Problem One
Problem Title: I Am Hungry!
The Problem: Dave was very hungry during
his Introductory Chemistry class. It was scheduled just before the lunch
hour. Therefore, as soon as Dr. Book finished describing the structure
of the carbon atom, he was out of there and first in line at the student
cafeteria. He bit into his juicy hamburger with gusto and immediately felt
better. Unkonwn, or at least not of immediate note to Dave, was the fact
that, with that first bite, the digestive process had already begun, taking
the nutrients in Dave's hamburger and eventually delivering them to the
various tissues and cells at work in Dave's body.
Most of the absorption of these nutrients would
take place many hours later in Dave's small intestine. By this time, the
digestive process would already be well on its way, having continued in
Dave's stomach. Digestion involves breaking down the larger biological
nutrient molecules into smaller pieces that can be brought into cells and
sent from them into the underlying blood and tissues. In the small intestine,
a special cell called an epithelial cell lines the opening of the intestine
(known as the lumen) and moves the smaller nutrient molecules through itself
and into the underlying tissues.
Question? If one of these nutrient molecules is a molecule of glucose, how could it move into the tissues from the intestinal lumen?
A clue to this process came from the observations of scientists studying the transport of glucose into the epithelial cells from the lumen. They noticed that if they prevented sodium from entering the cell, they also stopped most of the glucose from coming in also.
Question? Think of some
sort of transport mechanism that would explain this observation.
Now that you have an idea how the glucose gets
into the epithelial cell, you need to figure out how it gets out to the
underlying tissues.
Question? What kind of transport system could accomplish this?
Looking at the answers you have to the above questions,
describe the entire process that is happening in the epithelial cell as
glucose moves through. It requires that three transport systems be functioning.
Be sure to discuss the role that each one plays in the process.
Dave is now asleep, giving his body a very well-deserved
rest!!