BP FL5 C/P

Pyrimidines

(cytosine, thymine, and uracil) have a single six-membered ring

What is the molar solubility of ferrous (II) hydroxide in water at 25°C? F2OX= Ksp = 3.2 x 10-14) Fe(OH)2 (aq) + O2 (g) ---> Fe2O3 (s) + H2O (l) A. 2.1 x 10-8 Show Explanation B. 8.2 x 10-8 Show Explanation C. 2.8 x 10-6 Show Explanation D. 2.1 x 10-5 Show Explanation

. 2.1 x 10-5 The passage states that the Ksp of ferrous (II) hydroxide is 3.2 x 10-14. When Ksp is known, we can determine molar solubility from the dissociation reaction. Fe(OH)2 (aq) + H2O (l) → Fe2+(aq) + 2 OH- (aq) Note that Fe(OH)2 dissociates into three ions (one Fe2+ and 2 OH-). Given this 2:1 ratio, Ksp = [Fe2+][OH-]2 = [x][2x]2 = 4x3, where x represents the molar solubility. Next, we must divide Ksp by 4, then take its cube root to solve for x. Dividing 3.2 by 4 is more difficult than dividing 32 by 4, so we can manipulate scientific notation and rewrite Ksp in an easier format. Ksp = 4x3 = 3.2 x 10-14 = 32 x 10-15 8 x 10-15 = x3 2 x 10-5 = x

Question 28 A pure sample of (R)-limonene has a specific rotation of +125.6. If a mixture of (R)-limonene and (S)-limonene has a specific rotation of +62.8, what are the percentages of the R and S enantiomers in this mixture? A. 75% R, 25% S Show Explanation B. 55% R, 45% S Show Explanation C. 45% R, 55% S This answer choice results from a miscalculation. D. 25% R, 75% S Show Explanation q-28

. 75% R, 25% S Since the enantiomers in this case must be present in unequal proportions, a weighted average of the components should be used. In this case, the weighted average is given; therefore, we can set up an equation. If we designate x as the percentage of R and 1 - x as the percentage of S, we can solve for x using this equation: (125.6)(x) + (-125.6)(1-x) = 62.8 125.6x - 125.6 + 125.6x = 62.8 251.2x = 188.4 x = 0.75 1 - x = 0.25 Therefore, R makes up 75% of the solution, while S comprises the remaining 25%.

triacylglycerol

A lipid consisting of three fatty acids linked to one glycerol molecule; also called a fat or triglyceride.

cholesterol

A lipid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids. 4 ring structure

The rates of diffusion of four drugs were tested: acetazolamide (pKa = 7.2), sulfadiazine (pKa = 6.5), warfarin (pKa = 5.0), and cephalexin (pKa = 3.6). Which drug will have the strongest conjugate base? A. Acetazolamide Show Explanation B. Sulfadiazine Show Explanation C. Warfarin Show Explanation D. Cephalexin Show Explanation

Acetazolamide The Ka and pKa values of acids are inversely related to each other (since pKa = -log [Ka], and to corresponding Kb and pKb values of their conjugate bases. Thus, the strongest conjugate base will be produced by deprotonating the weakest acid. As pKa values decrease, acid strength goes up. Thus, the weakest acid present, acetazolamide, has the greatest pKa value. You can also use the shortcut that at standard temperatures (which are present unless otherwise stated on the MCAT), pKa + pKb = 14. Thus as pKa increases, pKb decreases, which indicates a stronger base.

Which of the following changes would lead to an increase in atomic radius? A. Removing an electron from a K atom to create a K+ ion Show Explanation B. Subjecting a dipeptide to proteolysis Show Explanation C. Adding an electron to a Cl atom to create a Cl- ion Show Explanation D. Removing two electrons from a Ca atom to create a Ca2+ ion Show Explanation

Adding an electron to a Cl atom to create a Cl- ion The question states that the channel favors larger solutes. Adding electrons to make a negatively charged ion would increase the radius of the particle, making it larger. Thus going from a Cl atom to a Cl- ion would increase the likelihood of it being transported by this channel.

