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Melanie's MCAT flashcards > Chem/Phys II > Flashcards

Chem/Phys II Flashcards

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1
Q

What is homotropic regulation?

A

When a molecule serves as a substrate for its target enzyme, as well as a regulatory molecule of the enzyme’s activity (O2 = homotropic allosteric modulator of hemoglobin)

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2
Q

Fluid pressure changes with depth are assumed to be linear. Which statement best explains why this does not hold true for atmospheric pressure changes?

A

The volume of a mass of air is not constant

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3
Q

With decreasing temperature:

A

Air is able to hold less H2O

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4
Q

The complete conversion of three moles of glucose by aerobic fermentation yields how many moles of acetic acid?

A

6

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5
Q

Which of the following phase changes are exothermic processes?

A

Liquid to solid and gas to solid

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6
Q

What is spectrophotometric absorbance?

A

Used to measure the concentration of metal ion remaining in aqueous solution following extraction (materials absorb light of a certain wavelength)

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7
Q

How does adding electron-withdrawing functional groups increase acidity?

A

They provide inductive stabilization of the conjugate base by pulling electron density away from the negatively-charged position

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8
Q

What is the Henderson-Hasselbalch equation?

A

pH = pKa + log [B] / [A]

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9
Q

When a patient is on the operating table for heart surgery, surgeons need to clamp major nearby blood vessels before cutting them because, according to Bernoulli’s equation, a volume of pressurized blood opened to the atmosphere:

A

Will convert its pressure to kinetic energy, rapidly exiting the body and causing shock

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10
Q

What is the principal quantum number?

A

The first quantum number (n), denotes the energy level of the electron, higher principal quantum numbers = greater energy, farther from the nucleus (relates to row of the periodic table)

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11
Q

What is the azimunthal quantum number?

A

Letter (l), denotes the subshell in which the electron is found, values range from 0 to n-1 (0 = s subshell, 1 = p subshell, 2 = d subshell, 3 = f subshell)

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12
Q

What is the magnetic quantum number?

A

Letter (ml), denotes the spatial orientation of the electron, values = -l to l

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13
Q

What is the spin quantum number?

A

Letter (ms), denotes the spin orientation of the electron, which relates to its angular momentum (m = +/- 1/2)

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14
Q

The high-energy radiation produced by the gamma rays has sufficient energy to:

A

Generate free radicals, excite electrons to higher energy levels, and eject electrons from molecular orbitals

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15
Q

Free radicals from ionizing radiation are highly unstable and have carcinogenic effects. These effects most likely result from damage to:

A

Nucleic acids

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16
Q

When electrons move from the excited to ground state:

A

There is a loss of vibrational energy

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17
Q

If a scientist chooses not to employ a SEC column, but wishes to fractionate a protein sample on the basis of only molecular weight, what technique would be most appropriate?

A

SDS-PAGE

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18
Q

What is another name for tert-butyl chloride?

A

2-chloro-2-methylpropane

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19
Q

Atrial fibrillation is the most common heart arrhythmia, causing palpitations, fainting and chest pain. According to the information in the passage, what is most likely to be observed in the ECG during atrial fibrillation?

A

Missing P waves and an irregular rate

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20
Q

What regions of an ECG are most likely to be explained by the movement of sodium ions into a cardiac neuron?

A

P, Q, and R

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21
Q

What is the formula for phosphorous acid?

A

H3PO3

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22
Q

Efforts to treat lactic acid buildup in muscles were attempted using dissected muscle specimens in the laboratory. One of these experiments involved ammonium formation from dissolved ammonia. Under conditions of excessive lactic acid:

A

The final concentration of ammonium will be higher than otherwise due to lower pH (ammonia will convert to its conjugate acid, ammonium)

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23
Q

How is Solubility Enhancement Ratio calculated?

A

By dividing the solubility of A in a certain media by its solubility in water

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24
Q

What of the following boundaries would give the lowest-quality image to a physician?

A

Muscle/bone

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25
Q

The piezoelectric effect, when generating ultrasound waves, involves the conversion of:

A

Electrical energy to mechanical energy (the piezoelectric effect begins with voltage generating a current through the crystal (electrical energy) and culminates in the crystal vibrating (mechanical energy))

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26
Q

Conversion of pyruvate into glucose requires enzymes present in:

A

Both the mitochondria and the cytosol

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27
Q

What is the chemical formula for alkanes, alkenes, and alkynes?

