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MCAT Exam Questions > Chem/Phys Questions > Flashcards

Chem/Phys Questions Flashcards

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MCAT flashcards
1
Q

how do beta and gamma radiation differ?

A

beta radiation aka electrons will be deflected in a magnetic field while gamma radiation aka photons will not

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2
Q

how do BP and BFR (blood flow rate) differ in pulmonary and systemic circulation?

A

BP is higher in systemic circulation - pulmonary circuit is shorter so has less resistance
BFR will be the same - pulmonary and systemic circulations are connected in series so flow rate is equal (analogous to current)

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3
Q

resistance and area

A

R = (rhoL)/A

shorter or wider will mean less resistance

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4
Q

what type of charged molecule will migrate towards the cathode?

A

cations (positively charged)

cathode behaves negative

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5
Q

acid strength

A

increased by having the most electronegative group (eg fluoroacetic acid)
stronger acid = more stable conjugate base

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6
Q

mutarotation

A

cyclic hemiacetal formations of monosaccharides can open and then re-cyclize, with equal amounts of alpha and beta anomers

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7
Q

infrared spectroscopy

A

sharp peak at 1700 means carbonyl group

O-H stretching frequency is 3200-3500

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8
Q

intensity is ____ proportional to area

A

inversely proportional to area

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9
Q

sound travels fastest in a ____

A

solid

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10
Q

furanose and pyranose

A

a furanose is 5 membered (fructofuranose)

a pyranose is 6 membered (glucopyranose)

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11
Q

which form of glucose can undergo oxidation?

A

linear form of glucose

not hemiacetal form!

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12
Q

chymotrypsin

A

preferentially cleaves peptide bonds next to large hydrophobic amino acids, preferentially aromatic amino acids

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13
Q

number of stereoisomers

A

2^n where n is the number of chiral centers

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14
Q

electric field lines

A

go from positive to negative charges
eg an axon is negatively charged and the extracellular solution has a zero net potential, so the field lines point inward

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15
Q

current depends on

A

Ohm’s Law V=IR

to determine resistance: use resistance per unit length and length

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16
Q

squalene

A

precursor to steroids

cholesterol, testosterone, cortisol, etc.

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17
Q

what is the concentration of Cl- ions in a 0.1 M solution of CaCl2?

A

0.2M

produces twice as many Cl- ions as Ca2+ ions when it dissolves

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18
Q

sucrose

A

does not possess a hemiacetal functional group and will not undergo mutarotation or be oxidized

saccharides undergo mutarotation if they are capable of ring-opening which occurs at the hemiacetal group (these are reducing sugars because they can be oxidized by Ag+)

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19
Q

Lineweaver-Burk plot

A

y-intercept: 1/Vmax

x-intercept: 1/Km

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20
Q

how does a barometer work?

A

air pressure outside is higher than air pressure inside
reaches equilibrium by building pressure inside through raising the liquid level so that air pressure + liquid pressure inside is equal to air pressure outside

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21
Q

1 m^3 equals

A

10^6 cm^3

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22
Q

the Doppler effect

A

relates the frequency of the ultrasound wave as detected by a moving detector to the frequency of the wave when the source is stationary, the speed of the source, and the speed of the detector

ultrasound requires speed of the sound and frequencies of sound waves emitted and observed

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23
Q

heat equation

A 
q = mCdT
C = specific heat
m = mass
dT = change in temperature
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24
Q

how can a single stereoisomer be formed?

A

neither reactant is chiral –> the enzyme is chiral

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25
Q

diverging lens

A

concave lens
used in myopia to focus light on the retina
converging lens is convex

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26
Q

calculate the density of a human body from its weight in air and its weight while submersed in water

A

density is proportional to:
Wair/(Wair-Ww)
Archimedes’ principle: ratio of the density of an object to the density of the fluid it is submersed in = ratio of the weight of the object in air to the difference of submersed weight and weight in air

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27
Q

amino acids that contribute to stabilization of ADP binding

A

histidine and arginine (or lysine)

positively charged side chains have favorable ionic interactions with the negatively charged phosphates of ADP

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28
Q

NADH to NAD+

A

oxidation

NAD+ is reduced to NADH

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29
Q

frequency of a photon

A

E = hf where h is Planck’s constant (6.62 x 10^-34)

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30
Q

power, work, time

A 
P = W/t
W = Pt
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31
Q

half-reaction for oxidation of NADH

A

NADH –> NAD+ + H+ + 2e-

balance hydrogens and then balance charge with e-

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32
Q

why do nickel ions form a green solution?

A

nickel has a partially filled d orbital

lower energy d orbital electrons will absorb visible light to move into higher energy orbitals

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33
Q

Hendersson Hasselbach equation

A

pH = pKa + log (conj base)/(conj acid)

if something dissociates at pka 6 and experimental pH is 8, ratio is 100:1 or 10^2

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34
Q

what increases the boiling point of a liquid?

A

hydrogen bonding
eg glycerine has 3 OH groups to participate in hydrogen bonding vs isopropyl alcohol only has 1 OH group, so glycerine will have a significantly higher boiling point

35
Q

atomic radius trends

A

increase down a period

decrease down a row - this is because the effective nuclear charge increases, holding electrons closer to the nucleus

36
Q

why does glycine form a dipolar ion in aqueous solution?

