Different models for sugar transport have been proposed through the years. Look through different editions of college texts to get some idea of the diversity of ideas. In the Eurekalerts, there is an announcement about a paper in this week’s PNAS with strong evidence supporting one specific hypothesis:
The theory of transporting sugar, the polymer trap model, was first proposed in 1991 by Robert Turgeon, Cornell professor of plant biology. He is also the senior author of the latest research published in the Dec. 4 issue of the Proceedings of the National Academy of Sciences. Ashlee McCaskill, Ph.D. ’07, who worked in Turgeon’s lab, is the paper’s lead author.
Turgeon’s theory suggested that as sucrose, a form of sugar, accumulates in leaves as a product of photosynthesis, it diffuses into the plant’s tubelike transport tissue, called phloem, along with other nutrients to move to other areas of the plant. Once in the phloem, small molecules of sucrose polymerize, or combine, to form larger, more complex sugars, which become too large to flow back into the leaf. The polymerized sugars are then forced to move away from the leaf to parts of the plant where they may be used or stored.
To prove the theory, Turgeon and McCaskill genetically engineered a plant closely related to a member of the figwort family, purple mullein (Verbascum phoeneceum L.), so that two genes involved with polymerizing sucrose into larger molecules were silenced. When they did so, sugars backed up in the leaves.
AP teachers in particular will want to be aware of this paper and model for transport.
For the past year or so KABT’er, Scott Sharp, has been asking me if I can help him generate a list of essential, core concepts that every biology student should learn–something a bit different than just a re-visitation of the science standards or a TOC from a text book. As we have carried on this discussion Scott usually seems to focus on trying to identify those little kernals of knowledge and understanding that open an entire realm of new exploration in biology understanding. At any rate, I’ve usually been a bit evasive on the subject; indicating that, yes I have a pretty good idea of the “essentials” in my mind but that varies each and every year that I teach and is highly subjective to who I am as a biology teacher. I suggest that he will develop his own as he continues to reflect upon his teaching.
Generally, for me the “essentials” of biology content probe the big questions in biology and how to answer them. The big questions have lead to big theories—evolution, cell theory, genetics, development, ecology. Scott, rightfully so, is not satisfied with this answer so he continues to explore which is exactly what I hope he does.
Recently, Scott found a paper by Robin Wright that has really got him thinking. Here’s how Scott introduced her paper in his email to members of a PLC:
“Here is a very interesting article from Dr. Robin Wright, Associate Dean and professor in the Department of Genetics, Cell Biology, and Development College of Biological Sciences at the University of Minnesota. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1201698 She makes a series of very convincing arguments that there are no essential concepts in biology (for non-majors), or any of the disciplines. What is essential to biological literacy is learning to think and act like a biologist, and the way that is done is through investigations that are of interest to the student and the teacher. Enthusiasm of the teacher, and guiding the students in their inquiry of topics is the only skill that matters. She makes MANY incredible arguments, and I think that some PLC time to discuss this perspective would be tremendously beneficial. This was really earth-shattering for me to read and contemplate.”
Take time to read this article and make comments on your thoughts here. We’ll try to get Scott involved in an discussion, as well. Mike Klymkowsky has a counter point to Robins article that you should check out that may add to the discussion.
Something I never, ever thought would happen in my lifetime–black-footed ferrets are roaming Kansas prairies, again.
Black-Footed Ferrets Return to Kansas Prairies Tuesday Dec. 20, 2007
A wondrous event occurred just before sunset on Tuesday evening–a week before Christmas. Twenty-four Black-footed Ferret pups were released in the wild to begin the restoration of a vibrant part of the Kansas wildlife heritage missing for fifty years. This was a heart-warming and historic occasion. The ferrets were released on private properties in Logan County, Kansas….
Here’s an opportunity passed on from one of the NSTA listservs. Don’t let being from KS stop you if you are interested. Projects like this want to see how well their approach works with landlocked classrooms too.
I am writing to invite you to consider piloting a new online unit on the COOL Classroom (http://new.coolclassroom.org). I have included more information about the new and improved COOL Classroom at the bottom of this email. Continue reading →
The UKanTeach program, through the Chemistry Department at the University of Kansas, invites individuals with either a master degree or a Ph.D. in education, science or math to submit applications to their ongoing Master Teachers Pool. This is a ten month – non tenure track position. Individuals must be extremely skilled, knowledgeable in at least one of the above fields. The pool will be reviewed on a regular basis. Information about the UKanTeach program can be found at http://ukanteach.ku.edu. For complete description and to apply go to http://jobs.ku.edu and search for position 00066566.
Some claim that I get a bit crazy with math while teaching biology. I was teaching my students the advantages of semi-log and double log paper back before computers and when I was in the boonies where I had to order the paper a year ahead of time. (while climbing uphill, both ways) At any rate, you can imagine my delight when I found this freeware application written by Dr. Pillippe Marquis that let me design my own graph paper. I thought it was no longer available but recently I ran across it, again and figured I’d better share it. Try it out, I think it will produce most any form of graph paper you are interested in. You can download it here.
An NABT’er by the username “kvhteach” has posted a YouTube video of Francis Collins’ sing-a-long at the recent NABT meeting in Atlanta. Rhoda Garcia and others asked about the lyrics. Here they are. Thanks to Dr. Collins and “kvhteach”
It is truly amazing what we can do today, isn’t it?
Congrats to the staff and board of NABT—they put on a very informative and enjoyable meeting at Atlanta. Not that I talk to all that many members (yea right) but I can say that I did not hear a single negative comment the entire time. I’m convinced that almost everyone attending found the meeting to be very rewarding and productive. Oh, and by the way–KABT’s own Todd Carter was in the middle of it all and of course officially begins his presidential duties after the first of the year.
KABT members from KS (besides Todd) I saw in attendance include: Paula Donham, Sandy Collins, Randy Dix, Eric Kessler, Pat Wakeman, Terry Callendar, Harry McDonald and Sondra Dubowsky. I apologize to those I left out, memory isn’t what it used to be. (Make sure you comment to the post and we’ll get you in.) You’ll notice that the presenters at the KABT Share-a-thon (Sandy, Randy, Paula and guess who) have provided handouts or resources here on the KABT BioBlog. The session was well attended and we had a number of comments on how folks really like the format and atmosphere. If you haven’t attended or presented, we divided the room in to four regions and rotated the group every 10-15 minutes so that every one had a chance to interact with the presenters. Pat W. was there taking beaucoup de picts that I hope will be appearing here on the BioBlog one of these days. I’m sure they will be evident in the newsletter.
One final NABT thing: This year is one of the most important transitional years our organization has faced. The board and staff have truly worked very well together to meet this extraordinary challenge–my hat’s off to them for a job well done. We have a new staff member at NABT who, I think, is a great addition to an already great staff–Jaclyn Reeves-Pepin. Her official title is Director of Development. Based on how much she’s accomplished already, I can’t wait to see what plays out over the next year.
If you are not a member of NABT, think about it. If you have any inkling at all that you think NABT membership is something you want to consider, do it right now. Click on the link in the upper right-hand corner, or here and join.