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AAMC Tests CP
Sample, FLE1, FLE2, FLE3, FLE4
Terms in this set (149)
How many stereoisomers are in a compound?
2^n, where n=#chiral centers
Chiral centers are usually atoms attached to 4 different molecules
When does precipitate form in terms of Ksp?
When the concentration of ions in solution is greater than Ksp
e.g. [Ca^2+][C2O4^2-] > Ksp
Note that the solubility product constant does not include solids!!
What is the charge distribution in an axon?
the interior is negatively charged and the exterior is positively charged
Electric field lines move from ___________ to ___________ charges
positive to negative
What is the relationship between conductivity and resistivity?
Since conductivity is the reciprocal of resistivity, decreased conductivity is the same as increased resistivity
True or False: One function of the myelin sheath is to increase the capacitance of the axon
False, Myelin decreases capacitance and increases electrical resistance across the axonal membrane
True or False: myelin sheath increases axon radius
False, axon radius is unchanged with the addition of the myelin sheath
True or False, myelin sheath is an insulating material
Channel X transmits only the smallest substances dissolved in the extracellular fluid through the axon membrane. Which ion (Na+, K+, or Cl-) does Channel X transmit?
sodium cations are the smallest
Note that there is a difference between atomic radius and ionic radius. When looking at ionic radius, consider the electron cloud radius.
On the periodic table, both atomic and ionic radius increases going down. Within the same row, a cation will always have a smaller radius than an anion
An action potential occurs at 100m/s over 1ms. What is the closest distance 2 electrodes can be placed on a nerve in order to measure the voltage change in response to a stimulus?
distance = velocity x time = (100m/s)(1*10^-3 s) = 0.1m
A nerve conduction velocity test (NCV) exploits the electrical properties of neurons to test for nerve damage. What information about an axon is required to calculate the current associated with an NCV pulse?
V = IR -> Current = Voltage/Resistance
So you need to know the potential (voltage), the resistance per unit length, and the length of the axon
What is the difference between resistance and resistivity?
RESISTANCE opposes the flow of free electrons whereas the RESISTIVITY is the property of the material which defines the resistance of the material having specific dimension.
Resistance = (resistivity x length)/cross-sectional area
The resistance of the material depends on the length, cross-section and area of conductor whereas the resistivity depends on the nature and temperature of the material.
The hydrogen ion concentration of the unknown aqueous solution was 1 × 10^-5 M. What was the pH of the unknown aqueous solution?
pH = -log[H+]
-pH = log(10^-5)
-pH = -5
pH = 5
An unknown compound completely dissolves in water and weakly conducts electricity. The hydrogen ion concentration of the unknown aqueous solution was 1 × 10^-5 M. The unknown compound was probably a: (strong or weak) (acid or base)?
Since the solution weakly conducts electricity, there is limited dissociation of ions (not a strong substance). The pH only slightly falls below neutral (indicated by concentration of 1 × 10^-5 M => pH 5), so it is not very acidic. Thus, the unknown compound is a weak acid.
Two compounds were studied: NO2(OH) dissolved in water and produced an acidic solution, and Ni(OH)2 dissolved only in an acidic solution. What type of compounds were these?
When NO2(OH) is dissolved in water (neutral solution), the pH of the solution falls. This is indicative of an acidic compound. If you rearrange the chemical formula, it looks more familiar: HNO3 (nitric acid).
In the compound Ni(OH)2, Ni is a transition metal. As a transition metal, Ni has a relatively low electronegativity. When taken in conjunction with the fact that the compound is found to dissolve in acidic solutions it can be assumed that the compound dissociates by breaking the Ni―OH bond. Low electronegativity = basic compound
Cholesterol forms into what type of hormone?
What is the concentration of Cl- ions in a 0.1 M solution of calcium chloride?
the formula for calcium chloride is CaCl2, so it produces twice as many Cl- ions as Ca2+ ions in solution when it dissolves. Thus, [Cl-] = 0.2M
Addition of which disaccharide (Cellobiose, Lactose, Maltose, Sucrose) to a solution of Ag2O in NH3(aq) will NOT result in the deposition of shiny silver mirror on the walls of the reaction vessel?
The deposition of silver metal represents a reduction of silver ions (gain of electrons to become solid Ag). Therefore, the question is asking which of the answer choices is not a reducing sugar. Reducing sugars contain either aldehydes or hemiacetals. So the answer would be Sucrose, which is the only disaccharide listed that contains no hemiacetal parts.
What is Mutarotation?
