UWorld

Isochoric process

A process in which volume remains constant and in which no net pressure-volume work is done

Fatty acid synthesis proceeds according to the following reaction: where n is a positive integer. Based on this, how many ADP and NADP+ molecules will be produced during synthesis of a 16-carbon fatty acid? A. 7 ADP molecules and 14 NADP+ molecules B. 14 ADP molecules and 28 NADP+ molecules C. 8 ADP molecules and 15 NADP+ molecules D. 16 ADP molecules and 32 NADP+ molecules

A. 7 ADP molecules and 14 NADP+ molecules

What is the order of the phase changes of water throughout the lyophilisation process after freezing? According to the passage, the lyophilisation process begins with a frozen sample, so the water in the sample starts out in its solid phase. Afterward, the frozen water is sublimated at low pressures, and sublimation is the phase change of a solid directly to a gas. In the last step, the sublimated water vapor (gas) is collected in a condensation chamber, and condensation is the phase change of a gas to a liquid. A. Solid to gas to liquid B. Solid to gas to solid C. Solid to liquid to gas D. Solid to liquid to solid

A. Solid to gas to liquid

A researcher builds a telescope with a magnification of 100 to view Mars from Earth using lenses with magnifications of either 10 or 25. To achieve the desired magnification, which of the following lenses were combined? A. Two lenses with magnification of 10 B. Two lenses with magnification of 25 C. Four lenses with magnification of 25 D. Two lenses with magnifications of 10 and 25

A. Two lenses with magnification of 10 10x10=100 M=M1M2

An astronaut pulls a cart of rock samples a distance of 60 m along flat ground using a tether attached to their spacesuit. The tether has a tension of 40 N and an angle of 30° relative to the horizontal. What is the approximate work the astronaut does on the cart? (Note: sin 30° = 0.50; cos 30° = 0.87) A. 1,200 J B. 2,000 J C. 2,400 J D. 2,800 J

B. 2,000 J W=Fdcostheta

Approximately how much heat in kJ was released from the combustion of the 1-g sample? 500 g The energy content of food is given in units of dietary calories (Cal), which is equal to 4.185 kJ, or 1,000 gram calories (cal). A gram calorie is the amount of energy required to increase 1 g of water by 1°C. A. 5 kJ B. 20 kJ C. 40 kJ D. 70 kJ

B. 20 kJ

In rainbow trout, body color is inherited in a Mendelian pattern, and blue body color is dominant to gray body color. A blue trout and a gray trout were crossed and produced 157 F1 offspring that were all blue. If two of these F1 offspring were then crossed and produced 200 offspring in the F2 generation, approximately how many F2 trout are homozygous dominant for this trait? A. 0 B. 50 C. 100 D. 150

B. 50

If the student repeated the experiment by replacing the water in the calorimetry device with an ice bath at 0°C, how would the experimental results differ? A. The temperature of the water would increase to 10°C. B. The temperature of the water would begin to increase at a later time. C. The heat released when ice melts increases the measured temperature. D. The amount of heat released from the combustion reaction would increase.

B. The temperature of the water would begin to increase at a later time. (Choice A) Because some of the heat released goes toward the latent heat of fusion of the ice to melt it, less heat will be available to increase the temperature of the water. Therefore, the magnitude of the temperature increase would be less than the 10°C temperature change in the original experiment. (Choice C) Ice absorbs heat when it melts. Conversely, liquid water releases heat equal to the latent heat of fusion when it freezes. (Choice D) The amount of heat released from the combustion would be unchanged because it depends on the mass of the reactants (powdered sample), which is unchanged. Educational objective:The phase transition from a solid to a liquid requires heat (energy) to break the bonds between molecules; this energy is the latent heat of fusion. When heat is added to a mixture of ice and water at 0°C, the heat will first go toward melting the ice before raising the temperature of the water.

Does the redox reaction between Cr2O72−(aq) and Fe2+(aq) require energy input? Cr2O72−(aq) + 14 H+(aq) + 6 e− → 2 Cr3+(aq) + 7 H2O(l): +1.33 Fe3+(aq) + e− → Fe2+(aq): +0.7 A. Yes; ∆G° = +2.09nF J/mol B. Yes; ∆G° = +0.57nF J/mol. C. No; ∆G° = −0.57nF J/mol. D. No; ∆G° = −2.09nF J/mol

C. No; ∆G° = −0.57nF J/mol The Gibbs free energy ∆G° of a reduction-oxidation reaction is related to the number of electrons n transferred in the overall reaction, the overall cell potential E°cell, and Faraday's constant F, according to the equation ∆G° = −nFE°cell. For irreversible reactions, a positive ∆G° (negative E°cell) indicates a nonspontaneous reaction whereas a negative ∆G° (positive E°cell) indicates a spontaneous reaction. General Chemistry Subject Solutions and Electrochemistry Foundation 2. Scientific Reasoning and Problem-solving Skill

wo astronauts use their jet packs to position a solar panel attached to a large space station by a pivot point, as shown above. The solar panel is at rest relative to the space station and not rotating. One astronaut applies 100 N of force 30 m from the pivot point toward the right. What is the force applied toward the left by the second astronaut, and how far from the pivot point is it applied to prevent the solar panel from rotating? A. 100 N force applied 10 m from the pivot point B. 100 N force applied 20 m from the pivot point C. 150 N force applied 10 m from the pivot point D. 150 N force applied 20 m from the pivot point

D. 150 N force applied 20 m from the pivot point

What is the ratio of the shortest to farthest distances between Earth and Mars as these planets orbit the Sun? A. 3:4 B. 1:3 C. 1:4 D. 1:7 On average, Earth is 150 million km from the Sun and Mars is 200 million km from the Sun.

D. 1:7

Metallic, elemental bismuth reacts with yellow fluorine gas to form a white solid of bismuth(V) fluoride according to the balanced equation above. How many grams of fluorine gas are needed to fully convert 836 g of bismuth in this reaction? A. 60.8 g B. 152 g C. 190 g D. 380 g

D. 380 g

in one experimental trial, the projectile was uniformly accelerated from rest to a distance of 2 m in 0.1 s. What was the acceleration of the projectile? A. 20 m/s2 B. 40 m/s2 C. 200 m/s2 D. 400 m/s2

D. 400 m/s2 d=vot+ 1/2 at^2

If the maximum pressure in a blood vessel is 7,000 Pa, what is the pressure in mmHg? (Note: The density of mercury is 14,000 kg/m3, and gravitational acceleration is 10 m/s2.) A. 0.05 mmHg B. 2 mmHg C. 20 mmHg D. 50 mmHg

D. 50 mmHg Ph=ρfgh=Patm

Which of the following molecules could participate in cell signaling without a second messenger?

