Pimp my MCAT Knowledge

ASDIC · Jan 26, 2005

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?

Shrike · Feb 28, 2005

Let me point out: firebird's question kinda got lost (scroll up). Someone owes him a nice, simple (remember, all, that's the idea) way to keep MHC I and MHC II straight.

(Clearly, I cannot help, as I am just the physics guy...)

SilvrGrey330 · Feb 28, 2005

thanks shrike and gujudoc, im gonna work on prac problems and take all that was said into consideration. by the way, im guju too, and live in orlando, go to UCF...saw u from Tampa

SilvrGrey330 · Feb 28, 2005

This is in response to: from earlier

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

-- So what can we say about Ideality/Reality regarding Temperature?
-- Would an Ideal calculation of Temperature be lower than that of Real gas due to kinetics? or would it be higher?

gujuDoc · Feb 28, 2005

SilvrGrey330 said:
thanks shrike and gujudoc, im gonna work on prac problems and take all that was said into consideration. by the way, im guju too, and live in orlando, go to UCF...saw u from Tampa

You are welcome. However, I would say to listen to Shrike's advice moreso than mine because his advice and explanations are just absolutely WONDERFUL!!!!!!!!!!!

Shrike,

Thanks for clearing that up. That helped me a bit too.

SilvrGrey330 · Feb 28, 2005

For rate laws,

What is k dependent on?
can you write a rate law for all solids/liquids and gases?

For Ksp,

What is K dependent on?
can you write the expression for all solids/liquids and gases?

For Keq and Q,

What is K dependent on?
can you write the expression for all solids/liquids and gases?

TicAL · Feb 28, 2005

SilvrGrey330 said:
For rate laws,

What is k dependent on?
can you write a rate law for all solids/liquids and gases?

For Ksp,

What is K dependent on?
can you write the expression for all solids/liquids and gases?

For Keq and Q,

What is K dependent on?
can you write the expression for all solids/liquids and gases?

1) In rate laws, k is dependent only one temperature and must be determined experimentally. However, k is NOT dependent on a change in time or the concentrations of either the reactants or products.
Rate laws are written as: Rate = k[A]^x^y, where the bracketed terms represent the concentrations of the reactants and the x and y values are the order of each of the reactants determined by experiment ( x + y gives the total reaction order).

2) Ksp represents the solubility product constant and can be dependent on on temperature, pressure, or volume.
To calculate Ksp, one uses the formula products/reactants where each of the products is raised to the exponent of it's coefficient in a balanced chemical equation. In these calculations only aqueous phase and gaseous phase products are considered; therefore in Ksp calculations there is never a denominator since the reactant is always a solid.

3) I believe Keq and Q are calculated in a similar way as Ksp (correct me if i'm wrong) and are effected by the same variables.
The calculation of Keq is the same products/reactants formula and are still only applicable to compounds in the aqueous of gas phases, but there may be a denominator in this calculation.

What is the basic composition of bone and what are the three different cell types associated with bone tissue?

gujuDoc · Mar 1, 2005

TicAL said:
1) In rate laws, k is dependent only one temperature and must be determined experimentally. However, k is NOT dependent on a change in time or the concentrations of either the reactants or products.
Rate laws are written as: Rate = k[A]^x^y, where the bracketed terms represent the concentrations of the reactants and the x and y values are the order of each of the reactants determined by experiment ( x + y gives the total reaction order).

2) Ksp represents the solubility product constant and can be dependent on on temperature, pressure, or volume.
To calculate Ksp, one uses the formula products/reactants where each of the products is raised to the exponent of it's coefficient in a balanced chemical equation. In these calculations only aqueous phase and gaseous phase products are considered; therefore in Ksp calculations there is never a denominator since the reactant is always a solid.

3) I believe Keq and Q are calculated in a similar way as Ksp (correct me if i'm wrong) and are effected by the same variables.
The calculation of Keq is the same products/reactants formula and are still only applicable to compounds in the aqueous of gas phases, but there may be a denominator in this calculation.

What is the basic composition of bone and what are the three different cell types associated with bone tissue?