A

CnH2n+2, CnH2n, and CnH2n-2

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28
Q

What is the Arrhenius equation?

A

k = Ae^-Ea/RT

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29
Q

What is the net charge on a valine molecule in the human body?

A

0

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30
Q

What is an example of an amphiprotic molecule?

A

Sodium bicarbonate, NaHCO3

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31
Q

What are the units of the Boltzmann constant?

A

J/K

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32
Q

What is true about solvents for TLC?

A

Anhydrous methanol has a greater eluting strength (adheres to the stationary phase) than pentane when used as solvents in a TLC procedure

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33
Q

An ideal buffer should have:

A

A pKa within 1 pH unit of the expected experimental conditions

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34
Q

What is normality?

A

The number of moles of protons per liter of solution

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35
Q

What is associated with higher antioxidant actiivity/thermodynamic favorability?

A

Lower enthalpy values

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36
Q

What is vitamin B1?

A

Thiamine, a coenzyme in metabolic processes including amino acids and carbohydrates (deficiency = Korsakoff’s syndrome -> memory derangement/language problems)

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37
Q

What is vitamin D?

A

A lipid-soluble molecule primarily involved in calcium metabolism

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38
Q

What is vitamin K?

A

A group of closely-related molecules that contribute to blood coagulation and clotting

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39
Q

In comparison to the cohesive forces between water molecules of the protein solution droplet, how can the strength of interaction between water and oil molecules at an oil-water interface be characterized?

A

Weaker, because they are forces created by induced polarity in nonpolar molecules

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40
Q

What is a spherical lens?

A

It can be converging or diverging, and it may not cause the light rays to converge any sooner

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41
Q

Light inside the thin glass tube of a laproscopic surgical device strikes the edge of the glass tube and is entirely reflected back into the tube, with none of the light exiting to the surrounding medium. Which of the following must be true?

A

Incident angle is greater than or equal to the critical angle

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42
Q

Which of the following acids is expected to generate the strongest hydrogen bonding?

A

HF

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43
Q

A researcher carries out a column chromatography at physiological pH, using a stationary medium with a net positive charge. If a solution containing the following oligopeptides is poured into the column, which oligopeptide will most likely be found in the first fraction collected?

A

Positively charged will elute first (won’t stick to stationary phase, elute the fastest with the mobile phase)

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44
Q

If a given channel in a nerve membrane shows a preference for transporting larger solutes, which of the following would increase the likelihood of a given particle being transported by the channel?

A

Adding an electron to a Cl atom to create a Cl- ion

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45
Q

Oligodendrocytes:

A

Serve to increase nerve conduction velocity in the central nervous system

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46
Q

What is the purpose of the long tail on Coenzyme Q10?

A

To allow CoQ10 to stay in and move in the hydrophobic portion of the inner mitochondrial membrane

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47
Q

Oxidation of aldehydes produces which functional group?

A

Carboxylic acids

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48
Q

What would result if CoQ accepted only one electron instead of two?

A

There would be a free radical

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49
Q

Which of the following characteristic changes in the IR spectrum would indicate the conversion of a fatty acid to an ester?

A

Disappearance of a broad peak in the 2500-3300 cm^-1 region only (loss of an OH group)

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50
Q

What is amperes equal to?

A

Coulombs per second

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51
Q

What equations can I use together?

A

V = IR and I = Q/delta T

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52
Q

Why are synthesized trans fats used as substitutes for saturated fats?

A

The hydrocarbon tails of trans fats stack more densely than those of comparable cis fats, making them less likely to be liquids at room temperature

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53
Q

Hematoporphyrin usually forms a complex with:

A

Fe2+

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54
Q

When NADH is oxidized, what happens to the hybridization of the nitrogen on the nicotinamide ring, and the C4 carbon atom opposite the nitrogen?

A

Both and nitrogen and the C4 carbon are converted from sp3 to sp2 hybridization

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55
Q

Even though enols are good nucleophiles, what are even better nucleophiles?

A

Their conjugate base, enolates

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56
Q

What is the process of a Claisen condensation?

A

An ester enolate reacting with another part of an ester

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57
Q

Surfactant-substrate interactions can involve which of the following intermolecular forces?