STERIOD Hormones Cells communicate through chemical signals called hormones. Hydrophilic molecules such as peptide hormones cannot cross the cell membrane and require second messengers. Hydrophobic molecules such as steroid hormones can cross the cell membrane and do not need second messengers.

Electric field lines

denote the direction and relative strength of the field. The field lines point toward the lowest voltage in the field and away from the highest voltage.

Trypanosomes were transfected with a new ion channel, Channel X. Channel X is found to open in trypanosomes that have been treated with APOL1 once pH neutralization occurs. Similarly, Channel X opens in trypanosomes that contain the nicotinic acetylcholine receptor (nAChR) when treated with acetylcholine (the ligand that opens nAChR). Neither pH nor acetylcholine open Channel X in trypanosomes without APOL1 or nAChR, respectively. Channel X is best described as a: A. mechanically gated ion channel. B. pH-activated channel. C. ligand-gated ion channel. D. voltage-gated ion channel.

D. voltage-gated ion channel.

Which of the following graphs shows the relationship between the torque generated by the weight of the ball and the angle the biceps makes with the lower arm in Experiment 2?

Torque τ is the product of the distance r from the pivot point and the perpendicular component of the force F: τ = rFsin θ, where θ is the angle between the force and the lever arm. The magnitude of sin θ (and torque) is greatest when θ is 90°.

Intermediate filaments

are composed of several protein types (eg, keratin, lamin) and perform the following functions: Work with microfilaments to determine cellular shape Make up the nuclear lamina (inner lining of nuclear envelope) Assist in anchoring organelles to specific compartments within the cell Provide crucial support for the cell to be able to withstand mechanical forces (eg, compression)

Isobaric

constant pressure

isothermally

constant temperature

primary structure

is the chemical structure of proteins and is stabilized by covalent bonds. Because proteins are polymers of amino acids, each of which has a defined chemical structure, the primary structure can also be described by the protein's amino acid sequence (also called the protein's primary sequence). Amino acids within a protein polymer are connected to adjacent amino acids by covalent peptide bonds; therefore, primary structure is stabilized by peptide bonds.

Quaternary structure

is the intermolecular interactions that result from multiple polypeptides coming together to form a single functional protein. Quaternary structure is stabilized by similar forces as tertiary structure (ie, hydrophobic interactions, hydrogen bonds, electrostatic interactions).

Secondary structure

is the local arrangement of the peptide backbone and is stabilized by hydrogen bonds between backbone amide hydrogens and backbone carbonyl oxygens. The most common examples of secondary structure are alpha helices and beta-pleated sheets.

Tertiary structure

is the overall three-dimensional shape of a single polypeptide chain. Tertiary structure is driven by hydrophobic interactions and is further stabilized by other noncovalent interactions (eg, hydrogen bonds, electrostatic interactions) involving the side chains of the amino acids within the single polypeptide.

The Doppler effect occurs

when the observed frequency and wavelength of a sound are shifted from those of the original due to relative motion between the source and the observer. The frequency shift is positive when the source velocity is negative (moving closer) and negative when the source velocity is positive (moving away).

Urinary retention in certain patients with poorly controlled diabetes mellitus is most likely the result of nerve damage that reduces the ability of smooth muscle to contract in which of the following structures? A. Bladder B. Urethral sphincters C. Kidney efferent arterioles D. Ureter

A. Bladder (Choice B) Urine can pass through the urethra and out of the body when the IUS and EUS are relaxed. When contracted, both the IUS and EUS block urine flow through the urethra. Therefore, a reduced ability to contract these muscles due to nerve damage would likely increase, not impair, urine flow. (Choice C) Diminished contraction of the smooth muscles (eg, of the efferent arteriole carrying blood out of the glomerulus) in the kidney due to nerve damage may alter the rate of urine production but would not affect the process of urination. (Choice D) Decreased contraction of smooth muscles in the ureter due to nerve damage may affect urine collection in the bladder. However, the ability to urinate, which is under control of the detrusor muscle, IUS, and EUS, would not be affected. Educational objective:Urine flows from the kidney to the bladder through the ureter. Once the bladder is full, urine exits the body via the urethra through the process of urination. Urination is controlled by the detrusor muscle (smooth muscle lining the bladder), the internal urethral sphincter, and the external urethral sphincter.

After the experiment had progressed for 2 min, the liquid in the thermometer rose 2 mm. How high will the liquid rise from the 25°C mark after the experiment had progressed for 4 min? A. 4 mm B. 6 mm C. 8 mm D. 10 mm

D. 10 mm ΔV=αvVΔT

An astronaut on Mars uses a short burst from a rocket engine to launch an atmosphere sampler vertically upward to different heights. If the speed of the rocket at the end of the engine burst were doubled, then the maximum height of the rocket would: A. increase by a factor of 4 B. increase by a factor of 2. C. decrease by a factor of 2. D. decrease by a factor of 4.

A. increase by a factor of 4

Laser Doppler flowmetry uses an infrared laser to measure blood flow velocity. Compared to ultrasound, the percent change in frequency using this technique is: A. smaller. B. the same. C. larger. D. zero.

A. smaller.

To structurally characterize the topology of the APOL1 ion channel, researchers used bioinformatics methods based on the APOL1 primary sequence to predict transmembrane regions as well as an experimental technique called the substituted cysteine accessibility method (SCAM) to determine extracellular and intracellular localization of the intervening loops The bioinformatic study described in the passage relies on the level of protein structure stabilized by: I. electrostatic interactions. II. hydrogen bonds. III. hydrophobic interactions. IV. peptide bonds. A. II only B. IV only C. III and IV only D. I, II, III, and IV

B. IV only

Excess post-exercise oxygen consumption is the extra amount of oxygen consumed after the completion of exercise and before respiration returns to resting levels. This extra oxygen is used to restore muscle fibers to their pre-exercise state by doing all of the following EXCEPT: A. replenishing the ATP stores within the muscle fiber. B. facilitating metabolic reactions to lower pH in the cytosol of the muscle fiber. C. restocking the myoglobin O2 stores within the muscle fiber. D. supplying the ATP used to replenish glycogen stores in the muscle fiber.