The rapid interconversion between different anomers of a sugar
What is the polarity of the mobile and stationary phases in reverse-phase high performance liquid chromatography (HPLC)?
polar mobile phase and non-polar stationary phase
What do Km and Kd have in common?
The expression for Km is the same as a dissociation constant (Kd) under conditions where "product formation is the rate-limiting step". Km values are a measure of the binding affinity of an enzyme for a particular substrate.
Know Slope and y-intercept!!
The overall reaction scheme for enzymes of the CYP450 enzyme family is shown with R representing the substrate.
NADPH + H+ + O2 + R-H → NADP+ + H2O + R-OH
In this reaction, NADPH functions as:
a reducing agent, because it is being oxidized
2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)
What type of reaction is this?
Oxidation/reduction, because Mg is oxidized (0 to +2) while H is reduced (+1 to 0).
How do fluid levels in a barometer rise/fall?
The level of the liquid inside a tube is higher than outside a tube which results from the fact that the air pressure outside is higher than the pressure inside. Pressure builds on the inside by raising the liquid level. When the sum of the inside air pressure plus liquid pressure equals the outside air pressure, the liquid level stops rising (attains equilibrium).
The average human body contains approximately 5 liters of blood. If the blood has a density of 1060 kg/m^3, what is the total mass of blood in the average human? (Note: 1 L = 1000 cm^3.)
density = mass/volume -> mass = density x volume = (1060 kg/m^3)(5L
1m^3/10^6 cm^3) = 5.3kg
An ultrasound examination could show the motion of a fetus. In order to image this motion, the ultrasound examination devices requires what minimal information?
Think about what can be directly measured versus what
the ultrasound probe is designed to discover indirectly. The purpose of the probe is to see motion
in the fetus, so knowing the speed of the moving object beforehand is unrealistic.
Ultrasound only requires the speed of the sound, and the frequencies of the sound waves emitted and observed.
Why is the boiling point of HF is abnormally high when compared to the boiling points of other Group 7A hydrides?
HF is affected by hydrogen-bonding interactions to a much greater degree than the other Group 7A hydrides.
What are the 4 quantum numbers that describe an electron?
The principal quantum number is a measure of what?
radial size of electron cloud = distance from nucleus = potential energy of an electron
1200 = C-O
1500 = C-C
*1600 = C=C
*1700 = C=O (carbonyl groups)
3000 = C-H
*3200 = OH (broad peak)
*3300 = N-H
In a reaction, if neither reactant is chiral, then how can a chiral product be formed?
A chiral product (stereoisomer) forms because the catalyst (the enzyme) is chiral. Enzymes are routinely chiral, built to be able to synthesize chiral compounds.
Which substance is NOT a product of squalene metabolism?
Glucose is not a product of squalene metabolism. Squalene is structurally similar to (and is the precursor to) steroids
Myopia is a condition of the eye where the crystalline lens focuses the light rays to a position between the lens and the retina. To correct for this condition, a thin lens is placed in front of the eye that will help to focus light on the retina. The type of lens required is:
A diverging lens will spread out the light before it reaches the lens of the eye which will cause light to focus on a point closer to the retina.
One method of isolating polypeptides and proteins from aqueous extracts is freeze drying. The aqueous solution of the polypeptide or protein is frozen. What procedure can be used to remove the water from the frozen sample?
The goal of most polypeptide and protein extraction methods is to keep the protein from denaturing. Sublimation, the phase change of water from solid to gaseous state, eliminates the water from the sample without raising the temperature and possibly denaturing the protein
The density of a human body can be calculated from its weight in air, Wair, and its weight while submersed in water, Ww. The density of a human body is proportional to:
the ratio of the density of an object to the density of the fluid it is submersed in is equal to the ratio of the weight of the object in air to the DIFFERENCE of submersed weight and weight in air.
Wair/(Wair - Ww)
What charge do phosphates have?
The amino acids Asp6, Asn9, Thr10, His11, and Arg27 are found near the ADP binding site of PanK3. The binding of ADP involves predominantly ionic interactions. Which two amino acids contribute to the stabilization of ADP binding described in the passage?
His11 and Arg27 because both His and Arg side chains can carry a positive charge. They would have favorable ionic interactions with the negatively charged phosphates of ADP.
Tc decays by emitting 140-keV gamma photons. What is the frequency of the emitted gamma photons? (Note: Use Planck's constant h = 6.6 x 10^-34 Js and the elementary charge e = 1.6 x 10^-19 C.)
