AAMC Chemical and Physical Foundations Biological Systems

The chemist dissolves 16 mmol CDP in 1 L of an aqueous solution containing PNP and Mg2+ and buffers the solution at pH 8.7. The pKa for the dissociation of H2PO−4 to HPO2−4 is 6.7. What is the initial ratio of [HPO2−4]:[H2PO−4] in the buffer solution of Experiment 1? 1:1 2:1 100:1 200:1

100:1, solve via henderson hasselbach.

What is the molar volume of an ideal gas at STP?

22.4 L/mol

A compound has 5 chiral centers. How many possible stereoisomers does it have?

32. 2^n

Which of the following statements most accurately describes the solubility properties of fatty acid salts? They are soluble in polar media only. They are soluble in nonpolar media only. They can partially dissolve in both polar and nonpolar media. They are completely insoluble in both polar and nonpolar media.

A fatty acid salt contains a long hydrocarbon chain, which is soluble in nonpolar solvents. The salt also contains the charged group -CO2-Na+, which is soluble in polar solvents. Thus, C is the best answer.

Which of the following formulas represents a general structure of a fatty acid salt produced in Reaction 1? (Note: Rn = R1, R2, or R3.) Rn—CH2- Na+ Rn—CH2O- Na+ Rn—C(O)- Na+ Rn—CO2- Na+

A fatty acid would have the general formula Rn—CO2H. The corresponding fatty acid salt would have the general formula Rn—CO2- Na+. Thus, D is the best answer.

Which single bond present in nitroglycerin is most likely the shortest? A.C-H B.C-O C.C-C D.O-N

A. All of the bonds listed are single bonds. Since 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.

Protein secondary structure is characterized by the pattern of hydrogen bonds between: A.backbone amide protons and carbonyl oxygens. B.backbone amide protons and side chain carbonyl oxygens. C.side chain hydroxyl groups and backbone carbonyl oxygens. D.side chain amide protons and backbone carbonyl oxygens.

A.backbone amide protons and carbonyl oxygens.

A 6.57-g sample of NiSO4•6H2O (molar mass 262.84) is dissolved in enough water to make 50.00 mL of a green solution, and 7.15 g of Na2CO3•10H2O (molar mass 286.14) is dissolved in enough water to make 50.00 mL of a colorless solution. The two solutions are mixed, and a green precipitate forms. The resulting slurry is divided into two equal portions. To one portion is added an excess of 6 M HCl, which results in the disappearance of the precipitate and a rapid evolution of a gas According to the information in the passage, the gas that evolves is: sulfur dioxide. sulfur trioxide. carbon dioxide. carbon monoxide.

According to the passage, the gas is given off when HCl is added to one portion of the slurry. HCl reacts with CO32- to form CO2(g). Thus, C is the best answer.

The chemist dissolves 16 mmol CDP in 1 L of an aqueous solution containing PNP and Mg2+ and buffers the solution at pH 8.7. The chemist monitors the reaction by measuring the amount of inorganic phosphate produced. No reaction is detected for 30 min, then the reaction appears to proceed at a constant rate until it stops with a final HPO2−4 concentration of 8 mM. The recovered polymer contains 7.5 mmol of cytosine. The chemist repeats Experiment 1 but adds enough manganese sulfate to precipitate the slightly soluble manganese hydrogen phosphate as it forms. The recovered polymer contains 11.4 mmol of cytosine. As an alternative to Experiment 2, the chemist also can improve the yield of the polymer obtained in Experiment 1 by increasing the amount of: H2O. PNP. Mg2+. CDP.

As an alternative to Experiment 2, the chemist could increase the yield of polymer product by increasing the amount of the reactant, CDP. The correct answer is D. The key is to recognize that this reaction is a catalyzed chemical reaction which will reach equilibrium. In Experiment 2, the stress was to remove product by precipitation. The system responded by making more product, counteracting that removal. In a similar manner, adding more reactant can serve as an alternative to Experiment 2. If more CDP is added, the system responds to counteract that change by using it up, thus producing more product.If a catalyst is used in such a reaction, it will only change the rate of attaining the equilibrium ratio of products and reactants; it will not change the equilibrium ratio. Thus, adding excess PNP and Mg2+, which act as catalysts, will have no effect on the amount of product formed, and responses B and C are incorrect. Response A, adding H2O, is also incorrect, since the effect would be to actually decrease the concentrations of the reactant, thus slowing the reaction. Thus, answer choice D is the best answer.

Why do kidney stones form in some individuals treated with Compound 1? A.[Ca2+] + [C2O42-] > Ksp B.[Ca2+][C2O42-] > Ksp C.[Ca2+] + [C2O42-] < Ksp D.[Ca2+][C2O42-] < Ksp

B. Precipitates occur when concentrations exceed Ksp (solubility product constant)

A patient puts on a mask with lateral openings and inhales oxygen from a tank as shown. What phenomenon causes static air to be drawn into the mask when oxygen flows? A.Doppler effect B.Venturi effect C.Diffusion D.Dispersion

B. Venturi effect

Which property of a substance is best used to estimate its relative vapor pressure? A.Melting point B.Boiling point C.Molecular weight D.Dipole moment

B.Boiling point

What is the net charge of the peptide Arg-Ala-Phe-Leu at pH 8? A.-1 B.0 C.+1 D.+2

C.

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.cylindrical. B.converging. C.diverging. D.spherical.

C. The answer to this question is C because 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

Two additional 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? A.Both were oxyacids. B.Both were bases. C.NO2(OH) was a base and Ni(OH)2 was an oxyacid. D.NO2(OH) was an oxyacid and Ni(OH)2 was a base.

D. The latter substance, Ni(OH)2, is apparently insoluble in neutral water, but will dissolve if the solution is acidic. This behavior is typical of substances that feature basic anions.

If Reactants X and Y are atoms, what is the shape of the product molecules? Linear Bent Trigonal planar The shape of the product molecules cannot be determined without more information.

D. The shape of a molecule depends on the number of valence electrons at the central atom since lone pairs of electrons exert stereochemical effects. Without the group numbers of the reactant atoms, it is impossible to determine the molecular shape of the product. If X = C, and Y = O, then the molecular geometry would be linear. If X = O and Y = H, however, the molecular geometry would be bent. Thus, D is the best answer.