In regards to Keq and Q as it pertains to Ksp.

What I read in the PR book is that

Ksp is basically the Keq for solubility.
Ka/Kb is basically the Keq for acids and bases respectively
Kw is the Keq for water dissociation

That's the easiest way to think about it.

SilvrGrey330 · Mar 1, 2005

This is in response to: from earlier

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

-- So what can we say about Ideality/Reality regarding Temperature?
-- Would an Ideal calculation of Temperature be lower than that of Real gas due to kinetics? or would it be higher?

TicAL · Mar 3, 2005

SilvrGrey330 said:
This is in response to: from earlier

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

-- So what can we say about Ideality/Reality regarding Temperature?
-- Would an Ideal calculation of Temperature be lower than that of Real gas due to kinetics? or would it be higher?

Whoa...forgot about this thread. We need to keep this going, it's really good review. I'll try to answer the above question to the best of my knowledge.

I'd guess that the temperature for a real gas would be lower than that of an ideal gas since the collisions between the particles in reality aren't completely elastic (part of the kinetic theory of gases). Since temperature is a measure of the average kinetic energy, the collisions between the particles transfer some of the energy to eachother, therefore making the kinetic energy slightly lower.

I'll ask the same question I asked earlier since no one answered it the first time:

What is the basic composition of bone and what are the three different cell types associated with bone tissue?

place · Mar 4, 2005

Calcium Phosphate
Osteoclasts
Osteoblasts
Osteocytes

Is gravity a conservative force or a non-conservative force? What about friction?

Phil Anthropist · Mar 4, 2005

Shrike said:
Let me point out: firebird's question kinda got lost (scroll up). Someone owes him a nice, simple (remember, all, that's the idea) way to keep MHC I and MHC II straight.

(Clearly, I cannot help, as I am just the physics guy...)

Re: firebird69guy

"Describe MHC I & MHC II - where are they found, and what do they do?"

MHC proteins are expressed on cells so that the immune system can identify "self" cells.

MHC-I are found on all nucleated cells. Therefore, you won't find them on RBCs (no nuclei).

MHC-II are found mainly on antigen-presenting cells (APCs). My way of remembering the major APCs is to think DMB (as in Dave Matthews Band): dendritic cells, macrophages, B cells.

This is a watered down version, but T-cytotoxic/CD8+/killer-T cells are MHC-restricted to MHC Class I.

T-helper/CD4+ are MHC-restricted to MHC Class II.

The way to keep the pairings straight is the "equals 8" rule:
___
___1___x___ 8___= 8
MHC I and CD-8

2 x 4 = 8
MHC II and CD 4

I'd be shocked if you had to know that much about the Major Histocompatibilty Complex for the MCAT though.

I'd ask a question, but I figure place's question still needs to be answered

place said:
Is gravity a conservative force or a non-conservative force? What about friction?

Shrike · Mar 4, 2005

place said:
Is gravity a conservative force or a non-conservative force? What about friction?

Gravity is conservative. On the MCAT, the other two conservative forces (the ones for which energy is conserved, meaning you can write a potential function) are electrostatic and springs. All other MCAT forces, including friction, are nonconservative.

Describe, in general terms, all of the cases in which the number of stereoisomers of a molecule is not equal to 2^n, where n is the number of stereocenters.

pseudoknot · Mar 4, 2005

Shrike said:
Describe, in general terms, all of the cases in which the number of stereoisomers of a molecule is not equal to 2^n, where n is the number of stereocenters.

Some of the stereoisomers would have to be identical due to symmetry, forming meso compounds. I think...

medicine_man · Mar 4, 2005

for the love of god, I am a junior and about to take the kaplan mcat review. please tell me that you guys don't know most of this stuff from your bio/chem classes, cause i looked at some of these questions, and i literally have no idea. where did you learn this stuff? you guys have already taken/reviewed for the mcat?

Edit: I didn't read all of the posts, so I am referring to the first 8-10 posts of course.

