MCAT Form CT what's an astrocyte? and more!

[Premed2003]

I had form CT, and one of the answer choices was astrocyte. Does anyone remember this question? Do you know what the answer was? I think it was "which is least likely" so I chose astrocyte since it sounded like it was an astronomy answer!

And another question was something like ATP is part of a. b. c. ogliosaccharides d. something else. I don't even remember what I chose, but I don't think I did ogliosaccharides. Does anyone know which was the right answer?

And muscles contract--does Z get shorter? Or actin, myosin, or both actin and myosin get shorter?

There was an orgo passage where it referred to 2a and 2b and 3a and 3b but it only showed 2 and 3 so I assume that they were referring to enantiomers? Am I right? and 5a and 5b were enantiomers? So in that question where it said which were conformational isomers, was it 4a and 3a, or something like that?

Thanks! I hope I guessed right!!!

Oh and the first passage there was a question with c. no ERGs or whatever that was, and d. no estrogen receptor. I put c, is this right? I hope!

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[Mossjoh]

Okay..I'll try to answer a few questions for you. Astrocytes are cells located in the brain that put the myelin sheath around the neurons in the CNS. In the PNS, the Schwann cells do this function. So..yes..astrocytes do exist and are actually pretty important.

ATP is adenosine tri phosphate, basically its a adenine attached to a ribose, then on the #5 carbon of the ribose is attached 3 phosphate groups. So, base sugar, 3 phosphates.

When muscles contract, neither actin or myosin get shorter..or decrease in length. The just move along each other via a reaction with ATP and the conformation change in the myosin heads.
I can't remember which line decreases in length.

 

[Premed2003]

Thanks so much.

The question had something to do with the structural importance of ATP. It said something like ATP is important for energy, but also for the structure of a) b) c) d). Do you know what it could be?
I think c) was glyco something and d) was oligosaccharides
woohoo! since myosin and actin don't shrink then I got it right !!! woohoo!

Thanks!!

 

[leorl]

On that note, what the hell is a vole? Like, I guessed right...it was a rodent-like mouse thing. But I do not know when or where I am supposed to have come across "vole" except maybe in the ecology chapter which I definitely didn't review for the MCAT, nor have I seen in 5 years! Voles. Pffff.

 

[Mr.D]

The H-zone and I-band decrease in length during muscle contraction (ie, when the thick and thin filaments slide past each other using the energy of ATP hydrolysis), the A and Z-bands remain constant.

 

[Premed2003]

I don't remember a vole on CT. Was it on form CT?

I hope not because if it was I didn't see it :-(

 

[Premed2003]

H and I weren't a choice, so I'm not sure...
it was
a) myosin
b) actin
c) both myosin and actin
d) Z lines

What do you think would be right?

Thanks!

 

[Premed2003]

Oh yeah, and what about that question in PS where you had to decide the pH of a solution that made methyl violet turn violet and methyl red turn red. Was it ph less than 1 or ph between 3-5? I put less than 1?? I hope that was right

 

[Kritenoel]

another question that was on CT - the whole thing with the marathon runners. I couldn't figure out what the trend between the decreasing lac. dehydrogenase was (it said something had to increase for it to decrease, and I could not for the life of me see a pattern!).

 

[Premed2003]

oh yeah, me too!
I put the dehydrogenase enzyme because since I couldn't find a trend I thought maybe it's just that the enzyme breaks it down.

What do you guys think? Was this the right logic? I hope!!

 

[Sm00th13]

•••quote:•••Originally posted by Premed2003:
•H and I weren't a choice, so I'm not sure...
it was
a) myosin
b) actin
c) both myosin and actin
d) Z lines

What do you think would be right?

Thanks!•••••The answer should be "D" b/c Z-line defines the sacromere unit decreases. Both the mysoin and actin stay the same length as they slide over during a muscle contraction. I thought this was a simple giveme point.

