Biology question - can someone confirm if I'm right?

A. Yes this is a homework question.
B. No, I don’t want you to do it for me.
C. Please just say yes or no.
D. IF I am right, and ONLY if I am right, feel free to add any tidbits that you think might be interesting.
E. If I’m wrong, please don’t tell me the answer. BUT, please feel free to tell me if I’m totally off track.

So, the question is:

What would you expect to find when looking through an SEM at a cell treated with an enzyme that cleaves proteins at their hydrophilic amino acids.
A) a cell surface that is devoid of any major structures
B) a cell surface covered with polysaccharides
C) a cell surface coated with hydrophilic proteins
D) a cell surface coated with lipids and polysaccharides
E) a cell surface without its outer phospholipid bilayer

I chose D and here’s my reasoning:

The enzyme only affects proteins at their hydrophilic amino acids. The phospholipid bilayer has embedded proteins. These proteins have hydrophilic parts exposed to the outer environment and hydrophobic parts safe and sound in between the layers with the hydrophobic tails of the bilayer.

Carbohydrates attach to the phospholipid layer to form glycolipids. Carbohydrates also attach to the proteins to form glycoproteins.

So, if the enzyme is only chopping off the heads of the proteins at their hydrophilic (exterior) parts, the carbs will get chopped off as well. But, the glycolipids will be unaffected. So, the cell surface will be covered with glycolipids (glycolipids=carbs+lipids=polysaccharides+lipids).
So, am I right or do I need to go back to the drawing board?

Given the context of the problem, I agree with your reasoning.

SWEET!!! I spent 3 days trying to figure that one out and it finally hit me when one of my friends mentioned glycolipids. I was so focused on the proteins that I totally forgot about them and was going to choose A.

Thank you!

Sounds good to me. I’m a bio prof.

Thanks for the extra confirmation Ivory. Now I’m fairly confident that I got everything on this assignment right. Then again, I was fairly confident that I passed the test that most of us failed, prompting him to give us this assignment over spring break.

I don’t get the wording of D. Cell surface coated with lipids? Lipids ARE the cell surface. Aren’t glycolipids just a carbohydrate attached to lipids in the bilayer? If so, then B would be correct. Either way it seems a little confusing…unless you can differentiate between “cell surface” and “lipids”

Awww, did you have to say that?
Actually, what you say does make sense. Even in my Bio for dummies book, it shows the cell surface with the glycolipids dangling off, looking like polysaccharides. The glycoproteins look like the cell surface has hairy moles (the mole is the protein and the carb is the hair). So, now that I think about it, what you say seems like the right answer.

I’m going to keep the answer I have already (D) but I’m going to ask my professor about it tomorrow morning, before class starts. I can’t wait until next week to find out what he expected the answer to be.

It seems that a few of the potential answers are poorly worded. I assume if you “know” the cell surface is lipid then D is redundant…unless there is something basic about glycolipids that I don’t remember.

What level Biology is this? That may determine the answer.

According to my lecture professor (the one who assigned this homework), the correct answer is A) a cell surface that is devoid of any major structures. He said that polysaccharides are not major structures (I’m supposed to know this after 8 weeks of Bio 101, when I’ve never even seen an SEM?)

My bio lab professor said that she agreed that A (if you want to be nitpicky), D (if you’re not hugely nitpicky), or B (correct) would have been the right answers and she was leaning toward B.

If A is correct then B has to be correct also. Just because they are not major structures does not mean they won’t be there. I don’t do any SEM work so I don’t know that polysaccharides on the cell surface would be visible using SEM. And, assuming that after 8 weeks you have not been exposed to many SEM images, how would your professor expect you to know?

The only SEM images I’ve seen are the 2 or 3 that were in the textbook section that explained different types of microscopes. I used my first microscope in 15 years today - a basic light microscope. I looked at my cheek cells. I am so qualified to determine what structures can be seen on an SEM image. :rolleyes:
I have come to the conclusion that I am not going to get an A in this class and I’m ok with it. I’m actually learning stuff and I am comfortable with my level of understanding. I’m taking 4 more lab sciences in the next 3 semesters so I’ll have more chances to prove that I’m not a complete scientific idiot.

The bio lab I work in has a few people who’ve used SEMs and some structure biologists, so I’ll pose the question to them and see what their reasoning is.

What is your major? I found the first year of Biology extremely tedious. The class sizes were large and the professors were necessarily assholes who were looking to weed out a good percentage of the freshman. Most of what you learn is complete BS. It does get much more interesting and involves much less rote memorization as you move forward. Of course, if you are not a biology major then chances are you are just suffering through a requirement.

chorpler: I’d be really interested to know what they say.

yorick73: My major is Liberal Arts but only because I’m in community college and we don’t have Biology majors. When I transfer though, I will be majoring in a biological science - hopefully Pathobiology.

So, I have to take 2 lab sciences for the liberal arts major but I haven’t taken any science classes since 1998 and some of my classmates weren’t even born the last time I took Biology. I remember that I loved it but I can’t remember a single useful thing because it has been so long. Unlike most of my classmates, I am taking Bio because I want to. I’ll also be taking A&P in the summer and Physics, Cell Biology, and Chemistry in the Fall (I only actually need to take Spanish in the fall so I’m filling out the schedule with stuff I WANT to take - to make up for the boring liberal arts and humanities classes I’ve been forced to take).

I think a large part of the problem with the class is that we have one 3 hour lecture per week and very few homework assignments, no quizzes, and only 1 test. It’s very hard to determine if you have learned anything by reading the textbook and attending lectures if you don’t really have anything to help gauge what you learned. He did seem to come to that same conclusion because he has given homework both weeks since he handed the tests back. Now we just need to work on the ambiguity in the multiple choice answers. He is very good with the lecture though. He is very knowledgeable and he’s good at rewording things if we don’t understand the first time. All in all, I like him as a professor. I just think the questions need a little work.
He is giving us the chance to earn up to 20 extra credit points that we can apply to either the test we already took, or the one remaining before the final. All we have to do is write a 1000-1500 word report on a topic that discusses the role of a biology field in social or public policy. All I have to do now is figure out what the hell I want to write about.

Interesting…I just found the Campbell’s answer to that question and the answer is A. I think that’s BS and those textbooks often word questions poorly. Looks like your prof took the easy way out.

Funny you should say that. My lab professor was looking at the test from a couple weeks ago because someone even with more obsessed with his grades than I am asked her to let him know if the test was unreasonable. She told me today that she could tell from a quick glance the test came from the textbook publisher and that she wouldn’t have used them because they don’t test whether the student actually understands anything.

Not only that but, often, multiple answers are correct. I don’t know who writes those questions but they should be shot.

You may find this link interesting:

Right, as long as lipids and polysaccarides will be visible, I’d say that either answer is correct, unless there are unstated guidelines in the assignment such as “For the following questions, if a question asks you about the presence or visibility of a substance or structure, ignore it unless that substance or structure is a major component of the cell or organism mentioned.”

If you hit a healthy person’s arm hard with a wooden ruler, what are you likely to see if you examine that person’s skin 10 minutes later?
a) No life threatening medical conditions
b) skin cancer
c) a ringworm infection
d) a bruise
e) a gunshot wound

A and D are both reasonable answers…

If you don’t mind, I might use that question you posted if I find the need to defend an answer in this class.

And no, there were no specific instructions although there WAS a comment made a couple weeks ago that there are right answers and more right answers and we should find the more right answer. I’m not sure if we have learned enough yet to distinguish between right and more right though.