Bio/Chem

[userah]

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.Negative pressure breathing in human lungs results from.

.I...contraction of the diaphragm..
.II...relaxation of the diaphragm..
.III...incompressibility of intra-pleural fluid.

. I only
I and II
I and III
II and III
I, II and III

i'll list answer after some people take a look and figure out. i wasn't really understanding the solution so hoping fellow studentdoctors would be up to the challenge of putting it in lamen's terms for me =)

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The initial source of electrons for noncyclic electron flow in photosynthesis comes from breakdown of water.
.H2O .à. 2 H+ + ½ O2 + 2 e-.

the question asked from breakdown of what but my question is, is it safe to assume that water's broken down for cyclic electron flow as well?

----

.What will happen to functioning acetylcholines at the end of their neural-signal transmission?
. .They will remain binding to receptors on the postsynaptic membrane. .
.They will diffuse through the postsynaptic membrane and are ready to be reused. .
.They will be absorbed by axon bearing the presynaptic membrane and are ready to be reused..
.They will accumulate at the synaptic cleft for a prolonged period of time..
.They will immediately be broken down by acetylcholinesterases at the synaptic cleft..


The answer's E but why is it not C?

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next two questions are chem based
.
How many milliliters of 0.05 M HCl are required to turn 20 ml of 0.05 M KOH into a solution of pH 2.00? .

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.Why does the freezing point of water decrease when its system pressure is increased?

i understand this one has something to do with the solid, liquid, gas curve and that for water the solid, liquid curve leans more to the left but beyond that i couldn't put two and two together on this one so any help would be greatly appreciated

thanks in advance for any help you may provide 🙂
.

 

[Predentknight]

1.I believe it would be I and III. I for sure because as the diaphragm contracts its shape flattens out which sucks air into the lungs due to the negative pressure created. Not 100% sure about III but it definately sounds familiar. Mayb someone else can explain further on this.

I will try and figure out the other ones a bit later

 

[Orgodox]

The initial source of electrons for noncyclic electron flow in photosynthesis comes from breakdown of water.
the question asked from breakdown of what but my question is, is it safe to assume that water's broken down for cyclic electron flow as well?

So in the noncyclic electron flow electrons are excited and then passed along to the next photo-system then down etc for atp. Therefore water is split to porduce low energy electrons to replace these 2 excited electrons. In the cyclical path nothing needs to be replaced because the same electrons will continue on their path and produce 1 atp per cycle.

 

[userah]

1.I believe it would be I and III. I for sure because as the diaphragm contracts its shape flattens out which sucks air into the lungs due to the negative pressure created. Not 100% sure about III but it definately sounds familiar. Mayb someone else can explain further on this.

I will try and figure out the other ones a bit later

you're right on it being I and III. I understood I but i wasn't able to figure out what the incompressibility of intrapleural fluid was. What it is and what function the intrapleural fluid has on pressure and breathing... wikipedia wasn't of much help =(

 

[smile101]

.Negative pressure breathing in human lungs results from.

.I...contraction of the diaphragm..
.II...relaxation of the diaphragm..
.III...incompressibility of intra-pleural fluid.

. I only
I and II
I and III
II and III
I, II and III

i'll list answer after some people take a look and figure out. i wasn't really understanding the solution so hoping fellow studentdoctors would be up to the challenge of putting it in lamen's terms for me =)
I would go with I only. If choice III had said intrapleural space then I would consider it. I think intrapleural fluid is to keep the lungs from collapsing.
----

The initial source of electrons for noncyclic electron flow in photosynthesis comes from breakdown of water.
.H2O .à. 2 H+ + ½ O2 + 2 e-.

the question asked from breakdown of what but my question is, is it safe to assume that water's broken down for cyclic electron flow as well?

Like orgodox said, the electron is recycled in cyclic photosynthesis, so you don't need an outside source of electrons.
----

.What will happen to functioning acetylcholines at the end of their neural-signal transmission?
. .They will remain binding to receptors on the postsynaptic membrane. .
.They will diffuse through the postsynaptic membrane and are ready to be reused. .
.They will be absorbed by axon bearing the presynaptic membrane and are ready to be reused..
.They will accumulate at the synaptic cleft for a prolonged period of time..
.They will immediately be broken down by acetylcholinesterases at the synaptic cleft..


The answer's E but why is it not C?

Definitely E, as long as E is there, I would dare not choose anything else. Choice C is incorrect because the acetylcholine is broken down first and then taken up by presynpatic membrane as a raw material to synthesize some more acetylcholine.
---------------
next two questions are chem based
.
How many milliliters of 0.05 M HCl are required to turn 20 ml of 0.05 M KOH into a solution of pH 2.00? .