Daichi Katase · Mar 4, 2005

i think we are not supposed to know most of the biology stuff on this thread. It is too damn specific?

isn't MCAT supposed to be a concepts test?

place · Mar 5, 2005

you are rignt, some of this stuff on this thread is pretty specific. But if you want to get those high scores e.g. 13s, you have to get the specific questions right on the MCAT

.

Lindyhopper · Mar 5, 2005

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

Since there isn't an obvious question on the table, I'll try this never answered question from post #20.
In the brain the action potential is intiated in neural tissue. In the heart it is intiated in specialized cardiac muscle tissue. But the opening of channels through which positive ions rush into the cell is the common trigger. These positive ions Ca+ &/or Na+ cause depolarization & initiation of the action potential.
In the brain the channels open in response to the binding of one of several neuro transmittors. There are different types of receptors but they are generally ligand (transmittor) gated.
In the heart an action potential is intiated by the opening of slow acting voltage gated Ca+ channels. These Ca+ channels open but pretty slowly in response to the negative resting potential. Therefore, the heart's action potential arises automaticly in respond to the neg resting potential while the brain's is triggered by a neuro transmittor.

How are K-max & K-m affected by competitive & non-competitive inhibition?

EDIT: AS NEXT POSTER POINTS OUT THIS SHOUD BE Vmax (not Kmax). Sorry about any confusion.

pseudoknot · Mar 5, 2005

Lindyhopper said:
How are K-max & K-m affected by competitive & non-competitive inhibition?

I believe you mean Vmax and Km. Vmax is lowered by noncompetitive inhibitors, but Km (the enzyme's affinity for substrate) is not affected. Competitive inhibitors lower the effective concentration and thus can raise Km, but they do not alter Vmax. Again, not an enzymologist, so I could be wrong.

firebird69guy · Mar 5, 2005

Physiology question for ya (since I didn't see one asked by the previous poster):

In a nutshell, how does the ear (and therefore the brain) differentiate between frequencies and intensities?

PUMA19KING · Mar 5, 2005

firebird69guy said:
Physiology question for ya (since I didn't see one asked by the previous poster):

In a nutshell, how does the ear (and therefore the brain) differentiate between frequencies and intensities?

is this physics Q?
Sound describes a set of longitudinal mechanical waves. Mechanical waves must travel through a medium that can be deformed by the wave. Sound can therefore travel through solids, liquids, and gases, but not through a vacuum, such as interstellar space. The wave is transmitted as particles in one deformed area of the medium strike other particles in a neighboring area, causing it to deform as well. If the first particles can strike lots of other particles, the wave will travel faster. Since solids are more dense than liquids, sound travels slower in liquids than in solids and even slower in gases.
Human hearing can detect waves that fall in the audible range, which includes frequencies from 20 to 20000Hz. Frequencies slower than 20Hz are known as infrasonic, while those above 20000Hz are called ultrasonic. The concept of pitch also describes frequency. Although pitch does not have a precise mathematical relationship to frequency, a high pitch corresponds to a high frequency, while a low pitch corresponds to a low frequency.

Sound can be produced either through the striking of a solid object, causing a vibration, or by a vibration of a column of air. This latter production of sound is also called an acoustic vibration.

Intensity of a wave is power per unit area. For sound waves, the intensity level b is measured in decibels and is defined as
(1) = 10 log

The quantity Io is a constant defined as

(2) Io = 10-12 W/m2

the lowest intensity sound wave detectable by humans.

My Q:

I'm having a snickers bar with 711 reg joe.... describe (in detail interms of what enzyme, where,) the digestion path in takes (towards my adipocyte) :laugh:

detail people!

aamartin81 · Mar 5, 2005

PUMA19KING said:
My Q:

I'm having a snickers bar with 711 reg joe.... describe (in detail interms of what enzyme, where,) the digestion path in takes (towards my adipocyte)

detail people!

alpha amylase in the mouth, pepsin (if there's any protein) in the stomach, trypsin/chemotrypsin in the small intestine for proteins, lipase in the SI for fats (helped by bile), pancreatic amylase in the SI for carbs

My question: what kind of chance do we have of getting a 30+ on this test (and why am I in on another Saturday night studying for the MCAT)?

