MCAT Chem/Phys Full Lengths (Part I)
clockwise orientation =
(R)-configuration
counter-clockwise orientation =
(S)-configuration
a second student, using the same experimental setup, wants to find the amount of work done by the gas if the pressure increased by 200 Pa, the amount of work done by the gas =
0 Joules without the container changing volume, the gas is NOT doing any work only the pressure was changed (increased by 200 Pa), NOT the volume
IR spectroscopy: Ethers
1050-1150 cm⁻¹ C-O
IR spectroscopy: Ketones
1700-1750 cm⁻¹ C=O
IR spectroscopy: Carboxylic Acids
1700-1750 cm⁻¹ C=O 2800-3200 cm⁻¹ O-H(broad)
@ STP, a mole of gas occupies
22.4 liters (T = 0°C, or 273° K)
IR spectroscopy: Alkynes
2200 cm⁻¹ C=C 3300 cm⁻¹ =C-H
IR spectroscopy: Aldehydes
2700-2900 cm⁻¹ (O)C-H 1700-1750 cm⁻¹ C=O
IR spectroscopy: Alkanes
2800-3000 cm⁻¹ C-H 1200 cm⁻¹ C-C
IR spectroscopy: Aromatic
2900-3100 cm⁻¹ C-H 1475-1625 cm⁻¹ C-C
IR spectroscopy: Alkenes
3080-3140 cm⁻¹ =C-H 1645 cm⁻¹ C=C
IR spectroscopy: Amines
3100-3500 cm⁻¹ N-H(sharp)
IR spectroscopy: Alcohols
3100-3500 cm⁻¹ O-H (broad)
blood flows through an artery such that the velocity at point A is 1/16 that at point B what is the ratio of the radius of the artery at point A to that at point B?
4:1
# of chiral carbons in morphine =
5
what would be expected to happen if 0.1 mol of I₂ is added to 1 L of solution containing 1.0 mol of precipitated AgI? [Note: Ksp for AgI₃ >> Ksp for AgI] all the I₂ would dissolve but only a portion of the AgI would dissolve
AgI (silver iodide) = very insoluble in normal circumstances, the concentration of iodide (I⁻) in solution is very slight, but it is in dynamic equilibrium with AgI(s): AgI(s) ⇌ Ag⁺(aq) + I⁻(aq)
continuity equation
A₁v₁ = A₂v₂ where A is the area & v is the velocity
suppose the diving bell is lowered to a depth at which the inside air pressure is twice its value on the surface of the ocean assuming air temperature is constant, how would you express the water level L inside the bell?
Boyle's Law states that the volume of a gas varies inversely with its pressure, assuming temperature is held constant since the pressure of the gas has doubled, its volume must have halved - the bell must be half full, so L = H/2
acetyl group
CH₃COR
the angle at which light is REFLECTED by a MIRROR =
CONSTANT & is NOT affected by wavelength
calcium hydroxide exists in solution according to the equilibrium:
Ca(OH)₂ ⇌ Ca²⁺ + 2OH⁻
where a cell membrane is myelinated, the capacitance of the membrane is
DECREASED because the myelin sheath increases the charge separation
the reaction that is being used to recharge the battery must have a voltage GREATER than the battery's original charge →
Ered,cathode - Ered,anode > Eoriginal therefore: Ered,cathode > Eoriginal + Ered,anode plugging in: Ered,cathode > 1.4 V + (-0.762 V) Ered,cathode > 0.638 V
dissociation constant equation of H₂O
H₂O ⇌ H⁺ + OH⁻ Keq = 10⁻¹⁴
a scientist attempts to measure the urinary excretion rate of diazepam using an ¹⁸O-labeled version of the drug what factors, if incorrectly calculated before the experiment begins, would lead to experimental error
I. abundance of naturally occurring oxygen-18 II. rate of conversion of diazepam to its primary metabolite II. concentration of diazepam in the labeled drug these must all be correctly accounted for because they will all affect the rate at which diazepam is cleaned (excreted) from the body via the urinary tract
identifying meso compounds
I. identify how many stereocenters the molecule contains II. see if the molecule has an internal mirror plane III. ensure that both halves are in fact mirror images of each other
A + B ⇌ C + heat will shift RIGHT if:
I. if more A or B added II. if C taken away III. if pressure applied or volume reduced (assuming A, B & C are gases) IV. if temperature reduced
A + B ⇌ C + heat will shift LEFT if:
I. if more C added II. if A or B taken away III. if pressure reduced or volume increased (assuming A, B & C are gases) IV. if temperature increased
SN2 reactions proceed in ONE concerted step:
I. nucleophile attacks @ the same time as the leaving group leaves II. nucleophile must perform BACKSIDE attack → leading to an inversion of stereochemistry the absolute configuration is changed - (R) to (S) & vice-versa
the wild-type strain can grow without being supplemented with any intermediates → its arginine biosynthesis pathway is normal & would be expected to have
LOW levels of each of the intermediates & a HIGH level of arginine
the ___________ the reduction potential (E°V) of a metal, the more vigorously it will react with HCl
LOWER
inhibition (or suppression) of gastric acid secretion would be expected to
LOWER intra-gastric [HCl], & therefore DECREASE intra-gastric [H⁺]
a group of patients is given cimetidine, which inhibits gastric acid secretion it can be hypothesized that the conductivity of the gastric juice in this group of patients, compared to that of a control group (patients who were NOT given cimetidine), will be:
LOWER, because intra-gastric pH increases
IUPAC name for acetaminophen
N-(4-hydroxyphenyl)ethanamide
a student mistakenly adds NaOH instead of HCl to the metal-containing flask what are the results of his experiment?
