20 Jan 2010

Metals in Biological Systems - Who? How? and Why?

Five Slides About

Submitted by Elizabeth Jamieson, Smith College
Categories
Description: 

This learning object was developed collaboratively by members of the IONiC Leadership Council.  The overall goal is to provide a general overview of metals in biological systems and introduce students to several of the important ideas in the field of bioinorganic chemistry.  Topics include toxic metals, metals used in biological systems and the overlap of these categories; issues associated with the uptake, transport and storage of metal ions; and the benefits gained by using metals in biological molecules.  

The learning object includes a PowerPoint presentation (with various animations).  There are notes included in the PowerPoint file for each slide providing additional background and details to introduce in class.  For convenience, the notes from the PowerPoint file have also been placed in a separate Word document.

Learning Goals: 

Learning goals for these slides include:

1.  Students will be able to give examples describing the "problem" of metals in biology: lack of bioavailability, toxicity and the importance of getting it just right.

2. Students will be able to give three reasons (with specific examples) of why metal binding and transport is important.

     Metals have to be accumulated in the body (you can't make metals and they're not naturally prevalent).

     They must be stored in inert forms (because they're toxic).

     They must be present above a threshold to support life (metals must get in and out).

3. Students can use their knowledge of VSEPR to describe structures likely in bioinorganic systems.

4. Students can use their knowledge of Lewis acid-base chemistry to describe reactivity in bioinorganic systems.

 

Implementation Notes: 

These slides could be used to give students a sense of the problems and benefits of using metals in biological systems as a way to introduce important ideas in bioinorganic chemistry.  Many of the ideas, for example metal ion transport & storage, also have the potential to be expanded upon, with details from a text on bioinorganic chemistry or examples from the current literature.

Time Required: 
Approximately 1 class (or more if one chose to expand on the topics)
Evaluation
Evaluation Methods: 

Students could be asked to provide some of the information presented in the "Learning Goals" section above as part of an exam or quiz question.  

Evaluation Results: 

This learning object was developed collaboratively by members of the Leadership Council who teach these topics in class regularly.  In general, we have found that students are interested in learning how metals are used in biological systems.  The issue of toxicity is always interesting since students do not always realize that you can have too much of a good thing (too much Fe can be toxic, for example).  We have found that students enjoy seeing how topics they have already learned, like acid/base and redox chemistry, are applicable in biology.

Creative Commons License: 
Creative Commons Licence

Comments

I used this over two class periods toward the end of my one-semester, cover everything, inorganic class and I really liked it. I took the first day to cover the first two slides and do the Siderophore Building: In class Exercise. We spent some time discussing the exercise together and then talked a little about transferrins and their antimicrobial properties. The in-class exercise provided an opportunity to briefly review hard soft acid base theory and structures of transition metal complexes.

On the second day, we covered the final three slides about "Why metals?" and did the Bioinorganic Chemistry- Metals in Purely Structural Roles in-class exercise. My students didn't know much about methods for determining protein structure or function, but it was good for them to review the importance of size and charge in metal complexes. They knew that protein structures could be determined by X-ray crystallography, but they didn't know about using NMR to determine protein structure, so I talked about that for a few minutes.

Here are three homework questions I asked them:

1. Metals have low bioavailability and high toxicity. This begs the question, "Why metals in biology?" Give three examples of why/how nature employs metals.

2. What does "metal transport" mean in biology and how does it work?

3. Carbonic anhydrase inhibitors are used to treat glaucoma. They reduce the flow of fluid into the eye and reduce intraocular pressure. Production of bicarbonate is key to the production of aqueous fluids in the eye. One carbonic anhydrase inhibitor is dorzolamide (topical), a sulfonamide. How might it act? (Carbonic anhydrases catalyze bicarbonate production.)

These look like great discussion starters and I plan to try using them next time I teach my bioinorganic course (toward the beginning of the course). 

I'd have one request if revisions are possible - on Hb structures of the last slide (in the upper left as well as in the structures that appear during the presentation), would it be possible to show the C=C double bond of the histidine rings, and perhaps show the N-H bonds (one from each His) rather than the two C-H bonds that are shown coming off the ring?  The N-H is important for H bonding (to the bound O2 in Hb, for instance), and showing both double bonds within the ring system emphasizes that this is an aromatic structure.

 Rob Scarrow Prof. of Chemistry, Haverford College

Smith had a series of talks a while back entitled "Science at the Center" where a faculty member would give a ~10 min general science talk in the lobby of one of the science center buildings just before the start of afternoon classes.  I was asked to give one of these and decided that this 5 slides would be a great thing to present.  The title of my talk was, "Why do metals need chaperones?"

My talk was videotaped, and it's now up on YouTube (http://youtu.be/YiyKqjvZJN4).  While I really don't like seeing myself on tape, I thought it might be interesting for folks to see how I've presented these slides in a very short talk.  As Joanne mentioned above, this material can certainly be expanded to fill several class periods, but it can also serve to give a very quick introduction to important issues in the field of bioinorganic chemistry. 

Todate I did not cover any bioinorganic CHM in my Fundamental Inorganic CHM course.

This ppt is excellent for me to present in the last class of the fundamental course as an overview and some specific examples of applications of bioinorganic CHM.

Professor Jamieson,

You will be teaching my class (at least for the first 10 min) to introduce the topic of bioinorganic chemistry.

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