A

London dispersion forces, hydrogen bonding, and ion-dipole interactions

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58
Q

Anion surfactants most likely reduce the rate of nucleophilic reactions of hydroxide ion with neutral compounds by:

A

Forming a negatively-charged surfactant-substrate complex that repels the nucleophile

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59
Q

When does beta positive decay occur?

A

When the proton-to-neutron ratio is too high

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60
Q

The surface temperature of the sun (5770 K) is much greater than that of the earth (298 K). As a result, solar photons have a much higher energy than Earth photons. Given that information, how does the frequency and velocity of an Earth photon differ from that of a solar photon?

A

The frequency of the Earth photon would be lower; the speed of the photons would be identical

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61
Q

What is a chaotropic agent?

A

Any molecule in aqueous solution that can disrupt the hydrogen bonding network including the bonds between water molecules

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62
Q

What does a high SASA (solvent-accessible surface area)?

A

It indicates the residue is located at the surface of the protein, and therefore is less likely to be critical for overall protein structure

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63
Q

Which of the following gases would decrease the pH when dissolved in an aqueous solution?

A

Carbon dioxide

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64
Q

Individuals with a large bone cross-section:

A

Are more likely to experience a fraction

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65
Q

Refractive myopia is corrected by the use of a diverging lens of appropriate optical power. When compared to a healthy eye, a myopic, but otherwise normal, eye’s near point is most likely:

A

Smaller than that of a healthy eye

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66
Q

What is an example of a stereoselective reagant?

A

Diethyl tartrate (stereospecific = SN2)

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67
Q

An object floats in water with 4/5 of its volume submerged. If the object is then placed in a type of oil with a density half that of water, which of the following is true about the object placed in the oil?

A

The object will sink to the bottom

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68
Q

p-p-nitrophenol has a pKa of 7.16, whereas ethanol has a pKa of 16. What best explains this difference?

A

Anion stability achieved by delocalized pi electrons across the phenolic salt

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69
Q

What is a molecule?

A

A group or cluster of two of more atoms held together by chemical bonds

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70
Q

What is a compound?

A

Two or more different types of elements combined chemically in a fixed proportion

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71
Q

What makes something a good nucleophile?

A

Electron density, negative charge, the conjugate base is always a better nucleophile, less electronegative

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72
Q

In polar aprotic solvents:

A

nucleophilicity increases going up the periodic table

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73
Q

In polar protic solvents:

A

nucleophilicity increases going down the periodic table

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74
Q

What is the difference between spring force and spring work?

A

F = -kx, W = kx/2

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75
Q

Remember!

A

AN OX and RED CAT

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76
Q

If a question is asking about how much charge is transferred:

A

It is probably good to write out a balanced equation

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77
Q

Remember:

A

Current and electrons always flow in opposite directions

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78
Q

At pH = 7.3, what is the bond order of the shortest bond to oxygen in glycine?

A

1.5 (at physiological pH, the carboxyl group is deprotonated, the negative charge is delocalized by resonance between the two oxygen atoms)

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79
Q

More energy is needed to evaporate water to vapor than to melt ice to water because:

A

No hydrogen bonds exist in water vapor

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80
Q

When looking at solubility:

A

Look at polarity

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81
Q

The rate-limiting step has:

A

The highest Ea

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82
Q

Short-chain saturated fatty acids present in some animal products can produce a rancid odor if they are released from a triglyceride. Which of the following methods would prevent this type of rancidity?

A

Dehydration and sterilization (saturated = no double bonds, hydrogenation won’t do anything)

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83
Q

Equation relating sound speed to wavelength and frequency

A

C = lambda * f

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84
Q

In classic Doppler ultrasound:

A

Readings become less accurate as cos theta approaches zero

85
Q

What is the prime example of transverse waves?

A

Electromagnetic waves, including visible light

86
Q

What would be a type of tissue used by Doppler ultrasound imaging?

A

Lymphatic tissue

87
Q

To separate enantiomers:

A

Use a stationary phase with associated chiral substances (fractional distillation would not work for enantiomers)

88
Q

In size-exclusion chromatography:

A

Smaller molecules get stuck in the pore system, while larger molecules pass right through

89
Q

Equation relating electric field to membrane potential (voltage) and distance:

A

E = v/d

90
Q

Why would critical protein residues be more likely to be conserved than non-critical residues?

A

Mutations to critical residues tend to produce a loss of function

91
Q

What is thin-layer chromatography used for?

A

To separate non-volatile mixtures, compounds that have different polarities

92
Q

What is recrystallization used for?