NO reaction takes place since elemental iron will NOT react with aqueous bases without O₂ gas
presence of non-conservative forces =
NOT an ideal system
SN2 reactions proceed in
ONE concerted step
power dissipated by resistors
P = IV = V²/R = I²R
proinsulin must undergo cleavage by protease, resulting in the two smaller units that become functional insulin protease's action represents modification of proinsulin's
PRIMARY structure (because the sequence of amino acids is altered, this constitutes a modification of proinsulin's primary structure)
Boyle's Law states that
PV = constant for gases & the volume of gas varies inversely with its pressure, assuming temperature is held constant
thiol group
R-S-H
image is on OPPOSITE side of LENS from light source =
REAL image
in a galvanic cell, the CATHODE is defined as the site of
REDUCTION
Boyle's Law
V = k / P
image is on SAME side of LENS as light source =
VIRTUAL image
methylmagnesium bromide (CH₃MgBr) =
a Grignard reagent
assume that aggregation will happen at any temperature the process of aggregation will most likely result in:
a decrease in enthalpy & an increase in entropy
non-conservative force =
a force that causes energy to be dissipated from a system includes: friction air resistance viscous drag
conservative force =
a force that does NOT cause energy to be dissipated from a system includes: gravity electrostatic forces springs (approximately conservative)
SN2 requires
a good nucleophile
in glucose, the carbonyl carbon can be attacked intramolecularly by the hydroxyl group of carbon-5 to form
a hemiacetal
the breaking of a covalent bond between the amino acids valine & isoleucine under biological conditions can best be described as
a hydrolysis reaction
identifying meso compounds: I. identify how many stereocenters the molecule contains
a meso compound is a stereoisomer &, thus, by default must have a stereocenter meso compounds require AT LEAST TWO(2) stereocenters a compound with only one stereocenter CANNOT be considered a meso compound as it would not be achiral & would not have another stereocenter to oppose its optical behavior
triacylglycerol is a useful starting material in the production of soaps (salts of long chain carboxylic acids) via a process known as saponification if this process was carried out by boiling the fat in aqueous sodium hydroxide & then extracting with toluene, what products would be seen in the aqueous layer?
a mixture of glycerol & sodium salts of fatty acids
in the reaction between phenylacetyl chloride & alanine, the amino group of alanine most likely acts as:
a nucleophile, attacking the electrophilic carbonyl carbon of phenylacetyl chloride
the axon can be thought of as
a parallel-plate capacitor, with the cell membrane acting as an insulator between the relatively negative inside of the neuron & the relatively positive outside
disulfide bonds are responsible for hair's curliness or lack thereof to change the curliness of someone's hair, a hairdresser must use:
a reducing agent (only a reducing agent could disrupt these covalent bonds)
racemic mixture =
a solution of a CHIRAL molecule, with equal amounts of the (R)-enantiomer & (S)-enantiomer
the human eye operates as
a thin converging lens
the reaction that is being used to recharge the battery must have
a voltage GREATER than the battery's original charge
non-alkylated fatty acids =
acids (NOT alcohols)
the Arrhenius equation, & thus rate of reaction, depend on
activation energy temperature gas constant pre-exponential constant A
as mentioned in the passage, purified thalidomide was unsuccessful therapeutically this is partially explained by the fact that thalidomide
acts as an acid
nodes of Ranvier contain
additional sodium channels that open to propagate the wave of depolarization their absence would result in the wave dying before it reaches the axon terminal
adenosine vs. adenosine monophosphate
adenosine = nucleoside adenosine monophosphate = nucleotide BOTH nucleotides & nucleosides have a base, here adenine, attached to a ribofuranose via a glycosidic linkage
assume that aggregation will happen at any temperature the process of aggregation will most likely result in: a decrease in enthalpy (∆H) & an increase in entropy (∆S)
aggregation will occur at any temperature = it is always a spontaneous reaction this means that the reaction always has a negative Gibb's free energy, which means that the change in enthalpy due to the reaction should be negative & that the change in entropy should be positive
which of the following is NOT a lipid derivative? I. waxes II. steroids III. carotenoids IV. albumins
albumins
researchers have discovered that the stereochemistry of the alkaloids is critical to their physiological effects for example, (-)-methadone produces powerful analgesic effects, while (+)-methadone produces no effect what is the most likely explanation for this difference in activity
alkaloids bind to stereospecific receptors
what would be expected to happen if 0.1 mol of I₂ is added to 1 L of solution containing 1.0 mol of precipitated AgI? Note: Ksp for AgI₃ >> Ksp for AgI
all the I₂ would dissolve but only a portion of the AgI would dissolve
on the other hand, with MIRRORS, the angle at which the incident light is REFLECTED is CONSTANT, & so →
all the light will be focused at the same point
alpha (α) decay
alpha particle is emitted ²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He
a patient with alkaline urine would need
an acid (such as ammonium chloride) to lower the pH
teratogen =
an agent or factor that causes malformation of an embryo
a nucleophile =
an electron-rich (lewis base) species that can attack an electrophile
the deacylation of aspirin =
an ester hydrolysis reaction - water attacks the carbonyl carbon of the ester, displacing the alcohol
the movement of particles (like sodium ions) from a region of high concentration to a region of low concentration is associated with
an increase in entropy (∆S)
the human eye operates as a thin converging lens that has a focal length of approximately 2.4 cm when looking at an object 100 m away, where will the image be produced after passing through the human eye?
