Pimp my MCAT Knowledge

[ASDIC]

Hi everyone,

this thread is designed so people can quiz each other about mcat concepts and provide some review for the actual test. So I will start off with a question:

Which molecule is the final acceptor of electrons in the electron transport chain? What does it then get converted to?

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[medicomel]

Hi everyone,

this thread is designed so people can quiz each other about mcat concepts and provide some review for the actual test. So I will start off with a question:

Which molecule is the final acceptor of electrons in the electron transport chain? What does it then get converted to?

oxygen is the final acceptor and it is converted to water.

What is the difference between a tropic hormone and a direct hormone?

 

[Sundarban1]

oxygen is the final acceptor and it is converted to water.

What is the difference between a tropic hormone and a direct hormone?

Direct hormones act dircectly on target cells while tropic hormones stimulate the secretion of other hormones that finally act on target cells.


What is the role of the kidney in fluid, electrolyte, and acid-base balance?

 

[ASDIC]

the kidneys filter the blood plasma by selective reabsorption and secretion. ion balance is achieved when the excess ion is secreted and the limiting ion is reabsorbed.

What are the 2 types of cells used in electrochemistry?

 

[tank you]

the kidneys filter the blood plasma by selective reabsorption and secretion. ion balance is achieved when the excess ion is secreted and the limiting ion is reabsorbed.

What are the 2 types of cells used in electrochemistry?

galvanic (voltaic) use spontaneous rxns to convert chemical energy to electrical energy, anode is -, cathode is +

electrolytic are not spontaneous, need outside electrical source,anode is +, cathode is -

list some properties of B-cells and T-cells.

 

[Daichi Katase]

this is more like....test my random science fact skills.

 

[Doko]

galvanic (voltaic) use spontaneous rxns to convert chemical energy to electrical energy, anode is -, cathode is +

electrolytic are not spontaneous, need outside electrical source,anode is +, cathode is -

list some properties of B-cells and T-cells.

this is just out of memory, so correct me if i'm wrong!


there are many types of b-cells, but mostly involved in acquired immunity. the body will produce millions and millions of b-cells with antibodies that present itself on it's membrane. once it recognizes an epitope on an antigen, it will start producing that antibody over and over again.

b-memory cells are cells that have recognized a specific antigen before (usually during a primary response) and can ellicit a full-out t-cell effect if it recognizes another antigen similar to it (called a secondary response).

t-cells (CD4's are helper and CD8 are killers), along with macrophages, have MHC II complexes which recognize certain antigens and will destroy anything that it recognizes... even possibly GOOD cells.

hope these are right.


QUESTION :: if the SA node actually sends action potentials faster than the beat of the heart, why does the heart actually contract slower than the number of AP it fires?

 

[scooter31]

this is just out of memory, so correct me if i'm wrong!


there are many types of b-cells, but mostly involved in acquired immunity. the body will produce millions and millions of b-cells with antibodies that present itself on it's membrane. once it recognizes an epitope on an antigen, it will start producing that antibody over and over again.

b-memory cells are cells that have recognized a specific antigen before (usually during a primary response) and can ellicit a full-out t-cell effect if it recognizes another antigen similar to it (called a secondary response).

t-cells (CD4's are helper and CD8 are killers), along with macrophages, have MHC II complexes which recognize certain antigens and will destroy anything that it recognizes... even possibly GOOD cells.

hope these are right.


QUESTION :: if the SA node actually sends action potentials faster than the beat of the heart, why does the heart actually contract slower than the number of AP it fires?[/QUOTE]

Because it is further slowed down the its electrical pathway by other pacemaker cells (Purkinje cells, Bundle of His, etc)

 

[medicomel]

this is more like....test my random science fact skills.

that's pretty much what i expected on this thread, unless somebody can write an mcat-style passage and formulate some question stems.

 

[Turkeyman]

Well then I guess I'll continue the MCAT Trivia...never hurts

What is a lung?