They give you the elementary charge to remind you that 1 eV = 1.6 x 10^-19 J
E = hf -> f = E/h = (140x10^3 eV × 1.6 x 10^-19 J)/(6.6 x 10^-34 Js) = 3.5×10^19 Hz.
What is an electron volt (eV)?
Change in energy by moving a single electron across an electric potential difference of one volt
1 eV = 1.6 x 10^-19 J
What electrically charged particle is emitted during β- decay and β+ decay?
β- decay = changes a neutron into a proton by releasing an electron
β+ decay = changes a proton into a neutron by releasing a positron
What particle is emitted during ⍺ decay?
releases a helium particle (2 protons and 2 neutrons)
The advantage of the Doppler ultrasound technique over the standard ultrasound technique is that it also allows:
Doppler ultrasound takes advantage of the Doppler Effect, which is useful for determining relative motion of the source and detector of a sound wave, because such motion causes a shift in the frequency between that emitted by the source and that received by the detector.
Blood flow can involve motion of blood toward or away from the detector, so this would be the advantage it holds over standard techniques.
During exercise on a stationary bicycle, a patient's heart has a load of 30 W. What is the work done by the patient during a 3-minute exercise on the bicycle?
Power = Work/Time -> Work = Power x Time = (30W)(3*60s) = 5400J
When choosing a buffer to use for an experiment conducted at pH 5.3, it would be best to choose one with a pKa of:
a good buffer has a pKa within 1 pH unit of the desired experimental conditions. So a good buffer would be between 4.3-6.3
An object with a mass of 0.1 kg absorbs 250 J of heat while changing temperature from 20°C to 25°C. What is the specific heat of the object?
q = mcΔT -> c = q/mΔT = 250/(0.1*5) = 500J/(kg·°C)
During glycolysis, pyruvate CH3C(=O)CO2- is reduced to lactate CH3CH(OH)CO2- by nicotinamide adenine dinucleotide (NADH). What is the balanced reaction for this conversion?
The balanced half-reaction for the reduction of pyruvate is CH3C(=O)CO2- + 2H+ + 2e- → CH3CH(OH)CO2-
[Balance was attained by first balancing hydrogen with H+ (adding two H+to the reactant side) and then the charge with e- (adding two to the reactant side, also).]!!! Important
The oxidation half-reaction is: NADH → NAD+ + H++ 2e-
Add these two together to get: CH3C(=O)CO2- + NADH + H+ → CH3CH(OH)CO2- + NAD+
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?
the relative amount of HYDROGEN BONDING to the stationary phase will determine the relative rate of migration of the various components in the sample.
How to calculate the Rf value?
Rf = distance moved by substance (the solute)/solvent front
Is the dehydration of malic acid to fumaric acid and maleic acid stereospecific?
No, because 2 products form.
stereoSPECIFIC reaction gives one specific product whereas stereoSELECTIVE reaction gives multiple products
What type of functional group is formed when an amino acid reacts with another amino acid to form a peptide bond?
An amide group
If 2-pentanol replaces 1-pentanol in a reaction, the rate of substitution is less because:
there is more steric hindrance at the 2-position of 2-pentanol than at the 1-position of 1-pentanol.
the rate of substitution of protonated alcohols is subject to steric hindrance. This inhibits the ability of nucleophiles to collide with the reacting electrophilic center and slows the rate of reaction.
The first peak observed in the gas chromatography trace is attributable to which compound?
the lowest molecular weight and also the weakest intermolecular forces of attraction bc this substance will migrate the fastest
- concerted reaction
- backside attack (the incoming nucleophile displaces the leaving group form the opposite side of the reacting center)
A person, whose eye has a lens-to-retina distance of 2.0 cm, can only clearly see objects that are closer than 1.0 m away. What is the strength S of the person's eye lens?
thin lens formula : 1/O + 1/L = S
S = 1/1 + 1/(2*10^-2) = 1 + 50 = 51
How do enzymes stabilize chemical reactions?
Stabilization of the transition state changes the activation energy of the reaction
How could you decrease the percentage ionization of 1.0 M acetic acid, CH3CO2H(aq)?
Add concentrated HCl(aq) because HCl is a strong acid that will increase the amount of H+ in solution and thus decrease the percentage of CH3CO2H that ionizes.
Need to know that adding a strong acid to a solution of weak acid will decrease the amount of ionization of the latter. Remember strong acids dissociate better!
