Warm Up 1 Student Responses
Remember...look at the lecture notes and do the readings before (or while) doing the Warm Up. You may need to look terms up in the book's glossary or on the CD (or on google!).

Please enter a nickname (in case your answer is used in class!)

QUESTION 1: In your own words, what are two major differences between bacterial cells (prokaryotes) and animal cells (eukaryotes)?

From cookie: q1: One major difference between the bacteria cell from the animal cell, is it doesn't have a nucleus which is telling us that the DNA is not seperate from the cytoplasm. Also the bacteria cell lacks internal organelles which makes the cell look different because it isn't filled with a bunch of scary looking parts, but rather it is filled with a few basic parts.
From drea: q1: Prokaryotes are very small, they lack internal organelles. Prokaryotes have one circular chromosome and they have tough external walls. The Eukaryotes are subdivided by internal membranes, they have DNA which is organized into chromosomes the cytoplasm surrouds their nucleus and organelles. The biggest difference between eukaryotes and prokaryotes is that the eukaryotes have a nucleus and the prokaryotes do not.
From Beth: q1: Prokaryotes seems to me to be a less sophisicated cell. They are basically a bunch of goo held in with a strong wall. Eukryotes have divisions. Unlike the pro's they have a nucleus.
From Ali: q1: The prokaryotic does not have a nucleus, therefor the DNA is floating. The eukaryotic has a nucleus, and that is where the DNA is stored. Animal cells do not have a cell wall, but Baterial cells do. Animal Cells are also considerably bigger than Bacterial Cells.
From the Glove: q1: I think the most significant difference between the two is that Prokaryotic cells lack a nucleus while Eukaryotic cells have a nucleus that encases their DNA. In a Prokaryotic cell the DNA is not seperated from the rest of the cell; the DNA just sits in the same compartment that everything else is in. The second difference I would point out is that the DNA itself in a Prokaryotic cell is comprised of only one chromosome while the DNA in a Eukaryotic cell consists of two. Is that correct or can Eukaryotic cells have more than two chromosomes? I think their differences can be summarized by saying the Prokaryotic cells are much simpler, less compartmentalized and smaller than their Eukaryotic counterparts.

QUESTION 2: All cells are surrounded by a plasma membrane, consisting of numerous proteins bobbing around in a fat-like layer of lipids. In your own words, describe one or two roles these proteins play in the functioning of the cell. In your own words, why do you think the lipid layer is crucial to maintaining the structure of the cell?

From Sunshine: q2: The proteins are a means of transportation for materials to enter or exit the cell. The lipid layer is crucial to maintaining the structure of the cell because if there was no lipid layer there wouldnt' be a structure and then it wouldnt' be a cell.
From Jason: q2: Proteins play a few roles in the functioning of a cell. Without the proteins materials may not be able to enter or exit the cell. Proteins along with lipids help keep the cell intact, kind of like its "skeleton." The lipid layer itself is also crucial in maintaining the structure of a cell, without it a cell would have no shape, it would be a blob of cytoplasm and enzymes.
From KC: q2: The lipid layer acts like a type of sack. It keeps the things inside the cell that need to be in, and it keeps the unwanted stuff out of the cell.
From B-rad: q2: The proteins in the plasma membrane have the responsiblity of filtering the things that try to enter and exit the membrane. Using receptor or recognition proteins, they might decide if a material can enter or exit the membrane. The transport proteins let the material in or out through diffusion or osmosis. I think the lipid layer is crucial because it acts as a "bodyguard" for the cell.

QUESTION 3: Most cells are microscopic (i.e. they can't be seen with the naked eye), ranging in size from about 50 microns for animal cells to as small as 1 micron for bacterial cells. Why do you think that cells - animal, plant, or bacteria - don't get any bigger than this? Why do you think we are made of 75 trillion (75,000,000,000,000) very small cells, rather than just a bunch of very large cells?