No no just kidding...that's way too difficult for the MCAT

How about:

Explain the initiation mechanism of the Renin-Angiotensin pathway and what each component is responsible for

 

[ASDIC]

The JG cells secrete renin and the liver secretes angiotensinogen, renin cleaves angiotensinogen into angiotensin I, angiotensin I gets converted to a more active angiotensin II by angiotensin-converting enzyme (ACE), angiotensin II stimulates the secretion of aldosterone. Aldosterone thus increases the selective reabsorption of Na+.

Renin is secreted by low concentrations of Na+.

What is the difference between an elastic collision, inelastic collision and a perfectly inelastic collision?

 

[Turkeyman]

Not too sure, but I'll try:

An elastic collision is a collision between two objects in which mechanical energy(potential and kinetic energy) is fully conserved and not lost to the surroundings.

An inelastic collision is where mechanical energy is lost to the surroundings, such as air resistance and deformation/shape change.

A perfectly inelastic collision is one in where ALL mechanical energy is lost to the surroundings(?) not sure haha

My question:

Describe how cellular respiration makes 36 ATP (i.e. just put NADH - X ATP, Glycolysis - X ATP, FADH - X ATP, etc etc --> no need to go too into detail)

 

[PUMA19KING]

Not too sure, but I'll try:

An elastic collision is a collision between two objects in which mechanical energy(potential and kinetic energy) is fully conserved and not lost to the surroundings.

An inelastic collision is where mechanical energy is lost to the surroundings, such as air resistance and deformation/shape change.

A perfectly inelastic collision is one in where ALL mechanical energy is lost to the surroundings(?) not sure haha

My question:

Describe how cellular respiration makes 36 ATP (i.e. just put NADH - X ATP, Glycolysis - X ATP, FADH - X ATP, etc etc --> no need to go too into detail)

the total cellular atp production is not set in stone I think (tpr, kap, and ek books all have diff numbers)....although this I know for sure: each kreb cycle produce 1 atp, 1FADH, and 3 NADH....and each NADH is good for about 2 ~3 atp production from ETC...feel free to elaborate if anyone is a Dr. Biochem

I'm reviewing chem so here goes my Q:

As hydrogen ions are added to an acidic buffer solution, what happens to the concentrations of undissociated acid and conjugate base?

 

[ASDIC]

if you add more H+ into the buffer, the buffer will tend to resist the decrease in pH by having the conjugate base bind to these added H+ ions and the undissociated acid will remain to be undissociated.



Force times velocity gives ____________?

 

[rtmcad2319]

if you add more H+ into the buffer, the buffer will tend to resist the decrease in pH by having the conjugate base bind to these added H+ ions and the undissociated acid will remain to be undissociated.



Force times velocity gives ____________?

Power :kg*m^2/s^3


With respect to the ideal gas law pv=nrt:
under what conditions is it most accurate?
and with respect to volume and pressure are the ideal calculations higher or lower ??

 

[Turkeyman]

PV=nRT is most accurate @ STP ==> 1 ATM and 0 degrees celcius

-Ideal calculations of pressure are higher than normal because the ideal gas law does not take into account the intermolecular attractive forces (van der waals forces). These attractive forces cause molecules to come closer together, lowering the pressure of the gas.

-Ideal calculations of volume are lower than the actual case because you now take into account the actual mass of each molecule, whereas ideally, you ignore it.


Let's see....
What's the equation for the downward force on an inclined plane, and what's the equation for the normal force of the track on object that resides on an inclined plane?

 

[gildas]

Let's see....
What's the equation for the downward force on an inclined plane, and what's the equation for the normal force of the track on object that resides on an inclined plane?[/QUOTE]

Downward force = mgsin()
Normal force = mgcos()


Question: What is the advantage of sexual reproduction over asexual reproduction.

 

[rtmcad2319]

Let's see....
What's the equation for the downward force on an inclined plane, and what's the equation for the normal force of the track on object that resides on an inclined plane?

Downward force = mgsin()
Normal force = mgcos()


Question: What is the advantage of sexual reproduction over asexual reproduction.[/QUOTE]


Its so much more fun!

seriously it adds to diversity of the organisms genetic code

Q:
Name at least 5 enzymes involved in food degradation that reside in the small intestine.

 

[medicomel]

Downward force = mgsin()
Normal force = mgcos()


Question: What is the advantage of sexual reproduction over asexual reproduction.