When the current in the micro-robot's circuit increases and the resistance of the circuit remains constant, the voltage of the circuit:
increases bc V=IR
Knowing that the speed of light in the vitreous humor is 2.1 × 10^8 m/s, what is the index of refraction of the vitreous humor? (Note: The speed of light in a vacuum is 3.0 × 10^8 m/s.)
index refraction = speed of light in vacuum/speed of light in medium (humor) = (3.0 × 10^8 m/s)/(2.1 × 10^8 m/s) = 1.4
The intensity of the radiation emitted by the oxygen sensor is directly proportional to the:
number of photons emitted.
the energy of electromagnetic radiation is directly proportional to the number of photons, and the intensity of electromagnetic radiation is defined as energy emitted per unit time. Thus, intensity is directly proportional to the number of photons emitted.
15-O has a half-life of 2 min. What fraction of a 15-O sample decays in 10 min?
in 10 minutes, there are 5 half-lives of 15-O. Therefore, only (1/2)^5 = 1/32 of the sample will be left after 10 minutes, while 31/32 of the sample will decay
Does cysteine undergo oxidation or reduction to made disulfide bonds?
oxidation (losing electrons)
Why is the velocity of blood flow slower in capillaries than in arteries?
The total cross-sectional area of capillaries exceeds that of arteries.
The high number of capillaries in the body means that the total cross-sectional area of these vessels is larger than any other vessel type in the circulatory system. This causes the velocity of the blood to decrease.
Rhodopsin has a maximum absorption at 500 nm. Additional opsin based receptors are expressed in specialized cone cells and have maximum absorptions at 420 nm, 530 nm, and 560 nm when reconstituted with 11-cis-retinal. The production of a variety of opsins functions to:
enable the detection of different colors. The wavelength of light absorbed by a molecule depends on its structure, and so the production of a variety of structurally related opsins functions to enable the detection of different colors.
The source of the phosphate groups that are added to rhodopsin is:
ATP, not rhodopsin kinase. The kinase only transfers phosphate groups from ATP to rhodopsin
What are the hybridization states of the carbon atoms involved in the conversion of trans to cisretinal?
double bonded carbons are sp^2 hybridized
The crystal structure of the protein lysosomal lipase (LipA) was determined. Which reaction is catalyzed by LipA?
Hydrolysis of triacylglycerides. LipA is a lipase, which means it must hydrolyze fatty acids.
By what factor is the proton concentration increased from a pH of 4 to pH of 7?
the pH scale is logarithmic (pH = −log([H+]). A difference of 3 pH units corresponds to a 10^3 = 1000-fold difference in proton concentrations.
Which type of bond is formed by glycogen synthase upon release of UDP?
Note that glycogen synthase always forms α-1,4-Glycosidic bonds!!!!
What bonds does glycogen synthase form?
Branching occurs through an ________ bond in glycogen
Gamma decay occurs when a nucleus emits:
a photon NOT a neutron
Each of the following equations shows the dissociation of an acid in water. Which of the reactions occurs to the LEAST extent?
A. HCl + H2O → H3O+ + Cl−
B. HPO4^2− + H2O → H3O+ + PO4^3−
C. H2SO4 + H2O → H3O+ + HSO4^−
D. H3PO4 + H2O → H3O+ + H2PO4^−
HPO4^2− has a high negative charge and so dissociation of it will occur to the least extent.
An object O is at a distance of 3 focal lengths from the center of a convex lens. What is the ratio of the height (H) of the image to the height of the object?
1/focal length = 1/Dobject + 1/Dimage
M = -Dimage/Dobject = Himage/Hobject
So, 1/f = 1/3f + 1/Di -> 1/Di = 1/f-1/3f = 2/3f -> Di = 3f/2
M = -(3f/2)/3f = -1/2
The ratio of image height to object height is 1/2
Which lens has a positive or negative focal length?
Convex lens = positive focal length
Concave lens = negative focal length
When is the distance of an object positive or negative? (lens)
positive = image is on the opposite side of lens to the object
negative = image and object are on the same side of lens
What will occur if a homogeneous catalyst CANNOT be separated from the products at the end of a reaction?
The products will be contaminated with the catalyst
How will the rate of a catalyzed reaction be affected if the solid catalyst is finely ground before it is added to the reaction mixture?
The rate will be faster because a greater surface area of catalyst will be exposed.
Would using electrical wire with a smaller diameter increase current?
No, bc R=p(L/A)
if you decrease diameter--> increase Resistance --> (V = IR) decrease Current
Would increasing the temperature of the electrical wire increase current?
No, because temperature and resistance are directly related
Increase temperature => increase resistance => decrease current (V=IR)
Would replacing a 0.5 Ω lightbulb with one that has a resistance of 0.2 Ω increase current?
