AAMC FL 2 Chem/Phys

Lens

-Diverging lens: focal length NEGATIVE; -Converging lens: focal length POSITIVE; Image distance: -If image and object are on the OPPOSITE sites (aka lens is in the middle of the two), image distance (di) is POSITIVE. -If image and object are on the SAME site (aka lens is not in the middle of the two), image distance (di) is NEGATIVE.

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

-In order to stand up, the person has to maintain a rotational equilibrium. -If they don't there will be a torque because their center of gravity will be at a distance from fulcrum of rotation (in this case their knees/legs), and their weight will produce a torque making it hard to stand up. -The answer is poorly worded because it just says equilibrium, there are two types of equilibrium, rotational and translational. -In this case, if the person doesn't lean forward or slide their feet under the chair, they won't have rotational equilibrium. -So leaning forward puts their center of mass above the fulcrum, making the torque zero (because Torque=distance from fulcrum x force sin (theta), and in this case that distance would be zero). -The other answers are wrong because A: obviously the goal isn't to increase the force required to stand up B: There will always be friction with the grown, even if you don't adjust your center of mass to stand up, and C: energy is a state function, if we are going from point A to point B (in this case sitting to standing) the amount of energy required to do so doesn't change.

What is the role of the solid-state catalyst in the Haber process? A. It increases the amount of ammonia produced per unit time. B. It increases the total amount of ammonia produced. C. It decreases the amount of ammonia that decomposes per unit time. D. It decreases the total amount of ammonia produced.

A because catalysts increase the rate of chemical reaction, which is the amount of product formed per unit time.

The concentration of enzyme for each experiment was 5.0 μM. What is kcat for the reaction at pH 4.5 with NO chloride added when Compound 3 is the substrate? A. 2.5 × 10-2 s-1 B. 1.3 × 102 s-1 C. 5.3 × 103 s-1 D. 7.0 × 105 s-1

A. 2.5 × 10-2 s-1 -rate of product formation did not vary over time for the first 5 minutes implies that the enzyme was saturated with substrate kcat = Vmax/[E] = (125 nM/s)/5.0 μM = 2.5 × 10-2 s-1

Which statement about the cooperativity of RIα/C activation and RIα protein folding is supported by the data in figures 2 and 3? A. Both activation and folding are cooperative. B. Activation is cooperative, but folding is not. C. Folding is cooperative, but activation is not. D. Neither activation nor folding is cooperative.

A. Both activation and folding are cooperative -A because both curves have a sigmoidal shape, which is indicative of cooperative processes

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

A. C-H Given bond enthalpies Strongest bond enthalpy will have the shortest bond

Which of the following species has the largest mass percent of oxygen? A. H2O B. CaCO3 C. CO2 D. HCO3-

A. H2O 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%.

Based on the information in the passage, PDK1 catalyzes the addition of phosphate to what functional group? A. Hydroxyl B. Amine C. Carboxyl D. Phenyl

A. Hydroxyl -because reactions involving either Ser or Thr would involve the hydroxyl group in the side chain of these amino acids

What atom is the site of covalent attachment of AMC to the model tetrapeptide used in the studies? A. I B. II C. III D. IV

A. I basically asking where does the bond between amc and Y break. since you know they are attached by a peptide bond, which means the peptide chain attaches to the amino group of the next amino acid( that's why an amino acid runs from the N-terminal to the C-terminal), the covalent attachment is at site 1

From the data presented in Figure 3, which RIα variant is the most stable? A. L203A B. I204A C. Y229A D. R241A

A. L203A -because a higher melting temperature is indicative of a more stable protein, as more energy is needed to unfold the protein. L203A has an approximate Tm of 50°C, therefore, it is the most stable and even more stable than the WT protein -Remember Tm is the halfway point

Based on the data presented in figures 2 and 3, what is the most likely role of Y229 in protein stability and cAMP activation? A. Y229 is important for protein stability but not critical for cAMP activation. B. Y229 is important for cAMP activation but not critical for protein stability. C. Y229 is important for protein stability and critical for cAMP activation. D. Y229 is not important for protein stability and not critical for cAMP activation.

A. Y229 is important for protein stability but not critical for cAMP activation. -because the thermal melt shows that removal of Y229 decreases stability, therefore Y229 is important for stability. -Removal of Y229 has little effect on protein activation, as the activation curve is similar to WT activation

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 secondary structure is represented by repeated patterns of hydrogen bonds between the backbone amide protons and carbonyl oxygen atoms

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

A. n-Pentane → 2-butanone → n-butanol → propanoic acid -the compounds have comparable molecular weights, so the order of elution will depend on the polarity of the molecule. -Since silica gel serves as the stationary phase for the experiment, increasing the polarity of the eluting molecule will increase its affinity for the stationary phase and increase the elution time (decreased Rf)

Lewis acid

Accepts electrons

Bronsted-Lowry base

Accepts protons

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.