Purines

Adenine and Guanine (2 rings)

Which of the following proteins is responsible for the retrograde transport of organelles in cells? A. Kinesin Show Explanation B. Myosin Show Explanation C. Selectin Show Explanation D. Dynein Show Explanation

Answer: Dynein Dynein is a motor protein that walks towards the minus end of the microtubules, which is oriented towards the center of the cell. Movement toward the center of the cell is described as retrograde. Kinesin Kinesin is a motor protein that is responsible for anterograde transport in cells. B. Myosin Myosin is a motor protein that is primarily responsible for attaching to actin filaments during muscle contractions. C. Selectin Selectin is a class of cell adhesion molecules (CAM) that mediate the inflammatory response, and is not a motor protein.

Question 53 If a signal is transmitted along a segment of nerve axon measuring 5 x 10-4 m, how much time is required for the signal to reach the end of the segment, assuming maximal transmission velocity? A. 2.5 x 10-6 ms This answer choice reflects a failure to convert to ms. B. 2.5 x 10-3 ms Show Explanation C. 1 x 10-1 ms This answer choice results from miscalculation. D. 1 x 10-1 s Show Explanation

B. 2.5 x 10-3 ms The passage tells us that signals can be transmitted up to 200 m/s, which would be the maximal velocity, and the question tells us that the distance traveled is 5 x 10-4 m. Dividing distance by the speed gives us time: 5 x10-4 m / 2 x 102 m/s = 2.5 x 10-6 s Converting to milliseconds, we get 2.5 x 10-3 ms.

Which of the following acids is expected to act as a hydrogen bond donor in aqueous solution? I. Acetic acid II. Hydrofluoric acid III. Hydrochloric acid IV. Nitric acid A. I only Acetic acid can donate hydrogen bonds in meaningful amounts, but so can hydrofluoric acid. B. I and II only Hydrogen bonding is a unique type of intermolecular force that occurs when H is bonded to highly electronegative elements like F, O or N. If the available choices, only acetic and hydrofluoric acids meet that criterion without being so electronegative that they dissociate from their protons completely (i.e., they are weak acids of oxygen and fluorine, respectively). C. II and III only Hydrochloric acid will not act as a hydrogen bond donor in meaningful amounts, as it is exceptionally strong and will almost completely dissociate from its protons. D. I, II, III, and IV Neither hydrochloric acid nor nitric acid will act as hydrogen bond donors in meaningful amounts, as both are exceptionally strong and will dissociate from their protons.

B. I and II only Hydrogen bonding is a unique type of intermolecular force that occurs when H is bonded to highly electronegative elements like F, O or N. If the available choices, only acetic and hydrofluoric acids meet that criterion without being so electronegative that they dissociate from their protons completely (i.e., they are weak acids of oxygen and fluorine, respectively).

In locations with very low dissolved O2 concentrations in drinking water, the observed Ksp of ferrous (II) hydroxide will be: A. slightly smaller. Show Explanation B. the same. Show Explanation C. slightly larger. Show Explanation D. much larger. Show Explanatio

B. the same. Equilibrium constants, including Ksp, are not affected by concentration. These constants are only altered by changing temperature, as shown below for a variety of salts:

Capacitance formula

C = ɛ0A/d, where A is the area of the plates and d is the distance between them.

Question 57 An unknown fluid has a specific gravity of 0.750. What is the volume of 22.5 kg of this fluid? A. 10 L Show Explanation B. 20 L Show Explanation C. 30 L Show Explanation D. 40 L Show Explanation

C. 30 L Volume = mass / density. Specific gravity relates the density of an object (or fluid, as is the case here) to the density of water, which is 1000 kg/m3. This fluid, then, must have a density of 750 kg/m3. Note also that 1000 L = 1 m3. 22.5 kg x (1 m3/750 kg) x (1000 L/1 m3) = 30 L

A marathon runner is jogging in a loop around the city with a velocity of 2.5 m/s. If the loop is perfectly circular and has a diameter of 3 km, after how many seconds will the runner reach his starting position? A. 67 s Show Explanation B. 2000 s Show Explanation C. 4000 s Show Explanation D. 40000 s Show Explanation

C. 4000 s C is correct. If the loop's diameter is 3 km, its circumference is 3π, or around 10, km. Since the runner's velocity is given in m/s, we'll need to convert the other value to either km or m. Let's convert 10 km to 10 × 103 m. We can thus see that traveling this distance will take 10 × 103 m ÷ 2.5 m/s = 4 × 103 s.