Yes, bc V=IR, if you decrease resistance then you increase current
In terms of standard reduction potential, when does a reaction occur spontaneously?
A spontaneous reaction occurs when E° is greater than zero
What volume of a 0.120 M CaI2 solution would contain 0.078 mol of the solute?
V=(0.078 mol)/(0.120 M)=~0.08/0.120=~2/3L=0.66L=660 mL
What are possible units for power?
the measurement unit of power is watt, defined as J/s = ft•lb/s = kg•m2/s3
catalytic efficiency equation
turnover number (kcat) equation
NEED TO KNOW THIS WELL
Absorption of ultraviolet light by organic molecules always results in what process?
Excitation of bound electrons
Is there enough energy in IR radiation to excite electrons?
No, there isn't enough energy in the photon to excite electrons, so the energy goes into vibrations.
IR = vibrations (remember this!!!)
True or False: Ketones are more polar than Alcohols
False, ketones are less polar than alcohols because they elute first in column chromatography when the stationary phase is silica gel
Column chromatography stationary phase
Alumina or silica gel (polar substance)
The half-life of a radioactive material is:
the time it takes for half of all the radioactive nuclei to decay into their DAUGHTER nuclei. Daughter nuclei may or may not also be radioactive
A person is sitting in a chair. Why must the person either lean forward or slide their feet under the chair in order to stand up?
To keep the body in equilibrium while rising. The person is in equilibrium only when the center of mass is directly above their feet. Otherwise, if the person did not lean forward or slide the feet under the chair, the person would fall backward due to the large torque created by the combination of the weight of the body (applied at the person's center of mass) and the distance along the horizontal between the center of mass and the support point.
What is the relationship between Energy and Wavelength?
E = hf = hc/λ
As wavelength increases, energy decreases
In designing the experiment, the researchers used which type of 32P labeled ATP?
γ32P-ATP because the phosphoryl transfer from kinases comes from the γ-phosphate of ATP. ATP has 3 phosphate groups, the closest phosphate to the sugar is alpha, then beta and lastly gamma.
An experiment was undertaken in the presence of a synthetic peptide that mimics the HM domain (sHM) of Ser/Thr kinases with the amino acid sequence FLGFTY. Phosphorylated sHM (spHM) was also used in place of sHM. When used in place of spHM, which peptide would be most likely to achieve the same experimental results?
The question is asking which amino acid most closely resembles Threonine when it is phosphorylated. The phosphorylated threonine would most likely be mimicked by glutamic acid in terms of size and charge. So the answer is D.
What causes duplex DNA with a certain (A + T):(G + C) ratio to melt at a higher temperature than comparable length duplex DNA with a greater (A + T):(G + C) ratio?
G-C base pairs form stronger π-stacking interactions than A-T base pairs, thereby creating the most thermal stability. This disparity has often been used to explain the increased melting temperature of DNA rich in GC content.
The phosphate backbones don't interact with the backbone of the opposite strand, so the electrostatic repulsion is minimal. Remember, electrostatic repulsion decreases exponentially as the distance between charges increases.
Which property of a substance is best used to estimate its relative vapor pressure?
What is effusion
A process by which gas particles pass through a tiny opening from high pressure to low pressure
What is the kinetic molecular theory?
as temperatures increases molecular movement increases (more elastic collision)
- gas particles are spread out and they have random motion
In an electrochemical cell, where does oxidation and reduction occur?
oxidation always occurs at the anode and reduction at the cathode of an electrochemical cell
The lone pair of electrons in ammonia (NH3) allows the molecule to:
act as a Lewis base in water
(a Lewis base is a substance that donates an electron pair in forming a covalent interaction)
Which of the following best describes the bonds between Cu^2+ and the nitrogen atoms of the ammonia molecules in [Cu(NH3)4]^2+?
Lewis acid-base interaction between a metal cation and an electron pair donor is known as a coordinate covalent bond.
[Cu(H2O)4]^2+(aq) + 4NH3(aq) <-> [Cu(NH3)4]^2+(aq) + 4H2O(l)
Would the concentration of [Cu(NH3)4]^2+ increase if the equilibrium were disturbed by adding hydrochloric acid?
No, because the equilibrium in Equation 1 would shift to the left
Hydrochloric acid will protonate ammonia in a Brönsted acid-base reaction and reduce the amount of ammonia present. The disturbed equilibrium responds in a way to restore ammonia, but this causes the amount of [Cu(H2O)2(NH3)2]2+ to decrease.
In [Cu(NH3)4]^2+, the subscript 4 indicates which of the following?