B. facilitating metabolic reactions to lower pH in the cytosol of the muscle fiber. Once motor neuron input ceases, the fiber relaxes and begins replenishing these energy reserves. Consequently, oxygen intake remains elevated even after physical activity has stopped because oxygen is required to resynthesize ATP and creatine phosphate (Choice A) and restock myoglobin saturation with oxygen (Choice C). In addition, glycogen stores broken down during exercise must be replenished. In a process known as the Cori cycle, lactic acid is transported to the liver, where ATP is used to metabolize lactic acid back to glucose. This and other glucose in the circulation is transported into muscle and stored as glycogen (Choice D) or metabolized to pyruvate. However, the increased demand for ATP hydrolysis (which produces protons) during exercise (not rest) leads to decreased pH and an increased reliance on anaerobic metabolic reactions in muscle. Therefore, these types of reactions would not require oxygen nor return muscle to a pre-exercise state. Educational objective:Oxygen intake remains elevated after exercise due to the increased demand in muscle cells for oxygen to replenish ATP, creatine phosphate, and glycogen stores and restock myoglobin with oxygen. The amount of additional oxygen consumed is called the excess post-exercise oxygen consumption, or oxygen debt.

An image intensifier has a photocathode-to-anode distance of d and an anode voltage of V. An electron with a mass of m and charge of q is ejected from the photocathode with negligible initial kinetic energy. What is the speed of the electron immediately before it reaches the anode? A. √2qV/dm B. √2qV/m C. 2qV/dm D. 2qV/m

B. √2qV/m PEi=qV KE: 1/2mv^2 PE=KE

At its top speed, a Mars rover generates a constant force of 400 N and uses 100 W of battery power. What is the top speed of the rover? A. 2.5 m/s B. 1.0 m/s C. 0.25 m/s D. 0.10 m/s

C. 0.25 m/s Its just Power formula: P = W/t = Fd/t = Fv

Litmus paper will turn blue when immersed in all of the following EXCEPT: A. Ca(OH)2 B. NH3 C. HNO3 D. NaCN

C. HNO3

The critical concentration of plasma glucose necessary to induce glycosuria is termed the renal threshold of glucose. The renal threshold of glucose in T2DM patients treated with canagliflozin compared to the threshold in untreated T2DM patients is: A. higher by approximately 75 mg/dL. B. higher by approximately 175 mg/dL. C. lower by approximately 115 mg/dL. D. lower by approximately 300 mg/dL.

C. lower by approximately 115 mg/dL.

Which of the following is true regarding I3−(aq)? I3−(aq) is a weaker oxidizing agent than Cr2O72−(aq). I3−(aq) cannot oxidize Fe2+(aq). I3−(aq) can be reduced in the Jones reductor column. A. I and II only B. I and III only C. II and III only D. I, II, and III

D. I, II, and III higher E= Stronger oxidizing agents & weak reducing agent lower E= weaker oxidizing agents & stronger reducing agent According to the reduction potentials in Table 1, I3−(aq) is a weaker oxidizing agent than Cr2O72−(aq) because it has a less positive E° than Cr2O72−(aq) (Number I). In addition, I3−(aq) is a weaker oxidizing agent than Fe3+(aq). As such, I3−(aq) cannot oxidize Fe2+(aq) (and therefore the second titration experiment in the passage will not work) because Fe3+(aq) has a stronger affinity for electrons than I3−(aq) (Number II). On the other hand, I3−(aq) is a stronger oxidizing agent than Zn2+(aq) and can oxidize Zn(Hg)(s). Therefore, I3−(aq) can be reduced in the Jones reductor column (Number III). Educational objective:A oxidizing agent is a chemical species that gets reduced and causes oxidation in another species in the process. Chemical species with higher, positive standard reduction potentials are more easily reduced and are stronger oxidizing agents than species with lower or negative standard reduction potentials. During a reduction-oxidation reaction, the stronger oxidizing agent gets reduced.

Palomino (golden brown) horses are bred for their coat coloration. A breeder will achieve 100% Palomino offspring by crossing a chestnut (dark brown) horse with a cremello (cream) horse. However, if a breeder crosses two Palomino horses, only 50% of the offspring will be Palomino, while 25% will be chestnut and 25% will be cremello. Genetic inheritance of coat color in these horses is best described as: A. codominance. B. complete dominance. C. variable expressivity. D. incomplete dominance.

D. incomplete dominance.

Based on the passage, a feature of the Joule-Thomson effect is that it occurs: (The temperature change of the gas exiting the valve is described by the Joule-Thomson effect, which occurs without heat transfer with the surroundings) A. isothermally. B. adiabatically. C. isochorically. D. isobarically.

B. adiabatically.

Two transverse waveforms (A and B) travel through the same medium with a phase difference of 180°. If the amplitude of the waveforms is ±100 m, what is the combined displacement of both waveforms as waveform A reaches maximum displacement? A. 0 m B. 100 m C. 175 m D. 200 m

A. 0 m

The compressor exerts a pressure of 400 Pa to compress nitrogen gas from 3 L to 1 L. If no heat transfer occurs, how much will the internal energy of the gas change? (Note: 1 m3 = 1000 L and 1 J = 1 Pa∙m3.) A. 0.8 J B. 1.2 J C. 800 J D. 1200 J

A. 0.8 J

According to the data in Table 1, which of the following makes noise at a frequency that resonates in the bore of an MRI magnet? (Note: The speed of sound in air is 350 m/s.) A. 1.0 T MRI B. 1.5 T MRI C. 3.0 T MRI D. Gas lawnmower

A. 1.0 T MRI

Visible light travels through the output phosphor at 1.6 × 10^8 m/s. What is the refractive index of the material? A. 1.9 B. 1.1 C. 0.88 D. 0.53

A. 1.9 n=c/v

A baseball traveling at 20 m/s strikes a player running at 5 m/s. The relative speed of the ball with respect to the player depends on the direction of travel of the ball relative to the player's direction of travel. What is the difference between the minimum and maximum possible speeds of the ball relative to the player? A. 10 m/s B. 15 m/s C. 20 m/s D. 25 m/s

A. 10 m/s The minimum relative speed v occurs when the ball and player are moving in the same direction. In this case, v equals the difference between the speed of the ball and the speed of the runner: v = 20 m/s - 5 m/s = 15 m/s The maximum v occurs when the ball and the player are moving in opposite directions. In this case, v is the sum of the ball and runner speeds: v = 20 m/s + 5 m/s = 25 m/s Therefore, the difference between the minimum (15 m/s) and maximum (25 m/s) possible values is 10 m/s

A cube with a side length of 5 cm floats on the surface of water. If 4/5 of the cube volume floats above the surface of the water, what is the density of the cube? (Note: Density of water = 1,000 kg/m3.) A. 200 kg/m3 B. 400 kg/m3 C. 800 kg/m3 D. 2,500 kg/m3

A. 200 kg/m3

A radioactive atom decays by 5 alpha, 3 beta minus, and 2 gamma emissions to yield 211Po. What was the original nucleus? A. 231Pa B. 223At C. 231U D. 191Ir

A. 231Pa

Amino acid catabolism releases nitrogen in the form of ammonia. In the liver, the urea cycle prepares ammonia for excretion. Which amino acid could undergo deamidation to produce ammonia for the urea cycle? A. Lysine B. Arginine C. Glutamine D. Aspartate

C. Glutamine (Choice A) Lysine contains an amine group in its side chain, not an amide. As such, it can undergo deamination but not deamidation. (Choice B) Arginine contains a guanidinium group in its side chain. This group does not contain a carbonyl, so it cannot be an amide group. (Note: Do not confuse arginine with asparagine, which does have an amide in its side chain.) (Choice D) Aspartate is the deamidated form of asparagine. It contains a carboxylate group in its side chain, not an amide. Educational objective:The urea cycle processes ammonia for excretion in the urine. The ammonia that enters the cycle is derived from the amino groups of amino acid backbones (deamination) and from the amide side chains of glutamine and asparagine (deamidation).