Question 32 A researcher carries out column chromatography at physiological pH, using a stationary medium with a net positive charge. If a solution containing the following oligopeptides is poured into the column, which oligopeptide will most likely be found in the first fraction collected? A. DDGE Show Explanation B. EILD Show Explanation C. KRVV Show Explanation D. VEGP Show Explanation

C. KRVV If the stationary phase has a net positive charge, then oligopeptides with negative charges will be attracted to the stationary phase and will move more slowly through the column. KRVV is lysine-arginine-valine-valine which would have a charge of +2. The positive charge would cause it to not bind the stationary phase and allow it to elute quickly.

Acetic acid

CH3COOH (weak acid)

geometric isomers

Compounds that have the same molecular formula but differ in the spatial arrangements of their atoms.

Several environmental scientists are monitoring the movement of a cheetah on an Ethiopian plain. They find that at t = 5 min, the cheetah is traveling at 5 m/s due west. At t = 15 min, it is moving at 12 m/s toward the west, while at t = 30 min it is moving at 2 m/s toward the east. If we call western movement positive, when is the cheetah's speed negative? A. During the entire interval from t = 15 to t = 30 min Show Explanation B. Only during part of the interval from t = 15 to t = 30 min Show Explanation C. During at least part of the interval from t = 15 to t = 30 min, and possibly at other times Show Explanation D. Never, since speed is not a vector quantity

D. Never, since speed is not a vector quantity Speed is a scalar, not a vector. Unlike velocity, which conveys both magnitude and direction, speed can only ever be a positive value.

Which of the following solvents would lead to the fastest SN1 reaction? A. n-hexane Show Explanation B. Benzene Show Explanation C. Tetrachloromethane Show Explanation D. Propanol Show Explanation

D. Propanol SN1 reactions proceed faster in polar protic solvents. SN2 reactions prefer polar aprotic solvents. The only polar protic solvent here is choice D.

Question 59 Which of the following are properly balanced complete combustion reactions? I. CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (l) II. C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l) III. C2H5OH (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (l) A. I only Show Explanation B. I and II only Show Explanation C. I and III only Show Explanation D. I, II, and III Show Explanation

D. (use your easier technique to find balanced equations) I, II, and III By determining the total number of carbon, hydrogen, and oxygen atoms on both sides of each reaction, one can conclude that all of the reactions are properly balanced (III). CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (l) Carbon atoms 1 = 1 Hydrogen atoms 4 = 2(2) Oxygen atoms 2(2) = 2 + 2(1) C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l) Carbon atoms 3 = 3(1) Hydrogen atoms 8 = 4(2) Oxygen atoms 5(2) = 3(2) + 4(1) C2H5OH (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (l) Carbon atoms 2 = 2 Hydrogen atoms 6 = 3(2) Oxygen atoms 1 + 3(2) = 2(2) + 3(1)

Conjugation

Depends on F factor plasmid In Gram-negative bacteria It confers the advantages of sexual reproduction on the bacterium. The plasmid benefits by being able to move from one host bacterium to another through the conjugation pilus.

What is the primary process responsible for the loss of latent heat and entropy from the ocean at the air-sea interface in Table 1? A. Precipitation Show Explanation B. Condensation Condensation should result in a positive latent heat for the ocean as it is a process that releases energy. C. Evaporation Show Explanation D. Melting Show Explanation

Evaporation A negative latent heat implies that the phase change that is occurring is consuming energy. Therefore, the phase change that is occurring is melting, evaporation or sublimation. The fact that this process is occurring at the air sea interface means that the phase change must involve the gas phase. That fact rules out melting. Since sublimation is not an option, this leaves evaporation. It makes sense that with evaporation, the ocean is losing entropy at the expense of the atmosphere which is gaining gas particles. Precipitation By the time that precipitation reaches the ocean's surface, it is no longer undergoing a phase change and so cannot contribute to a loss or gain of latent heat. B. Condensation Condensation should result in a positive latent heat for the ocean as it is a process that releases energy. C. Evaporation Show Explanation D. Melting Melting involves only the solid and liquid phases, but not the gas phase. Since this process occurs across the air sea interface, it needs to involve the gas phase in some way.