The coordination number of Cu2+ only. Because ammonia is neutral, the number 4 reflects only the number of ammonia molecules that bind to the central Cu2+ cation and does not indicate anything about its oxidation number.
Coordination number vs oxidation number
Oxidation state is the charge of the central transition metal if all the ligands were removed.
Coordination number is the total number of bonds or attachments between the central transition metal and its ligands.
Which of the following atoms will be expected to have the smallest second ionization energy?
Metals have lower ionization energies than non-metals as long as the ionization event involves a valence electron. Since Na is an alkali metal, it has only one valence electron and has a large second ionization energy. Ca is an alkaline earth metal and has two valence electrons - it will therefore have the smallest second ionization
Which of the following species has the largest mass percent of oxygen?
mass percent of oxygen is calculated by multiplying the coefficient for oxygen in the formula of the substance by 16 and then dividing by the molar mass of the substance. Water has the highest percentage of oxygen by mass of the compounds listed (16/18) × 100 = 89%.
^What is the concentration of Ca2+(aq) in a saturated solution of CaCO3? (Note: The solubility product constant Ksp for CaCO3 is 4.9 × 10^-9.)
Ksp = [Ca^2+][CO3^2-]
Since equal quantities of Ca^2+(aq) and CO3^2-(aq) are produced when CaCO3 dissolves, this expression reduces to 4.9 × 10^-9 = x^2, or 49 × 10^-10 = x^2. -> x = 7 × 10^-5
A glass rod is rubbed with a silk scarf producing a charge of +3.2 × 10^-9 C on the rod. (Recall that the magnitude of the proton and electron charges is 1.6 × 10^-19 C.) The glass rod has:
the number of charges in excess can be computed as +3.2 × 10^ -9 C/1.6 × 10^ -19 C = +2.0 × 10^10. This means that the rod has an excess of positive charge, created by removing a number of +2.0 × 10^10 electrons from the material
Which single bond is most likely the shortest?
C-H bc hydrogen has a much smaller atomic radius than second period elements, the covalent bond between C and H is shorter than any of the other bonds listed
What is the average power consumed by a 64-year-old woman during the ascent of the 15-cm-high steps, if her mass is 54 kg and it takes her 27s to climb 30 steps?
Power = Potential Energy / Time = mgh/t = (54kg x 10m/s^2 x 30 steps x 0.15m/step)/27s = 90W
How much work did an 83-year-old female do while stretching the rubber band to the limit of her strength (Maximum stretching of an elastic band: 20cm)? (Note: The volunteers stretched an elastic band whose elastic constant is k = 200 N/m.)
Work = 0.5 × kx^2 where x = 0.20 m.
So W = 0.5 × 200 (N/m) × (0.2 m)^2 = 4.0 J
What kind of image is formed by the lenses of the glasses worn by a 68-year-old male who sees an object 2m away? (Focal length of glasses -70cm)
the glasses have a negative focal length which means they are diverging lenses. Such lenses form virtual and reduced images of objects situated at distances larger than the focal length.
Which of the following energy conversions best describes what takes place in a battery-powered resistive circuit when the current is flowing?
Chemical to electric to thermal
the chemical energy of the battery elements is used as electrical energy to set the charge carriers in motion through the resistor, where they experience drag from the crystal lattice of the resistive conductor and dissipate their energy as heat from the resistor
Protein secondary structure is characterized by the pattern of hydrogen bonds between:
backbone amide protons and carbonyl oxygens.
A reaction in which an aldehyde or ketone acts as both the electrophile and nucleophile, resulting in the formation of a carbon-carbon bond in a new molecule called an aldol.
What is the total amount of charge and energy, respectively, that a 100 mF capacitor will store if it is connected to a 12 V battery on the railcar?
Charge = Capacitor x Voltage = (100x10^-3)(12V) = 1.2 C
Potential energy = 0.5CV^2 = (0.5)(100x10^-3)(12)^2 = 7.2
This system can generate a maximum braking force of 14,000 N. The rolling friction of the wheels and the internal friction between the wheels and axles contribute a continuous 1000 N decelerating force any time that the railcar is in motion. If no braking occurs, a total of how much power would be required to keep the railcar moving at 40 m/s?
the power required must match the work done by the friction force that tends to slow down the railcar, which is equal to the decelerating force multiplied by the constant speed, so 1000 N × 40 m/s = 40 kW
The speed of the car decreases in time such that the decelerating force declines linearly with speed. What is the relationship between velocity and time for this car?