 

[CaliBoy]

•••quote:•••Originally posted by Premed2003:
•H and I weren't a choice, so I'm not sure...
it was
a) myosin
b) actin
c) both myosin and actin
d) Z lines

What do you think would be right?

Thanks!•••••I agree with aesculapian. None of those shorten during contraction, so the question might have been worded differently

edit: Z-lines don't shorten during contraction, but adjacent Z-lines move closer together. Maybe that's what the question was really asking

 

[Premed2003]

WoOHOO I got it right.
YAY.

 

[Legend]

•••quote:•••Originally posted by leorl:
•On that note, what the hell is a vole? Like, I guessed right...it was a rodent-like mouse thing. But I do not know when or where I am supposed to have come across "vole" except maybe in the ecology chapter which I definitely didn't review for the MCAT, nor have I seen in 5 years! Voles. Pffff.•••••Damn... I put 'snake'.

Man.... English is not my first language.
I have never heard of that word.

 

[Ice Man]

Yeah, none of those shorten in muscle contaction.... weird. Also, astrocytes are scar formers in the CNS (they also regulate potassium). Oligodendricytes make the myelin in the CNS.

 

[Sm00th13]

•••quote:•••Originally posted by aesculapian:
•The H-zone and I-band decrease in length during muscle contraction (ie, when the thick and thin filaments slide past each other using the energy of ATP hydrolysis), the A and Z-bands remain constant.•••••I believe all ATP is needed for is to release the myosin head off from its binding site on actin. ATP does not cause the two filaments to slide pass each other. Once ATP is available it will allow myosin to unbind from it's binding site on the actin. That's why rit mortitis (spell wrong) occurs during death b/c no ATP is available causing the myosin-actin binding to hold (of course if you add ATP, the binding will undo itself) .

 

[Premed2003]

Thanks Daffy,
Oh no :-( I don't think I picked DNA. Why is it DNA?

Thanks!!

 

[Premed2003]

I'm just remembering some more questions. There was one about proteins. I forget the exact question, but I remember one of the answers was peptide. Does anyone remember this question? I picked a) peptide. I hope I'm right?

Also, the Pb fills what orbital by Aufbau? I think it was p, but now I think I might have put d instead. I think I put the wrong one, thinking it was p and wrote d. but I hope not.

Does anyone else remember some questions? I hope we guessed right on the tough ones!

 

[Premed2003]

Oh, for that question about the kidney and was it the marathon runners? The choices were glomerulus and loops of henle and 2 others. I put glomerulus. Was I right? I hope!

 

[Premed2003]

Oh, for that question about the kidney and was it the marathon runners? The choices were glomerulus and loops of henle and 2 others. I put glomerulus. Was I right? I hope!

 

[Forensic Chick]

Your test sounds a lot harder than mine was. All of the stuff that I had no clue as to what it was (or how to say it) was explained in a passage. I guess I lucked out with form FH!

 

[Resident Alien]

•••quote:•••Originally posted by Mossjoh:
•Okay..I'll try to answer a few questions for you. Astrocytes are cells located in the brain that put the myelin sheath around the neurons in the CNS. In the PNS, the Schwann cells do this function. So..yes..astrocytes do exist and are actually pretty important.
•••••I beg to differ with you, Mossjoh. Astrocytes assist in neuronal transport (by controlling neurotransmitter release), not laying down myelin. Unless astrocyte = oligodendrocyte (which i dont think), they are not the same functionally as Schwann cells.

 

[Premed2003]

I remembered the kidney question. A patient has large proteins in their urine and is hypertensive. What isn't working right?
c) glomerulus
d) loop of henle

Which was it?
Thanks!

 

[Sm00th13]

•••quote:•••Originally posted by Premed2003:
•I remembered the kidney question. A patient has large proteins in their urine and is hypertensive. What isn't working right?
c) glomerulus
d) loop of henle

Which was it?
Thanks!•••••i believe the answer was c b/c at that point things are selectively filtered at near the glomerulus. This form wasn't too bad, I've heard worst over at EK forum.