A solution of Compound 1, shown below, absorbs light maximally at 448 nm in the absence of copper(II) ions but shifts to a 623 nm absorption maximum upon the addition of Cu2+. Which of the following best describes this process? A. Changes in electronic structure cause the solution to change from yellow to blue. B. Changes in vibrational modes cause the solution to change from green to yellow. C. Changes in the mass-to-charge ratio (m/z) cause the solution to change from violet to orange. D. Changes in nuclear spin cause the solution to change from colorless to violet.

A. Changes in electronic structure cause the solution to change from yellow to blue. According to the given information, Compound 1 absorbs violet light (448 nm), so it appears yellow (complement of violet). After Cu2+ is added, the absorption maximum changes to 623 nm and the compound absorbs orange light, causing it to appear blue (complement of orange). Therefore, upon the addition of Cu2+, Compound 1 must undergo a change in electronic structure that causes the solution to change from yellow to blue. (Choice B) Vibrational modes are excited by infrared light, which is not visible to the eye. They do not affect the color of a solution. (Choice C) The mass-to-charge ratio (m/z) is measured for ions generated from samples analyzed by mass spectrometry and pertains to the molecular mass of the ions, which does not affect color of the sample. Compound 1 absorbs violet light initially and then absorbs orange light when Cu2+ is added; the color perceived is not the color absorbed, but rather the complement of the color absorbed. (Choice D) Nuclear spin is probed by radio frequencies in nuclear magnetic resonance (NMR) spectroscopy and does not affect color. Educational objective:The color of a substance is determined by the wavelengths of light it absorbs, which is determined by the electronic structure of the molecule. In general, a substance appears to be the color that is complementary to the color of light that is maximally absorbed.

.Which thermodynamic quantity involved in the Hampson-Linde cycle is a state function? A. Entropy of nitrogen, because it describes an equilibrium state of the system B. Entropy of nitrogen, because it describes a path to an equilibrium state of the system C. Work done by the compressor, because it describes an equilibrium state of the system D. Work done by the compressor, because it describes a path to an equilibrium state of the system

A. Entropy of nitrogen, because it describes an equilibrium state of the system

Consider the reaction: R ⇌ P Reaction kinetics data with and without enzyme E are shown in the following table: Substance Concentration (mM) Initial (0 min) 1 min 10 min 100 min 1,000 min No enzyme R 300 300 300 300 300 P 20 20 20 20 20 With 5 nM enzyme R 300 263 100 50 50 P 20 57 220 250 250 Based on the data, which of the following statements are accurate? The enzyme-catalyzed reaction has reached equilibrium by 100 minutes. The reaction with no enzyme begins the experiment at equilibrium. The enzyme-transition state complex has lower free energy than either R or P. The ∆G between the transition state and the product P is smaller in the presence of enzyme than without. A. I and IV only B. II and III only C. I, II, and III only D. I, II, III, and IV

A. I and IV only

Researchers determined that the blood velocity in the afferent arterioles of their model was four times larger than physiological measurements. Which of the following changes to their model could correct this discrepancy? (Note: Assume ideal fluid flow.) A. Increase the radius of the afferent arterioles by 100% B. Increase the radius of the afferent arterioles by 75% C. Decrease the radius of the afferent arterioles by 75% D. Decrease the radius of the afferent arterioles by 100%

A. Increase the radius of the afferent arterioles by 100% Q=Av

What additional information do the researchers need from the crash test dummy to estimate the power of the collision in the experiment shown in Figure 2? A. Mass of the head B. Time until the head stops moving C. Tension of the neck during the collision D. Velocity of the head at the end of the collision

A. Mass of the head power is the rate of work per unit time, and work is equal to the change in the kinetic energy of an object. Kinetic energy is due to motion, and it is calculated from an object's mass and velocity: KE=12mv2KE=12mv2.

How will the work done by the Lorentz force on an electron traveling through the magnetic field of an MRI scanner change if the magnetic field strength is increased? A. The work will not change, because it is always zero. B. The work will increase, because the velocity of the electron will increase. C. The work will increase, because the force on the electron will increase. D. The work will decrease, because the velocity of the electron will decrease.

A. The work will not change, because it is always zero. In this question, the value of B increases, which causes F to increase. However, the value of θ is always 90° because d is the same direction as v, and F is always perpendicular to v. Therefore, W must always equal 0 J because cos 90° is always equal to 0. F=qvB sin θB W=Fd cos θ

Is the vacuum chamber in an x-ray image intensifier an electrical insulator? A. Yes, because only electrons ejected from the photocathode can travel through the vacuum chamber B. Yes, because no electrons can travel through the vacuum chamber C. No, because electrons can travel through the vacuum chamber even without x-rays at the input phosphor D. No, because electrons in the vacuum chamber are not exposed to a voltage difference

A. Yes, because only electrons ejected from the photocathode can travel through the vacuum chamber

SGLTs transport glucose against its concentration gradient across the luminal membrane of the proximal tubule. The energy to drive this form of glucose transport is most likely directly provided by: A. an electrochemical Na+ gradient. B. an action potential. C. ATP hydrolysis. D. simple diffusion of Na+ ions.

A. an electrochemical Na+ gradient. (Choice B) An action potential is a brief reversal of cell membrane polarization that involves the movement of ions through membrane channels along their concentration gradients. Action potentials are not involved in the transport of substances (eg, glucose) against their concentration gradients. (Choice C) By establishing the electrochemical gradient of Na+, ATP hydrolysis by the Na+/K+ pump indirectly powers the secondary active transport of glucose. However, glucose reabsorption is directly facilitated by the potential energy that is released when Na+ flows along its concentration gradient. (Choice D) Because it is charged, Na+ cannot cross directly through the lipid bilayer via simple diffusion. Instead, it crosses the membrane via facilitated diffusion (ie, with the help of membrane proteins). Educational objective:Primary active transport uses the energy from ATP hydrolysis to move a substance against its concentration gradient. Secondary active transport uses the energy released by the passive transport of another molecule.