What modification of Compound 1 will favor transport of Na+ relative to K+? Replace X with CH3. Replace Y with CH3. Increase the ring size by adding one -CH2CH2O-. Decrease the ring size by removing one -CH2CH2O-.

From the passage, it was stated that K+ is transported within the central portion of Compound 1. Since Na+ is chemically similar to K+ it is reasonable to assume that there might be a way to favor its transport over K+ by changing the size of the ring. The change necessary would be to decrease the ring size since Na+ is smaller than K+.

Knowing that the speed of light in the vitreous humor is 2.1 × 108 m/s, what is the index of refraction of the vitreous humor? (Note: The speed of light in a vacuum is 3.0 × 108 m/s.)

How light and sound interact with matter." The answer to this question is B because the index of refraction of a medium is equal to the ratio of the speed of light in vacuum to the speed of light in the medium, thus it is equal to (3.0 ´ 108 m/s)/(2.1 ´ 108 m/s) = 1.4.

[Cu(H2O)4]2+(aq) + 4NH3(aq) <------> [Cu(NH3)4]2+(aq) + 4H2O(l) What is the effect of adding HCl to this system at equilibrium?

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. This means that the equilibrium shifts to the left.

Which of the following is the most plausible explanation for the fact that the saponification of the triacylglycerol in the passage resulted in four different fatty acid salts? The triacylglycerol molecule consisted of four different fatty acid units. Glycerol was transformed into a fatty acid salt under the reaction conditions. One of the fatty acid salts was unsaturated, and it completely isomerized under the reaction conditions. One of the fatty acid salts was unsaturated, and a small percentage isomerized under the reaction conditions.

If one of the R groups in the triacylglycerol contained a carbon-carbon double bond and if isomerization of the double bond occurred during the saponification reaction, four fatty acids would be obtained instead of three. Thus, D is the best answer.

What are the oxidizing and reducing agents, respectively, in the reaction below? 2HCl + H2O2 + MnO2 → O2 + MnCl2 + 2H2O H2O2; HCl H2O2; MnO2 MnO2; HCl MnO2; H2O2

In the reaction pictured, Mn is reduced from +4 to +2; therefore, MnO2 is the oxidizing agent. O is oxidized from -1 in H2O2 to 0 in O2; therefore, H2O2 is the reducing agent. Thus, D is the best answer.

If red litmus paper is dipped into the Na2CO3 solution, it will: A. remain red, because carbonate is an acidic salt. B. remain red, because sodium carbonate is neutral. C. turn blue, because carbonate reacts with water to produce OH-. D. turn blue, because sodium ions form sodium hydroxide in water.

In water, carbonate will undergo the following reaction: CO32-(aq) + H2O(l) → HCO3-(aq) + OH-(aq). Red litmus paper will turn blue in a base. Thus, C is the best answer.

Consider the above unbalanced equation. For this reaction, how many mL of a 2 M solution of Na2CO3 are required to produce 11.2 L of CO2 at STP? 125 mL 250 mL 375 mL 500 mL

It is an important fact that one mole of an ideal gas, at STP, will occupy a volume of 22.4 L. Therefore, 11.2 L of CO2 gas, at STP, must represent 0.5 mole of CO2. (Virtually all gases can be approximated as ideal gases at common temperatures and pressures.) According to the balanced chemical equation, one mole of CO2 is produced when one mole of Na2CO3 reacts. Therefore, the amount of Na2CO3 required to produce 0.5 mole of CO2 gas must also be 0.5 moles. We must find the volume of 2 M Na2CO3 solution which contains the required 0.5 moles of reactant. Working through the numbers for this problem, we find that the answer is 250 mL. Thus, answer choice B is the best answer.

Hydroxylamine nitrogen

NHOH

How much sodium hydroxide is needed to completely saponify a triacylglycerol? A. A catalytic amount, because OH- is continuously being regenerated during saponification B. One-third of an equivalent, because each OH- ion reacts to form three fatty acid salts C. One equivalent, because each OH- ion reacts to produce one molecule of glycerol D. Three equivalents, because one OH- ion is required to saponify each of the three fatty acid groups

One hydroxide ion is required to hydrolyze one ester linkage of a triacylglycerol molecule. Because there are three ester linkages in a triacylglycerol, three equivalents of sodium hydroxide will be needed to completely saponify the triacylglycerol. Thus, D is the best answer.

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? time to climb up 30 steps (s) 27 A.10 W B.20 W C.40 W D.90 W

P=PE /time = mgh/t. From Table 1, there are 30 steps and t = 27 s. Then P = (54 kg × 10 m/s2 × 30 steps × 0.15 m/step) / (27s) = 90 W.

In the membrane of an axon in respect to its extracellular environment, which direction would electric field lines be drawn?

Pointing from extracellular fluid to the inside of the axon membrane. Electric field lines exit from positive and enter negative charges. The axon is negatively charged. The extracellular solution has a zero net potential.

A group of students measured the relative rate of Reaction 1 under various conditions. 2I−(aq) + S2O82−(aq) → I2(aq) + 2SO42−(aq) The students measured the amount of time that passed until a fraction (X moles) of the I−(aq) was converted into I2(aq) by adding the corresponding amount of Na2S2O3(aq) to react with the I2(aq), as shown in Reaction 2. I2 (aq) + 2S2O32−(aq) → 2I−(aq) + S4O6 2−(aq) They used starch as an indicator to detect the excess I2(aq) that accumulated when the S2O32−(aq) was used up. The solution turned dark blue when starch and I2(aq) combined. The students prepared two solutions. Solution A contained KI(aq) and Na2S2O3(aq). Solution B contained (NH4)2S2O8(aq) and starch. They combined Solutions A and B and measured the length of time for the combined solution to turn dark blue. They varied the volumes of Solution A, Solution B, and H2O (Tubes 1, 2, and 3) and the temperature (Tubes 4 and 5). The students added 1 drop of 0.1 M CuSO4(aq) to Tube 6. The results are summarized in Table 1. The results in Table 1 would most likely NOT be affected if the students had added excess: KI(aq) to Solution A. Na2S2O3(aq) to Solution A. (NH4)2S2O8(aq) to Solution B. starch to Solution B.

