MCAT Physics
STP
1 atm 273k = 0C
1 mole of gas
22.4L
speed of light
3*10^8 m/s
Planck's constant
6.62*10^-34 J/s
controls
A is correct. A positive control is a control group that is not exposed to the experimental treatment but that is exposed to some other treatment that is known to produce the expected effect. The scientists wished to test the effect of the analogs on enzyme activity. Using a known inhibitor is an example of comparing the expected effects of this inhibitor to those of the analog treatment. Thus, it is a positive control. B: A negative control group is a control group that is not exposed to the experimental treatment or to any other treatment that is expected to have an effect. C: In randomized controls, the groups that receive different experimental treatments are determined randomly. There was nothing random about this selection. D: A false negative is when a test result appears negative when it should have been positive. An example of a false negative would be if a particular test of a known ADAMTS inhibitor returns a result that shows no change in enzyme activity.
what is the difference between the pressure for liquids and gases, in relation to density?
Hydrostatic pressure for liquids is linear because as depth changes, the density of the liquid remains constant. Gases, however, have densities that change according to the forces applied to them. Gases are compressible, while liquids and solids are not.
alkane formula
C(n)H(2n+2)
air bubbled through distilled water
CO2 undergoes hydrolysis in liquid water to produce HCO3- weak acid has a pH less than water
1/2 life
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wavelength of photons
E = hc/wavelength
downward pulling force
Force(net) = mgsin(theta) - (static frictional force)mgcos(theta) Force = Ma, so masses will cancel mgsin(theta)
Indicators desired range
Indicators function in acid-base titrations to identify, via color change or a similar mechanism, that an expected pH, and thus the titration endpoint, has been reached. In order to function in this way, an indicator must undergo a color change near the desired pH. This typically occurs because of a reversible change in the protonation state of the indicator. It is desirable then that the pKa of a chosen indicator be within ±1 unit of the target pH. For the titrations performed in the study of acetic acid, a weak acid, and sodium hydroxide, a strong base, the endpoint of the titration will occur at a pH greater than 7. Of the possible pKa values given as answer choices, only D could function well as an indicator for a pH in this range.
velocity of an object dropped
KE = PE 1/2 mass * velocity (squared) = mass * gravity * height
Henderson-Hasselbach
Ka + Kb = 10^-14 The equivalence point on the graph is where all of the starting solution (usually an acid) has been neutralized by the titrant (usually a base). It can be calculated precisely by finding the second derivative of the titration curve and computing the points of inflection (where the graph changes concavity); however, in most cases, simple visual inspection of the curve will suffice. In the curve given to the right, both equivalence points are visible, after roughly 15 and 30 mL of NaOH solution has been titrated into the oxalic acid solution. To calculate the acid dissociation constant (pKa), one must find the volume at the half-equivalence point, that is where half the amount of titrant has been added to form the next compound (here, sodium hydrogen oxalate, then disodium oxalate). Halfway between each equivalence point, at 7.5 mL and 22.5 mL, the pH observed was about 1.5 and 4, giving the pKa. In monoprotic acids, the point halfway between the beginning of the curve (before any titrant has been added) and the equivalence point is significant: at that point, the concentrations of the two species (the acid and conjugate base) are equal. Therefore, the Henderson-Hasselbalch equation can be solved in this manner: pH=pKa (monoprotic) Therefore, one can easily find the pKa of the monoprotic acid by finding the pH of the point halfway between the beginning of the curve and the equivalence point, and solving the simplified equation. In the case of the sample curve, the Ka would be approximately 1.78×10−5 from visual inspection (the actual Ka2 is 1.7×10−5) **Why ten to the -5?
electric power
P = IV
hydrostatic pressure
P is absolute pressure Po is pressure at the surface p is density of the fluid g is acceleration due to gravity z is depth
elastic potential energy
SI unit = joules
gravitational potential energy
SI unit = joules
capacitance - what are the units?
SU unit = faraday
substrate analog
Substrate analogs (substrate state analogues), are chemical compounds with a chemical structure that resemble the substrate molecule in an enzyme-catalyzed chemical reaction. Substrate analogs can act as competitive inhibitors of an enzymatic reaction
pI
The isoelectronic point or isoionic point is the pH at which the amino acid does not migrate in an electric field. This means it is the pH at which the amino acid is neutral, i.e. the zwitterion form is dominant. A table of pKa and pI values can be found on the next page. The pI is given by the average of the pKas that involve the zwitterion, i.e. that give the boundaries to its existence. 1/2 (pKa1 + pKa2)
object rolling down a ramp
U = mgh
work equation (for kinematics)
W = fdcos (theta)
binding energy
energy that holds the protons and neutrons together in the nucleus, defined by the equations E=mc2, where m is mass defect and c is the speed of light in a vacuum
Newton's second law
f = ma
archimedes principle
a body that is fully or partially immersed in a liquid will be buoyed upwards by a force that is equal to the weight of the liquid displaced by the body F(buoy) = density(fluid)*volume(submerged)*gravity
Newton's third law
action and reaction
Mechanical advantage
advantage compared to not lifting straight up hypotenuse/height = MA **Think about right triangle rules
amide, amine, imine, thirster, thioketone
amide: carboxyl group, alpha nitrogen amine: nitrogen attached to 2 R groups mine: nitrogen in the double bond thioester: sulfur with two R groups thiokeytone: sulfur in a double bond, 2 R groups attached to the Carbon
heat of transformation
amount of heat required to change the phase of a substance
electric potential energy
amount of work required to bring a test charge q from a point within the electric field of some source charge Q U = qV. V = kQ/r
logarithm
base 10 base 2.72 = ln
Beta minus
negative, so positrons are attracted to it
agonist antagonist
causes an action stops an action
For mirrors, are the images in front of a concave mirror converging/diverging? real/virtual? for concave, if the object is placed at the focal point? are the images in front of a convex mirror real or virtual?