A clinical study reports that the time required for the pulse wave to arrive at the kidney increases after renal artery ablation. A possible explanation for this could be that: A. decreasing blood pressure causes the wavelength of the pulse wave to decrease. B. decreasing blood pressure causes the wavelength of the pulse wave to increase. C. decreasing blood pressure causes the frequency of the pulse wave to decrease. D. decreasing blood pressure causes the frequency of the pulse wave to increase.

A. decreasing blood pressure causes the wavelength of the pulse wave to decrease. In this question, ablation of the renal arteries causes an increase in the travel time for the pulse wave to reach the kidney. Therefore, the pulse wave v decreases after renal artery ablation. Because f depends only on the heart rate, it does not change before and after ablation. Furthermore, according to the equation above, λ is directly proportional to v. Therefore, λ must decrease when v is decreased. (Choice B) A decrease in pulse wave velocity causes the wavelength to decrease, not increase. (Choices C and D) The pulse wave frequency depends only on the heart rate and is the same before and after ablation. Educational objective:The pulse wave velocity is equal to the product of the frequency and the wavelength. When the frequency is constant, changes in the pulse wave velocity cause a proportional change in the wavelength.

Administration of canagliflozin increases urinary output most directly by increasing the: A. osmotic pressure of the tubular filtrate. B. osmotic pressure of the peritubular capillaries. C. hydrostatic pressure of the renal artery. D. hydrostatic pressure of Bowman's space.

A. osmotic pressure of the tubular filtrate. The passage states that SGLTs cotransport glucose and sodium out of the proximal tubule so they can be returned to the circulation through the peritubular capillaries. Therefore, SGLT inhibitors (eg, canagliflozin) most likely prevent glucose and sodium reabsorption from the tubule. This leads to increased solute concentration within the tubule, thereby increasing the osmotic pressure of the tubular filtrate. Consequently, less water is reabsorbed, and more water is drawn into the tubule, increasing urine output. (Choice B) Increasing the osmotic pressure of blood in the peritubular capillaries would increase water retention by osmosis and decrease urinary output. (Choice C) According to the passage, SGLT inhibitors like canagliflozin typically decrease (not increase) BP. If decreased hydrostatic pressure in the renal artery also reduced glomerular capillary pressure, the decreased pressure would reduce the amount of fluid being filtered into Bowman's capsule from the glomerular capillaries, thereby decreasing (not increasing) overall urine output. (Choice D) Hydrostatic pressure within the glomerulus pushes fluid into Bowman's space. This movement is opposed by the hydrostatic pressure in Bowman's space. Therefore, increasing the hydrostatic pressure in Bowman's space would impede fluid from entering the nephron and would decrease urinary output. Educational objective:The kidneys regulate blood osmolarity and, in turn, blood pressure by selectively modulating the reabsorption and secretion of water and solutes.

Piezoelectric crystals likely create sound by: An ultrasound device consists of an array of piezoelectric crystals and an acoustic lens. The piezoelectric crystals generate sound when an alternating voltage is applied, and the acoustic lens increases the transmission efficiency from the device to the body by reducing sound reflection at the skin. A. rapidly expanding and contracting. B. emitting high-energy photons. C. generating heat waves. D. sending pulses of electricity.

A. rapidly expanding and contracting. Sound is propagated in the form of longitudinal waves of oscillating pressure. Compressions (areas of high pressure) and rarefactions (areas of low pressure) are formed through the back-and-forth vibrations of the molecules of the medium. The passage states that piezoelectric crystals produce sound when an alternating voltage is applied to them. It is reasonable to conclude that the expansion and contraction of the crystals will cause molecules in the surrounding medium to vibrate, creating sound waves. (Choice B) A photon is a packet of energy that makes up electromagnetic radiation (light). The emission of photons would generate light, not sound. (Choices C and D) Sound energy is propagated in the form of pressure waves, not heat waves or electric waves. Educational objective:Sound is propagated in the form of pressure waves by the vibrations of the molecules in a medium. The rapid expansion and contraction of crystals creates pressure waves (sound) by vibrating nearby particles.

For the combustion reaction of the sample into CO2 (g) and H2O (g) in the bomb cell: A. ΔH and ΔS are both positive. B. ΔH and ΔS are both negative. C. ΔH is negative and ΔS is positive. D. ΔH is positive and ΔS is negative.

C. ΔH is negative and ΔS is positive. (Choices A and D) Although the enthalpy (heat) of the surroundings increases, ΔH describes the reaction. ΔH would be positive (endothermic) if energy is absorbed in a chemical reaction. (Choice B) ΔS would be negative if disorder decreases (order increases). Educational objective:Enthalpy (H) is a measure of bond energy, and a change in the enthalpy of a reaction results in the release or absorption of heat. Entropy (S) is a measure of disorder, and it is highest in gases and lowest in solids due to their respective molecular structures. In the combustion of a solid to a gas, heat is released (ΔH is negative) and the products are more disordered (ΔS is positive).

When a stationary head is hit by a moving projectile, a contrecoup injury is likely to occur due to: In addition to direct injury at the site of an impact, the rapid acceleration-deceleration of the head may cause the brain to move within the skull and result in injury to the part of the brain opposite the impact site. This is known as a contrecoup injury. A. the inertia of the brain. B. the weight of the skull. C. the center of mass of the head. D. the potential energy of the projectile.

A. the inertia of the brain. (Choice B) An object's weight is the gravitational force exerted on its mass. The weight of the skull does not cause the continued relative motion of the brain within the skull. (Choice C) An object's center of mass is the average position of its distribution of mass. The head's center of mass changes as a result of the movement of the brain within the skull, but the center of mass itself is not responsible for the movement of the brain. (Choice D) An object's potential energy is its "stored" energy due to its height above the ground. The potential energy of the projectile does not cause the continued movement of the brain relative to the skull. Educational objective:An object's inertia is its resistance to changes in its velocity; objects tend to stay in motion or stay at rest. Due to the brain's inertia, the brain can continue to move independently of the skull and result in a contrecoup injury.