Its so much more fun!

seriously it adds to diversity of the organisms genetic code

Q:
Name at least 5 enzymes involved in food degradation that reside in the small intestine.[/QUOTE]

lipase, enterokinase, nuclease, pancreatic amylase,
trypsin, chymotrypsin

what is a chiral molecule?

 

[Freakedout]

It has 4 diff. sub attached.

Discuss the process of action potential initiation in Brain vs. Heart.

 

[jdovez]

the total cellular atp production is not set in stone I think (tpr, kap, and ek books all have diff numbers)....although this I know for sure: each kreb cycle produce 1 atp, 1FADH, and 3 NADH....and each NADH is good for about 2 ~3 atp production from ETC...feel free to elaborate if anyone is a Dr. Biochem

I'm reviewing chem so here goes my Q:

As hydrogen ions are added to an acidic buffer solution, what happens to the concentrations of undissociated acid and conjugate base?

Just passing through. But, the reason that books sometimes have different values for total atp production usually lies in the "equivalents". Ie FADH2 is usually said to be worth 2 atp and NADH is worth 3, however, there is debate over the real value of these. One of my biochem teachers (who studies energy production) says that it is actually closer to 2.5 for NADH and 1.5 for FADH2 based on the ATP needed to transport the different molecules around. Good luck to all you MCATers!!

 

[Miss155]

Hi

Describe how blood is pumped through the heart (e.g. the pulmonary and systemic circulation)?

 

[Turkeyman]

Starting with the left ventricle, the sequence is as follows:

Left ventricle --> aortic semilunar valve --> aorta(begin systemic circulation) --> arteries --> arterioles --> capillaries --> venules --> veins --> vena cava (end systemic circulation) --> right atrium --> tricuspid valve --> right ventricle --> pulmonary semilunar valve(begin pulmonary circulation) --> arteries, arterioles, capillaries, venules, veins, pulmonary vein (end pulmonary circulation) --> left atrium --> mitral valve(bicuspid) --> and finally to the left ventricle once again!

Name five carboxyllic compounds

 

[ASDIC]

methanoic acid, ethanoic acid, methyl butanoate, propanoic acid, butanaoic acid

Arrange the following bonds in terms of bond strength starting with the strongest and in terms of bond length starting with the longest.

single bond, double bond, triple bond

 

[tank you]

methanoic acid, ethanoic acid, methyl butanoate, propanoic acid, butanaoic acid

Arrange the following bonds in terms of bond strength starting with the strongest and in terms of bond length starting with the longest.

single bond, double bond, triple bond

strongest: triple > double > single
longest: single > double > triple


how is the acidity in the blood regulated? what happens if u have alkalosis? what would happen if u had diabetes, which increases ur amount of organic acids in the blood??

 

[Turkeyman]

methanoic acid, ethanoic acid, methyl butanoate, propanoic acid, butanaoic acid

Arrange the following bonds in terms of bond strength starting with the strongest and in terms of bond length starting with the longest.

single bond, double bond, triple bond

eek sorry about my question...i meant 5 carboxyllic functional groups :-(

carboxyllic acid, aldehydes, ketones, esters, and amides

 

[ASDIC]

eek sorry about my question...i meant 5 carboxyllic functional groups :-(

carboxyllic acid, aldehydes, ketones, esters, and amides

I think you meant 5 Carbonyl groups...ketones and amides are carbonyl compounds and carboxyl derivatives.

 

[Turkeyman]

whoops, i messed up again, sorry! haha I hate organic chemistry

 

[Shrike]

A perfectly inelastic collision is one in where ALL mechanical energy is lost to the surroundings(?) not sure haha

In case anyone's studying from this thread, the above answer is false. A perfectly inelastic collision is one in which the maximum possible amount of mecahnical energy is lost, consistent with conservation of momentum; in general, not all energy is lost in some such collisions. In practice, collisions in which the objects stick together rather than bouncing apart are perfectly inelastic.