Because the decelerating force is directly proportional to the deceleration acceleration, it follows that the decelerating acceleration itself declines linearly with speed. Finally, because the decelerating acceleration is rate of change of velocity, or the slope of the velocity vs. time graph, then the slope of the graph must decrease in time [NOT LINEAR].
The relative thermodynamic stability of isomeric organic compounds can be inferred from what type of experimental data?
the relative thermodynamic stability of isomers can be determined based on the amount of heat produced when the compounds are combusted
less heat = greater stability
Key word is here "isomeric," meaning they have the same molecular formula but different connectivities. Because they are isomeric, their boiling points will probably be very close to each other (or close enough that it would be very difficult to distinguish between individual molecules).
Heats of combustion, however, differs significantly. For example, if you have 2-methylbutane vs pentane, because that methyl carbon is branched (as a tertiary carbon) will confer more stability than as a pentane molecule.
Radioactive tritium (3H) labeled guanine has been used to measure the rate of biochemical processes that involve its binding or incorporation. Given that water is the solvent for this type of experiment, what would be the best site for tritium labeling?
the best site for tritium labeling would not exchange the tritium ions for protons in water. Look for non-electronegative atoms that do not have lone pairs or excess hydrogens.
Sterilization caused by the UV radiation (200-300 nm) generated by the electron transitions within the plasma plume. What is the maximum energy of the UV photons generated by this plasma pencil? (Note: Speed of light is c = 3.0 × 108 m/s; Planck's constant is h = 6.63 × 10-34 J•s.)
E = hf = hc/λ
the question is asking for MAXIMUM energy, so you would want to minimize the denominator, so use 200nm for wavelength
E = (6.63 x 10^-34 J.s)( 3.0 x 10^8 m/s)/ (200 x 10^-9 m) = 1 x 10^-18
A group of students prepared an aqueous solution of glucose from a crystalline supply at a concentration of 72 g/L. What is the total mass of D-glucose dissolved in a 2-μL aliquot of the solution used for this experiment?
The stock solution consisted of 72 g of glucose in 1.0 L of solution (72 μg/μL). Therefore, 2 μL contains 144 μg, or 1.4 × 10-4 g of the solute.
If 0.67 μmol of electrons were measured in a two-electron oxidation reaction, what mass of glucose was present in the sample? (Note: The molar mass of glucose is 180 g/mol = 180 μg/μmol.)
the stoichiometry of the reaction is 2 mol e- per mole of glucose consumed.
0.67μmol of electrons/2 μmol electrons = 0.35 μmoles of glucose
0.35 μmole glucose x 180 μg/μmol = 60 μgrams glucose
The device measured 0.67 (2/3) μmol of electrons, indicating that 0.33 (1/3) μmol of glucose was consumed. This weighs 60 μg, based on its molar mass of 180 g/mol.
The pH of a 1 L phosphate buffer solution was measured as 7.6, but the experimental procedure calls for a pH 7.2 buffer. Which method will adjust the solution to the proper pH? (Note: The pKa values for phosphoric acid are 2.2, 7.2, and 12.3.)
in order to lower the pH of a buffer, the proportion of acidic buffer component must be increased. So Alter the ratio of monosodium/disodium phosphate added to favor the monosodium species.
Adding strong base, diluting with water, or adding a different basic salt will not lower the pH.
When two amino acids are joined via a peptide bond, what is the mass of the byproduct of this reaction?
Peptide bond formation is a type of dehydration reaction, so water is lost. H2O weighs 18amu
What experimental conditions are necessary to achieve reliable data for Michaelis-Menten enzyme kinetics?
1. Initial velocity is measured under steady state conditions.
2. Solution pH remains constant at all substrate concentrations.
3. The concentration of enzyme is lower than that of substrate.
The reaction is NOT allowed to reach equilibrium before measurements are taken, because if it does then measurement of Vo will be impossible and the kinetic data will look the same regardless of substrate concentration.
True or False: diluting a solution changes its pH
False, diluting a solution does NOTHING to the pH because you are diluting A- and the HA the same amount. The ratio does not change in the Henderson-Hasslebach equation.
What is the concentration of hydroxide ion for the solutions with pH 10?
At the pH 10, the [H3O+] is 10^-10 M. This means that [OH-] is 10^-4 M, because [H3O+] × [OH-] = 10^-14
What enzyme would do hydroxylation of a methyl group?
A common column material used in size-exclusion chromatography is dextran, a polysaccharide of glucose. Which type of interaction most likely occurs between proteins and the dextran column material?