B. Blood flow was heard when the pressure of the cuff was greater than 130 mmHg. -least likely is that there is blood flowing when the pressure external (from the cuff) is greater than the pressure exerted by the artery at its greatest pressure point (systolic) If an exterior pressure is greater than the greatest pressure which can be exerted within the artery, it stands to reason that the artery would be collapsed regardless of the cardiac cycle.

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 because of the properties listed, the boiling point of a substance will give the best estimate of its relative vapor pressure.

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

B. Excitation of bound electrons -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

Consider the reaction shown in Equation 1 at equilibrium. Would the concentration of [Cu(NH3)4]2+ increase if the equilibrium were disturbed by adding hydrochloric acid? A. Yes, because the equilibrium in Equation 1 would shift to the left B. No, because the equilibrium in Equation 1 would shift to the left C. Yes, because the equilibrium in Equation 1 would shift to the right D. No, because the equilibrium in Equation 1 would shift to the right [Cu(H2O)4]2+(aq) + 4NH3(aq) [Cu(NH3)4]2+(aq) + 4H2O(l)

B. No, because the equilibrium in Equation 1 would shift to the left So HCl is a strong acid. NH3 is more basic than H2O (this is because the Nitrogen is less electronegative than Oxygen based on periodic table trend). Remember that a base is defined as a proton acceptor (Bronsted-Lowry Definition) and an electron donor (Lewis Acid definition). So what will happen is the Nitrogen in NH3 has a lone pair on it. It will donate that lone pair of electrons and take the H+ proton from HCl. Thus, it will become NH4+. So what happened was after we added the HCl we have less NH3 because that NH3 turned into NH4+. So, the equation will shift to the left in order to try to replenish that NH3.

In [Cu(NH3)4]2+, the subscript 4 indicates which of the following? A. The oxidation number of Cu only B. The coordination number of Cu2+ only C. Both the oxidation number of Cu and the coordination number of Cu2+ D. Neither the oxidation number of Cu nor the coordination number of Cu2+

B. The coordination number of Cu2+ only (number of atoms surrounding Cu)

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

B. Three fatty acids ester-linked to a single glycerol

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 because oxygen pressure is the sum of the oxygen static pressure P and the oxygen flow pressure ρv2/2. In the area of the mask openings, Pair = P + ρv2/2, 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

In the overall electrochemical reaction: A. nitrogen is oxidized at the anode, and hydrogen is reduced at the cathode. B. nitrogen is reduced at the cathode, and hydrogen is oxidized at the anode. C. nitrogen is reduced at the anode, and hydrogen is oxidized at the cathode. D. nitrogen is oxidized at the cathode, and hydrogen is reduced at the anode.

B. nitrogen is reduced at the cathode, and hydrogen is oxidized at the anode. oxidation always occurs at the anode and reduction at the cathode of an electrochemical cell. Since nitrogen decreases in oxidation state during the reaction, it is reduced. Hydrogen, on the other hand, increases in oxidation state and is, therefore, oxidized.

What is the ratio of the minimum sound intensities heard by a 64-year-old male and a 74-year-old female? A. 20 B. 40 C. 50 D. 100

Bf = Bi + 10 log (If / Ii) So basically, If is the intensity that corresponds to the decibel Bf. And Ii is the intensity that corresponds to the decibel Bi. Here's how I did it: Bf = Bi + 10 log (If / Ii) The B will always be decibels, and the I will always be intensity. So it would be: 40 dB = 20 dB + 10 log (If / Ii) ---- subtract 20 ------- 20 dB = 10 log (If / Ii) ------ divide by 10 ------- 2 = log (If / Ii) ------ take 10 to the power on both sides so log gets cancelled out -------- 10^2 = If / Ii

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)

C. (6.62 × 10-34) × (3.0 × 108) × [1 / (360 × 10-9) - 1 / (440 × 10-9)] E = hf = hc/λ Excitation occurs at λe = 360 nm, but fluorescence is observed at λf = 440 nm so I guess it's excitation - fluorescence ?