A

To make sure impurities are not within the final lattice structure; by slow cooling, the lattice forms slowly, and impurities are not trapped within the lattice structure

93
Q

To separate enantiomers:

A

Use chiral resolution

94
Q

When looking at chromatography:

A

The compounds will follow the STATIONARY PHASE

95
Q

Which of the following is (are) present in a mixture of NH3 and BF3?

A

Bronsted-Lowry base (it is not a BL acid because there are no protons to donate)

96
Q

Because hydrogenation usually decreses the oxidation number of hte atom the H becomes attached to:

A

It is generally considered reduction (ex. NAD+ -> NADH)

97
Q

Halogens are often:

A

Leaving groups in nucleophilic substitution reactions

98
Q

The transmembrane region of a protein:

A

Spans the lipid bilayer, largely hydrophobic (nonpolar)

99
Q

Turbulent flow in humans is a major risk factor for atherosclerosis, the buildup of plaque on arterial endothelium. Ignoring any potential effects of turbulence, what effect would atherosclerosis have on blood flow?

A

Narrowing of the artery causes the velocity to increase and the hydrostatic pressure to decrease (would not change osmotic pressure because composition of blood would not change)

100
Q

A carbohydrate:

A

Only contain carbon, hydrogen, and oxygen, not phosphorus

101
Q

A steroid:

A

Is a hormone derived from cholesterol, would not characteristic ring structures

102
Q

A peptide:

A

Is a relatively small polymer of amino acids

103
Q

During an experiment involving the effect of roller coaster riding on neck muscles, all participants reported a feeling of weightlessness in the loop segment of the roller coaster ride. At which of the following positions did this feeling occur?

A

At the top of the loop

104
Q

What is the equation for the decibel level of sound?

A

dB = 10log (I/Io)

105
Q

Which of the following enzymes is LEAST likely to be synthesized in the outer mucosal layer of the colon?

A

Fructokinase

106
Q

A way to identify sucrose among sugars is to use the Benedict’s test for reducing sugars. As the first carbon of glucose and the second of fructose are locked together in the sucrose molecule, no carbon is easily oxidized, and the Benedict’s test is negative. Starch contains a great deal of glucose but gives a negative Benedict’s test because:

A

Each starch molecule has only one free aldehyde carbon available for oxidation, and the resultant reaction is too slight to be observed

107
Q

Gases generally have greater solubility:

A

As the partial pressure of the gas increases, and in cooler liquids

108
Q

In which of the following aqueous carbohydrate solutions would a given vesicle have the greatest buoyancy?

A

Buoyancy = displacement of fluid when an object is submerged, depends on density of solution

109
Q

If the average bone mineral density is 3.88 g/cm3, which of the following is a reasonable estimation of the density of the average human body?

A

1 g/cm^3

110
Q

A physician hypothesizes that the PA effect could be generated by modulating the intensity of radiation delivered by a continuous light source, rather than by illumination with pulsed light. Is this physician correct?

A

Yes, because the magnitude of thermal expansion and contraction will vary with the intensity of incident radiation

111
Q

Sound waves reaching the ultrasonic transducer propagate through brain tissue via which of the following mechanisms?

A

Collision of adjacent particles within the tissue

112
Q

What are sphingolipids?

A

Glycosylceramide lipids containing a sphingosine backbone, an 18-carbon amino alcohol, bound to a fatty acid head group through an N-acyl linkage (25% of lipids in myelin sheath)

113
Q

What is sphingomyelin?

A

A complex phosopholipid formed by the ester linkage of ceramide to a molecule of phosphocholine or phosphoethanolamine (derived from sphingolipids)

114
Q

During the synthesis of bile, cholesterol is conjugated by the addition of a carboxylic acid residue. Bile salts are thus able to solubilize lipids in aqueous digestive secretions because bile salts:

A

Have a polar region and a nonpolar region, thus increasing the water-solubility of lipids

115
Q

What is true about IR spectra of alcohols?

A

The infrared spectra of most alcohols are typically recorded as neat liquid films or Nujol mulls

116
Q

Where are singly bonded C-O stretches typically found in IR?

A

1100-1000 cm^-1

117
Q

In the fluorometry methods described in the research, the wavelength of emitted radiation depends on:

A

The wavelength of excitatory radiation and the electronic structure of the molecule being analyzed (produces wavelength and intensity of emission spectrum)

118
Q

Would it be possible for the researchers to use gas chromatography (GC) for the isolation of retinol during SRA?

