Keeping it together (cell mechanics and cell mechanisms)

Introduction

Our first unit is to be on the topic of ‘keeping it together’, a concept that I’m sure will be troubling some of you by now! But it’s not just, how are we going to keep it together doing this course? The title also refers to how the human body ‘keeps itself together’. So we will explore biochemistry, organelles, cell structure, tissues and possibly the skin, with a view to working out what it is that stops us from being a load of chemical soup, with no bodily organisation.

I know what you did last year, so we will be building on that. (If you have forgotten it, you need to revise a bit! Start in Chapter 3.) The “what to do” below explains first, what to read and then what to make notes on. You are trying to pick out what is important for holding things together. There are hints on how to make notes, many of them being questions. It may be useful to think how structure helps or allows function. For example, a rope is useful for pulling my baby cow along, but it is not much use to push her away when she is a bit too full of ‘attitude’. You can’t push with a rope. What features of a rope are there, that allow pulling but not pushing? Finally, don’t make your notes too long! I don’t want an essay on every sub-topic. What we want is an essay on the whole topic (Keeping it together), written by lots of people.

If you can add to your notes (in any form) by finding useful stuff from other sources, that would be awesome (rewardably awesome – the more awesome you are, the more marks you end up with!). We need to know where it came from and you need to judge its academic validity. Finally, if you are really smart, you might like to think how this might relate to massage therapy.

I want everyone to do all the reading, but I don’t mind at all if you divide up the note taking among yourselves*, so that not everyone makes notes on every topic. What I will want to see is that everyone has made notes on something. You can post your notes as comments to this blog post. If you can’t manage that, see if someone else in the class can help you do it. At the very least, bring your notes to our first session.

*I can’t divide it up myself because you haven’t introduced yourselves yet!

OK, here is part 1 of “keeping it together”, the biochemical, organelle and cellular part:

What to do

Step 1: Read “The Plasma membrane: Structure” (pp66-70: text finishes on p69, diagrams on p70).

Notes: How does the membrane keep it together?

A. The membrane itself.

The plasma membrane holds things inside the cell and also keeps things out. What are the ‘things’? How does it keep them in/out (what is it made of and how does that work)? It does let some ‘things’ pass through, how does it do that (what kinds of ‘holes’ does it have)? Note which diagrams/pictures are useful. Here is an idea – imagine the membrane is like the nylon part of a tent, with all the zips, air flaps, etc, etc, does that help at all?

B. Membrane junctions

The junctions hold the cells together. How do they do that? What types of junction are there and what does each type specialise in? Try thinking of what they are trying to allow/prevent. Does the name tell you anything (look up desmo in the front of the textbook)? OK, so we don’t usually put our tents that close to each other, but suppose that’s all we had to live in, would we make junctions?

Step 2: Look at Fig 3.9 (p74). Ignore the bit about why the cells have gone like that (that’s revision!), and just think of the cell membrane shape. It’s not just a balloon, is it? Something is holding a shape. What holds a tent in shape?

Step 3: Jump to the Cytoskeleton. Read “Cytoskeleton” and “Cellular extensions” (pp90-95: text finishes on p95, but ignore table 3.3 on pp94-5.

Notes: How does the cytoskeleton keep it together?

C. Tubules and filaments

Make notes on the types that exist. What structural features do they have and how does that help them do what they are specialised for? We are talking protein biochemistry here! (If you need to revise, go back to Chapter 2, pp50-52, structural levels of proteins, Fibrous and globular proteins, Protein denaturation.) What are the ‘subunits’? Does that tent analogy help with this?

D. Movement

Some things move along microtubules, how? Microtubules can make cilia and flagella move, how? Microfilaments make the cell membrane move, how (have a look back at fig 3.3 p67)? Can you see, now, how that red blood cell changes shape? If so, try to explain it!

Step 4: This one goes all over the place, but it’s really about cells moving around. Read “Developmental aspects of cells” (p111), but stop at the bit about cell aging (p112), unless you are interested. Then read “Extracellular materials” (p111). Then jump all the way back to Fig 3.4, p68. Make sure you understand what all those proteins (purple blobs) are doing. With all that on board, read “Cell environment interactions” pp83-84.

Notes: How do cells know where they are/should be?

E. Make notes on when cells might move about, and when they might need to know who they should be next-door to.

F. Make notes on what they may need to move through (what surrounds cells – what are the various possibilities)?

G. Make notes on how cells recognise each other. You need to talk about glycoproteins. Find a picture of one?

H. Make notes on the glycocalyx. How do CAMs and membrane receptors help the cells to hold together in a way that is organised? How do membrane receptors help cells know ‘what to do’ at the right time?

Step 5: Congratulate yourselves. We are on track!

Resources

Marieb, E., & Hoehn, K. (2007). Human anatomy & physiology (7th ed.). San Francisco: Pearson Benjamin Cummings.

Wikipedia

You Tube

Other text books….

Other places online….