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.) A. 2.4 × 10-4 M B. 4.9 × 10-5 M C. 7.0 × 10-5 M D. 4.9 × 10-9 M

C. 7.0 × 10-5 M Ksp = [Ca2+][CO32-] 4.9*10^-9 = x*x 4.9*10^-9 = x^2 sqrt 4.9*10^-9 = x 7*10^-5 = x

Which amino acid will contribute to the CD signal in the far UV region, but NOT the near UV region, when part of a fully folded protein? A. Trp B. Phe C. Ala D. Tyr

C. Ala Says side chains with amino acids absorb in near region

Why does NH3 displace H2O in the formation of [Cu(NH3)4]2+? NH3 contains more lone pairs of electrons than H2O. NH3 is a stronger Lewis base than H2O. NH3 donates a lone pair of electrons more readily than does H2O. A. I and II only B. I and III only C. II and III only D. I, II, and III

C. II and III only reaction proceeds in the forward direction indicates that NH3 is a better Lewis base toward Cu2+ than H2O. This also means that NH3 donates a lone pair of electrons more readily than does H2O.

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? A. Stronger van der Waals forces of pyrimidines B. Stronger van der Waals forces of purines C. Increased π- stacking strength D. Reduced electrostatic repulsion of phosphates

C. Increased π- stacking strength -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 -look at the AT pair, it obviously has the A+T, but sandwiched in between is one more "ring" bc of the H-bonds. look at the GC pair, it has G+C but also two more "rings" because of its extra H bond pair. so yes GC stacks more

In designing the experiment, the researchers used which type of 32P labeled ATP? A. α32P-ATP B. β32P-ATP C. γ32P-ATP D. δ32P-ATP

C. γ32P-ATP -because the phosphoryl transfer from kinases comes from the γ-phosphate of ATP. -Therefore, the experiment should require γ32P-ATP.

Mirrors

Concave mirror: focal length POSITIVE. -Convex mirror: focal length NEGATIVE. -If image and object are on the OPPOSITE sites (aka mirror is in the middle of the two), image distance (di) is NEGATIVE. -If image and object are on the SAME site (aka mirror is not in the middle of the two), image distance (di) is POSITIVE.

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: A. 5.1 × 1011 protons added to it. B. 5.1 × 1011 electrons removed from it. C. 2.0 × 1010 protons added to it. D. 2.0 × 1010 electrons removed from it.

D. 2.0 × 1010 electrons removed from it. number of charges in excess can be computed as +3.2 × 10 -9 C/1.6 × 10 -19 C = +2.0 × 10 10 means that the rod has an excess of positive charge, created by removing a number of +2.0 × 10 10 electrons from the material, as it is not possible to add protons in a manner described in this question.

At STP, the volume of N2(g) produced by the complete decomposition of 1 mole of nitroglycerin would be closest to which of the following? A. 5 L B. 10 L C. 20 L D. 30 L

D. 30 L Based on the balanced equation provided, 4 moles of nitroglycerin produce 6 moles of N2(g). Therefore, 1 mole of nitroglycerin will produce 1.5 moles of N2(g). At STP 1.5 moles of N2(g) will occupy 33.6 L since the molar volume of an ideal gas at STP is 22.4 L/mol

Which of the following atoms will be expected to have the smallest second ionization energy? A. Na B. C C. O D. Ca

D. Ca -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 energy of the four atoms listed, which include Na and two non-metals

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

D. Chemical to electric to thermal -chemical energy in a battery (A lot like a galvanic cell) allows electrons to move and since electrons are moving charges, they constitute an electrical current so therefore you have electrical energy. -The electrons flowing through the circuit's wire collide with the walls of the wire, which gives off energy as heat

Which of the following best describes the bonds between Cu2+ and the nitrogen atoms of the ammonia molecules in [Cu(NH3)4]2+? A. Ionic B. Covalent C. Coordinate ionic D. Coordinate covalent

D. Coordinate covalent -Remember ionic versus covalent is due to the difference in electronegativity not just metal and nonmetal. Greater than 2.0 difference then it is ionic, 0.5-2.0 then it's polar covalent, less than 0.5 it's covalent. You typically need one extreme ( top right corner) or another (first column) to get to ionic, otherwise it's usually covalent. Coordinate comes from the fact that one atom (nitrogen) is supplying both electrons for the bond.

When used in place of spHM, which peptide would be most likely to achieve the same experimental results? A. FLGFAY B. FLGFQY C. FLGFGY D. FLGFEY

D. FLGFEY -The question is basically asking "which sequence is most similar to FLGFTY". All the answers are replacing T (threonine with R = OH) with some other amino acid. The goal is to find which substitution is most similar to Threonine -We are NOT looking for a sequence similar to FLGFTY, we are looking for a sequence similar to the PHOSPORYLATED spHM. Glutamate is the right choice because it is charged, like the phosphate would be

In industrial use, ammonia is continuously removed from the reaction mixture. This serves to drive Reaction 1 because of: A. Boyle's law. B. Charles's law. C. Heisenberg's principle. D. Le Châtelier's principle.