I do not know the exact answer to this question, but I am going to try. Since you want the pH to be 2, the acid concentration should be 10^-2 M. At, 20ml you will have pH7. So the answer is def more than 20 because you want the pH in acidic range. I'd say 24ml, but don't take my word for it.
------------

.Why does the freezing point of water decrease when its system pressure is increased?

i understand this one has something to do with the solid, liquid, gas curve and that for water the solid, liquid curve leans more to the left but beyond that i couldn't put two and two together on this one so any help would be greatly appreciated

thanks in advance for any help you may provide 🙂
.

Ice is less dense than water, so when it melts, it occupies a smaller volume. According to the LeChatlier's Principle, the equilibrium will be maintained if increase in pressure is relieved by decrease in volume (which means ice melting to water). In order to freeze the water at this high pressure, the temp will have to reduce...and therefore the freezing point depresses at high pressure.

Hope this helps!

 

[DRHOYA]

The electrons split from water are used to fill the "electron holes" that are present in the first photosystem, after the electrons have moved on to the second. The P680 (2nd) does not need to fill "electron holes".

 

[Predentknight]

you're right on it being I and III. I understood I but i wasn't able to figure out what the incompressibility of intrapleural fluid was. What it is and what function the intrapleural fluid has on pressure and breathing... wikipedia wasn't of much help =(

I just remembered but again not 100% sure.. just going to throw it out there and feel free to correct if I am wrong. If the intrapleural fluid were to some how get punctured it would lead to pneumothorax which I believe is lung collapse. Therefore, the incompressibility helps maintain the integrity of the lungs and prevents collapase, so the fact that the intrapleural space is incompressible allows for the negative pressure or vacuum for the lungs to suck in air.

 

[userah]

The electrons split from water are used to fill the "electron holes" that are present in the first photosystem, after the electrons have moved on to the second. The P680 (2nd) does not need to fill "electron holes".

kaplan book states that in noncyclic electron flow, the excited electrons from the first photosystem are transferred to electron acceptor NADP+ which then becomes NADPH. the electron holes in the first photosystem are filled by the excited electrons from photosystem II. and theeeese electron holes are filled by splitting water and using the electrons from there.

i think you have it the other way around?

 

[userah]

can someone explain the fast block and slow block to multiple fertilizations of an egg cell?
i believe that the slow block is the cortical reaction, where the sperm uniting with the egg's plasma membrane alters the zonal pellucida which prevents other sperm from binding to and entering the egg.

achiever mentions something about a acrosomal process of membrane depolarization on egg cell being the fast block but i don't really understand the process.
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I was wondering if someone could clarify how monocytes can also differentiate into osteoclasts. I understand that when monocytes go from the blood to the tissues, they differentiate into macrophages. So then is it safe to assume that when monocytes go from the blood to bone (if that's possible!?), they differentiate into osteoclasts? I couldn't find any information on it so that's what i'm assuming. clarification on the matter would be super. =)

any help would be greatly appreciated. thanks fellas =)

 

[userah]

more questions =P

The following statements on photosynthesis are true EXCEPT for one. What is that one EXCEPTION?

.A total of 6 Calvin cycles is required to produce one glucose molecule.

..Of all pigments known, only chlorophyll a is directly involved in the light reactions.

..Classified as the dark reactions, Calvin cycles may only occur in the absence of light

..Light reactions generate ATP and NADPH molecules.

..Calvin cycles occur in the stroma of chloroplasts.

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ok i know C is way off and dark reactions are coupled to the light reactions but my question is with choice B. Isn't chlorophyll B p680 also directly involved with the light reactions? .

 

[userah]

bump! nobody knows? =(

 

[osimsDDS]

Here's how you do that chem problem with the ph=2.

First you start off to find how many ml you need to neutralize the solution.
So basically: (.05M)(ml)=(20ml)(.05)....this will give you 20ml

Then you use the Molarity they gave you for HCl which is .05M and the ph=2 which is really .01M (10x10^-3 or simply 1x10^-2) concentration of H+ protons.
So: (.05M HCl)(x in ml)=(.01M concentration of H+)(40 + x)
*The 40 was the addition of 20ml + 20ml to neutralize the solution.

Simplified: .05x=.4 +.01x ====> .05x - .01x=.4 ===> x=10ml

Now that you know you need to add 10 ml to make the ph=2 its simple math to figure out how much to add. 40ml of the entire solution + 10ml of HCl you added to entire solution to make the ph=2 which gives you 50ml. Then you subtract 20ml of the NaOH base from the entire HCl solution you just figured out which will give you 30ml (50ml -20ml =30ml).

This might be long but simplify it and understand it your own way and you will understand it in a shorter more concise manner.

 

[nixon13]

I had the negative breathing question on Achiever and the answer said contraction of the diaphragm and incompressibility of intra-pleural fluid.

So C. 1 and 3. 👍