an object 100 m away from the eye can be considered to be at infinity, since 100 x 10³ cm is much, much greater than 2.4 cm - therefore, distance between the image & the lens should be 2.4 cm, the same as the focal length since the object distance is greater than the focal distance, the object will be REAL so it will appear BEHIND the lens of the eye i.e., 2.40 cm behind the lens of the eye
the work done by a gas relies on
any change in VOLUME of the container that is holding it (W = p∆V)
identifying meso compounds: II. see if the molecule has an internal mirror plane
any molecule can have stereoisomers, but not all have internal mirror planes. the mirror plane should bisect the molecule
which of the following would affect the boiling point of an aqueous solution without altering its electrical conductance? methanol (CH₃OH) acetic acid (CH₃COOH) sodium chloride (NaCl) sodium benzoate (NaC₇H₅O₂)
any solute in water will affect its boiling point, but only those that become ions in solution will conduct electrical charges methanol is freely soluble in water, so it will affect the boiling point of water in solutions - however, it does NOT ionize to any appreciable amount in solution, & thus will NOT conduct electricity
a scientist uses a diving bell to study ATP synthase in aerobic bacteria as the bell is lowered, ATP synthase activity is likely to increase, due to an increasing partial pressure of oxygen
at greater depths, partial pressure of oxygen inside the bell will be greater while oxygen is NOT a reactant in the synthesis of ATP, it is required to establish the proton gradient which is necessary for ATP synthesis - hence, it is most logical to infer that ATP synthase activity would INCREASe the the depth of a diving bell
which of the following, if present in the urine in significant quantities, is likely to be a constituent of uroliths? I. iron II. barium III. bromine IV. potassium
barium, like calcium, is an alkali earth metal if calcium is a common substituent of uroliths, it is likely that barium could form them as well
the axon can be thought of as a parallel-plate capacitor, with the cell membrane acting as an insulator between the relatively negative inside of the neuron & the relatively positive outside →
because the presence of the myelin sheath INCREASES the distance between these two "plates", capacitance is decreased according to the formula: C = ε₀(A/d) as d is increased, C will go down
electrostatic interactions =
become a factor particularly in TERTIARY structure when charge amino acid R-groups are brought into close contact & interact due to the folding of the proteins
adenosine, once attached to a phosphate group →
becomes a nucleotide
the researchers chose ³⁶Cl because of its relative stability & half live ³⁶Cl primarily decays by beta-minus decay what is the primary product of ³⁶Cl decay?
beta-minus decay is (essentially) the conversion of a neutron into a proton & a beta-minus particle hence, the atomic number of the daughter nucleus will be one higher than that of the parent → Ar
the breaking of a covalent bond between the amino acids valine & isoleucine under biological conditions can best be described as a hydrolysis reaction
by realizing that cysteine is the only amino acid that forms disulfide bonds, infer that the bond between valine & isoleucine must be a PEPTIDE bond
a catalyst does NOT
change the energy of any intermediates or the product
enzymes do NOT
change the potential energy, initial state, or final state of the reaction
methanol dimers =
composed of two molecules of methanol bonded to each other
generation of electric fields from biological sources is limited to environments where
conductivity is high & resistivity is low (i.e., aquatic environments)
bomb calorimeters =
constant-volume calorimeters (because they measure the heat of reaction while holding the volume constant & resisting large pressures)
tautomerization results in
constitutional isomers
beta (β) decay
convert neutron → proton; beta particle is emitted ¹⁴₆C → ¹⁴₇N + ⁰₋₁e
non-conservative forces are pathway _________________
dependent
the angle at which light is REFRACTED by a LENS =
dependent on the wavelength
Arrhenius equation
describes the rate of the reaction
volume of gas =
directly proportional to its temperature in kelvin
DSG (Na₂C₅H₇NO₄) =
disodium glutamate = the sodium salt of glutamic acid because the acidic groups have been deprotonated, they will not contribute protons to the solution the unprotonated amine group is weakly basic & capable of accepting a proton - thus, a good prediction is "mildly basic", pH > 7
how would addition of potassium citrate to a saturated calcium hydroxide solution affect the pH of that solution?