Osmolarity, the number of moles of osmotically active species (osmoles) per liter of solution (Osmol/L), equals the molar solute concentration M multiplied by the van 't Hoff factor i. Osmolarity is calculated by dividing osmotic pressure Π by RT, where R is the gas constant and T is the absolute temperature. If the osmotic pressure of blood plasma is 6.9 atm at 37 °C, what is its osmolarity? (Note: Assume R = 0.08 L·atm/mol·K, and i = 2.) A. 0.14 Osmol/L B. 0.28 Osmol/L C. 1.2 Osmol/L D. 2.3 Osmol/L

B. 0.28 Osmol/L

The cysteine-MPBS reaction is a redox reaction involving the nucleophilic attack on MPBS by a deprotonated cysteine side chain. If the reaction were attempted at pH 7.0, approximately what percent of cysteine side chains would be in the deprotonated, anionic form? (Note: Assume that the cysteine side chains all have pKa of 8.0.) A. 0% B. 10% C. 50% D. 75%

B. 10%

How much farther will a 5 MHz signal penetrate compared to a 10 MHz signal when the initial intensity of each signal decreases by a factor of 100? A. 1 cm B. 2 cm C. 4 cm D. 10 cm

B. 2 cm

What is the period of an ultrasound signal that is attenuated by 20 dB after it travels 4 cm into soft tissue? 5mHZ A. 5 × 10−9 s B. 2 × 10−7 s C. 5 × 10−6 s D. 2 × 10−4 s

B. 2 × 10−7 s

Which of the following is closest to the expected drop in pressure in the arterioles for an organ with only one capillary network? A. 100 mmHg B. 70 mmHg C. 40 mmHg D. 20 mmHg

B. 70 mmHg In this question, the mean blood pressure in different vascular regions of the kidney is provided in Figure 1. However, the kidney has an unusual vascular architecture with two capillary networks. In an organ with only one capillary network, the arterioles must reduce the blood pressure at the end of the arteries, approximately 90 mmHg, to the value at the beginning of the second capillary network, approximately 20 mmHg. Therefore, the pressure drop across the arterioles is 70 mmHg. (Choice A) 100 mmHg is the total blood pressure drop across all of the vascular regions, not the pressure drop across the arterioles. (Choice C) 40 mmHg is the blood pressure drop across the glomerular capillaries and the efferent arterioles in the kidney. (Choice D) 20 mmHg is the blood pressure at the beginning of the capillary network. Educational objective:The arterioles are responsible for reducing the blood pressure from the major arteries (high blood pressure) to the capillary networks (low blood pressure). As a result, the arterioles are the primary pressure-reducing vascular region of the circulatory system.

Based on the passage, the inclusion of which amino acid is most likely responsible for the changing localization (soluble lumenal to integral membrane) of APOL1 upon pH manipulation? A. Isoleucine B. Glutamate C. Histidine D. Lysine

B. Glutamate The passage states that APOL1 starts off in the aqueous lumen but partitions to the membrane as the lumen acidifies. Thus, the amino acids responsible for this shift must be responsive to pH changes. Furthermore, the amino acids should be soluble in the aqueous lumen at a neutral pH but less soluble when acidified. Glutamate is an acidic amino acid that changes protonation state at different pH levels. At neutral pH, the glutamate side chain is negatively charged, and therefore highly soluble. When the pH drops, glutamate becomes protonated, which neutralizes its charge and makes it less water-soluble under acidic conditions. Therefore, the inclusion of glutamate is most likely responsible for the changing localization of APOL1.

Which of the following is NOT a property of sound? A. It attenuates most in soft materials. B. It is fastest in a vacuum. C. It is a longitudinal wave. D. It is a pressure wave.

B. It is fastest in a vacuum Sound propagates through the vibrations of molecules in a medium. This vibration creates oscillations of compressions (areas of high pressure) and rarefactions (areas of low pressure), resulting in a propagating pressure wave (Choice D). Sound is a longitudinal wave; the molecules vibrate back and forth parallel to the direction of propagation (Choice C). Attenuation (damping) is the decrease in the amplitude (intensity) of a wave due to absorption and scattering. The magnitude of the attenuation depends on the properties of the medium; attenuation is greater for softer materials (Choice A). Sound is also attenuated as a function of distance traveled by the inverse-square law. Intensity is inversely proportional to the square of the distance from the source. The speed of sound is slowest in gases, faster in liquids, and fastest in solids. Because sound propagates through the vibrations of the molecules in a medium, sound cannot propagate through a vacuum. Educational objective:Sound propagates through the vibrations of the molecules as longitudinal pressure waves, and therefore cannot exist in a vacuum. The attenuation of sound is greatest in soft materials and increases with distance. Sound travels most slowly in gases and most quickly in solids.

Which of the following best describes the direction of the magnetic force on a positron traveling inside the magnetic field of an MRI scanner? (Note: Assume that the direction of the positron's velocity is not the same as the direction of the magnetic field.) A. It is in the same direction as the magnetic field. B. It is perpendicular to the magnetic field. C. It is in the same direction as the positron velocity. D. It is in the opposite direction as the positron velocity.

B. It is perpendicular to the magnetic field

Suppose the physical characteristics of the crash test dummy accurately represent those of a human. What is the expected injury from an impact lasting 10 ms that accelerated the head to a velocity of 10 m/s? A. No injury B. TBI and no skull fracture C. Skull fracture and no TBI D. TBI and skull fracture

B. TBI and no skull fracture

In the range from 0 to 10 ms in Figure 2, which of the following represents the velocity of the head at 10 ms? A. The length of the curve B. The area under the curve C. The maximum height of the curve D. The maximum slope of the curve

B. The area under the curve (Choice A) The length of the curve does not represent an important physical quantity. (Choice C) The maximum height of the curve represents the maximum acceleration of the head. (Choice D) The slope (change in the y-axis over the change in the x-axis) of the acceleration vs. time graph in Figure 2 gives the rate at which acceleration changes per unit time, not velocity. The slope of a distance vs. time graph would represent velocity (v = d/t). Educational objective:Acceleration is the rate at which velocity changes over time, and therefore the product of acceleration and time is the change in velocity. On a graph, the product of the axes' quantities is represented by the area under a curve. Therefore, the area under the curve on an acceleration vs. time graph represents the change in velocity.

Which of the following describes the order of the phase changes when helium moves to the collection system and returns to the MRI scanner? Liquid helium that boils out of the MRI scanner is stored in a collection system, cooled back into a liquid, and returned to the MRI scanner. A. Condensation followed by vaporization B. Vaporization followed by condensation C. Vaporization followed by deposition D. Deposition followed by vaporization

B. Vaporization followed by condensation

Which of the following describes the concentration of Fe2+(aq) after 4.75 mL and 9.50 mL of K2Cr2O7(aq) have been added to the solution, respectively? A. [Fe2+] = [Fe3+], [Fe2+] > [Fe3+] B. [Fe2+] = [Fe3+], [Fe2+] = 0 C. [Fe2+] > [Fe3+], [Fe2+] = 0 D. [Fe2+] < [Fe3+], [Fe2+] < [Fe3+]

B. [Fe2+] = [Fe3+], [Fe2+] = 0 The passage states that the equivalence point is reached after 9.50 mL of K2Cr2O7(aq) (the titrant) has been added to the Fe2+(aq) solution (ie, Fe2+ is fully oxidized to Fe3+). Consequently, when half this amount is added (ie, 4.75 mL), [Fe2+] = [Fe3+], and the molar concentration of Fe2+(aq) (ie, [Fe2+]) is zero after 9.50 mL of K2Cr2O7 (aq) have been added. (Choices A, C and D) At the equivalence point (9.50 mL of titrant added), [Fe2+] = 0. At the half-equivalence point (4.75 mL of titrant added), [Fe2+] = [Fe3+]. Educational objective:In a redox titration, the equivalence point occurs when all the analyte in the solution has been oxidized by the added titrant (an oxidizing agent). At the half-equivalence point, the molar concentrations of the non-oxidized analyte and oxidized analyte are equal.