A

Yes, provided retinol vaporized without degradation

119
Q

Is hexane polar or nonpolar?

A

Very nonpolar

120
Q

Absorption of radiation corresponding to what portion of the electromagnetic spectrum is most likely to excite Aequorea fluorophore, a green fluorescent protein used in biological experiments?

A

Green flourescence = low energy/frequency, needs to be excited by a high frequency radiation = ultraviolet light

121
Q

In order to image target blood vessels, researchers must first determine the index of refraction of skull bone. What is the minimum information required to make this determination?

A

The velocity of light in the sample (equation: n = c/v)

122
Q

More double bonds/more of a conjugated system would result in:

A

A more stable structure

123
Q

If entropy increases:

A

Disorder increases (order decreases)

124
Q

Which of the following must be true for a biochemical reaction at equilibrium?

A

Delta G = 0

125
Q

The structures of glycine and asparagine are displayed below. What type of interactions would be increased for a protein if glycine is mutated to asparagine?

A

Hydrogen bonding

126
Q

The only amino acid that forms covalent bonds with other side chains are:

A

Cysteine

127
Q

Copper (II) ions in aqueous solutions cannot be directly extracted into organic solvents without an extractant because the ions:

A

Have greater solubility in water than organic solvents unless complexed with extractant

128
Q

Hydrogen bonding between molecules will be present when:

A

The molecules contain an O, N, or F atom covalently bonded to an H atom

129
Q

Dipole-dipole interactions occur between:

A

Only polar molecules

130
Q

London dispersion forces only occur between:

A

Nonpolar molecules

131
Q

What are induced dipole interactions?

A

An electrostatic force (the attractive force between positively-charged and negatively-charged atoms)

132
Q

The blood-brain barrier prevents molecules from easily entering the central nervous system unless they are able to pass through the lipophilic plasma membranes of the cells making up the barrier. Which of the following is most likely to be true?

A

Diethyl phthalate is more likely to cross the blood-brain barrier than phthalic acid because it lacks hydrogen-bonding hydroxyl groups

133
Q

Many hydrotopes, like sodium benzoate, are synthesized by the reaction of a weak acid with a strong base. This is similar to the synthesis of:

A

Soaps (surfactants)

134
Q

A chiral molecule in solution is found to rotate light in the clockwise direction. This species successfully undergoes a unimolecular nucleophilic substitution reaction. The product solution will rotate plane-polarized light:

A

Not at all (SN1 reaction = 2 products, racemic mixture -> no net light polarization)

135
Q

A particular biomolecule is known to have 30 diastereomers and does not exist in any meso forms. How many chiral centers must this molecule have?

A

2^n = 32 -> n = 5

136
Q

Isooctane and n-octane are best described as:

A

Structural isomers

137
Q

What is the different between anomers and epimers?

A

Both similarities differ at one place, but for anomers they would only differ at the anomeric carbon

138
Q

For two carbohydrates to be considered anomers, what must be true?

A

They need to have different stereochemistry solely at the anomeric carbon, which is the atom that serves as the carbonyl carbon in the molecule’s straight-chain form

139
Q

What are Grignard reactions used for?

A

To alkylate compounds that contain carbonyl functionalities

140
Q

How does branching affect boiling point?

A

Increases surface area available for intermolecular attractions -> ability for molecules to attract each other -> lower BP

141
Q

How would halogenating n-heptane change the boiling point?

A

Produce a polar bond between the halogen atom and one carbon, allow the product to experience dipole-dipole forces, raising the BP

142
Q

Which isomeric form of 2-chloro-3-bromobutane is most thermodynamically stable?

A

Alkanes do not have cis and trans isomers

143
Q

In organic chemistry, radicals are extremely reactive species that possess at least one unpaired valence electron. Radical reactions, such as free-radical halogenation, can be instigated in a number of ways. Potential radical initiators include:

A

UV light and di-tert-butyl peroxide

144
Q

What is an example of an alkyl halide under SN1 conditions that would form the most stable carbocation?

A

2-bromo-2-methylpentane (tertiary alkyl halide)

145
Q

Between cis-2-pentene and trans-2-pentene, which one would have the higher melting point?