dissociation of calcium hydroxide would be favored & the pH would increase
light spreads out after passing through the lens =
diverging lens
nucleosides =
do NOT have a phosphate group attached
in glucose, the carbonyl carbon can be attacked intramolecularly by the hydroxyl group of carbon-5 to form a hemiacetal
due to the presence of a carbonyl group & a hydroxyl group on glucose, a hemiacetal will form when the molecule cyclizes
since electric fields rely on the generation of electric currents →
electric fields from biological sources (such as fish) will NOT be able to form where the resistivity of the medium is too high (i.e., the air)
electroperception =
electrons flowing from an area of high electron density to an area of low electron density = electric field created around the fish (biological source)
in the absence of oxygen or acid
elemental iron will NOT react to form any products & NO reaction will take place (acid WILL react with elemental iron, even when NOT in the presence of oxygen)
power =
energy / time
two sugars that differ in configuration about a single stereocenter =
epimers
waxes =
esters of fatty acids & monohydroxylic alcohols (i.e., lipid-derivatives)
microbial fuel cell =
example of a galvanic or voltaic cell, since it generates electricity
in a myelinated axon with no nodes of Ranvier, individual sodium ions would travel
father, but depolarization would NOT reach the axon termini
aqueous layer =
fats are insoluble
organic layer =
fats are soluble
carotenoids =
fatty acid-like carbon chains containing conjugated double bonds & carrying six-membered carbon rings at each end lipid-derivatives
electric shock plates are sometimes used to restore the natural rhythm of a heart attack victim the shock plates are run off a 10-V battery & draw current at a constant 30 A if each shock draws 300 J of electrical energy, what is the duration of the shock?
first use P = IV thus power = (30)(10) = 300 J/s since power = energy/time, time = energy/power = time = (300 J) / (300 J/s) = 1 sec
pressure is equal to
force over area P = F / A
albumins =
globular (plasma) proteins that act as carriers or enzymes, & have a variety of other functions in the body NOT derived from lipids
in sphingolipids, sphingosine takes the place of _____________
glycerol (which provides the backbone for most phospholipids) - thus, glycerol is not generally found in sphingolipids
a biomedical engineer attempts to recharge a Ni-Cd hearing-aid battery using a Zn-HgO cell if the reduction potential at the anode of the Zn-HgO cell is -0.762 V, and the fully-charged Ni-Cd battery has a voltage of 1.4 V, the reduction potential at the cathode must be:
greater than 0.638 V
as a cyclist rides down a hill without pedaling, describe the relationship between his lost potential energy, U, and his kinetic energy gained, K
he must content with non-conservative forces like wind resistance, which reduces the amount of kinetic energy he can develop from a given loss of potential energy consequently, not all of the lost potential energy is converted into kinetic energy, and U > K
_______ does NOT denature fatty acids
heat
the question stem states that sample A has more calories than sample B, therefore → sample A must be more saturated or contain less bonds than sample B
higher degrees of unsaturation would DECREASE the calorie count
steroids =
include cholesterol & estrogen lipid-derivatives
a scientist uses a diving bell to study ATP synthase in aerobic bacteria as the bell is lowered, ATP synthase activity is likely to
increase, due to an increasing partial pressure of oxygen
conservative forces are pathway __________________
independent & associated with a potential energy function
relationship between magnitude of electric field & distance =
inversely related magnitude of the electric field decreases with distance, so objects further away would NOT be detected as well as closer ones
AgI(s) ⇌ Ag⁺(aq) + I⁻(aq) when iodine is added to the silver iodide solution,
it converts the small amount of iodide in solution to triiodide & silver iodide dissolves to replenish the iodide removed until equilibrium is re-established in other words, iodine stresses the silver iodide system by removing iodide from solution
from table 1, strain 2 can grow when supplemented with arginine or citrulline, but NOT with ornithine or just the precursor molecule, which is the starting point for the pathway - therefore →
its mutated enzyme cannot convert ornithine to citrulline
keto-enol tautomerization =
ketone will be transformed into an enol since there is bond breaking & making, the atoms in the molecule are connected to each other differently - i.e., they are actually different molecules & are thus constitutional isomers
differences in electronegativity =
key to bond strength
if a light ray strikes an interference fringe at a 35° angle with respect to the normal plane, the reflected angle with respect to the interference fringe will be
larger than 35°
when chromatic aberration occurs, the light that forms the image is NOT brought to an exact focus at a single point describe why the use of mirrors MINIMIZES chromatic abberation
lenses REFRACT light at an angle that depends on its wavelength, whereas mirrors REFLECT light of all wavelengths at the SAME angle
a MIRROR absorbs _________ light in REFLECTING than a LENS absorbs in REFRACTING
less
peptide bonds
link the primary sequence of amino acids in a protein, but they are NEVER observed when a polypeptide bends or folds to form a secondary structure in addition, when the polypeptide folds into a 3D shape (tertiary structure), peptide bonds do NOT form
under what conditions will liquid water have absolutely no ions in solution
liquid water will ALWAYS have some ions in solution H₂O ⇌ H⁺ + OH⁻ Keq = 10⁻¹⁴ this makes the concentration of hydrogen & hydroxide ions 10⁻⁷ M each in solution, regardless of any other conditions
disruption of structure =
loss of function
a student is using an electron scanning microscope to examine the structure of hemoglobin at a pH of 3 what could account for the student not being able to identify hemoglobin in the sample?