Starch is not a participant in any of the reactions, acting only as an indicator of excess I2. Thus, D is the best answer.

What is the best explanation for the fact that a solution of NaNO2(aq) is basic? NO2- is hydrolyzed with the formation of OH -(aq) ions. Na+ is hydrolyzed with the formation of OH -(aq) ions. NaNO2(aq) decreases the Ka of HNO2(aq). NaNO2(aq) increases the Ka of HNO2(aq).

The NO2- reacts with water, forming OH- ions. Thus, A is the best answer.

Lafora disease is a fatal progressive epilepsy that is characterized by the formation of deposits of sparsely branched, insoluble glycogen-like polymers called Lafora bodies (LBs). LBs contain a much larger amount of covalently-linked phosphate compared to normal glycogen. The abundance of phosphate has been linked to a mutation in the gene for laforin, a phosphatase specific to carbohydrates. Compared to normal glycogen, the amount of what type of bond is decreased in Lafora bodies? A.Phosphomonoester B.Phosphodiester C.α-1,4-Glycosidic bond D.α-1,6-Glycosidic bond

The answer D because it is stated in the passage that the lack of branching is a characteristic of Lafora bodies. Branching occurs through an α-1,6-glycosidic bond in glycogen. So basically: alpha 1,4 linkage occurs to polymerize glucose into glycogen. alpha 1,6 linkage is where branching happens. Lafora causes sparsely branched polymers thus it decreases amount of alpha 1,6 bonds.

In addition, known BSA binders warfarin and ibuprofen (Figure 1) were used to determine the specific binding site of CPFX, since warfarin and ibuprofen have been shown to specifically bind to separate sites (sites I and II, respectively) Sites I and II are most likely lined with the side chains of which amino acids? A.R and L B.E and Y C.D and E D.D and H

The answer is A because sites I and II recognize hydrophobic and anionic substrates. It is therefore most likely that positively charged and hydrophobic side chains point into the binding pocket to make favorable interactions.

Which type of bond is formed by glycogen synthase upon release of UDP? A.α-1,4-Glycosidic bond B.α-1,6-Glycosidic bond C.β-1,4-Glycosidic bond D.β-1,6-Glycosidic bond

The answer is A because the bond that is formed by glycogen synthase is the main chain linkage of glycogen, which is an α-1,4-glycosidic bond. UDP release means that only glucose was added.

Which data suggest that the differences in Compound 1 metabolism between the variant and wild-type CYP2C9 enzymes are NOT due to changes in the binding affinity toward Compound 1? A.Compound 1 is still eliminated from the body of patients expressing the CYP2C9*3 allele. B.The KM values for the variant enzymes do not differ significantly from the wild-type enzyme. C.The amino acid substitutions at positions 144 and 359 do not change the binding pocket of the variant enzymes. D.The side chains of the amino acid residues at positions 144 and 359 are charged at physiological pH.

The answer is B because KM values can be used to represent a measure of the binding affinity of an enzyme for a particular substrate.

The amino acids Asp6, Asn9, Thr10, His11, and Arg27 are found near the ADP binding site of PanK3. Which two amino acids contribute to the stabilization of ADP binding described in the passage? A.Asn9 and Thr10 B.His11 and Arg27 C.Asp6 and Arg27 D.Asp6 and His11

The answer is B 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

The stabilization of pantothenate in PanK3 is most likely due to an active site: A.arginine. B.asparagine. C.aspartate. D.glutamine.

The answer is C because, of the choices listed as response options, only aspartate has the necessary carboxylate side chain.

Researchers used reverse-phase high performance liquid chromatography (HPLC) (polar mobile phase and non-polar stationary phase) to separate Compound 2 from Compound 1. Which statement accurately describes this process? **Compound 2 has an extra CH2OH group that Compound 1 does not have A.Increasing the polarity of the mobile phase will decrease the retention time of Compound 1 relative to Compound 2. B. Compound 1 will elute first because it is more polar than Compound 2. C.Decreasing the affinity of Compound 1 for the stationary phase will increase its retention time relative to Compound 2. D.Compound 2 will elute first because it does not interact as favorably with the stationary phase as Compound 1.

The answer is D because Compound 2 is more polar than Compound 1 due to the methyl hydroxylation. In RP-HPLC, the more polar compound will elute first.

Which naturally occurring biological molecule would be most likely to bind in the same site as ibuprofen? A.Glucose B.ATP C.Glycerol D.Palmitoleic acid

The answer is D because fatty acids consist of a hydrocarbon tail and a carboxylic acid, which most closely resembles ibuprofen based on the structure shown in Figure 1.

Mevalonate (Compound 2, Reaction 3) is expected to display prominent absorption in which region(s) of its infrared spectrum? (Contains CO2H and OH group) 3200-3500 cm-1 1700-1750 cm-1 1580-1610 cm-1 A.II only B.I and II only C.II and III only D.I, II, and III

The answer to this item is B because mevalonic acid contains both -CO2H and -OH groups, but does not contain a conjugated or aromatic C=C bond. The carboxyl group C=O stretching frequency falls in the region 1700-1750 cm-1, whereas the O-H stretching frequency is expected to fall in the region 3200-3500 cm-1.

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? A.Sublimation under reduced pressure B.Distillation using steam C.Extraction with organic solvent D.Addition of magnesium sulfate

The answer to this question is A because only sublimation of the water under reduced pressure will keep the mixture cold and will maintain the protein in its native state.

This solution is introduced into a patient prior to a test that involves observing the heart at rest and during exercise on a stationary bicycle with a load of 30 W What is the work done by the patient during a 3-minute exercise on the bicycle? A.5400 J B.90 J C.6 J D.0.16 J

The answer to this question is A because power P is work W done in a time t interval: P = W/t. Solving for W yields: W = Pt. Using the values given in the text, load P = 30 W and time t = 3 min, leads to W = 5400 J.