 

[Akshay]

good going guys!! keep it coming.....OK here's one:

describe the steps involved in muscle contraction and relaxation

 

[Turkeyman]

In case anyone's studying from this thread, the above answer is false. A perfectly elastic collision is one in which the maximum possible amount of mecahnical energy is lost, consistent with conservation of momentum; in general, not all energy is lost in some such collisions. In practice, collisions in which the objects stick together rather than bouncing apart are perfectly inelastic.

thanks for correcting me, wasnt sure as I said in the post before.

Btw, I assume you mean a perfectly inelastic, rather than perfectly elastic?

Thanks!

 

[Daichi Katase]

effector nerve cells trigger the release of calcium ions from the sarcoplasmic reticulum. The calcium facilitates the binding of actin and myosin fibers causing the muscle to contract. A repeated simulation of the muscles from effector cells causes the summation of muscle twitches and creates a more effective contraction.

Question:
When the potential of an axon is more negative than normal....what is this state called? and what follows?

PS. this thread doesn't really help study for the MCAT, it is just kinda fun. : D

 

[Shrike]

Btw, I assume you mean a perfectly inelastic, rather than perfectly elastic?

Thank you; yup, that's what I meant, and have corrected it.

 

[firebird69guy]

effector nerve cells trigger the release of calcium ions from the sarcoplasmic reticulum. The calcium facilitates the binding of actin and myosin fibers causing the muscle to contract. A repeated simulation of the muscles from effector cells causes the summation of muscle twitches and creates a more effective contraction.

Question:
When the potential of an axon is more negative than normal....what is this state called? and what follows? D

Hyperpolarization. Some voltage-gated potassium channels remain open, resulting in movement of potassium out of the cell. This hyperpolarizes the cell. By the end of hyperpolarization, all of the potassium channels are closed. During repolarization and hyperpolarization, we have the absolute refractory period and relative refractory period. Immediately after the absolute refractory
period, the cell can generate a weaker action potential, but only if it is depolarized to a value more positive than normal threshold (because some sodium channels are still inactive and some potassium channels are still open.

The lengths of the absolute and relative
refractory periods determine
how fast neurons can
generate action potentials.

The cell has to be depolarized to a more
positive membrane potential than normal
threshold to open enough sodium channels
to begin the positive feedback loop.


If, theoretically, an element undergoes 2 alpha decays, two Beta(-) decays, a gamma decay and one beta(+) decay, how does its final mass/atomic numbers differ from the original element's mass/atomic numbers?

 

[rtmcad2319]

If, theoretically, an element undergoes 2 alpha decays, two Beta(-) decays, a gamma decay and one beta(+) decay, how does its final mass/atomic numbers differ from the original element's mass/atomic numbers?

Would it be a mass less 8 and a Atomic number less 3.

Ok explain in as muh detail as you want, what aldosterone does and where its made in the body.

 

[ASDIC]

aldosterone causes Na+ reabsorption in the nephron and its produced in the adrenal cortex.

what is terminal velocity?

 

[firebird69guy]

aldosterone causes Na+ reabsorption in the nephron and its produced in the adrenal cortex.

what is terminal velocity?

The speed at which drag matches the pull of gravity, resulting in a constant fall rate.


Q: What are the shapes of cocci, bacilli, and spirilla respectively?

 

[ASDIC]

cocci: spherical
bacilli: rods
spirilla: spiral



Explain the purpose of the salt bridge in a voltaic cell.

 

[PUMA19KING]

cocci: spherical
bacilli: rods
spirilla: spiral



Explain the purpose of the salt bridge in a voltaic cell.

ummm....positive ion goto cathode where reduction is taking place, and neg. ion goto anode where oxidation is taking place... feel free to elaborate on this...

Ok... what is capacitor? and do u relate this to PE?

 

[gujuDoc]

ummm....positive ion goto cathode where reduction is taking place, and neg. ion goto anode where oxidation is taking place... feel free to elaborate on this...

Ok... what is capacitor? and do u relate this to PE?

Capacitance relates to PE by taking the integration of C with respect to Voltage, such that

PE =1/2CV^2.

I have to brush up on the rest though.

One more thing, Capacitance is related to Charge and Voltage both through the following:

Q =CV

thus, C =Q/V

The units for C are the Faraday.

