Warm Up 13:
Photosynthesis and Respiration
...and how to keep cats from answering your warmups.

QUESTION 1: Suppose you wanted to purchase a "grow light" for your houseplants that emitted the wavelengths of visible light necessary for photosynthesis. At the store, you discover that there are 4 colors available: red, blue, green, and yellow. Assuming you only had enough money to purchase one, which one would you buy and why? If there was a "two for one" sale, which two would you buy and why?

From RV: Q1 = I would buy a red light and if there were a two for one sale it could be a blue light. It is the red and blue colors that the plants take in but they reflect green.

From Ang: Q1 = I would choose either red or blue because chlorophyll absorbs those colors the best and green plants contain chlorophyll.

From Scooby: Q1 = I would buy blue and red because the plants soak up those color wavelengths of the sun and reflect back the green. Those colors help electrons from the chlorophyll to higher levels.

From Lily: I would purchase red and blue grow lights since wavelengths in the blue and red spectrum are the most important. For plant growth red rays promote stem growth and flowering, while blue rays encourage leaf formation and dark green foliage.

Note from Dr. Marrs: It is true that the sun appears yellow to us, and does emit all wavelengths of light - ROY G BIV as well as untraviolet. However, chlorophyll in chloroplasts is most excited by red and blue wavelengths.

QUESTION 2: Anemia is a disease that is caused by abnormally low hemoglobin levels or too few red blood cells. What do you think happens in the body cells of people who are anemic that makes them feel tired and weak? Please read the notes before answering this question! )

From DS: Q2 = You know, I've never even really thought about this question. My mother is anemic, so she's always exhausted by the time she gets off of work. But I don't really know what causes you to become so tired.

From SP: Q2 = Just a guess, but people who are anemic feel tired and weak because having fewer red blood cells means their bodies get less oxygen and can't burn sugar well. Since their bodies break down sugar less often they have less energy and are weak because of the low red blood count.

From Mo: Q2 = In an anemic person, the blood cannot provide the tissues with enough oxygen. Thus makes the person weak and tired.

From The Countess: Q2 = I think that their cells are not getting enough oxygen. I'm not really sure. I read the notes but I still don't know. I think it probably does have something to do with the lack of oxygen though. That would explain why the person is tired and weak.

Note From Dr. Marrs: We will discuss this on more detail in class. Many of you wrote that RBCs carry oxygen, and a lack of oxygen makes people feel tired, but WHY does a lack of oxygen cause a person to feel tired? What's so special about oxygen that having more of it makes you less tired???

(Answer: Our bodies use oxygen to fuel the process of cellular respiration. In the same way that a fire needs oxygen to burn, our cells must have LOTS of oxygen to burn up that sugar to make ATP! More oxygen = more cellular respiration = more ATP = more work can be done!
Not enough oxygen = less cellular respiration = less ATP = less work can be done before you feel tired.)

Now, everyone take a deep breath!!! :-)

QUESTION 3: In the absence of oxygen, yeast cells are able to undergo a partial breakdown of glucose to yield 2 molecules of ATP and a waste product, ethanol (or ethyl alcohol). What prevents the yeast cells from breaking the sugar all the way down to CO2 and water? Please read the notes before answering this question! Why do you think that beer and wine both have an alcohol content of ~12% [this is not in the notes!]

From CT: Q3 = In anaerobic respiration there is no oxygen present to allow for the formation of CO2 or H2O. Perhaps 12% is the largest percentage of waste material (alcohol) that can be tolerated by the yeast.

From SG: Q3 = It is prevented because it does not go through the mitochondria, therefore cannot run respiration without oxygen. 12% is all that it can tolerate without killing the yeast.

From Johnny Q3 = I have no clue why beer and wine have an alcohol content of ~12%, however let me say, that I am a big fan of both.

From Dr. Marrs: Again, lack of oxygen causes this situation, which results in an ineffecient breakdown of sugars. The cell can extract enough ATP without oxygen to survive, but can only break the sugar down partially, releasing alcohol as a waste product. In the case of beer or wine, the yeast cells can survive in that waste product until they are literally pickled in their own juices, so to speak...! When the level of the alcohol reaches a concentration of 12%, it is just too much for the poor cells, and they die (happy, maybe, but they still die...). [Do you know how to calculate your Blood Alcohol Content?]

Q4 Comments or questions? Suggestions for the last weeks of class?

Q4 = Oh, let's have a big biology party!

Q4 = I am looking forward to going over photosynthesis. Finally, there is going to be a topic that I am semi-familiar with. And thank God we are done with DNA, RNA, and all of that stuff.

Q4 = Really go over the objectives, and tell us specifically what is going to be on the last exam.

Q4 = I watched some on the program on the human genome project. Something like that would be very interesting to watch in class. There was a segment on tay sachs and it made the disease a lot more "human" as opposed to just words on a paper from the lecture notes. It is a horrible diesease.

Q4 = My cat jumped onto my computer and caused everything to be underlined. Not sure how to get rid of it. I guess he wanted to "help" me with my homework!

Note from Dr. Marrs (a kitty lover) familiar with the above predicament: PawSense: the first computer software designed to detect cat typing from human typing!!!