A

Trans = lower boiling; higher melting

146
Q

Ethene is exposed to H2 in a solution containing a chunk of solid palladium. If it reacts successfully, the original alkene will:

A

Be reduced to form ethane (hydrogenation = a form of reduced)

147
Q

If you wish to promote an E1 reaction, you should use:

A

A tertiary substrate, a mild base, heat, and a polar protic solvent

148
Q

What is UV-Vis spectroscopy mainly used for?

A

Conjugated system

149
Q

To increase the pKa, or make the proton less acidic:

A

We are looking for an electron-donating group, like tert-butyl

150
Q

To donate hydrogens:

A

A molecule must contain a hydrogen atom that is covalently bound to either oxygen, nitrogen or fluorine

151
Q

Consider the course of a typical SN1 reaction. The intermediate generated by the rate-limiting step is best described as:

A

An unstable intermediate with vacant orbitals

152
Q

Tert-butanol is a common laboratory reagent that spontaneously degrades in solution to yield 2-methylpropene. To prevent this reaction and prolong the shelf life of tert-butanol, which of the following measures would be effective?

A

Adding a small amount of pyridine to the storage vessel, and storing the tert-butanol in a cold place

153
Q

A chemist fills two separate beakers, one with 70% ethanol and the other with 70% ethanethiol. If subject to standard conditions, both beakers will have a pH of:

A

Less than 7, with ethanethiol having the lower pH of the two

154
Q

4-tert-butylcyclohexanol can be classified as:

A

A secondary alcohol (OH = next to carbon attached to 2 alkyl groups)

155
Q

Between ethoxide, ethanol, tert-butoxide, and tert-butanol, the strongest base is:

A

Tert-butoxide (tert-butanol = very weak acid, negative charge on tert-butoxide is fully concentrated on the lone oxygen atom)

156
Q

In the chromatography of the reaction mixture, water absorbed on cellulose functioned as the stationary phase. What was the principal factor determining the migration of individual components in the sample?

A

Hydrogen bonding

157
Q

What type of functional group is formed when aspartic acid reacts with another amino acid to form a peptide bond?

A

An amide group

158
Q

In gas-liquid chromatography:

A

The molecule with the lowest molecular weight/weakest intermolecular forces will be the first peak

159
Q

If the amount of H+ in a solution is increased:

A

The perecentage of ionization would decrease

160
Q

The energy of electromagnetic radiation is directly proportional to:

A

The number of photons -> intensity = energy emitted/time

161
Q

Work is equal to:

A

Power x time

162
Q

What reaction is catalyzed by lipase A?

A

Hydrolysis of triacylglycerides

163
Q

If there is an amino acid subsitution like R33G:

A

The wild-type amino acid (R) changes to a variant amino acid (G)

164
Q

UDP contains uridine, which is a nucleis acid used in:

A

RNA

165
Q

In beta-minus decay:

A

An electron is emitted, so a neutron in the molecule is converted into a proton

166
Q

Branching occurs:

A

Through an a-1,6-glycosidic bond in glycogen

167
Q

If a molecule has a high negative charge:

A

The dissociation of it will occur to the least extent

168
Q

Which of the following most likely will occur if a homogeneous catalyst CANNOT be separated from the products at the end of a reaction?

A

The products will be contaminated

169
Q

A reaction is spontaneous if:

A

E is positive

170
Q

What are four ways to define power?

A

J/s, ftlb/s, W, kgm^2/s^3

171
Q

What are some true statements about aldehydes and ketones?

A

Acetals cannot form under basic conditions, and hemiacetals and hemiketals exist in equilibrium with aldehydes and ketones

172
Q

What is an alpha hydrogen?

A

A hydrogen that is bound to the carbon immediately adjacent to a carbonyl carbon (very acidic)

173
Q

Reaction of 4-methyl-1-pentanol with chromic acid should produce:

A

4-methylpentanoic acid

174
Q

Since the kinetic enolate is favored by low temperatures, it also is:

A

Less stable

175
Q

Compared to its analogous acyl chloride, a carboxylic acid is considered:

A

Less electrophilic due to resonance

176
Q

What is the compound with the best and worst leaving group?

A

Acid anhydride = best; ester = worst (very unstable)

177
Q

What is the stability of acid anhydrides and esters?

A

Acid anhydrides are less stable/more reactive than esters

178
Q

What is transesterification?

A

The conversion of one ester to another via reaction with an alcohol

179
Q

If you wished to convert octanoic acid into a significantly more reactive molecule, you would most likely:

A

Expose it to SOCl2

180
Q

Why is acetyl iodide a better leaving group than acetyl fluoride?