The other thing to note is that the PE can also be expressed as 1/2QV

or Q^2/2C

For parallel Capacitors,

C = C1 + C2 +C3 etc.

For series 1/C = 1/C1 +1/C2 etc. and then you take the reciprocal of 1/C to get the answer.

The other way to do it is to say C = C1C2/(C1 + C2)

 

[virilep]

gujudoc, u forgot to pose a question. my Q:

how much would a woodchuck chuck if a woodchuck could chuck wood?

 

[gujuDoc]

gujudoc, u forgot to pose a question. my Q:

how much would a woodchuck chuck if a woodchuck could chuck wood?

Its not that I forgot to pose a question, so much as I was thinking about what I should ask as my question.

Ok here's a question for you all:

What types of cells and tissues come from the ectoderm, the endoderm and mesoderm, respectively?

In other words, distinguish between which tissue/organs comes from each of the cell lines mentioned above.

 

[ASDIC]

Ectoderm: epidermis, nervous system, epithelial lining of the mouth and rectum
Mesoderm: bones, muscles, dermis, circulatory, respiratory, excretory systems
Endoderm: epithelial lining of the GI tract and glands


whats the function of a dielectric in a capacitor?

 

[gujuDoc]

Ectoderm: epidermis, nervous system, epithelial lining of the mouth and rectum
Mesoderm: bones, muscles, dermis, circulatory, respiratory, excretory systems
Endoderm: epithelial lining of the GI tract and glands


whats the function of a dielectric in a capacitor?

The dielectric serves two purposes:

1. To keep the plates from touching each other
2. To increase the capacitance and thus allowing for a greater amount of stored potential energy.


So I don't know if this question has been posed yet but how would you define stress and strain and what are the formulas for different types of stress? Also name the different types of stress and strain that the formulas go to.

 

[firebird69guy]

The dielectric serves two purposes:

1. To keep the plates from touching each other
2. To increase the capacitance and thus allowing for a greater amount of stored potential energy.


So I don't know if this question has been posed yet but how would you define stress and strain and what are the formulas for different types of stress? Also name the different types of stress and strain that the formulas go to.

Basic form:

F/A = E X (delta L/L0)
(stress = Young's modulus x strain)

F=-kx is also a form of stress/strain for springs

shear strain: F/A = G x X/L0

(Hooke's Law claims that stress = modulus x strain)


Don't know if I answered all of your questions..



MY QUESTION: Describe MHC I & MHC II - where are they found, and what do they do?

 

[SilvrGrey330]

Confused on Work, been seeing so many different definations im getting confused, please someone clarify.

Im trying to get all the formulas for work correct, heres what i have so far:

W = Fnet * d * cos & (& is theta)

W(gravity) = none , because & = 90 degrees
W(Normal force) = none , again because & = 90 degress

W(friction) = - F(friction) * d (- because & is 180 degrees)

Work energy theorem = delta KE = 1/2 mVf^2 - 1/2 mVi^2

when exactly do we use the Work energy theorem???

W(spring) = 1/2 k(Xf^2 - Xi^2)


Im confused over W(gravity) being none because I also thought that W(gravity) is mgh which is potential energy, can someone clarify work or gravity and potential energy for me and explain WET as well, i know this is a lot of questions in one, but its very confusing to me. Thanks!

 

[jdovez]

Confused on Work, been seeing so many different definations im getting confused, please someone clarify.

Im trying to get all the formulas for work correct, heres what i have so far:

W = Fnet * d * cos & (& is theta)

W(gravity) = none , because & = 90 degrees
W(Normal force) = none , again because & = 90 degress

W(friction) = - F(friction) * d (- because & is 180 degrees)

Work energy theorem = delta KE = 1/2 mVf^2 - 1/2 mVi^2

when exactly do we use the Work energy theorem???

W(spring) = 1/2 k(Xf^2 - Xi^2)


Im confused over W(gravity) being none because I also thought that W(gravity) is mgh which is potential energy, can someone clarify work or gravity and potential energy for me and explain WET as well, i know this is a lot of questions in one, but its very confusing to me. Thanks!