One function of catecholamines released by the adrenal glands during times of stress is to: A. stimulate secretion of melatonin by the pineal gland. B. increase dilation of bronchioles in the lungs. C. inhibit glucose reabsorption by the kidneys. D. promote the release of digestive enzymes.

B. increase dilation of bronchioles in the lungs. (Choice A) Melatonin, a hormone that promotes drowsiness and sleep, is released by the pineal gland in response to low light levels (detected by the retina). Adrenal gland activity is not involved in the regulation of the pineal gland. (Choice C) Although glucose reabsorption occurs in the kidney, adrenal hormones (eg, aldosterone) do not affect this process. However, aldosterone does stimulate the reabsorption of sodium and water in the kidneys. (Choice D) By decreasing blood flow to the stomach and other digestive organs, the actions of hormones secreted by the adrenal gland will decrease digestive activity, likely inhibiting the secretion of the digestive enzymes that break down food. Educational objective:During the stress response, catecholamines secreted from the adrenal medulla act to promote the "fight-or-flight" response. Some effects of catecholamines include redirected blood flow to maximize the delivery of oxygen and other nutrients to organs essential for immediate survival (eg, brain, lungs, skeletal muscles), increased heart rate, and dilated airways.

What is the temperature change of the renal artery from the RF ablation system described in the passage? (Note: The specific heat of renal artery tissue is 3.3 J/(g∙°C).) 100 J & 3kg A. 1 °C B. 3 °C C. 10 °C D. 30 °C

C. 10 °C

The net reaction occurring in the Jones reductor column is: A. Fe3+(aq) + Zn(Hg)(s) + e− → Fe2+(aq) + Zn2+(aq) + Hg(l) + 2 e− B. Fe3+(aq) + Zn2+(aq) + Hg(l) → Fe2+(aq) + Zn(Hg)(s) C. 2 Fe3+(aq) + Zn(Hg)(s) → 2 Fe2+(aq) + Zn2+(aq) + Hg(l) D. 2 Fe3+(aq) + Zn(Hg)(s) + 2 e− → 2 Fe2+(aq) + Zn2+(aq) + Hg(l) + 2 e−

C. 2 Fe3+(aq) + Zn(Hg)(s) → 2 Fe2+(aq) + Zn2+(aq) + Hg(l)

Which of the following best describes the type of heat transfer that occurs in the external cooler of the Hampson-Linde cycle apparatus? A. Conduction occurs as dry ice loses heat to the coil of the external cooler. B. Convection occurs as the coil of the external cooler loses heat to dry ice. C. Conduction occurs as the coil of the external cooler gains heat from nitrogen gas. D. Convection occurs as nitrogen gas gains heat from the coil of the external cooler.

C. Conduction occurs as the coil of the external cooler gains heat from nitrogen gas. As the nitrogen gas flows through the coil of the external cooler, it transfers energy obtained during the compression stage to different sections of the coil. Therefore, the heat transfer results from the physical contact of the nitrogen gas and the coil and is primarily a conductive transfer of heat.

What happens to the chromium atoms in K2Cr2O7(aq) during the titration in the passage? Cr2O72−(aq) + 14 H+(aq) + 6 e− → 2 Cr3+(aq) + 7 H2O(l) A. Cr6+ is oxidized to Cr3+ B. Cr7+ is oxidized to Cr3+ C. Cr6+ is reduced to Cr3+ D. Cr7+ is reduced to Cr3+

C. Cr6+ is reduced to Cr3+

An apparatus consists of a cart that can move along a horizontal track inside a sealed tube that can be filled with various gases. Researchers attached a speaker to the cart, and a sensor that can measure sound is located at one end of the tube. Which of the following procedures will allow the researchers to change the speed of the sound created by the speaker? A. Set the cart in motion either toward or away from the sensor B. Change the frequency of the sound produced by the speaker C. Fill the tube with a different gas D. None of these actions will change the speed of the sound

C. Fill the tube with a different gas (Choice A) The Doppler effect implies that the motion of the cart changes the frequency and wavelength of the sound received by the sensor. However, wave speed is not affected by the motion of the source. (Choice B) The speed of the sound is independent of its frequency. (Choice D) The speed of a wave is not universal but rather depends on the medium of propagation. Educational objective:The speed of a wave depends only on the properties of the medium of propagation. Changing the medium (eg, changing the gas in a tube) changes the speed of sound in that medium.

The scientists hypothesize that genetic leakage has occurred in some of the studied yeast lineages over time. Which of the following observations best supports this hypothesis? A. Hybrid individuals express certain phenotypes that differ from those expressed in the parental species. B. Hybrid individuals exhibit reproductive isolation with some other Saccharomyces species. C. Hybrid individuals can produce some viable offspring when mated with their parental species. D. Hybrid individuals frequently pass genetic information to clones of themselves via asexual reproduction.

C. Hybrid individuals can produce some viable offspring when mated with their parental species. (Choice A) Hybrid organisms may express phenotypes (ie, traits) that differ from those expressed in their parental species. However, genetic leakage occurs only when these hybrids are able to produce viable offspring with one of their parental species. (Choice B) When two different species are unable to produce viable or fertile offspring from mating with each another, they are said to be reproductively isolated. Genetic leakage relies on the formation of fertile hybrids that can mate and produce viable offspring with one of their parental species. Therefore, the occurrence of reproductive isolation between hybrids and other Saccharomyces species would not support the hypothesis. (Choice D) Frequent production of clones via asexual reproduction would allow hybrids to continuously pass their genes on to identical offspring but would not allow for the transfer of genes between hybrids and one of their parental species via genetic leakage. Educational objective:Hybrid offspring are produced when members of two different species mate. If these hybrid offspring mate with either parental species that produced the hybrid, genetic leakage (ie, the transfer of genes between different species) may occ

Which of the following enzymes are used in the synthesis of glucose from lactate? I. Lactate dehydrogenase II. Fructose-1,6-bisphosphatase III. Pyruvate kinase IV. Phosphoglycerate kinase V. Glyceraldehyde-3-phosphate dehydrogenase A. I, II, and V only B. III, IV, and V only C. I, II, IV, and V only D. I, II, III, IV, and V

C. I, II, IV, and V only (Number III) Pyruvate kinase catalyzes a glycolytic reaction with a large, negative ∆G. Its reverse reaction has a large, positive ∆G, is nonspontaneous under physiological conditions, and therefore is not used in gluconeogenesis to produce glucose from lactate. Educational objective:Glucose is synthesized from precursors (eg, pyruvate, lactate) through gluconeogenesis. Gluconeogenesis shares seven enzymes with glycolysis; however, the irreversible steps of glycolysis are bypassed by distinct enzyme-catalyzed reactions unique to gluconeogenesis.