Which of the following properties of a 2.3 MHz ultrasound wave remains unchanged as it passes into human tissues? A.Frequency B.Wave speed C.Amplitude D.Wavelength

The answer to this question is A because the frequency of a wave is not affected by the medium through which it propagates

Suppose that at the end of Reaction 1 the level of the aqueous solution were 26 cm higher inside the buret than outside. Compared to ambient pressure, the pressure of the gas inside the buret would be: A.lower. B.the same. C.2 times greater. D.26 times greater.

The answer to this question is A because the level of the liquid inside is higher than outside 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).

Which measurement unit CANNOT be used to express power? A.kg•m2 •s2 B.J•s-1 C.ft•lb •s-1 D.W

The answer to this question is A because the measurement unit of power is watt, defined as J/s = ft•lb/s = kg•m2/s3. (N/s is kg/s2. Thus N (F) x area (m2) per time unit (s), would be kg m2/ s3). The stem is missing one unit of s-1.

The principal quantum number is a measure of which of the following? A.Approximate radial size of an electron cloud B.Approximate shape of an electron cloud C.Number of valence electrons that orbit a nucleus D.Number of protons and neutrons found in the nucleus of an atom

The answer to this question is A because the principal quantum number n is most closely associated with the potential energy of the electron. Since potential energy is proportional to the square of the distance of two oppositely charged particles by Coulomb's Law, it is also true that n is associated with the radial "size" of the electron cloud.

The reaction products were separated by SDS-PAGE and visualized by autoradiography that detects the products of β− decay The radioactive decay described in the passage results in the formation of which two atoms? A.N and S B.B and Si C.B and S D.N and Si

The answer to this question is A because the type of radioactive decay is b-1 so a neutron is converted into a proton, which results in carbon becoming nitrogen and phosphorus becoming sulfur.

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: A.Wair/(Wair - Ww). B.(Wair - Ww)/Wair. C.(Wair - Ww)/Ww. D.Ww/(Wair - Ww).

The answer to this question is A because, according to Archimedes' Principle, 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.

Gamma decay occurs when a nucleus emits: A.a photon. B.a proton. C.a neutron. D.an electron.

The answer to this question is A because, by definition, gamma decay means the emission of photons by the nucleus.

In its lowest-energy electron configuration, zinc has a: A.filled 3d energy level and a filled 4s energy level. B.half-filled 3d energy level and a filled 4s energy level. C.filled 3d energy level and a half-filled 4s energy level. D.half-filled 3d energy level and a half-filled 4s energy level.

The answer to this question is A, based on subshell filling rules, the 12 valence electrons occupy 4s and 3d subshells, which are completely filled.

If a solution containing the compounds shown in Figure 4, is injected into a gas-liquid chromatograph, the first peak observed in the gc trace is attributable to which compound? A.2-Methyl-2-butanol B.2-Methyl-2-butene C.2-Chloro-2-methylbutane D.2-Bromo-2-methylbutane

The answer to this question is B because 2-methyl-2-butene will exhibit the lowest molecular weight and also the weakest intermolecular forces of attraction. This substance will therefore migrate the fastest and be the first peak in the gas chromatograph (gc) trace.

The advantage of the Doppler ultrasound technique over the standard ultrasound technique is that it also allows: A.distinguishing between fluids and tissue. B.measuring the blood flow. C.measuring the tissue density. D.measuring the heart wall thickness.

The answer to this question is B because Doppler ultrasound takes advantage of the Doppler Effect in which a sound wave emitted by, or reflected from a moving object, will change its frequency based on the relative speed of the object, in this case, the flow of blood in a vessel.

How do the mechanisms of a cation exchange column work?

The answer to this question is B because a cation-exchange column only binds to positively charged proteins, which only occurs when the pH is less than the pI.

What is the Venturi effect?

The answer to this question is B because oxygen pressure is the sum of the oxygen static pressure P and the oxygen flow pressure rv2/2. In the area of the mask openings, Pair = P + rv2/2, thus Pair > P. Air enters the mask because the static pressure of the air is larger than the static pressure of the oxygen in flow. This is the Venturi effect, and the mask is called the Venturi mask.

Channel X transmits only the smallest substances dissolved in the extracellular fluid through the axon membrane. Which substance does Channel X transmit? A.Proteins B.Sodium ions C.Potassium ions D.Chloride ions

The answer to this question is B because sodium cations are the smallest of the species listed. You can use the periodic table to establish that sodium ions are smaller than either potassium or chloride ions

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 speeds of the sound and of the moving object. B.The speed of the sound, and the frequencies of the sound waves emitted and observed. C.The speeds of the sound and of the moving object, and the frequencies of the sound waves emitted and observed. D.The speeds of the sound and of the moving object, and the frequencies and wavelengths of the sound waves emitted and observed.

The answer to this question is B because the Doppler effect is used with ultrasound waves to provide fetal images. The Doppler effect relates the frequency of the ultrasound wave as detected by a moving detector to the frequency of the wave when the source is stationary, the speed of the source, and the speed of the detector. Three of the four quantities involved in the effect are required.

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.) A.2.11 × 10 35 Hz B.3.38 × 10 19 Hz C.3.01 × 10 -20 Hz D.1.45 × 10 -47 Hz

The answer to this question is B because the frequency f of a photon can be found from its energy using E = hf which gives f = E/h where h is Planck's constant (6.62 × 10-34 J·s).

The hydrogen ion concentration of the unknown aqueous solution was 1 × 10-5 M. What was the pH of the unknown aqueous solution? A.4 B.5 C.9 D.10

The answer to this question is B because the pH of the solution is, by definition, -log([H+]). Since the hydrogen ion concentration for the unknown aqueous solution was given as 1 × 10-5, the pH of this solution is 5.

What is a pK value?

The answer to this question is B because the pK is the pH at which the fraction of folded DNA is 0.5.