Haven't done this stuff for awhile. But the simplest way to remember work is that whatever direction you are applying the force, must also be the direction of motion. Therefore, if you are pushing something horizontally, gravity is doing no work because its effect is perpendicular to the direction of motion (there is no component of motion in the direction of force). If however, you are pulling something straight up, then you must do enough work to counteract gravity before that sucker is going anywhere (vice versa if you are pushing something down). Hope that helped a little....if not, my bad.

 

[SilvrGrey330]

Thanks for your input, unfortunately, I already understood those fundamentals, but im still confused. If anyone else can put in their 2 cents, that would be awesome.

 

[gujuDoc]

Silver grey, the important thing to remember about all the formulas is that formula for KE is always the same no matter what.

However, PE formulas change depending on the type of force involved. PE is nothing more than the calculus integration of Fdx, or simply stated the integration of F with respect to some change in distance, whether it is height in mgh or r in the electric potential energy or x in the elastic potential energy.

KE on the other hand is the integration of momentum with relation to change in velocity.

KE may also be found by substituting F/m for a in the v^2 = Vi^2 +2ax formula.

Furthermore, it is important to remember that you need to combine Work-Energy theorem with PE

To get that PEi + KEi = PEf + KEf because as you lose KE, you gain PE, and vice versa.

Don't know if that clears up your question, but I'm actually a bit confused on figuring out what exactly it is you one.

 

[Shrike]

Hell, I'm confused now. So lets make things easier.

Guju is correct that KE is always the same formula.

But potential energy? Um, yeah, it's always the definite integral of the dot product of force and displacement, but that is a seriously flawed way for an average premed to think about it. You just learn the different formulas, and use them. If there's gravity, it's mgh, if there's a spring, yadda yadda. Just know them. I hate that the conceptual approach is not right, but it isn't.

Work-Energy Theorem? Vastly overrated in terms of difficulty. In all cases, change in energy is work done. That's all. If there's more energy at the end (potential plus kinetic) then work got done to raise it. If there's less, then negative work got done (or, another way to think about it, the system did work on something else). On the MCAT this can be applied to two types of questions:

- If the total energy (kinetic plus whatever type of potential is relevant to this problem) changes, then that change is the work done by some force you haven't accounted for (in other words, a force that wasn't dealt with in your potential energy term). Friction is the usual suspect, plus any outside force specified by the problem.​

- If you are asked how much work is done by one of the conservative forces (for MCAT purposes, a complete list is gravity, electrostatic, and springs, I think), then work done is just the change in the relevant potential energy term. If there's less potential energy at the end, then it dropped because that force did work -- it must have, because the (potential) energy had to go somewhere. If more, the force did negative work (work was done to raise the PE).​

The second problem type may account for grey's confusion about gravity: work done by gravity is not necessarily zero. In all cases (all cases), work done by gravity is the change in gravitational potential energy. If something winds up lower than it started, gravity did work, regardless why or how it got lower. If it winds up higher, gravity did negative work (work got done to raise that PE). Use mgh.

Similarly -- for electric fields, if a charged something winds up at a spot with a different potential from that where it started, work got done by the electric field. Use the formula. If something attached to a spring winds up at a spot with different displacement from where it started, work got done by the spring. Use the formula.

In practice, use the work done, and thus the change in some form of energy (usually kinetic), whenever either:

(1a) the path (direction and/or speed) or mechanism (such as a collision, if you are asked for work done by the collision) is complicated or unknown; or
(1b) you don't care how, or how fast, whatever it is got wherever it is;

and

(2a) one of the three conservative forces is present; or
(2b) a non-conservative force (i.e., any force besides those three) is present, and you can see from the problem how to use the work formula (Fdcos(theta)) on it, and it's simple to do so. Usually, but not always, only one of 2a and 2b is present in a problem.​

That's Work-Energy. I think it's confusing because they call it a theorem and give it capital letters; maybe the lesson is to avoid capitalizing it.

Great big breath. When I write the definitive MCAT physics book, y'all have to tell your friends to buy it, 'kay?

(This was longer than I thought it would be -- I think I'm doing some dead horse beating. I suppose that means Q is going to jump in here any time, because we know she's into that...)