Instructor Exchange

Cells

Using Waves at the Beach to Describe Concentration Gradients

Written by Jennifer A. Metzler, Ball State University

When discussing passive versus active transport and the difference between an input of cellular energy, I ask students to imagine they are at the beach or at a wave pool. Since passive transport is going down a concentration gradient, I tell them to liken it to having the waves at their back and moving into shore. It is not a problem for them at all and they do not need to expend any energy as they are going with the flow. With active transport going against the concentration gradient, I tell them to imagine turning around and having the waves hit their chest and try to move away from shore. In this case they must expend energy as they are going against the flow of the waves.

Customize Your Auto Like Proteins Are Customized in the Cell

Written by Dave Sheldon, St. Clair County Community College

When discussing the function of the Golgi apparatus, I ask my students to picture a friend, two identical automobiles and an automotive customization shop. I ask them if they and their friend purchased 2 identical cars (same color, make model etc.), would it be possible to customize or detail them in a way that would result in two totally different appearing and performing cars? The answer always comes back “yes” and we discuss ways to modify an automobile. Ground effects, spoilers, window tinting, sound systems, paint jobs and fancy rims are usually mentioned. The car in this analogy represents a newly formed protein that has just been sent via a transport vesicle from the rough endoplasmic reticulum (auto dealership) to the Golgi apparatus (detailing shop). They imaginary car pulls into the receiving or Cis side of the shop and leaves via the shipping or Trans side of the shop. While in the Golgi detailing shop, the modifications represent chemical reactions such as phosphorylation, glycosolation and manipulation of the size of the polypeptide chain.

Aerobic Respiration Gives a Cell More “Spending Power”

Written by Jennifer Wiatrowski, Pasco-Hernando Community College

Relating the value of aerobic respiration to the real world. The students in introductory biology have very little interest in cellular respiration. But, I want them to understand that there is greater value (in terms of ATP yield) between aerobic and anaerobic respiration (like with exercise). So, I relate the processes to “dollars in your pocket” and “spending power at a fancy restaurant.” Anaerobic processes give your 2 ATP or 2 dollars in your pocket. Could this buy you anything at a fancy restaurant? No! This is not a lot of spending power. If you complete aerobic respiration, you have approximately 38 ATP or dollars in your pocket. Could this buy you something at a fancy restaurant? Yes! Now, you have spending power.

Energy Conversion and iPods

Jennifer Wiatrowski, Pasco-Hernando Community College

Relating the function of mitochondria and energy conversion to the real world. I ask students if they could charge their iPods by plugging it into a lump of coal or a waterfall (they generally laugh and say “no”). I then ask them if there is energy in a lump of coal or a waterfall (they  say “yes”). So, I reason that in order to utilize the energy in the coal or the falling water, it must be converted to another form. For charging their iPod, it must be changed into electricity and this is accomplished by a power plant. Now, I ask them what is the main energy source for cells? (They usually know this is sugar from earlier in the semester). I then explain that sugar is like a lump of coal to a cell. Full of energy, but inaccessible in that form. So, the job of the mitochondria is to convert the energy in sugar into a form the cell can use, ATP.Roblox HackBigo Live Beans HackYUGIOH DUEL LINKS HACKPokemon Duel HackRoblox HackPixel Gun 3d HackGrowtopia HackClash Royale Hackmy cafe recipes stories hackMobile Legends HackMobile Strike Hack

Using Food and Drink to Describe Osmosis

Written by Jennifer Wiatrowski, Pasco-Hernando Community College

I use two different analogies to relate osmosis to the real world:

a. I use two large beakers (beakers A and B), a jug of water and lemonade mix or fruit punch mix (these are dry powders). I then tell the class I am going to mix two classes of a refreshing beverage (nice in a hot climate like Florida). I tell them that I will make the first beverage very sweet, and pour in a large amount of lemonade or punch mix. The second beverage will not be nearly as sweet and I pour in a small amount of the powder. I then fill each of the beakers to equal volumes. I then ask the class if the two beakers have equivalent solutions. (They say no!). So, although the two beakers appear to have equal volumes, the amount of water is varies between the beakers. This shows students that the amount of water in a given space is influenced by the amount of solute. I then ask the students to imagine connecting the beakers together with a selectively permeable membrane and then ask them which way the water would flow  (from beaker A to B or B to A?)

b. I then talk about Martha Stewart. Martha always says that you should never toss your salad until your guests arrive or you are ready to serve it (I was recently informed by my students that “toss the salad” has taken on additional meaning……so this gets a good laugh out of the class). So, at the beginning of class, I take a bag of salad and some dressing and mix them. I then put it aside for awhile. In the meantime we talk about hypertonic and hypotonic. I then ask to think about the scenario with the salad and the dressing. They eventually reason that the salad is hypotonic to the dressing (or the dressing is hypertonic to the salad) and the consequence of this is a watery salad as the dressing pulls water out of the greens. This would make Martha HORRIFIED.  To finish, we take look at the salad we mixed earlier.