The second system allows the person to slow the railcar by the friction of its wheels against a stationary surface in a manner similar to that of the brakes on an automobile. 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? A.16 kW B.40 kW C.600 kW D.800 kW

The answer to this question is B because 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 maximum and minimum blood pressures of a healthy adult (the systolic Ps and the diastolic Pd pressures, respectively) are about Ps = 120 mmHg and Pd = 75 mm Hg. The mean arterial pressure PMPA is given by PMPA = Pd + (Ps - Pd)/3 Pp = Ps - Pd What percentage of standard atmospheric pressure is the pulse pressure of a healthy adult? A.10% B.6% C.2% D.1%

The answer to this question is B because the pulse pressure in a healthy adult is (120 − 75) mmHg = 45 mmHg, and so the percentage is 45 mmHg/760 mmHg = 6%.

An inflatable cuff was used to temporarily stop blood flow in an upper arm artery. While releasing the pressure to deflate the cuff, a stethoscope was used to listen to blood flow in the forearm. The blood pressure reading was 130/85. Given this information, which of the following statements is LEAST likely to be true? A.85 mmHg was the diastolic pressure. B.Blood flow was heard when the pressure of the cuff was greater than 130 mmHg. C.130 mmHg was the systolic pressure. D.Blood flow was heard when the pressure of the cuff was 90 mmHg.

The answer to this question is B because the question indicates that the cuff was inflated to temporarily stop blood flow in the artery. The systolic pressure is determined from the first sound of blood flow that can be heard once the pressure exerted by the inflatable cuff falls below the pressure in the artery. The blood pressure reading was 130/85, which indicates that blood flow started again when the pressure was 130 mmHg. Therefore, blood flow was not heard when the pressure of the cuff was greater than 130 mmHg

A nerve impulse lasts about 1ms. If the signal is conducted at 100 m/s, What is the closest distance the electrodes used in an NCV test can be placed on a nerve in order to measure the voltage change as a response to the stimulus? A.0.01 m B.0.1 m C.1.0 m D.10 m

The answer to this question is B because the shortest time duration that can be detected is not less than the action potential time response of 1 msec, according to Figure 1. The distance travelled by the impulse during this time is 1 msec × 100 m/s = 0.1 m, which is the closest distance the electrodes must be placed on the nerve.

Absorption of ultraviolet light by organic molecules always results in what process? A.Bond breaking B.Excitation of bound electrons C.Vibration of atoms in polar bonds D.Ejection of bound electrons

The answer to this question is B. The absorption of ultraviolet light by organic molecules always results in electronic excitation. Bond breaking can subsequently result, as can ionization or bond vibration, but none of these processes are guaranteed to result from the absorption of ultraviolet light.

The average human body contains approximately 5 liters of blood. If the blood has a density of 1060 kg/m3, what is the total mass of blood in the average human? (Note: 1 L = 1000 cm3.) A.0.212 kg B.0.530 kg C.5.30 kg D.10.6 kg

The answer to this question is C because m = ρV = 1060 kg/m3 × 5 L × 1000 cm3/L × 1 m3/106 cm3 = 5.30 kg.

The best-performing PANI had a maximum conductivity of 5.0 × 10-3 (Ω∙cm)-1 What is the resistivity of the best-performing PANI described in the passage? A.0.002 Ω•cm B.50 Ω•cm C.200 Ω•cm D.500 Ω•cm

The answer to this question is C because resistivity is the inverse of the conductivity, which is 1/5.0 × 10-3 (Ω∙cm)-1 = 200 Ω∙cm.

A researcher attempted to identify an unknown AOm(OH)n compound. The compound completely dissolved in water and weakly conducted electricity. The hydrogen ion concentration of the unknown aqueous solution was 1 × 10-5 M. It can be theorized that if the central atom, A, is an alkali or alkaline earth metal, the compound is basic. But if A is a nonmetal, the compound is acidic. The central atom, A, of the unknown compound was most likely: A.an alkali or alkaline earth metal. B.a transition metal. C.a nonmetal. D.a noble gas.

The answer to this question is C because the compound produces an acidic solution when dissolved. Compounds with the general formula AOm(OH)n are acids if A is a non-metal.

intensity of fluorescence emission at 440 nm (excitation at 360 nm) was monitored for 20 minutes. What expression gives the amount of light energy (in J per photon) that is converted to other forms between the fluorescence excitation and emission events? A.(6.62 × 10-34) × (3.0 × 108) B.(6.62 × 10-34) × (3.0 × 108) × (360 × 10-9) C.(6.62 × 10-34) × (3.0 × 108) × [1 / (360 × 10-9) - 1 / (440 × 10-9)] D.(6.62 × 10-34) × (3.0 × 108) / (440 × 10-9)

The answer to this question is C because the equation of interest is E = hf = hc/λ, where h = 6.62 × 10 −34 J ∙ s and c = 3 × 10 8 m/s. Excitation occurs at λe = 360 nm, but fluorescence is observed at λf = 440 nm. This implies that an energy of E = (6.62 × 10 −34) × (3 × 10 8) × [1 / (360 × 10 −9) − 1 / (440 × 10 −9)] J per photon is converted to other forms between the excitation and fluorescence events.

What type of functional group is formed when aspartic acid reacts with another amino acid to form a peptide bond? A.An amine group B.An aldehyde group C.An amide group D.A carboxyl group

The answer to this question is C because the functional group that forms during peptide bond formation is known as an amide group.

A researcher attempted to identify an unknown AOm(OH)n compound. The compound completely dissolved in water and weakly conducted electricity. The hydrogen ion concentration of the unknown aqueous solution was 1 × 10-5 M. The unknown compound was probably a: A.weak base. B.strong base. C.weak acid. D.strong acid.

The answer to this question is C because the hydrogen ion concentration for this solution is greater than 1 × 10-7 but much less than the concentration of the unknown compound itself. This means that the compound only partially ionized to form hydrogen ions. This is behavior that defines a weak acid.

The 99Mo decays to 99mTc, releasing a beta particle β- and an antineutrino ῡ. The electrically charged particle emitted during the decay of 99Mo is: A.a photon. B.a neutrino. C.an electron. D.a positron.

