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Advanced Honors Biology

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Enzyme Cofactors

Many enzymes use "cofactors" to help carry out their function. The one above is a "Heme." We will see a lot of these and similar structures. The ring is called a porphyrin ring. A heme is a porphyrin ring with an iron in it. The iron can carry oxygen molecules. We discussed hemoglobin earlier. That protein carries oxygen in your blood. Or, to be more correct, that protein carries a 4 heme groups, each of which carries an iron, each of which carries oxygen.
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Enolase detail

I Thought I would take a minute to talk about a reaction mechanism. This is not something on which I would test you. However, I thought getting into the mechanism…even just the idea of a mechanism…would be useful.
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Intro to Enzyme Kinetics

Enzymes really are at the heart of how our bodies work. The brief definition is a "bio-catalyst." These are almost always proteins. They lower activation energy of a particular reaction and as such speed it up, both in the forward and backward direction. Almost all enzymes will be able to work either "backwards" or "forwards." Some are effectively one-directional because of large negative delta G0, for example involving ATP hydrolysis. But, even most of these can be reversed.
Enzyme function requires particular structures. Structures of proteins can be altered by the binding of other proteins or other smaller molecules, or the addition of a phosphate to the enzyme at a specific point, or the local pH or charge distribution…so, every step of enzyme function can be regulated.

Cytoskeletal discussion

I have a little assignment for you. broken up by group. I want to discuss the cytoskeleton and it's applications when we next get together.
The cytoskeleton is often the worst represented of cellular structures. In the image above, microtubules (made of tubulin) are in green, microfilaments (actin) are in red. Intermediate filaments (Keratins) are not shown.
As the name implies, they are all involved in providing structure to cells. Microtubules are the largest in diameter and ALWAYS grow out from an MTOC (centriole). Microfilaments are the thinnest and can grow anywhere in the cell. Intermediate filaments are…well, intermediate. They also tend to be on the long axis of large cells and sort of make up "cross members" in cube shaped (cuboidal) cells.
They all have some superpower that allows them to be repurposed very broadly in cells and in multicellular organisms.
Two of them have "motor proteins" associated with them. Two can be assembled and disassembled rapidly from subunits. One is insanely stable under virtually all conditions.
For your assigned structure, identify its superpower (motor protein or insane stability), how it is used in a single cell (Some are used more than one way) and how it can be repurposed for other applications in single cells and in an organism.
Look forward to the discussion.
You can start with the wikipedia entry on cytoskeleton and go on from there. Don't go crazy on this. I want you to see how they can be used.

Ryan, Lucius, Ethan, Evan: Actin: This one has a really dramatic use in animals
Dolce, Mira, Clare, Bella: Tubulin: This one has many uses in the cell…
Andrea, Ha Ha, Miller: intermediate filaments. Also repurposed dramatically in animals.
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