low pH causes α and β subunits to dissociate & disrupts tertiary structure
infrared spectroscopy =
measures molecular vibrations of characteristic functional groups
molecular vs. empirical formula
molecular formulas tell you how many atoms of each element are in a compound, & empirical formulas tell you the simplest or most reduced ratio of elements in a compound many compounds with different molecular formulas have the same empirical formula
partial transesterification of triacylglycerol can result in the formation of 'diols' these compounds can also be described as
monoesters of glycerol
Gibb's free energy is _____________ for spontaneous processes
negative
the flow of sodium into neurons of the optic nerve during an action potential is associated with a
negative change in Gibb's free energy & a positive change in entropy
main constituent in air =
nitrogen gas
morphine can be reacted with 2 equivalents of ethanoyl chloride (acetyl chloride) to form heroin in this reaction, the hydroxyl groups of morphine function as
nucleophiles the reaction proceeds through nucleophilic attack by the hydroxyl oxygen (of morphine) on the electrophilic carbonyl carbon of acetyl chloride
gamma (γ) decay
nucleus in excited state; high NRG gamma ray is emitted ¹²₆C → ¹²₆C + γ
intramolecular hydrogen bonding =
one of the primary causes of SECONDARY structure in proteins & gives rise to characteristic structures, such as α-helices and β-sheets hydrogen bonding also stabilizes the 3D conformations in TERTIARY structure
a quaternary carbon =
one that is bonded to four alkyl groups, which means it must be sp³ hybridized
a diester of glycerol will have
only ONE free OH group
no internal mirror plane =
optically active
+ internal mirror plane =
optically inactive
what is the ratio of the oxidation number of iodide ion to the oxidation number of iodine in Cu₂I₂ in the following reaction: Cu²⁺(aq) + I⁻(aq) → I₂ + Cu₂I₂(s)
oxidation # of I⁻ = -1 oxidation # of I₂ in Cu₂I₂ = -1 1:1 ratio
the following process neutralizes sulfur dioxide, which is highly toxic to human life: 2H₂S(g) + SO₂(g) → 3S(s) + 2H₂O(l) one of the reasons that oxygen is able to remove the bound hydrogen atoms from sulfur is that:
oxygen has greater electronegativity, electron affinity & ionization energy - thus, oxygen is able to remove the bound hydrogen atoms from sulfur
what is the average oxidation state value for the carbons in the citrate ion (C₆H₅O₇³⁻)?
oxygen normally has an oxidation number of -2, while hydrogen's is +1 to produce a NET charge of -3 for the molecule, carbon's oxidation number must be +1
iron will NOT react with water without the addition of
oxygen, which oxidizes the iron (forming rust)
regardless of the solution, the hydrogen ion concentration & pH are related by the equation:
pH = -log[H⁺]
pyruvic acid is a weak acid - what is the likely pH for an aqueous solution of sodium pyruvate?
pH = 8
DSG (Na₂C₅H₇NO₄) is a common food enhancer produced by neutralizing glutamic acid with two equivalents of NaOH what is the most likely pH of a solution created by adding DSG to water?
