Lesson #1

[Rockonman]

I've been meaning to post something about health related, whether it be on the topic of dieting, medicine, anatomy and physiology, etc., for a while now, and just recently I had an idea. Why not start at the most basic subject of the related subjects - the cell.

So what is a cell? It is the most basic unit that can be called 'life'. It is a small membrane-enclosed unit containing an aqueous solution, endowed with the ability to make new copies of itself (more on that later). I don't want to talk about the history of discoveries, just know that people have known about it since the mid-17th century.

Some general facts about cells:

On average, cell size is about 0.5 µm to about 30 µm in diameter, with the largest being the ostrich egg, going in at about 152 mm.
There are three corollaries of cell theory, composed from some German scientists:
All cells are fundamentally alike in chemical composition. All cells store and process info in the same way, as DNA. All cells arrive from other cells through cell division.

Moving on to more specific, cells can be divided into either being a prokaryote or an eukaryote. Prokaryotes include bacteria and archea. While there are many thousands of types of bacteria, only a handful, maybe a couple hundred, cause diseases. Most (I think) don't really have anything to do with the human body, but a few (I'm not sure how many) are beneficial, even life-saving. For example, there are bacteria that live in your stoumach that help you digest food, and there are bacteria that 'swim' on your eyes that kill foreign invaders, and protect your eyes. Eukaryotes, on the other hand, are the more complex organisms.

---------- Post added at 07:17 PM ---------- Previous post was at 06:58 PM ----------

(Sorry for the double post, but I didn't want it to get too long.)

The 'organs' of a cell, by the way, are called "organelles" which I'm pretty sure means 'little organs'.

There are several main organelles that are important for cell function:

A) Nucleus: This is the defining characteristic of eukaryotic cells. The nucleus has a membrane that surrounds the majority of the cell's DNA and protects it from being degraded by the cytoplasm.

B) Nucleolus: This dark-stained body within the nucleus serves as a site of ribosome production, which is needed in protein synthesis.

C) Mitochondria: This is the "powerhouse" of the cell - it produces nearly all of the cell's power in the form of adenosine triphosphate, abbreviated as ATP. The mitochondria is interesting, because it has its own DNA, which gives it the ability to create protein, and it has a similar size and shape to some bacteria. Because of this, a majority of scientists believe that it used to be a bacteria that used oxygen that formed a symbiotic relationship with a eukaryotic cell.

D) Chloroplast: A structure unique to plant cells, this organelle has the ability to create and capture energy from the sun through photosynthesis. It is similar in size, shape, and structure to the mitochondria.

E) Cell Membrane: This defines the boundaries of the cell.

F) Cytoplasm: Everything in the cell minus the nucleus. A related term is the cytosol, which is everything in the cell minus the organelles.

G) Endoplasmic Reticulum: There are two forms of this. The rough endoplasmic reticulum is covered in ribosomes. The rough E.R. serves as a site for protein synthesis. The other form is the smooth endoplasmic reticulum, which lacks ribosomes. The smooth E.R. serves as a site for the production of lipids.

H) Golgi Apparatus: Sorts proteins made by the rough E.R. and sends them to their final destination.

I) Lysosome: This membrane-bound structure contains the cell's digestive enzymes. It serves to break down things brought into the cell.

J) Peroxisome: The site of reaction with hydrogen peroxide, since the products of this reaction can be harmful.

K) Vacuole: (plant only) Large structure that stores things.

L) Vesicles: Membrane bound structures that transport thins around the cell.

M) Cytoskeleton: Network of proteins that functions as the skeleton and the muscular system.


Edit: In interest of the whole 'religion vs. science' bit#@ fight, I am not proving either side in these notes. Any questions, post below and I will either answer then or in a later lecture.

[Tyemdi]

Pretty good lesson. But you could be more straightfoward about some things. For instance, you should state mitochondria deals with all the things you mentioned as well as its main purpose: Cell respiration.

You should never used the word "thing" when defining something. Lysosomes break down waste and the vacuole stores liquids and also seperates and stores waste products from the plant. And you should describe what is in that 'everything' the cytoplasm contains, instead of giving a broad generalization of it.

[Rockonman]

As for the mitochondria, I'm trying to put things in terminology that the average layperson can understand.

As for the lysosome, it destroys most all substances that are harmful to the cell, as well as other things that the body wants to be broken down. There are different things that are beneficial to the body that it may want broken down by cells with strong lysosomes, so I can't really be too specific there until I describe those processes. The cytoplasm actually does refer to everything in the cell except for the nucleus.

[Tyemdi]

Still, you should include its main purpose and maybe explain that even.

I'd still say it mainly breaks down waste.

Not exactly. It's the gel-like substance and then there are the ribosomes, mitochondria and other organelles other than the nucleus that are not refered to as the cytoplasm.

[Rockonman]

Still, you should include its main purpose and maybe explain that even.

I'd still say it mainly breaks down waste.

I'll get there, all in good time

Not exactly. It's the gel-like substance and then there are the ribosomes, mitochondria and other organelles other than the nucleus that are not refered to as the cytoplasm.

I think you're getting confused between the terms cytoplasm and cytosol. The cytoplasm is everything in the cell except for the nucleus. This includes the organelles and the liquid that makes up most of the cell. The cytosol, however, refers only to that liquid. No organelles or nucleus, just the liquid.

[Tyemdi]

Ah OK. My bad. I got a bit confused there.

[Zola]

You haven't mention that Nucleus has it's own membrane and that nucleoplasm is in it (similar to cytoplasm) and that Nucleus takes part in cell division. I agree with Tymedi for mitochondria you should have mentioned about cell respiration (it's not hard to link it to breathing of cell etc). I liked that you mentioned ATP but I think it's a bit confusing for other persons than cell respiration. I almost forgot many bacterias that are daily in our organism are potential threat because if their number grows they could cause some disease. As for other parts of the cell you did a great job

[Rockonman]

You haven't mention that Nucleus has it's own membrane and that nucleoplasm is in it (similar to cytoplasm) and that Nucleus takes part in cell division.

I did say that the nucleus surrounds the DNA, which implies that it has a membrane, but I could clarify further.

I agree with Tymedi for mitochondria you should have mentioned about cell respiration (it's not hard to link it to breathing of cell etc). I liked that you mentioned ATP but I think it's a bit confusing for other persons than cell respiration.

Yea, I just was just putting it in simple terms for everyone to understand, that the mitochondria goes through respiration to produce energy for the cell. And that is to call it the "powerhouse of the cell."

I almost forgot many bacterias that are daily in our organism are potential threat because if their number grows they could cause some disease.

That's how the bad bacteria work. I think that's an answer, because you're not really clear with your statement there.

[Tyemdi]

[QUOTE=Zola;321943]I agree with Tymedi for mitochondria you should have mentioned about cell respiration (it's not hard to link it to breathing of cell etc).QUOTE]

Respiration isn't exactly breathing. It more precisely refers to the transport of oxygen and carbon dioxide.