÷ 64) 0.375. That’s very small.]
Basically, if the cell is too big, then it’s hard for the nutrients and substances to get to the middle of the cell, to be given to the ribosomes, mitochondria and other organelles that need them.
We also learned about prokaryotes and eukaryotes and were told that we could compare the two to bicycles and cars. Prokaryotes which are the oldest types of cells, are single-celled, don’t have nuclei and membrane-bound organelles, and are only about 1 to 10 µm in size, are the bicycles. They are of older class and are somehow more antique and limited.
Eukaryotes however, are the cars. They do have nuclei, they have many organelles and can go up to 1000 µm in size. They can be compared to cars because they’re more advanced, they’re bigger, do more than just ring a bell on the pavement while the user pedals, and can travel a lot faster.
We learned a little bit about bacteria and how they’ve evolved throughout the ages. (The ones that survived antibiotics are the ones that go on and continue their genetics.) We also learned that bacteria multiplies by using binary fission and can multiply by thousands in an hour.
Finally, we were reintroduced to the concept of phospholipids (a type of lipid made out of one phosphate group and two fatty acids, and as a result, they make little jelly-fish-looking lipids) acting as an important role in a cell’s structure. They form the cell’s cell membrane. I think, throughout the entire class, this was probably the most vital information to relate to our essay question. The phospholipids have double personalities. One side, the phosphate side (the head, say), actually likes water and is polar. The other, the fatty acids, are hydrophobic and the result of these two different preferences cause the phospholipids to act like magnet, forming walls that look like this (very roughly like this):
Basically. And I think this type of structure can actually show you that they make a kind of boundary, like a castle’s wall and keeps unwanted things and substances out of the castle or cell. Also, the many proteins that cover the cell membrane are like the knights who manage what goes in and goes out of the castle or cell, making sure only the right substances and right nutrients come in. All in all, I can see that from what I can see in the phospholipids’ structure, because they form a wall, I know that that’s part of their function, to act as a protective wall for a cell.