pH > 7
which structure is most likely to be the precursor of ornithine
paragraph 2 references the enzyme responsible for converting the precursor of ornithine → ornithine: acetylornithinase deacetylase "deacetylase" indicates the enzyme's function = it removes an acetyl group (CH₃COR) from the precursor - therefore, the correct answer should have the structure of ornithine with an extra acetyl group on it
if a light ray strikes an interference fringe at a 35° angle with respect to the normal plane, the reflected angle with respect to the interference fringe will be larger than 35°
paragraph 3 states that interference fringes behave like tiny plane mirrors & obey the law of reflection - thus the reflected angle must be the same as the incident angle the reflected angle with respect to the interference fringe must then be complementary to 35° → since this is a 55° angle, the reflected angle with respect to the interference fringe will be larger than 35°
which of the following types of bonds has the LEAST influence in determining the secondary/tertiary structure of a protein? I. hydrogen bonding II. hydrophobic interactions III. electrostatic interactions IV. peptide bonds
peptide bonds
sphingolipids =
phospholipid with a sphingosine backbone (instead of glycerol) amide-linked to a fatty acid
enantiomers like (-)-methadone & (+)-methadone do NOT differ in their
physical or chemical properties they can only have different physiological effects by interacting with a stereospecific receptor - a receptor that is itself chiral
hydrophobic interactions =
play a major role in the arrangement of amino acid R-groups in aqueous environments, which affects the overall shape of the protein (i.e., globular vs. fibrous proteins)
peptide bonds = only observed in ____________ structure
primary NOT secondary or tertiary
according to Henry's Law (P=kC), the solubility of a gas in liquid is
proportional to its partial pressure
amount of heat required to raise anything to a certain temperature
q = mc∆t
1 mole each of two pure sample of lipids that have the same number of carbons are combusted in a bomb calorimeter if sample A is found to contain more calories than sample B, what can be concluded?
sample A is MORE SATURATED than sample B
the question stem states that sample A has more calories than sample B, therefore →
sample A must be more saturated or contain less bonds than sample B
bases (unlike BF₃) will ______________ triglycerides
saponify
which IR absorption pattern, if present, would allow a scientist to be able to distinguish between Demerol & methadone
sharp peak at 1700 cm⁻¹ demerol does NOT have a carbonyl carbon & thus will NOT exhibit a sharp peak at 1700 cm⁻¹ methadone does have a carbonyl carbon & thus will exhibit a sharp peak at 1700 cm⁻¹
sphingomyelin is a type of _________________ commonly found in myelin sheaths
shingolipid
tin (E°V = -0.14) nickel (E°V = -0.25) iron (E°V = -0.44)
since iron has the LOWEST reduction potential, it will be the metal that produces the most vigorous reaction with HCl in the stomach
electric fields also rely on the electrolytic conductivity of the medium →
since saltwater has a higher conductivity than freshwater, electroperception is more likely to occur in saltwater fish
calcium hydroxide exists in solution according to the equilibrium: Ca(OH)₂ ⇌ Ca²⁺ + 2OH⁻
since, as stated in paragraph 3, citrate would bind to free calcium ions, the equilibrium would thus be shifted toward the production of more free calcium ions (to the RIGHT) this means that there would be more dissociation of calcium hydroxide, producing more hydroxide ions, & thus making the solution more alkaline
the amide nitrogen of metoclopramide is
sp²-hybridized & planar
the ______________________ produces amino acids, the ____________________ binds them together
strecker synthesis kent reaction
energy for DNA synthesis is stored in the phosphate bonds of the dNTPs sulfate can make similar bonds but is NOT used in the same way what might constitute a reason this is so?
sulfur is more electronegative than phosphorus, resulting in a weaker bond to oxygen (phosphorus being less electronegative will give a stronger bond to oxygen)
Gay-Lussac's Law: (P₁/T₁) = (P₂/T₂)
temperature must be in Kelvin & pressure in atm to use this law
disulfide linkages contribute to the _____________ structure of proteins
tertiary
disulfide bonds may determine
tertiary or quaternary structure disulfide bonds do NOT contribute to primary or secondary structure
a negative (-) ∆E value indicates
that energy is being ADDED to the system
disulfide linkages, which contribute to the tertiary structure of proteins, often arise due to
the COVALENT interaction between two cysteine residues
if there were any unreacted triacylglycerol it would be found in
the ORGANIC layer, NOT the aqueous layer
peptide bonds are broken via
the addition of water i.e., a hydrolysis reaction
assuming equivalent experimental volumes & tissue types, which of the following would most likely cause aggregation (as measured by # of cells aggregating per minute) to occur more quickly? I. a higher pressure II. a lower pressure III. a larger quantity of dissociated cells IV. a smaller quantity of dissociated cells
the aggregation of cell parts is essentially a chemical reaction - look for things that will speed up all chemical reactions, & one of those things is more reactants a larger quantity of dissociated cells will be like having more reactants & will push the reaction to occur quicker (& more just like Le Chatelier's principle)
an athlete inflates his bicycle tires & then waits a few hours, at which time the air temperature has risen by 10°C how does the air pressure within the tires compare to what it was when they were inflated