From KiaB: q3: A large cell would have trouble moving things through the cytoplasm. Small cells can e asily move around materials.
From M.K.: q3: After reading the explanation of the surface-to-volume ratio, in which the cell's volume will increase faster than it's surface area, it's obvious that the plasma membrane cannot support the voume change and the cell will not get enough nutrients or have enough by-products removed to be able to survive. I also think that "safety in numbers" is helpful to organisms, as smaller cells may be able to reproduce themselves more rapidly to replace dead or dying cells.
From Babydoll: q3: If a cell grew bigger that it is suppose to be it would have to produce more cytoplasm. A larger cell would also slow down the flow of nutrients and wastes. If we were made of larger cells it would not only have the problems listed above but would also have trouble moving things through its cytoplasm. This would put us more at risk of ending up with a bunch of dead cells.
From Steele: q3: By having more small cells versus less larger cells the smaller cells are able to be more task oriented. If we had fewer cells they would have to multitasking to be able to make up for what the 75 trillion cells do currently.
From tigger: q3: Since the question stated "why do you think", rather than "what is the reason", I am assuming that there is no wrong answer for this question. So here it goes. The reason that cells are so small is that they simply MUST be. The bigger they get in size, the more "food" they have to eat and the more wasts they will produce, eventually killing the cell due to the fact that these processes will become unstable; they will not balance out. Also, the smaller the cell, the more efficient the preocesses will become. Smaller cells move materials through their cytoplasm much faster than if the cell was as big as a basketball. Something I feel is not very clear to me is the "surface-to-volume ratio" theory. From what I understand, the larger the cell expands and the more it increases in size, the inside will evidently grow faster than the cell wall. From this theory, the answer is explained a little better, although I still need some more explanation in the classroom.

Note from Dr. Marrs: A lot of people also answered something like this: 'Q3 = I look at this as if you have more you can afford to lose more of them????? If we only had 5 cells and one died, it would be bad news... but if we lost one out of 75 trillion, we would still have 74.99999999 trillion left to take their place! ' This is a good point as well.

However, the bottom line is that our cells are so small due to the surface-to-volume requirements - the bigger the cell gets, the more difficult it is to exchange oxygen and carbon dioxide (and other waste products) efficiently. See your CD for an interactive exercise on this! Living organisms use all kinds of ways to increase the surface area of their cells and organ systems...for instance: Surface area of human...

Skin: ~2 square meters, and the thickness of a paper towel.
Lungs: About the size of your textbook, but divided up into 300 million alveoli cells to result in a surface area of ~ 160 square meters (the size of a tennis court!) - 80 times the surface area of our skin! All that surface area is needed to exchange O2 and CO2!
Digestive system: 20 feet long, but cells lining the intestines are highly folded and have "ruffled" edges (kind of like shag carpeting...) to result in a surface area of ~ 300 square meters!! All that surface area is needed to absorb the water and digested food we eat!

QUESTION 4. Any thoughtful comments, grumpy complaints, glowing praise, or harsh criticism about N100 so far? :) Any question about the material you would like me to address - life, scientific process, 3 domains, cells...?

Material:
q4: Actually the only materials I am having trouble with is the material we are going over right now, chapter 4. It is so many thigns going on inside the cells and so many things to remember that it becomes confusing. I've read over the material a few times, I just can't get it, I think it is mostly because how much I dislike science, but it gets better when you go over it in class. Thanks.
q4: Question number 3 was really freakin' tricky. NO MORE HARD QUESTIONS!!!!!

Course:
q4: I am just wondering what the test will be like.... how detailed, how long, those types of things? Thanks
q4: I dont understand what chapters we are on so i can not read them and study them... i guess i am just confused about that.
q4: I have been having problems reading and fully understanding the material. The CD ROM helps a lot but I didn't know if that was the same as reading the material? Most classes the cd doesn't cover half of what the book covers.

Misc:
q4: I like the class alot so far... I get alittle confused because you talk fast sometimes but other than that I think this class will be alot of fun.
q4: So far, I like the class. However, I think it would be cool to do things with microscopes and things like that. Although, I do not know how possible that would be with such a large class.
q4: this is a very small thing, and i feel kind of silly mentioning it, but when you lecture you drag the computer mouse over the words you are reading and it is kind of distracting to me. I like that you are showing where your lecturing from, but maybe just underneath the words, or point at the sentence...its just right on top of the words that makes it hard for me to follow along. OK! : )

Some nicknames...just for fun :)