The answer to this question is C because the negative beta particle is the name given to the electron emitted during the nuclear decay of a heavy nucleus

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? (Note: Use the thin lens formula 1/O+1/I=S.) A.-50 D B.-10 D C.51 D D.55 D

The answer to this question is C because the strength of the eye lens is equal to the inverse of the focal length of the eye lens. Its numerical value is given by (1 m)-1+(0.02 m)-1=1 D+50 D=51 D

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.) A.Add enough 1 M Na2HPO3 to increase the phosphate anion concentration ten-fold. B.Add 1 M NaOH to neutralize a portion of the hydronium ions found in the solution. C.Alter the ratio of monosodium/disodium phosphate added to favor the monosodium species. D.Add 100 mL distilled, deionized water to dilute the basicity of the buffer.

The answer to this question is C because, in order to lower the pH of a buffer, the proportion of acidic buffer component must be increased. Adding strong base, diluting with water, or adding a different basic salt will not lower the pH.

Calcium and magnesium belong to what group on the periodic table? A.The alkali metals B.The metalloids C.The alkaline earth metals D.The halogens

The answer to this question is C, because magnesium and calcium both appear in Group 2 of the Periodic Table of the Elements. This family of elements is commonly known as the alkaline earth metals

A person is sitting on a chair as shown. Why must the person either lean forward or slide their feet under the chair in order to stand up? A.To increase the force required to stand up B.To use the friction with the ground C.To reduce the energy required to stand up D.To keep the body in equilibrium while rising

The answer to this question is D because as the person is attempting to stand, the only support comes from the feet on the ground. 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.

The design enabled heat from the wire to be transferred to the skin. At room temperature the wire had a length L of 4 mm, a diameter D of 4 × 10-4 m, and a mass M of 4 × 10-3 kg. What is the approximate density of the wire at 473 K? (Note: The volume of the wire is 5 × 10-7 m3.) A.2000 kg/m3 B.3600 kg/m3 C.6400 kg/m3 D.8000 kg/m3

The answer to this question is D because density is the ratio of mass to volume, which in this case is 4 × 10-3 kg/5 × 10-7 m3 = 8000 kg/m3.

During Trial 5, the wire was heated from 293 K to 673 K while V was held constant at 28 V. How did the current through the circuit change during this time?

The answer to this question is D because of the linear relationship between resistivity and temperature. If the temperature T increases by a factor of 673/293 ≅ 2.3, the resistance R will increase by the same amount. From Ohm's Law, current and resistance are inversely proportional, thus current will decrease by a factor of 2.3, from 4.6 A to 2 A.

Which experimental condition is NOT necessary to achieve reliable data for Michaelis-Menten enzyme kinetics? A.Initial velocity is measured under steady state conditions. B.Solution pH remains constant at all substrate concentrations. C.The concentration of enzyme is lower than that of substrate. D.The reaction is allowed to reach equilibrium before measurements are taken.

The answer to this question is D because once the reaction reaches equilibrium, measurement of Vo will be impossible and the kinetic data will look the same regardless of substrate concentration. Hence, response D is not necessary (nor desirable) to achieve reliable data for Michaelis−Menten enzyme kinetics. In contrast, Distractors A−C are essential to obtain reliable Vo versus substrate concentration data to calculate KM and Vmax using Michaelis−Menten enzyme kinetics.

Addition of which disaccharide 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 answer to this question is D because sucrose does NOT possess a hemiacetal functional group, will NOT undergo mutarotation, and will NOT be oxidized by Ag+. Saccharides undergo mutarotation if they are capable of ring-opening. The process of ring-opening occurs at a hemiacetal group, and the intermediate is an aldehyde. Such sugars are termed "reducing sugars" as a result of their ability to be oxidized by Ag+

The intensity of the radiation emitted by the oxygen sensor is directly proportional to the: A.propagation speed of the radiation. B.wavelength of the radiation. C.polarization of photons emitted. D.number of photons emitted.

The answer to this question is D because 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.

The half-life of a radioactive material is: A.half the time it takes for all of the radioactive nuclei to decay into radioactive nuclei. B.half the time it takes for all of the radioactive nuclei to decay into their daughter nuclei. C.the time it takes for half of all the radioactive nuclei to decay into radioactive nuclei. D.the time it takes for half of all the radioactive nuclei to decay into their daughter nuclei.

The answer to this question is D because the half-life of a radioactive material is defined as the time it takes for half of all the radioactive nuclei to decay into their daughter nuclei, which may or may not also be radioactive.

If 2-pentanol replaces 1-pentanol in the reaction shown in Figure 3, the rate of substitution is less because: A.the C-O bond in 2-pentanol is stronger than the C-O bond in 1-pentanol. B.there is a competing elimination reaction that slows the rate of substitution. C.there is more steric hindrance at the oxygen atom in 2-pentanol than in 1-pentanol, making protonation less likely. D.there is more steric hindrance at the 2-position of 2-pentanol than at the 1-position of 1-pentanol.

The answer to this question is D because the rate of substitution of protonated alcohols is subject to steric hindrance.

The relative thermodynamic stability of isomeric organic compounds can be inferred from which of the following types of experimental data? A.Boiling points B.UV-visible absorption spectra C.Mass spectroscopic fragmentation patterns D.Heats of combustion

The answer to this question is D because 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.

That the electric field is uniform between the electrodes means that the electric field lines: A.are more closely spaced at the positive electrode than at the negative one. B.intersect halfway between the electrodes. C.are more closely spaced at the negative electrode than at the positive one. D.are equally spaced at both electrodes and between them.

The answer to this question is D because, by definition, electric field lines are equally spaced in a uniform field.

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? A.125 J/(kg·°C) B.250 J/(kg·°C) C.375 J/(kg·°C) D.500 J/(kg·°C)

The answer to this question is D which can be obtained by dimensional analysis of the units. (250 J/(0.1 kg·5°C) = 500 J/(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? A.CH3C(=O)CO2- + 2NADH → CH3CH(OH)CO2- + 2NAD+ B.CH3C(=O)CO2- + 2NADH + 2H+ → CH3CH(OH)CO2- + 2NAD+ C.CH3C(=O)CO2- + NADH + 2H+ → CH3CH(OH)CO2- + NAD+ D.CH3C(=O)CO2- + NADH + H+ → CH3CH(OH)CO2- + NAD+

The answer to this question is D, which can only be arrived at by using half-reactions. 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). The oxidation half-reaction is: NADH → NAD+ + H+ + 2e-, which is balanced in a similar manner. At this point the half-reactions are added in such a way that the e- involved will cancel. Since two e- are involved in both the oxidation and the reduction, the two half-reactions can be added directly to provide the balanced reaction.