 

[Premed2003]

Woohoo!! YAY

 

[Cobragirl]

Just for the record:

Within the CNS, ALL of the connective tissue consists of GLIA with the exception of the fibrous connective tissue that forms the coverings around the CNS (the 3 meninges). The glial tissue contains ASTROCYTES, oligodendrdrocytes, microglia & ependymal cells (a type of epithelium).

Astrocytes come in 2 flavors:
1)Protoplasmic (in the gray matter)
2)Fibrous (in the white matter)

They provide support scaffolding for the CNS & blood brain barrier endfeet on vessels and meninges. They function AS the extracellur space of the CNS and contol ionic balance in addition to scavenging and binding "spent" neurotransmitter molecules (remember, neurotransmitter is released into an "open" space, the synaptic cleft.) They modulate neuronal metabolism and polarization (by allowing molecules in/out of neuron).

They do NOT control neurotransmitter release (except by regulation of ions coming and going...but that's regulation, not the actual MECHANISM of NT release), and they are NOT the same as Schwann cells. Schwann cells secrete myelin (among other jobs) in the PNS, and their counterparts in the CNS are the oligodendrites.

But you guys will know all this stuff by this time next year! :wink:

Hope this helps and good luck!!!!

 

[Papa Smurf]

•••quote:•••Originally posted by Cobragirl:
•Just for the record:

Within the CNS, ALL of the connective tissue consists of GLIA with the exception of the fibrous connective tissue that forms the coverings around the CNS (the 3 meninges). The glial tissue contains ASTROCYTES, oligodendrites, microglia & ependymal cells (a type of epithelium).

Astrocytes come in 2 flavors:
1)Protoplasmic (in the gray matter)
2)Fibrous (in the white matter)

They provide support scaffolding for the CNS & blood brain barrier endfeet on vessels and meninges. They function AS the extracellur space of the CNS and contol ionic balance in addition to scavenging and binding "spent" neurotransmitter molecules (remember, neurotransmitter is released into an "open" space, the synaptic cleft.) They modulate neuronal metabolism and polarization (by allowing molecules in/out of neuron).

They do NOT control neurotransmitter release (except by regulation of ions coming and going...but that's regulation, not the actual MECHANISM of NT release), and they are NOT the same as Schwann cells. Schwann cells secrete myelin (among other jobs) in the PNS, and their counterparts in the CNS are the oligodendrites.

But you guys will know all this stuff by this time next year! :wink:

Hope this helps and good luck!!!! •••••Ah, to be a wise MS1 at UF! :wink: Haha, $20 says you'll probably forget half of that stuff before Step 1. Hell, I'd probably forget all of it. :wink:

 

[Sonya]

Hi,

I didn't take the MCAT, but here are a few answers

Why DNA?
DNA = deoxyribonucleic acid This identifies the DNA backbone.
That meants it has a "deoxyribo" meaning a ribose-like sugar missing one oxygen.

"Nucleic acid" is that it has nucleic acids in it. EG, the ATG&C A = adenosine.

DNA also has phosphates.

ATP = Adenosine tri phosphate.

As we see, DNA has a adenosine bonded to phosphate -- Just like ATP.

There are three types of glial cells.
Astrocytes, oligodendrocytes, and schwann cells.

Oligodendryocytes fight attack.
Scwann cells lay down myelin.
Astrocytes maintain the overall concentration and ionic balance.

Astrocytes sound like astronomy b/c that's how they were named. If you looked at an astrocyte (especially under microscope), you might say it looked liked an astronomical feature, or a pattern of stars. This is because astrocytes need to be in all parts of the neuronal tissue, so they have to be very spread out.

Hope this is helpful!

 

[Premed2003]

Oh, another question.
Are blood cells made by the mesoderm?
There was a question that said which is not made from the mesoderm?
bone
muscle
blood cells
something else

I put blood cells. Am I right? I know it's not bone and muscle, but I wasn't sure if it was blood cells or d) something else that I don't remember
Thanks!