the air pressure is greater than when the tires were inflated application of Gay-Lussac's Law: (P₁/T₁) = (P₂/T₂)
the amide nitrogen of metoclopramide is sp²-hybridized & planar
the amide nitrogen of metoclopramide has 3 sigma bonds & a lone pair that participates in resonance with the sp²-hybridized carbonyl carbon, which involves a pi bond - so it is sp² hybridized & planar
in the reaction between phenylacetyl chloride & alanine, the amino group of alanine most likely acts as a nucleophile, attacking the electrophilic carbonyl carbon of phenylacetyl chloride →
the amino group nitrogen has a lone electron pair = nucleophilic as for phenylacetyl chloride, since oxygen is strongly electronegative, the C-O double bond is polarized, giving the oxygen a partial negative charge, & the carbon a partial positive charge as a result of this charge distribution, the carbon is attacked by the nitrogen atom, resulting in displacement of the chloride & the formation of an amide link
to float →
the buoyant force must be equal in magnitude to the gravitational force (Fb =Fg) - that is to say, pgv = mg because g is present on both sides of this equation, it is NOT a factor in determining whether the man will float - i.e., the man will always float
if the student measure the amount of food in the calorimeter incorrectly & inflated the actual mass →
the calculated energy of combustion would be LOWER than the actual value
as mentioned in the passage, purified thalidomide was unsuccessful therapeutically this is partially explained by the fact that thalidomide acts as an acid
the chiral carbon contains a bonded hydrogen that, due to the electronegativity of adjacent members, is ACIDIC detachment of this hydrogen would lead to a temporary plan conformation that could rearrange as the opposite stereoisomer
an enzyme's activity varies directly with
the concentration of its substrates
alkoxide =
the conjugate base of an alcohol & therefore consists of an organic group bonded to a negatively charged oxygen atom written as RO−, where R is the organic substituent
in a galvanic cell, the CATHODE is defined as the site of REDUCTION →
the correct answer must be a balanced reduction reaction: 4H⁺ + 4e⁻ + O₂ → 2H₂O
partial transesterification of triacylglycerol can result in the formation of 'diols' these compounds can also be described as monoesters of glycerol →
the diol formed would be the remains of the triglyceride after two fatty acid residues have been removed - the term "diol" would therefore refer to glycerol with one remaining fatty acid attached to it, & so it could be described as a monoester of glycerol
in a galvanic cell, the anode =
the electrode where OXIDATION (loss of electrons) takes place; in a galvanic cell, it is the NEGATIVE electrode, as when oxidation occurs, electrons are left behind on the electrode these electrons then migrate to the cathode (positive electrode)
in a galvanic cell, the cathode =
the electrode where REDUCTION (gain of electrons) takes place; in a galvanic cell, it is the POSITIVE electrode, as less oxidation occurs, fewer ions go into solution, and fewer electrons are left on the electrode
∆E combustion =
the energy of combustion is INVERSELY related to the mass of the sample, so increasing the amount of the sample would decrease the calculated energy of combustion ↑mass of sample = ↓∆E combustion
if the catalyst is omitted from a reaction →
the energy of the transition state will be INCREASED under standard conditions, the reaction will be SLOWER the energy of the products will be UNCHANGED
AgI(s) ⇌ Ag⁺(aq) + I⁻(aq) if the iodide in solution is removed in any way →
the equilibrium is disturbed & more silver iodide dissolves
when triacylglycerol is boiled in aqueous sodium hydroxide during saponification →
the hydroxide group attacks & adds to the carbonyl carbon of the ester, forming a tetrahedral intermediate - which in turn decomposes to give a carboxylic acid & an alkoxide ion the alkoxide then deprotonates the acid → yielding the sodium salt of the acid & glycerol
if light is NOT brought to an exact focus, that means that →
the light is spread over an extended area
a skydiver jumps from a plane, begins to approach a constant terminal velocity, & then hits the ground describe the magnitude of his acceleration as a function of time
the magnitude of acceleration will remain constant for a while as the skydiver approaches a constant (terminal) velocity, his acceleration will start to approach zero, & then will increase sharply as he touches the ground
a man on earth weighing 200 pounds floats with 1/10th of his body above water this man would NOT float on a planet whose gravitational pull is
the man would ALWAYS float
identifying meso compounds: III. ensure that both halves are in fact mirror images of each other
the meso compound must be symmetric about the internal mirror plane each opposing stereocenter must have differing absolute configurations & the attachments on each stereocenter must be the same if the opposing stereocenters have the same absolute configurations or the attachments on either side are different, then one half will not be a mirror image of the other half
one of the best nucleophiles =
the methoxide ion (= an alkoxide ion)
tautomerization =
the movement of an α hydrogen atom & movement of a double bond
in purifying hemoglobin from human red blood cells, a biochemist suspects that some of the molecules have lost their quaternary structure if she used a gel filtration column to separate the denatured & non-denatured proteins:
the non-denatured protein would elute first
after analysis, the student determines that the cooking oil has 0% fatty acid content what could account for these results?