What information about an axon is required to calculate the current associated with an NCV pulse? A.Conductivity, resistivity, and length B.Potential, conductivity, and radius C.Potential, resistivity, and radius D.Potential, resistance per unit length, and length

The answer to this question is D. This is a question about Ohm's Law, I = V/R. To determine R, the resistance per unit length, the length, and the potential V are needed.

porphyrin ring

The basic unit of a porphyrin is the pyrrole ring, a five-sided heterocycle containing one nitrogen atom.

If a leak develops in the vacuum distillation apparatus, the boiling points of the two components of caraway seed oil will: both increase. both decrease. both remain the same. become more similar.

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the surface pressure. The normal boiling point is measured at 1 atm pressure. The vapor pressure of a liquid increases with increasing temperature. Hence, the boiling point of a liquid decreases as the pressure on the surface of the liquid is decreased. If a leak develops in the apparatus, the surface pressure will increase, as will the boiling points of both liquids. Thus, answer choice A is the best answer.

When glycerol reacts with three different fatty acids, how many stereogenic centers does the product triacylglycerol contain? 0 1 2 3

The correct answer is B. When glycerol reacts with three different fatty acids, only carbon 2 in the resulting triacylglycerol is attached to four different groups. Thus, B is the best answer.

An ebulliator was lowered into the distillation flask to introduce small air bubbles into the system. The most likely function of the ebulliator is to: A. keep the condensed vapors cool in the receiving flask. B. promote the establishment of a high vacuum in the system. C. prevent superheating of the liquid to be distilled. D. provide an outlet when the pressure inside the system becomes too high.

The correct answer is C. The passage mentions that the ebulliator was added to introduce small air bubbles into the system. This is the same function provided by a boiling chip at atmospheric pressure. The air bubbles break the surface tension of the liquid being heated and prevent superheating and bumping. Thus, answer choice C is the best answer.

The ion responsible for the color of the solutions is: sulfate, because sulfur has s and p orbitals. nickel(II), because it has a charge of +2. nickel(II), because it has unfilled d orbitals. sulfate, because it is a resonance-stabilized anion.

The correct answer is C. The solution containing nickel(II) ions is green-colored. The color arises because nickel(II) ion has partially filled d orbitals and the electrons in the lower energy d orbitals absorb visible light to move to the higher energy d orbitals. Thus, C is the best answer.

Ignoring stereochemistry, how many different tripeptides may exist that contain the same three amino acids as the molecule shown below? 1 3 6 9

The formula for the number of possible peptides that contain one each of n amino acids is n! (n factorial). For n = 3 (a tripeptide), n! = 3! = 3 × 2 × 1 = 6 = Answer C.

At room temperature the wire had a length L of 4 mm, a diameter D of 4 × 10-4 m, and a mass M of 4 × 10-3 kg. The wire was connected in series with an ammeter, a power supply, and a switch. What is the minimum amount of heat energy required to increase T from 373 K to 573 K? (Note: The specific heat capacity of iron is 460 J/kg·K.) A.368 J B.550 J C.1840 J D.3680 J

The heat q required is given by the relation q = mCΔT, where m is the mass of the iron, C is the specific heat of the iron, and ΔT is 200 K. The answer is q = (4 × 10-3 kg)(460 J/kg·K)(200 K) = 0.8 × 460 J = 368 J.

What is the sum of the protons, neutrons, and electrons in strontium-90? 90 126 128 218

The number of protons in the nucleus of an element is given by the atomic number. In a neutral atom, the number of electrons is equal to the number of protons. The number of neutrons can be found by subtracting the atomic number from the mass number. The atomic number of strontium (Sr) is 38; so the number of neutrons is 90 - 38 = 52. The sum of protons, neutrons, and electrons in strontium is 38 + 38 + 52 = 128. This value is given as answer choice C.

When 2.0 mL of 0.1 M NaOH(aq) is added to 100 mL of a solution containing 0.1 M HClO(aq) and 0.1 M NaClO(aq), what type of change in the pH of the solution takes place? A slight (<0.1 pH unit) increase A slight (<0.1 pH unit) decrease A significant (>1.0 pH unit) increase A significant (>1.0 pH unit) decrease

The pH will increase because a strong base is added. The increase will be small because the base is being added to a buffer solution. Thus, A is the best answer.

Which of the following properties is associated with the existence of glycine as a dipolar ion in aqueous solution? High dipole moment High molecular weight Low dielectric constant Low solubility in water

The problem states that glycine exists "as a dipolar ion in aqueous solution" and asks which of four properties is associated with this fact. Polarity in neutral molecules results from an uneven distribution of electron density, which can arise from separation of unlike charges. This occurs in zwitterions and in ylides. In addition, molecules that contain strongly electron-withdrawing or electron-donating substituents are highly polar and possess correspondingly high dipole moments. Thus, answer choice A is the best answer.

A student uses thin layer chromatography on silica plates to monitor the progress of the reaction below. Does the product have a higher or lower Rf than the starting material? *Product has alcohol group where reactant had carbonyl A. Higher, because the product is more polar than the starting material B. Higher, because the product is less polar than the starting material C. Lower, because the product is less polar than the starting material D. Lower, because the product is more polar than the starting material

The product of the reaction contains an -OH group and is therefore more polar than the starting material. Because of the -OH group, the product interacts with silica more strongly than the starting material and thus, has a lower Rf than the starting material.

What are the units for the rate constant ku discussed in the passage? M-1•s-1 M•s M•s-1 s-1

The protein unfolds by a unimolecular mechanism. The rate of unfolding has units of M/s and is given by the expression Δ[unfolded protein length]/Δt = ku[folded protein length]. The units of ku are therefore s-1.

