Dance Club Patrons Describe Water Molecules

Written by Dave Sheldon, St. Clair County Community College

I approach the changing density of H2O by having students imagine a high energy dance club. They imagine the loudest and most energetic night club that they can, and describe it in detail. They focus on the intense energy, the motion of the people and the number of people on the dance floor. I include some techno music to get them thinking! Once focused on the high energy and rapid motion of the patrons, I modify the scenario. First I drastically reduce the energy by cutting the music, killing the strobes and bringing up the house lights. My students describe a ringing of ears and a much slower movement by the club patrons. Second, I describe every person as an H2O molecule with their arms outstretched in front of them at a 90° angle. Their hands represent two Hydrogen atoms and the middle of their back represents their Oxygen atom. Hydrogen bonding causes them to place their hands on the backs of two other people while two more people place one of each of their hands on your back. With low energy in the club, these bonds last for a relatively long time and the water molecules form a low density crystalline lattice. The people on the dance floor during the high energy rave would no longer fit in this low energy orientation. Some even note that they may actually be forced out of the club through windows and doors, which is what happens when water freezes.

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.

Amino Acids Are Like the Letters of the Alphabet

Written by SuEarl McReynolds, Palo Alto College, San Antonio, TX

When I’m talking about proteins, I tell the students that there are only 20 different amino acids. Yet from just those 20 “building blocks”, an infinite number of proteins can be formed. At first that idea is hard to grasp. Then I ask how many letters there are in the alphabet. They reply “26”. Then I ask how many words can be formed from those 26 letters. The light goes on. Then I comment on the fact that there are 26 letters but only 20 amino acids, but in forming words what makes the difference is the particular letters that are used, the number of those letters and the sequencing of those letters. All of the same variables are true in forming proteins from amino acids—PLUS the three-dimensional arrangement of the amino acids. It’s like playing 3-dimensional Scrabble.

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

Lock and Key Analogy with Enzymes

Written by Michelle Zurawski, Moraine Valley Community College

This is an analogy that is used during the enzyme discussion. I compare the enzyme substrate complex with a lock and key. My car is a cheap fuel efficient little car so I tell the students that I would like upgrade to a nicer Prius. I ask them if I could go to the parking lot and open a nice new Prius with my key. I then tell them that this is one of the ways that enzymes work to save energy. You only need a small amount of enzyme (1 key) to work with a specific substrate (1 car). Just think if you had to make a new key every time you opened up your car door. That saves energy by using that same enzyme (car key) over and over for the same reaction (car). Enzymes are specific to one substrate just like the key to my car is specific to my car. You can also use the two puzzle pieces fitting together like an enzyme and a substrate only fitting together in one way.

The Energy Barrier for a Chocolate-Craving Pregnant Woman

Written by Kelly A. Hogan, University of North Carolina at Chapel Hill

When discussing the energy of activation (EA) related to enzymes, I tell students about when I was pregnant and ate ice cream every night. I explain that after dinner I would sink into my deep, fluffy sofa. When I deemed it ice cream time, it was challenging to get up to get from the sofa with a big belly. I would complain and huff and puff,  etc. But sometimes, my lovely husband would hold his arm out and help to pull me off the sofa. In this analogy, my husband is the enzyme (catalyst) because he lowered the energy barrier for me. However, he didn’t make the impossible happen—I would have gotten that ice cream on my own—he just made it easier and faster for me to be a happy pregnant woman full of ice cream (the product of the reaction).

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.

The Earthquake Richter Scale and the pH Scale

Written by SuEarl McReynolds, Palo Alto College, San Antonio, TX

When discussing how the pH scale is logarithmic and a one number change is equivalent to 10 times as acidic or basic, I ask if they know what the Richter Scale is. Usually several people know that it has to do with measuring earthquake strength. So I ask how much difference they think there would be between earthquakes with a magnitude of 8 and a magnitude of 9. It’s “only one number.” In reality a magnitude 8 can cause serious damage over several hundred miles, but a magnitude 9 can cause devastating damage over several thousand miles. So one number change is a big difference in these kinds of scales.

When I get to buffers, I have a picture in my PowerPoint of a man working on a floor with a big buffering machine. He’s smoothing out the drastic high spots and low spots on the floor, making it more even. Or a person may act as a buffer between two friends with opposite personalities—again making things more smooth, the differences less pronounced—maybe helping the shy one feel freer to express opinions and the loud one less likely to interrupt and dominate the conversation.

Relating Chemical Bonds to Everyday Ideas

Written by SuEarl McReynolds, Palo Alto College, San Antonio, TX

I use several analogies when talking about chemical bonds. I compare them to different kinds of glue. I ask the students if they have a “junk drawer” at home. They smile, and I ask if it’s got some different kinds of glue in it—maybe paper glue, Elmer’s glue, wood glue, Super Glue.  Just like you need different kinds of glue to stick different materials together, you need different kinds of bonds to hold different kinds of atoms together. Probably a lot of people compare the attraction of the oppositely charged ions in an ionic bond to the attraction of the opposite ends of a magnet. Another common analogy probably is to compare the sharing of electrons in covalent bonds to holding hands (as in carbon is an atom that has four hands sticking out to hold with other atoms). Covalent bonds could also be compared to kids who want to play with the same toy. So they set a timer and switch off who gets to play with the toy.

When I talk about polar covalent bonds, which result from an unequal sharing of electrons, such as in the water molecule, I tell this story: “Suppose I come to class with a big chocolate chip cookie. I tell you that I’m feeling generous and am going to share my cookie with you. You anticipate that I’m going to break the cookie in half and keep half and give you half. But that’s not what I do! I really, really like chocolate chip cookies—so I break off a little piece for you and keep most of it for myself! Well, I did share.  I just didn’t share equally!”

When I get to the much weaker hydrogen bonds, I compare them to Post-It notes. I ask the students to visualize some inventor trying to formulate a new kind of Super Glue. He tries a lot of different variations and comes up with something that will hold things together when you want them held together but will release them without tearing them up or using a lot of energy when you want them separated. That’s the kind of adhesive that’s found in Post-It notes. It’s just a good thing he didn’t throw it in the trash because he had started out looking for a new kind of Super Glue! What would we do without Post-It notes? (I usually have one or two on my folders right there.) That’s what hydrogen bonds are like. An example would be the hydrogen bonds holding the two strands of DNA together. The strands need to be reliably held together most of the time, but sometimes they need to separate (of course I haven’t talked about replication or protein synthesis yet). It must happen without tearing the strands up or using an atom bomb’s worth of energy to make it happen. Then sometimes the strands will need to go back together (protein synthesis). That’s why the weak hydrogen bonds are important.