Question 46 A single sports fan is capable of yelling at an intensity level of 80 dB from a given distance. If 10,000 similar fans were all yelling from the same distance, which of the following would be closest to the observed intensity level? A. 84 dB Show Explanation B. 120 dB Show Explanation C. 160 dB Show Explanation D. 320 dB Show Explanation

How I did it: raised 80^4 , = 64+64 = 128 which was close to the answer Correct way: 120 dB 10,000 fans would be capable of yelling at an intensity 10,000, or 104, times greater than the single fan alone. According to the decibel scale, this would correspond to an increase of 40 dB.

Sphingolipids

Lipids with a sphingosine backbone: ceramide, sphingomyelins, glycosphingolipids, gangliosides

Myelin forms when glial (supporting) cells wrap around the axon. In the PNS these glial cells are called...

Schwann cells

If the majority of the baseball's kinetic energy comes from power generation in the legs and hips, approximately how much energy do the lower extremities produce in the pitch? A. 65 J Show Explanation B. 70 J Show Explanation C. 140 J Show Explanation D. 810 J Show Explanation refer to passage q# 3

The kinetic energy of the baseball can be calculated using the equation 1/2 mv2. Paragraph 2 tells us that the average velocity of the ball is 30 m/s and its mass is 150 g, which is equivalent to 0.15 kg. KE = (½)(0.15 kg)(30 m/s)2 KE = (½)(0.15)(900) KE = (0.15)(450) = 67.5 J The ball ends up with 67.5 J of KE, but the question asked for how much energy the lower extremities generated (eliminate choice A). Table 1 shows us the overall efficiency of each energy transfer. Using these, we can calculate how much energy was needed to end up with 67.5 J of KE in the ball. The overall efficiency of the kinetic chain can be calculated by multiplying the efficiencies of each step, and we can round the numbers to make our calculations easier. Efficiency = (0.9)(0.9)(0.7)(0.8) = 9*9*7*8 x 10-4 = (81)(56) x 10-4 ≈ (80)(60) x 10-4 = 4800 x 10-4 = 0.48 ≈ 0.5 Thus, the total energy generated in the lower extremities in order to ensure that 67.5 J makes it to the ball is 67.5 J / 0.5 = 135 J. If you are uncomfortable choosing a number that is not exactly what was calculated, you only need to remember that we estimated by rounding up to 0.5. Thus, our denominator in the final calculation, 67.5/0.5, is a bit larger than it should be, making our final value smaller than it would be had we not rounded or used a calculator (exact value of 67.5/ 0.48 =140 J). Thus, we round up and choose choice C.

If the average pitcher is releasing the ball from a height of 1.8 m above the ground, and the pitcher's mound is 0.2 m higher than the rest of the baseball field, at what height would the catcher need to hold his glove to catch the pitched ball? (Note: neglect air resistance, estimate the acceleration due to gravity as 10 m/s2, and assume the pitcher is throwing the ball only in the horizontal direction.) A. 2.0 m above the ground Show Explanation B. 1.8 m above the ground Show Explanation C. 0.5 m above the ground Show Explanation D. 0.2 m above the ground Show Explanation

The passage tells us that pitchers throw the ball at an average of 30 m/s and that the ball travels 18 m horizontally. This means the ball's flight time is: (18 m) / (30 m/s) = (18/30) s = 3/5 s = 0.6 s The ball is released from a position 2 m off the ground (0.2 m from the pitcher's mound and 1.8 m from the pitcher). To calculate the distance the ball falls during 0.6 s, we can use the equation d = v0t + 1/2at2: d = (0 m/s)(0.6 s) + 1/2(10 m/s2)(0.6 s)2 d = 1/2(10)(0.36) = 1/2(3.6) = 1.8 The ball has fallen 1.8 m from an initial height of 2.0 m. Thus, the catcher must hold the glove 0.2 m above the ground to catch the pitch.