concave = real, converging, light converges in front of mirror, parallel rays converge at the focal point, if the object is within the focal point, it's a virtual image. IF object at the focal point, then there is no image concave mirror with a positive focal length, convex = light is virtual and appears in front while a diverging mirror is convex mirror with a negative focal length. Diverging mirrors always produce virtual images
equipotential lines
concentric circles emanating from a source charge that cross its electric field liens perpendicularly. No work is required for a test change to travel along the circumference of an equipotential line because the potential at every point along that line is the same
Bernoulli's equation
conversation of energy in fluid flow for a given depth, linear flow speed and pressure are inversely related
partial pressure
convert pressure to desired unit 1 atm = 760 mmHg = 760 torr = 100,000 Pa Then, look for percentage composition of that gas and multiply
wavelength
crest to crest, trough to trough
exponential decay
decrease in the amount of a substance N at an exponential rate y(t) = a × ekt (k=-wavelength)
focal length
distance between the focal point and the mirror or lens. spherical mirrors = focal length = 1/2r
conservative force
doesn't dissipate gravity electrostatic forces elastic forces
current -what kind of charge is this? what does current depend on -besides resistance?
flow of charge/time potential difference (voltage) Current is denoted I delta q/time (theoretical positive charge)
second law of thermodynamics
for any process, the entropy of the universe either increases (for irreversible processes) or remains constant (for reversible processes)
torque
force creating rotation about an axis; measured as the lever arm (the distance between the fulcrum and the applied force) times the magnitude of the force times the sine of the angle between them
nonconservative force
force that dissipates
pressure
force/area
gamma decay
gamma particles = high-energy photons
half-life
half life = ln2/decay constant
alpha decay
helium emitted
sigmoidal curves
increased concentration of binding substance on a molecule increases binding capacity for the substance
viscosity
resistance to flow, denoted by n
dielectric
insulating material placed in between the two plates of a capacitor, increases capacitance
First Law of Thermodynamics
internal energy of a system is equal to the heat transferred into a system minus the work done by the system delta U = Q -W
kinetic energy
k = 1/2mv(squared) unit: joules
sound level
loudness measured in decibels I is intensity of the sound I knot is the reference intensity of 10(-12) W/m(2)
magnification
m= -I/o
scalar
magnitude but no direction
density
mass/volume specific gravity
mass
measure object's inertia
kcat/Km
measure of the efficiency of an enzyme - Vmax decided by the total turnover number, this is the slowest/rate determining step Kcat = turnover molecular number (units = 1/sec)
Ideal gases
more ideal the higher the temps, but colder air can hold less water
dispersion/equation for n in light refraction (in terms of wavelength)
n = c/f(wavelength)
snell's law
n1sin1 = n2sin2
translational equilibrium
no net movement
frequency
number of cycles per second 1Hz = 1 cycle per second
conservation of mechanical energy
only conservative forces act on an object and work is done, energy is conserved delta E = delta U = delta K = 0
weak acids
pH = -log [H+] [H+] = 10 raised to the -pH
percent dissociation
percent original acid concentration that has dissociated
normal force
perpendicular component of the force caused when two surfaces push against each other, denoted by N
photoelectric effect
phenomenon observed when light of a certain frequency causes a metal to emit electrons. W = work function calculates the residual kinetic energy of an electron emitted by a metal K = hf - W
gauge pressure
pressure above and beyond atmospheric pressure. h = depth
plane mirrow
produces virtual image that appears to be the same distance behind the mirror as the object is in front of the mirror
resistivity
property of a conductor used to measure its resistance in the equation r = resistivity*length/area r=resistance area=cross-sectional area
electromagnetic spectrum
radio microwave infrared ROYGBIV ultraviolet Xray gamma
index of refraction
ratio of the speed of light in a vacuum to the speed of light through a medium
laminar flow
smoothest type of liquid flow through a tube wherein thin layers of liquid slide over one another. occurs as long as the linear flow speed remains below a critical speed.
wave speed
speed of a wave
work-energy theorem
states that the net work performed on an object is related to its change in energy.
homotropic/allosteric regulation
substrate for the enzyme as well as regulator for the enzyme
kirchoff's loop rule
sum of the voltage sources in a circuit loop is equal to the sum of voltage drops along that leap
electric potential
the amount of electric potential energy per unit charge; the work required to bring a positive test charge from infinity to within an electric field of another positive source charge, Q, divided by that test charge's magnitude. V = kQ/r
total internal reflection
the condition in which the incident angle of light traveling from a medium with a high n to a medium with a low n is greater than the critical angle theta. This results in all of the light being reflected and none of it being refracted.
mass defect
the difference between an atom's atomic mass and the sum of masses of its protons and neutrons
potential difference
the difference in the electrical potential between two points in a an electric field, also called voltage
coulombs law
the law describing the electrostatic force that exists between two charges
continuity equation
the mass flow rate of fluid must remain constant from one cross-section of a tube to another a1v1 = a2v2 relates much more to compressibility than viscosity
0th law of thermodynamics
two objects that are in thermal equilibrium with a third object are also in thermal equilibrium with each other
force
unit = Newton
acceleration
vector describing a change in velocity over time a= change in velocity/time
Ohm's Law
voltage = current*resistance
pascal's principle
when a pressure is applied to one point of an enclosed fluid, that pressure is transmitted in equal magnitude to all points within the fluid and to the walls of its container. This principle forms thesis of the hydraulic lift
interference
when superimposed waves are in phase, their amplitudes add (constructive interference). When superimposed light waves are out of phase, their amplitudes subtract (destructive interference)
power in terms of work
work/time SI unit = watt