A

I -> bigger molecule -> better able to delocalize negative charge

181
Q

The reaction between propanal and cyanide forms a:

A

Cyanohydrin (cyanohydrin reaction = aldehyde or ketone with a cyanide anion or nitrile)

182
Q

Many hydrolysis reactions form:

A

Carboxylic acids

183
Q

An amide is to a lactam as an ester is to a:

A

Lactone

184
Q

A student is attempting to isolate several products from the organic layer of an extraction. Initially, her solution contains an alkene, a phenol, a secondary alcohol, and a tertiary alcohol. If she begins the separation process by adding a moderately strong base, which substance is most likely to move into the water layer?

A

The phenol (during extractions, substances move into the water layer when they become charged/deprotonate the strongest acid)

185
Q

How are polar and nonpolar solvents used for monosubstitution/polysubstitution?

A

Nonpolar = monosubstitution; polar = polysubstitution

186
Q

What is the halogenation of a phenol?

A

Reacting p-chlorophenol with chlorine in carbon disulfide (nonpolar solvent = monohalogenation)

187
Q

Out of lactose, sucrose, maltose, and starch, which one has a beta-acetal linkage?

A

Glucose (beta-1,4 linkage)

188
Q

What would cause a positive Benedict’s test?

A

Containing a free aldehyde

189
Q

Why are ketals resistant to nucleophilic attack under basic neutral conditions?

A

Alkoxide ions constitute relatively poor leaving groups

190
Q

What is the difference between IR spectroscopy and UV-Vis spectroscopy?

A

IR = absorption of incident light directly into chemical bonds, UV-Vis = electronic excitation from the HOMO to the LUMO

191
Q

What is the difference between NMR spectroscopy and mass spectroscopy?

A

NMR = determining the content and purity of a sample as well as its molecular structure; mass = measures mass-to-charge ratio, is shown by mass spectrum (a plot of intensity as a function of the mass-to-charge ratio)

192
Q

Why is SDS a useful reagant for gel electrophoresis?

A

SDS confers a uniform charge density to all proteins in the sample, and it is amphipathic, allowing it to denature most globular proteins

193
Q

Compared to UV-Vis spectroscopy, IR spectroscopy is:

A

Reliant on the use of lower-energy radiation (UV-Vis = good for conjugated systems)

194
Q

What direction would electric field lines go for a neuron?

A

Positive to negative charge (+ extracellulaar fluid to - axon interior)

195
Q

What is the concentration of Cl- ions in a 0.1 M solution of calcium chloride?

A

Calcium chloride = CaCl2 = [Cl-] = 0.20 M

196
Q

What makes something a reducing sugar?

A

Contains a hemiacetal group, undergoes mutarotation, and will be oxidized by Ag+

197
Q

What charge do the C terminus and N terminus contribute to the charge of the peptide?

A

C-terminus = -1, N-terminus = +1

198
Q

If the level of aqueous solution was higher inside the buret than outside, the pressure of the gas inside the buret would be:

A

Lower (Pressure outside = higher)

199
Q

An ultrasound examination could show the motion of a fetus. In order to image this motion, the ultrasound examination devices requires what minimal information?

A

The speed of the sound, and the frequencies of the sound waves emitted and observed

200
Q

What is the relationship between boiling point and vapor pressure?

A

Higher boiling point = lower vapor pressure

201
Q

What is the difference between the principal and azimunthal quantum number?

A

Principal = radial size of an electron cloud, azimunthal = shape of an electron cloud

202
Q

What does a fatty acid consist of?

A

A hydrocarbon tail and a carboxylic acid

203
Q

If neither reactant is chiral, a chiral product can still form because:

A

The catalyst (the enzyme) is chiral

204
Q

What is nearsightedness also called?

A

Myopia (diverging lens)

205
Q

What procedure can be used to remove the water from the frozen sample?

A

Sublimation under reduced pressure

206
Q

What are two examples of amino acids that can carry a positive charge?

A

Histidine and Arginine

207
Q

What does lactate dehydrogenase do?

A

Converts lactate to pyruvate and back, oxidizes NADH to NAD+

208
Q

When choosing a buffer conducted at a certain pH, it would be best to choose one with a pKa of:

A

Within one value of pH

Melanie's MCAT flashcards (6 decks)

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