Good luck

firebird69guy · Mar 5, 2005

firebird69guy said:
Physiology question for ya (since I didn't see one asked by the previous poster):

In a nutshell, how does the ear (and therefore the brain) differentiate between frequencies and intensities?

it was a Bio question, but your answer was very thorough as far as physics is concerned... I was looking more for an answer that included the basilar membrane, organ of Corti, eardrum, hair cells and their location, action potential frequency, afferent pathway, etc...

TicAL · Mar 6, 2005

firebird69guy said:
it was a Bio question, but your answer was very thorough as far as physics is concerned... I was looking more for an answer that included the basilar membrane, organ of Corti, eardrum, hair cells and their location, action potential frequency, afferent pathway, etc...

I'll try to answer it with a little bit of a bio twist. First, sounds waves enter the outer ear through the Pinna which serves to slightly amplify the sound. The sound then travels through the ear canal and causes the Tympanic membrane to vibrate. These vibrations set off vibrations in the Malleus, Incus, and Stapes which are bones which lead into the inner ear. Vibrations in the fluid of the Cochlea and the hairs in the Orgin or Corti causes signals via an afferent pathway to be sent to the brain where it is recognized.

Describe the differences between the boiling points and freezing points of a solution compared to that of a pure solvent. What causes these differences? Which quality is more important when determining a difference in boiling/freezing points of a solution vs a solvent: what the solute is composed of, or to what degree the solute dissociates?

freesolo · Mar 6, 2005

im having a tough time with reduction potentials, if your + does that mean your a strong oxidizing agent?

SilvrGrey330 · Mar 12, 2005

This is going to be hard, but ill try my best:

What are the tensions of the rope in: T1 and T2 in the diagram below. All objects are at rest. How do u figure this out?

------------------------------- <--- Ceiling
..................l
..................l
..................l
..................l (T1)
..................l
..................l
..................l
...............[50N] <----- A block thats 50N
..................l
..................l
..................l
..................l (T2)
..................l
..................l
..................l
.............[[100N]] <---- A block thats 100N

- do i get props on the artistic rendition?

gujuDoc · Mar 13, 2005

Phil Anthropist said:
Re: firebird69guy

"Describe MHC I & MHC II - where are they found, and what do they do?"

MHC proteins are expressed on cells so that the immune system can identify "self" cells.

MHC-I are found on all nucleated cells. Therefore, you won't find them on RBCs (no nuclei).

MHC-II are found mainly on antigen-presenting cells (APCs). My way of remembering the major APCs is to think DMB (as in Dave Matthews Band): dendritic cells, macrophages, B cells.

This is a watered down version, but T-cytotoxic/CD8+/killer-T cells are MHC-restricted to MHC Class I.

T-helper/CD4+ are MHC-restricted to MHC Class II.

The way to keep the pairings straight is the "equals 8" rule:
___
___1___x___ 8___= 8
MHC I and CD-8

2 x 4 = 8
MHC II and CD 4

I'd be shocked if you had to know that much about the Major Histocompatibilty Complex for the MCAT though.

I'd ask a question, but I figure place's question still needs to be answered

I just wanted to say that I like your way of remembering the MHC I/II. I never thought about it that way. Also I like your mneumonic for remembering the APC's.

My question:

Describe the differences and similarities in cardiac, skeletal, and smooth muscle.

Then describe the action potential of cardiac muscles.

firebird69guy · Mar 13, 2005

Abe said:
im having a tough time with reduction potentials, if your + does that mean your a strong oxidizing agent?

Negative potential = strong reducing agent (wants to lose electrons)

Positive potential = strong oxidizing agent (wants to gain electrons)

just look at the potential chart.. if you have a positive potential, that means that the forward reaction will occur (and you will gain electrons (oxidizing agent)). If you have negative potential, that means that the reverse reaction will occur (and you will lose electrons (reducing agent)).

this all happens because of the equation: delta G = (-)nFE

(You want to look for the half reactions that will yield a positive cell potential so you will have a negative delta G and therefore predict what will happen).

Hope this helps

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