A 6.57-g sample of NiSO4•6H2O (molar mass 262.84) is dissolved in enough water to make 50.00 mL of a green solution, and 7.15 g of Na2CO3•10H2O (molar mass 286.14) is dissolved in enough water to make 50.00 mL of a colorless solution. How many sodium ions are in the initial 50.00-mL solution of Na2CO3? 1.50 × 1022 3.00 × 1022 6.02 × 1023 12.0 × 1023

The solution contains 7.15 g Na2CO3×10H2O. Dividing by the molar mass will give the number of moles: (7.15 g)/(286.14 g/mol) = 0.0250 mol. Because each mole of Na2CO3×10H2O contains 2 mol Na+, there is 0.0500 mol Na+. Using Avogadro's number, the number of sodium ions is (0.0500 mol)(6.02 × 1023 ions/mol) = 3.01 × 1022 ions. Thus, B is the best answer.

Subsequent dehydration of malic acid results in the formation of fumaric acid (mp 286°C) and its cis isomer, maleic acid (mp 130°C). Which of the following statements does NOT correctly describe the dehydration of malic acid to fumaric acid and maleic acid? A.The reaction occurs most readily with tertiary alcohols. B.The reaction involves the loss of a water molecule. C.The reaction has a carbocation intermediate. D.The reaction is stereospecific.

This is an Organic Chemistry question that falls under the content category "Nature of molecules and intermolecular interactions." The answer to this question is D because the fact that both fumaric and maleic acid are produced means that the dehydration of malic acid is NOT stereospecific

What is the mechanical work done by the cantilever when the extension increases from 10 nm to 15 nm? 2.00 × 10-22 J 4.70 × 10-20 J 2.50 × 10-19 J 5.00 × 10-18 J

This question requires you to apply the graphical method of calculating the work done by a variable force, namely the elastic force, W = ksx2/2. Mechanical work by an elastic force is W = ksx2/2 = Fx/2. Graphically, it is the area under the force-extension graph between the corresponding data points. From Figure 2, the correct response is {[(100 - 0) × 10-12]N ×[(15 - 10) × 10-9]m}/2 = 2.50 × 10-19 J.

The compound shown above is the β-derivative of the D-glucuronic acid. The α-D-glucuronide differs in configuration from the β-derivative at: C-1. C-2. C-3. C-4.

When cyclic hemiacetals and acetals are formed, the ring carbon atom derived from the carbonyl group in the open-chain form of a monosaccharide (i.e., the carbon atom that bears two oxygen substituents) is called the anomeric carbon. The prefixes "α" and "β" are employed to define the stereochemistry of the C-OR bond at the anomeric carbon atom. The α-D-glucuronide differs in configuration from the corresponding β-derivative (its anomer) at C1. Thus, answer choice A is the best answer.

What does "n" mean in front of a compound name?

all carbons form a continuous, unbranched, linear chain

What is sphingosine? What is it used for?

an 18 carbon amino alcohol. Sphingolipid metabolites, such as ceramides, sphingosine and sphingosine-1-phosphate, are lipid signaling molecules involved in diverse cellular processes.

Acetylation

attachment of RC=O

Alkali metal location

group 1

2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g) What type of reaction is Reaction 1? A.Oxidation/reduction B.Lewis acid/Lewis base C.Double replacement D.Ionization

he answer to this question is A because atoms involved in Reaction 1 change oxidation states during the reaction. For instance, Mg changes from an oxidation state of 0 to +2 in converting from elemental Mg to MgCl2

Compound 1 was designed to exhibit pH-dependent self-assembly. What feature(s) of the molecule is(are) responsible for the pH dependence of aggregation (Equation 1)? A.Thiol side chains that can hydrogen bond B.Long alkyl tail that exhibits predominantly London forces C.Side chains whose net charge responds to pH D.Covalent linkages that reversibly hydrolyze

he answer to this question is C because the molecule contains mainly acidic side chains that were deprotonated and negatively charged at high pH. This inhibited aggregation due to electrostatic principles. At low pH these groups are neutral and this allowed aggregation.

Four organic compounds: 2-butanone, n-pentane, propanoic acid, and n-butanol, present as a mixture, are separated by column chromatography using silica gel with benzene as the eluent. What is the expected order of elution of these four organic compounds from first to last? A.n-Pentane → 2-butanone → n-butanol → propanoic acid B. n-Pentane → n-butanol → 2-butanone → propanoic acid C.Propanoic acid → n-butanol → 2-butanone → n-pentane D.Propanoic acid → 2-butanone → n-butanol → n-pentane

n-Pentane → 2-butanone → n-butanol → propanoic acid

The side chain of tryptophan will give rise to the largest CD signal in the near UV region when: A.present as a free amino acid. B.part of an α-helix. C.part of a β-sheet. D.part of a fully folded protein.

part of a fully folded protein.

What are the structural features possessed by storage lipids? A.Two fatty acids ester-linked to a single glycerol plus a charged head group B.Three fatty acids ester-linked to a single glycerol C.Two fatty acids ester-linked to a single sphingosine plus a charged head group D.Three fatty acids ester-linked to a single sphingosine

the answer to this question is B because triacylglycerols are neutral storage lipids. They consist of three fatty acids ester-linked to a single glycerol.

Which of the following energy conversions best describes what takes place in a battery-powered resistive circuit when the current is flowing? A.Electric to thermal to chemical B.Chemical to thermal to electric C.Electric to chemical to thermal D.Chemical to electric to thermal

the answer to this question is D because 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.

Focal length of glasses worn (cm) −50 What kind of image is formed by the lenses of the glasses worn by a 68-year-old male who sees an object 2 m away? A.Real and enlarged B.Real and reduced C.Virtual and enlarged D.Virtual and reduced

the answer to this question is D because the lenses 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.

What factor explains how a single stereoisomer is formed in Reaction 2? A.One of the reactants is chiral. B.Both reactants are chiral. C.The solvent medium is chiral. D.The enzyme is chiral.

the answer to this question is D since it is the only possible explanation for the observed stereospecificity of the reaction. Neither reactant is chiral, but a chiral product forms because the catalyst (the enzyme) is chiral.

Which phosphate on an ATP molecule is used to phosphorylate molecules via kinases?

the phosphoryl transfer from kinases comes from the γ-phosphate of ATP.

What is the y-intercept of the Lineweaver-Burk plot?

y-intercept of a Lineweaver-Burk plot is equivalent to 1/Vmax