Hydrogen bonding bc a polysaccharide of glucose has numerous hydroxyl groups that can hydrogen bond to the polar side chains that are typically exposed on a protein surface
What property of an ultrasound wave remains unchanged as it passes into human tissues?
Frequency is not affected by the medium it propagates through. Wave speed, amplitude, and wavelength are affected.
Suppose that a blood vessel of cross-sectional area A carries microbubbles at a speed v into a capillary bed. If the capillary bed is made up of n capillaries, each with cross-sectional area a, with what speed will the blood flow in the capillary bed?
according to the continuity equation, if u is the speed of flow in the capillary bed, then A × v = n × a × u, so u = A × v/(n × a)
It was observed that the burst microbubbles made openings of 2.5 × 10^4 μm^2 through the capillary walls. Assume that in the study with the rat tissues, fluid flows at a speed of 0.30 mm/s through a typical capillary opening caused by a burst microbubble. Given this, which of the following is closest to the volume flow rate of fluid passing through the opening?
Flow Rate = Av = (2.5 × 10^4 μm^2)(0.30 mm/s) = 7.5 × 10^6 μm3/s
True or False: solids are included in Ksp
False, solids are not included
When a reaction is spontaneous, what is the value of K?
K = [products]/[reactants], so if a reaction is spontaneous, then K>1 bc more products
A tall tube is evacuated, and its stopcock closed. The open end of the tube is immersed into a container of water (density 10^3 kg/m^3) that is open to the atmosphere (pressure 10^5 N/m^2). When the stopcock opened, how far up the tube will the water rise?
The water will rise until the weight (mass multiplied by gravitational acceleration) of the water column equals the atmospheric pressure multiplied by the tube cross-sectional area A.
mg = PA -> (density x volume)(gravity) = (pressure)(area) -> (density x area x height)(gravity) = (pressure)(area) -> h = pressure/(density x gravity) = 10^5/(10^3 * 10) = 10m
What is a second period element that is a covalent network solid in its standard state?
Carbon forms graphite (covalent network solid)
Suppose a blood sample tested glucose concentration above the range (6.0 mg/dL) of the standards used in the experiment. What modification will provide a more precise reading by data interpolation as opposed to extrapolation using the same standards?
Add a solvent to dilute the sample and lower the concentration of glucose back into the range that it can be tested
Which has a higher boiling point: 1-chlorobutane or 1-butanol?
The boiling point of 1-chlorobutane is substantially lower than that of 1-butanol.
Hydroxyl groups can hydrogen bond
NH3 acts as a weak base in water with Kb = 1.76 × 10^-5 at 25°C. The corresponding equilibrium is shown below.
NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)
At 25°C, the equilibrium concentration of the NH4+ ion in a 10 M aqueous solution of NH3 would be closest to which of the following?
Kb = [NH4+][OH-]/[NH3] = 1.76 × 10^-5
[NH4+][OH-]/10 = 1.76 × 10^-5
[NH4+]^2 = 1.76 × 10^-4
[NH4+] = 1.32 × 10^-2
intramolecular transesterification that yields a cyclic ester called a lactone
If a thin thread is placed between a screen and a bright source of light, a pattern of parallel dark and bright fringes appears on the screen. The phenomenon best explaining the formation of this pattern is:
The thin thread disrupts the propagation of light by impeding light to pass through it. Diffraction causes the initially plane-parallel wave-fronts of light to change direction and partially enter the shadow region behind the thread due to its narrowness. The overlapping of different wave-fronts on the screen causes the pattern of dark and bright fringes on the screen according to the phase difference between the wave-fronts that interfere there.
Diffraction v.s. refraction
Suppose a defibrillator successfully returns a baby's heart to normal beating. Suppose further that 20 g of blood enters the heart at 25 cm/s and leaves 0.10 s later at 35 cm/s. What is the estimated average force on the 20 g of blood as it moves through the baby's heart?
According to Newton's second law, the average force is equal to the mass of blood multiplied by the average acceleration of the blood. The average acceleration is (35 cm/s - 25 cm/s)/0.10 s = 100 cm/s^2 = 1 m/s^2. The average force is 20 g × 1 m/s^2 = 0.020 kg × 1 m/s^2 = 0.020 N
The electric field inside each of the conductors that forms the capacitor in the defibrillator is zero. Which of the following reasons best explains why this is true?
Conductors contain both atom-bound electrons and free electrons. Free electrons arrange themselves on the surface of conductors, and their collective electric field produced inside the conductor cancels any external electric field. The resulting electric field inside the conductor is zero.
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