the organic layer was above the aqueous layer, & the student analyzed the bottom layer
paragraph 2 states that there must be enough oxygen to let the reaction go to completion for the first experiment - since the student is using more food mass for the second experiment →
the reaction could be limited by the availability of oxygen in the chamber (since it is sealed) & thus return a lower calorimeter reading since the bomb will not heat as much i.e., there was NOT enough oxygen to combust the larger sample
which type of molecule most likely plays an important role in the formation of cellular aggregates: I. lipids II. nucleotides III. oligosaccharides IV. water
the recognition of or binding to complex side chains of oligosaccharides that exist on the surface of cells implicates a role in guiding cell-cell interactions
a researcher inadvertently leaves a bottle of trypsin in a 70°C water bath overnight before using it in an experiment to test the preferential aggregation of cells with cells of their own tissue type what are the expected results?
the results of such an experiment would be as expected: the cells would be found in tissue-specific aggregates - however, the reason the cells were found in this configuration is that, due to the high temperature, the trypsin was rendered ineffective the inactivation of trypsin occurs because trypsin is an enzyme that functions normally at physiologic pH & at higher temperatures most likely undergoes denaturation - as a result of the trypsin inactivation, the cells were NOT separated & are found in tissue-specific aggregates
pyruvic acid is a weak acid the likely pH for an aqueous solution of sodium pyruvate = 8
the salt of a weak acid will hydrolyze in aqueous solution according to the equilibrium expression: A⁻ + H₂O ⇌ HA + OH⁻ since hydroxide ion, OH⁻ is formed by this hydrolysis, the solution acquires a basic pH further, since the weak acid, HA is also formed, an equilibrium persists, keeping the pH below that expected for a similar concentration of a strong base (like NaOH) which will be 100% ionized in aqueous solution
when the quaternary structure of a protein is lost → these conglomerates separate into their individual component proteins - it is evident that each of these components will be smaller than the conglomerate & will thus run through the gel filtration column more slowly:
the smaller proteins will enter the porous beads, while the larger conglomerate (non-denatured protein) would run rapidly through the column thus, the non-denatured protein would elute first
the only difference between a catalyzed reaction & an uncatalyzed reaction will be that
the uncatalyzed reaction will have a HIGHER activation energy (potential energy, initial state & final state are unchanged)
the rate of a reaction will be highest when →
there is the lowest energy of activation the lower the activation NRG, the greater the exponent, & thus - the greater the reaction rate
the student doubles the mass of the food sample, but his calculated energy content is only 50% greater than that in the original sample →
there was NOT enough oxygen to combust the larger sample
when the quaternary structure of a protein is lost →
these conglomerates separate into their individual component proteins - it is evident that each of these components will be smaller than the conglomerate & will thus run through the gel filtration column more slowly
peptide linkages do NOT arise between polypeptide chains →
these linkages arise WITHIN peptide chains to link amino acids, but NOT between peptide chains to link amino acids
a catalyst lowers the activation energy of the reaction →
thus lowering the transition state
if the pH of carbonated water is 5, what is the hydrogen ion concentration
to find the hydrogen ion concentration, take the antilog of the pH of 5, which = 1 x 10⁻5 M
in an ideal system →
total mechanical energy, the sum of potential & kinetic energy, is CONSERVED E = U + K
the cyclist in the previous example is NOT in an ideal system, thus →
total mechanical energy, the sum of potential & kinetic energy, is NOT conserved thus, the relationship between lost potential energy & kinetic energy gained is NOT U = K
saponification =
triglyceride (fat or oil) + 3NaOH ↓ glycerol + 3 soap molecules
ribosomal protein synthesis in cells occurs
unidirectionally from the N-terminal to the C-terminal
voltage-gated channels only exist in significant quantities where the cell membrane is
unmyelinated
the deacylation of aspirin = an ester hydrolysis reaction - water attacks the carbonyl carbon of the ester, displacing the alcohol
water = acting as a nucleophile, as the carbonyl carbon has a partial positive charge owing to the electron withdrawing effects of the attached oxygens the reaction can be labeled as "nucleophilic acyl substitution" because one nucleophile, water, is replacing another nucleophile, alcohol the reaction is equilibrium controlled, since the alcohol can reciprocally displace the water from the carboxylic acid to form an ester
carbonated water =
water with dissolved carbon dioxide
the titration of a monoprotic weak acid with a strong base →
we expect a low starting pH & an inflection point ABOVE pH 7
since, for a LENS, the angle of REFRACTION is dependent on wavelength, & since light of different wavelengths is refracted at DIFFERENT angles by a lens →
when the incoming light is bent at slightly different angles, that causes the focal point to become an extended area
silver (E°V = 0.80) & copper (E°V = 0.34)
will NOT react with HCl
lowering the pH of a sample of hemoglobin this much (to pH = 3) →
will cause a break up of the quaternary structure as well as some dissociation of tertiary structure this will cause the hemoglobin tetramer to split up into its α and β subunits, meaning the student would see smaller molecules than expected
radioactive iodine, I-131, is used in thyroid cancer treatment - what accounts for its ability to cause cell death?
β decay; the loss of an electron or positron
equation that relates Gibbs free energy & Keq
∆G = -RTlnKeq