D. Le Châtelier's principle. -removing a product as it forms causes a displacement from the equilibrium condition. The system will respond by shifting more reactants to the product side. This is an example of Le Châtelier's principle

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

D. Virtual and reduced If I plug in the given values (f=-.5m, o = 2m), then I get i = -1/2.5 It it safe to assume the (-) mean a virtual image, and since -1/2.5 is smaller than 2

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.

D. part of a fully folded protein the passage says that asymmetry due to tertiary structure gives rise to signal in the near UV region and that aromatic rings absorb in this region as well. A fully folded protein is expressing tertiary structure and tryptophan has an aromatic ring hence answer choice D.

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.

D. the time it takes for half of all the radioactive nuclei to decay into their daughter nuclei. -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

Lewis base

Donates electrons

Magnification

M=(-di)/(do) -When M is positive, your image maintains its original orientation. -When M is negative, your image is inverted. -For multiple lens system, you multiple all the M.

dB

The decibel scale is a logarithmic scale of intensity; dB = 10log(I/Io), where Io is the lowest-intensity sound that we can here. Therefore, every unit of 10 you go up in the decibel scale corresponds to a power of 10 difference in intensity. If sound 1 is 10 decibels louder than sound 2, it is 10 (10^1) times as intense. If sound 1 is 20 decibels louder than sound 2, it is 100 (10^2) times as intense. If sound 1 is 30 decibels louder than sound 2, it is 1000 (10^3) times as intense.

At 25°C, the formation of [Cu(NH3)4]2+ according to Equation 1 is most likely a: A. spontaneous process with positive ΔG°. B. spontaneous process with negative ΔG°. C. nonspontaneous process with positive ΔG°. D. nonspontaneous process with negative ΔG°.

Think about Delta G (standard) = -RTlnKeq If Keq > 1 then it will be spontaneous equilibrium favors the products if Keg is small (less than 1), there would be more reactants than products resulting in a positive delta G. If Keg is large (greater than 1) more products would be formed, giving a negative delta G. If Keq is 1, the delta G will be zero and the reaction will be in equilibrium :P

Continued nitrogen, hydrogen redox question

Way 1: look at the half reactions, the electrons cancel out (ignoring balancing) and everything checks out. If you specifically look at half reaction 3, the electrons are on the left side, meaning that Nitrogen is GAINING electrons, thus being reduced. If you look at half reaction 2, the electrons are on the right, meaning H2 has LOST electrons and therefore was oxidized.

The lone pair of electrons in ammonia allows the molecule to: A. assume a planar structure. B. act as an oxidizing agent. C. act as a Lewis acid in water. D. act as a Lewis base in water.

a Lewis base is a substance that donates an electron pair in forming a covalent interaction

Bronsted-Lowery Acid

donates a proton

Sugar phosphate backbones form the ...... of the double helix

exterior

Tertiary structure bonding

folding or 3D shape that involves hydrogen bonding as well as the side chain interactions (disulfide bonds in cystine, etc).

Secondary structure bonding

hydrogen bonding between amino hydrogen's and carbonyl oxygens in alpha helices and beta pleated sheets.

basic log stuff

log (10) = 1 log(100) = 2 log(1000) = 3 log (0.1) = -1 log(0.01) = -2 log(0.001) = -3

covalent bond

sharing of electrons between two atoms

One double bonded atom is...

sp2

coordination number

the number of atoms (or ions) surrounding an atom (or ion) in a crystal lattice

Venturi Effect

the reduction in fluid pressure that results when a fluid flows through a constricted section of a pipe.

Saturating refers to....

when adding more substrate does not increase the rate. That would refer to the top of the Michaelis-Menten curve or where the y axis is Vmax. The hyperbolic curve levels off remember that. So at a saturating amount of substrate the rate is kcat or the turnover number which is the maximum rate substrate can be converted to product

Quaternary structure

when you have protein subunits (multiple proteins in tertiary structure) so if it starts talking about subunits think quaternary

How much work did an 83-year-old female do while stretching the rubber band to the limit of her strength? A. 4 J B. 5 J C. 6 J D. 7 J

work done is W = 0.5 × kx2 where x = 0.20 m. So W = 0.5 × 200 (N/m) × (0.2 m)2 = 4.0 J. Work and energy are interchangeable but work and force are not.