A

high dipole moment

zwitterion means highly electron withdrawing and electron drawing substituents which add to polarity

37
Q

phase difference

A

half a wave phase difference = 180 degrees = destructive interference
full wave phase difference = 360 degrees = constructive interference

38
Q

frequency and period

A

T = 1/f

39
Q

Hertz (frequency) to s (period)

A

100 Hz = 1/100 s-1 = 0.01 seconds

200 Hz = 1/200 s-1 = 0.005 seconds

40
Q

amide group

A

bond that forms between amino acids in a peptide

amine group + carboxyl group

41
Q

first peak in gas chromatography

A

molecule with lowest molecular weight and weakest intramolecular bonds –> migrates the fastest

42
Q

inversion of stereochemistry

A

incoming nucleophile displaces the leaving group from the opposite side of a reacting center during an SN2 reaction

43
Q

speed and index of refraction

A

index of refraction in a medium = speed of light in vacuum/speed of light in the medium

44
Q

work power time

A

W = P t

45
Q

hybridization of central atom of octahedral compound

A

d2sp3

has 6 sigma bonds and no lone pairs

46
Q

why do we have a variety of opsins?

A

to enable the detection of different colors

47
Q

how can you tell a molecule is hydrophobic?

A

primarily made up of Cs and Hs

binding site will also be hydrophobic

48
Q

chain linkage of glycogen

A

alpha-1,4-glycosidic bond

branching in glycogen is alpha-1,6

49
Q

dissociation of acid in water

A

negative charge eg HPO42- will make dissociation weaker/less likely

50
Q

electrochemistry: what makes a reaction spontaneous?

A

when E>0, the reaction is spontaneous (opposite of delta g)

51
Q

kcat

A

when enzyme is saturated with substrate, kcat = Vmax/enzyme concentration

52
Q

absorption of UV light by organic molecules results in

A

excitation of bound electrons

53
Q

stationary phase of column chromatography is silica gel

A

silica gel is polar

most nonpolar compounds will elute first, most polar will elute last

54
Q 
sort by polarity:
alcohol
ketone
carboxylic acid
alkane
A 
most to least polar:
carboxylic acid
alcohol
ketone
alkane
55
Q

charged amino acids at pH 7

A

positive - lysine (K), arginine (R), histidine at lower pH

negative - glutamic acid (E), aspartic acid (D)

56
Q

Venturi effect

A

air enters a mask because the static pressure of the air is larger than the static pressure of the oxygen in flow

57
Q

why do G-C base pairs have a higher melting point than A-T pairs?

A

increased pi bond stacking strength

58
Q

what property of a substance is best used to estimate its vapor pressure?

A

boiling point

59
Q

storage lipids

A

triglycerides/triacylglycerols

3 fatty acids attached to a single glycerol

60
Q

in an electrochemical cell, where do oxidation and reduction occur?

A

oxidation always occurs at the anode

reduction always occurs at the cathode

61
Q

coordinate covalent bond

A

Lewis acid-base interaction between a metal cation and an electron pair donor
eg the bond between Cu2+ and nitrogen atoms of ammonia in (Cu(NH3)4)2+

62
Q

coordination number

A

number of molecules that bind to a central cation

63
Q

what forms the exterior of the double helix?

A

sugar-phosphate backbone

64
Q

highest bond energy =

A

shortest bond length

C-H is short bc of H’s small atomic radius

65
Q

work done stretching

A

W = 1/2kx^2

66
Q

ratio of 20dB to 40dB

A

100

decimal log of the ratio of their intensities is 2 –> ratio is 100

67
Q

negative focal length of a lens

A 
diverging lens (concave)
forms virtual, reduced images
68
Q

energy conversions in a battery-powered resistive circuit

A

chemical energy to electrical energy to thermal energy

energy is dissipated as heat from the resistor

69
Q

protein secondary structure is characterized by the pattern of hydrogen bonds between

A

backbone amide protons and carbonyl oxygens

side chain protons/oxygens are not involved

70
Q

most likely to undergo SN1 reaction

A

tertiary carbocation is most stable

71
Q

kinetic energy of a photon

A

energy of the photon Hf - work function

72
Q

energy power time

A

E = P t

73
Q

for concentration questions

A

remember to account for amount of solution actually used

eg 0.1 mM of 800 g/mol MW would be be 80 mg in 1 L, but in 1 mL the answer is divided by 1000

74
Q

compound 1 elements are mixed and do not combine but compound 2 elements do combine when mixed, what does this tell us about kinetic/thermodynamic control?

A

compound 1 is kinetically controlled - elements do not mix spontaneously so they do not convert to most thermodynamically stable forms
compound 2 is thermodynamically controlled - elements do mix by converting to most thermodynamically stable forms

75
Q

mixing suspensions

A

results in average concentration

eg mixing 0.1 and 0.2 concentration will give a single peak at 0.15

76
Q

note for electron configurations

A

if a configuration looks like 4s23d5 it actually loses the 4s2 electrons first to leave 3d7
fill in 3d orbitals before 4s

77
Q

power force velocity

A

power = force x velocity

78
Q

experimental data which indicates thermodynamic stability

A

heat of combustion

79
Q

Kb

A

Kw/Ka for conjugate acid
Kb > Ka indicates more basic, Ka > Kb indicates more acidic
Kw = (Ka)(Kb)

80
Q

FAD

A

cofactor oxidant

FADH and NADH are reducing agents

81
Q

byproduct of peptide bond formation

A

H20 - 18 amu

82
Q

heme component

A

porphyrin

pyrrole ring - 5 membered ring including nitrogen

83
Q

resistivity

A

inverse of conductivity and vice versa

84
Q

property of a wave unaffected by medium

A

frequency

MCAT Exam Questions (3 decks)

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