 

[Premed2003]

Thanks everyone for the astrocyte explanation. I appreciate it!

Does anyone who took test CT know what was the correct answer to that particular question?

Thanks!

 

[Cobragirl]

Papa, I've forgotten more this year than I learned in all of undergrad... :wink:

But I remember the stuff that counts...

 

[Premed2003]

Questions keep coming back to me
What about that question for C13 with that structure where you had to say how many resonances for C13 and H's.
I think I put 4 and 4. Was I right? I hope so! I counted wrong the first time and then counted again and got 4 and 4 so I hope I didn't make a careless mistake. Did anyone else put 4 and 4?

Thanks!

 

[Medical123]

•••quote:•••Originally posted by Premed2003:
•Oh, another question.
Are blood cells made by the mesoderm?
There was a question that said which is not made from the mesoderm?
bone
muscle
blood cells
something else

I put blood cells. Am I right? I know it's not bone and muscle, but I wasn't sure if it was blood cells or d) something else that I don't remember
Thanks!•••••I would guess that the answer would be blood cells.

 

[Premed2003]

Woohoo! Does everyone else think so too? I hope!

 

[Doctortobee]

The something else was the brain

 

[Premed2003]

Oh no. I just looked it up and I think the right answer was brain :-( Oh man!

 

[Legend]

I am also looking up every single question I got wrong, but what's the point ??? :wink:

There is nothing to be done about it...
Our scores will stay the same !!

 

[Kritenoel]

•••quote:•••Originally posted by Legi:
•I am also looking up every single question I got wrong, but what's the point ??? :wink:

There is nothing to be done about it...
Our scores will stay the same !! •••••That's how I'm looking at it! I should probably stop looking at this thread - I had CT, and now I'm second guessing what I put and didn't put (not as though I can change it now!). I'm glad it's over, and just hope I did well enough to not have to take them again.

 

[Legend]

•••quote:•••Originally posted by Kritenoel:
• •••quote:•••Originally posted by Legi:
•I am also looking up every single question I got wrong, but what's the point ??? :wink:

There is nothing to be done about it...
Our scores will stay the same !! •••••That's how I'm looking at it! I should probably stop looking at this thread - I had CT, and now I'm second guessing what I put and didn't put (not as though I can change it now!). I'm glad it's over, and just hope I did well enough to not have to take them again.•••••haha...
I had form EH, but I keep thinking that I bubbled in EG instead....

 

[Green912]

CNS= oligodendrocytes = myelin
PNS= schwann cells = meylin
Astrycotes = CNS, supportive, buffering & nutrients. :wink:

 

[Neuronix]

•••quote:•••Originally posted by Doctortobee:
•The something else was the brain•••••The brain is definately ectoderm. Blood cells are made in bone marrow (I guess technically part of mesoderm), and bone and muscle are both mesoderm. Sorry

Thanks developmental biology!

 

[Premed2003]

Oh, another question

The virus becomes crystallized. What was the answer to that one? I don't remember what I put. What was that answer? <img border="0" title="" alt="[Frown]" src="frown.gif" />

 

[SDN]

Moving to MCAT forum.

 

[Premed2003]

Oh, what was that question about papayas? I forget what it was about. Does anyone remember?

 

[MD/PhDApplicant]

I took the DK form in San Francisco.

For the virus question, I answered that viruses have a defined geometry formed by the capsid proteins. The head of the virus has a unique geometric shape. Because the head has a defined geometry, I believe it can be crystallized and have crystallography performed on it.

The papaya has an enzyme that was told to cleave myosin heads. Therefore, I believe the answer would be that the enzyme is used as a meat tenderizer. Meat is stiff since there is no ATP present and so the myosin heads cannot release from the actin filament. Using an enzyme that cleaves the myosin head will allow the sarcomere to relax. The other answer choices made no sense.