Biovisions

These are some great biology videos from Harvard University.

Biovisions - Inner Life of a Cell
https://www.youtube.com/watch?v=wJyUtbn0O5Y

Biovisions - Powering the Cell: Mitochondria
https://www.youtube.com/watch?v=RrS2uROUjK4

and a lot more available at:
http://multimedia.mcb.harvard.edu/media.html

The Youtube versions are better for a projector screen than the ones you can get on the Harvard site. (Larger and clearer).


Inner Life of a Cell is a great way to introduce cell parts, either for juniors and seniors.

I find it best to run through the video about three times:

1. First time I just show them the video without any prompting other than writing the video title on the board. Don't tell 'em anything about the video, just start playing it. Make sure you have sound.
2. Then I tell them. "This is a computer-generated animation of the processes that occur within a single human cell. It was developed by Harvard University as the beginning of one of their biology courses. Nearly everything you see in this video is scientifically accurate. They've left out the water molecules so that you can actually see the different cell parts clearly, and they've made the motions a little smoother than what actually happens. But everything you see comes from our understanding of what happens inside human, and other cells." Then I run through the video again, with the sound muted, stopping and starting at each section, telling them the names of the cell parts, and what they do. I also write the cell parts on the board in a table (see below).
3. Then I usually play the video once more with sound from start to end.

The rest of the lesson is dedicated to helping the students fill in the table below. This acts as a brilliant way to start cell parts, and act as a summary.

Parts of a Cell	Found …	Function
Cell Membrane     membrane proteins     phospholipid bilayer
Cytoskeleton     actin filaments         actin-cutting enzymes     microtubules
Motor Kinases
Vesicle
Centrosome     centrioles
Nucleus     nuclear pores     messenger RNA
Ribosomes
Mitochondria
Endoplasmic Reticulum
Golgi Apparatus

There are a lot of concepts that are embedded in this video. Not all are appropriate for junior students, but you can teach a lot from this video:

1. All the bits you see are made up of molecules, collections of atoms. This deserves emphasis.
2. The cell membrane is a 2 dimensional "sea" of oily particles. That's why animal cells are flexible. Plants have an extra cell wall outside the cell membrane to make them rigid.
3. The cell membrane has lots of proteins that float in it, and act as pumps, sensors and messengers to other cells. In the video, the white blood cell is rolling along the wall of a blood vessel, until it receives a message from the cell in the blood vessel wall. Most of this video occurs in the blood vessel cell, and the blood vessel cell is trying to tell the white blood cell that there is an infection.
4. The actin and microtubule filaments in the cytoskeleton are dynamic, built up and broken apart - without this, the cell wouldn't be able to move.
5. Kinases actually move like that! Maybe not as smoothly as shown in the animation, but they actually step along microtubules.
6. The centrosome helps control the cell cytoskeleton, and are involved in cellular reproduction and division. "They act as anchors."
7. The ribosome reads the mRNA exactly like that. The first bit of it's motion after joining the mRNA is a quick scan to find the start codon (Start code). Once this is found, the ribosome reads the mRNA and builds a protein from the information it finds in the mRNA. When it hits a stop codon, the ribosome falls off the mRNA. Nearly everything on this planet shares the same start and stop codon sequence.
8. Some proteins are released into the cytoplasm. The video shows one going towards the mitochondria, the power plant of the cell. In high level classes, it deserves mentioning the symbiotic theory of mitochondria and chloroplasts.
9. Over 90% of proteins are released into the endoplasmic reticulum instead. The ER is full of proteins that modify the proteins - trimming them, folding them and adding sugar molecules. I like to say that the ER is like a conveyor belt in a factory. The ribosome welds the protein together, the ER proteins then sand, shape and "paint" and "tag" the protein.
10. The Golgi Apparatus is like a post office. It reads the tags on the proteins from the ER, packs them up into vesicles and sends them on their way to different parts of the cell. It also builds the phospholipids for the different membranes.
11. The last part of the video inside the cell, shows a vesicle from the Golgi Apparatus reaching the edge of the cell and merging with the cell membrane. This is not only how membrane proteins get to the edge of the cell, but it is also how the cell membrane grows and is repaired.

The other two videos in this series are good, but not as clear as Inner Life.