If an IR absorption spectrum were obtained for the dimer in Figure 1, a strong signal at 1750 cm-1 would most likely indicate the presence of: A. an O-H bonds. Show Explanation B. a C=O bonds. Show Explanation C. a C≡C bonds. Show Explanation D. a C-O bonds. Show Explanation

This question requires you to recall some facts about the IR frequency of various bonds. C=O bond stretching typically exhibits a frequency range of 1650-1750 cm-1. A. an O-H bonds. O-H bond stretching in a carboxylic acid typically exhibits a frequency range of 2500-3300 cm-1. C. a C≡C bonds. C≡C bond stretching typically exhibits a frequency range of 2100-2260 cm-1. D. a C-O bonds. C-O bond stretching typically exhibits a frequency range of 1000-1320 cm-1.

In solids as temperature increases, solubility increases True/False higher temps, higher solubility lower temps, lower solubility

True

a gas becomes less soluble as temperate increases (hotter) bc KE energy increases T/F -inverse relationship

True The solubility of gases in liquids decreases with increasing temperature. Conversely, adding heat to the solution provides thermal energy that overcomes the attractive forces between the gas and the solvent molecules, thereby decreasing the solubility of the gas. higher temps, less gas dissolves lower temp, more gas dissolves

speed is a

a scalar quantity. It can only be positive value.

ozonolysis results in the formation of an

aldehyde and a ketone https://youtu.be/ID79wLZLzbA

Transformation

bacteria take up DNA from their surroundings, the media in which they are immersed

Endothermic processes involve breaking

breaking of bonds or intermolecular interactions, which require a source of heat.

Peptide bonds are formed through

condensation and nucleophillic acyl substition

exothermic phase changes

condensation, freezing, and deposition —release heat into the environment.

The capacitance of a nerve membrane can be increased by: A. decreasing the width of the membrane. Show Explanation B. decreasing the surface area of the membrane. Show Explanation C. decreasing the charge stored across the membrane. Show Explanation D. increasing the voltage difference across the membrane. Show Explanation

decreasing the width of the membrane. For the MCAT, you should remember that capacitance is directly proportional to area but inversely proportional to the distance between the two sides of the capacitor. Thus, decreasing the width of the membrane (choice A) would actually increase capacitance.

A closed system

energy exchange but not mass exchange Earth satisfies both conditions of a closed system, namely that there is energy exchange but not mass exchange with the surroundings.

An open system exchanges

exchanges mass and energy with its surroundings

peptide bonds are broken through

hydrolysis

exothermic processes typically involve bond formation or an increase in intermolecular force strength.

involve bond formation or an increase in intermolecular force strength.

An isolated system

is unable to exchange energy or matter with its surroundings

Inflation of the lungs in mammals is accomplished by:

negative pressure pumping action -lung stays in contact with the thoracic wall as it enlarges due to contraction of the diaphragm and the external intercostal muscles, a pressure that is lower than atmospheric pressure (negative pressure) is generated within the alveolar sacs

Myelin forms when glial (supporting) cells wrap around the axon. In the CNS, these glial cells are called...

oligodendrocytes

In the lungs pressure

pressure increases as volume decreases and pressure decreases as volume increases

Transduction

process whereby genes are transferred by a virus

. Constitutional isomers

same molecular formula, different connectivity

A security guard is patrolling his sector by traveling in large circles around a house. The gardener's displacement is: A. always equal to the distance he has traveled. Show Explanation B. sometimes equal to the distance he has traveled. Show Explanation C. sometimes equal to zero. Show Explanation D. never a negative value. Show Explanation

sometimes equal to zero. Displacement is the direct distance that separates the initial and final positions. Each time the guard makes a full circle, he winds up where he originally began. At those times, the distance between start and finish is zero meters.

Epimers are

stereoisomers that differ from each other in their configuration at a single carbon atom. carbohydrates that differ in the location of the -OH group in one location

Displacement

the vector quantity that defines the distance and direction between two positions

endothermic phase change are

—melting, evaporation, and sublimation —require the input of heat,