A train is traveling west at a velocity of 25 m/s. Another train is traveling east directly toward the west-bound train at a velocity of 15 m/s. The west-bound train blows its whistle with a frequency of 600 Hz when the two trains are 1000 m apart and then blows its whistle again 10 seconds later. For passengers on the east-bound train, how will the perceived frequency of the first whistle compare with the perceived frequency of the second whistle? (Note: Use 350 m/s for the speed of sound in air.) A. It will be 60% higher than the frequency of the second whistle. B. It will be 40% higher than the frequency of the second whistle. C. It will be approximately identical to the frequency of the second whistle. D. It will be 40% lower than the frequency of the second whistle.

C. It will be approximately identical to the frequency of the second whistle.. f=(v±vo/v∓vs)fs (Choices A, B, and D) The velocities of the trains are the same for the first and second whistles. Therefore, the perceived frequency of the whistle for passengers on the east-bound train will be the same for both situations. Educational objective:The Doppler frequency shift depends on the velocities of the source and observer but does not depend on the distance between them. Physics Subject Light and Sound Foundation 1. Knowledge of Scientific Principles Skill

Two x-ray photons with wavelengths of 0.06 nm and 0.03 nm are traveling in a vacuum. How will the speed of the 0.06 nm x-ray photon compare with the speed of the 0.03 nm x-ray photon? A. It will be 1/4 as fast B. It will be 1/2 as fast C. It will be equal D. It will be 2 times faster

C. It will be equal (Choices A, B, and D) All x-rays are electromagnetic radiation and have the same speed in a vacuum, c (ie, 3 × 108 m/s). X-rays can have different values for λ, but their speed is always c. Educational objective:X-rays are electromagnetic radiation and have a speed in a vacuum equal to the speed of light, independent of the wavelength of the x-rays.

Researchers want to measure the efficiency of the photocathode for converting visible light into electrons. Which of the following measurements should they make? A. Number of x-rays incident on the input phosphor and number of visible light photons generated at the output phosphor B. Number of visible light photons incident on the output phosphor and number of electrons incident on the photocathode C. Number of visible light photons incident on the photocathode and number of electrons incident on the output phosphor D. Number of visible light photons incident on the photocathode and number of electrons generated by the input phosphor

C. Number of visible light photons incident on the photocathode and number of electrons incident on the output phosphor

The bomb cell and the calorimetry device used in the experiment are what types of thermodynamic systems? The bomb cell was submerged in 500 g of water at room temperature (25°C) in an enclosed and completely thermally isolated calorimetry device. A. Both are closed systems. B. Both are isolated systems. C. The bomb cell is a closed system, and the calorimetry device is an isolated system. D. The bomb cell is an isolated system, and the calorimetry device is a closed system.

C. The bomb cell is a closed system, and the calorimetry device is an isolated system.

How many times greater is the intensity of the sound from a 1.0 T MRI scanner compared to the intensity of the sound from a vacuum cleaner? 1.0 T: 110 dB Vacuum cleaner: 70 dB A. 40 B. 100 C. 1,000 D. 10,000

D. 10,000 dB=10 log10 (I1/I2)

A tissue sample at 275 K is submerged in 2 kg of liquid nitrogen at 70 K for cryopreservation. The final temperature of the nitrogen is 75 K. What is the heat capacity of the sample in J/K? (Note: Assume no heat is lost to the surrounding air.) Specific heat (liquid phase) 2 kJ/kg⋅K A. 0.05 J/K B. 0.1 J/K C. 50 J/K D. 100 J/K

D. 100 J/K

In individuals with glycosuria, glucose that is not reabsorbed in the proximal tubule flows into which of the following nephron structures? A. The distal tubule B. The collecting duct C. The loop of Henle D. The Bowman capsule

C. The loop of Henle The filtrate passes from the Bowman capsule into a long tubule that is composed successively of the following segments: Proximal tubule: In this segment, important nutrients (eg, amino acids, vitamins, salts, glucose, water) are reabsorbed from the nephron and incorporated back into the blood through the peritubular capillaries that surround the tubule. Waste products not filtered by the Bowman capsule are actively secreted from the peritubular capillaries into the nephron. The loop of Henle: This segment is a hairpin structure composed of two limbs. The descending limb extends down into the relatively salty medulla (inner portion of the kidney) and is permeable to water, allowing the passive reabsorption of water via osmosis. The ascending limb transports filtrate out of the medulla and back to the cortex (outer portion of the kidney). This limb is permeable to salt but impermeable to water; this leads to active reabsorption of ions only, which concentrates the medullary interstitial fluid (maintains its saltiness) and prevents its dilution. Distal tubule (Choice A): Antidiuretic hormone (ADH; vasopressin) and aldosterone promote the reabsorption of water in this segment of the tubule. Additional waste products are secreted into the nephron from the peritubular capillaries. Collecting duct (Choice B): ADH and aldosterone act on the collecting duct in the same way they act on the distal tubule. The now-concentrated urine is emptied into the ureters for excretion. Educational objective:Fluid that is filtered by the kidney first enters Bowman's capsule before passing into a long tubule where water is reabsorbed and solutes are selectively reabsorbed or secreted. Waste and metabolites are excreted as urine.

Keratins are a large family of intermediate filament proteins. Scientists studying the effect of keratins in the liver generated model organisms deficient in keratins. These organisms may display abnormal hepatocyte phenotypes because keratin deficiency may reduce the: A. ability of cells to undergo cytokinesis. B. intracellular transport of substances. C. capacity of cells to resist mechanical forces. D. number of cilia on the cell surface.

C. capacity of cells to resist mechanical forces. In this question, scientists are studying the effect of keratins (a large family of intermediate filament proteins) in hepatocytes (liver cells). They generated model organisms deficient in keratins, which would make the organisms' hepatocytes more fragile and unable to withstand/resist mechanical forces. Accordingly, these model organisms may display abnormal hepatocyte phenotypes. (Choice A) Microfilaments are made of actin protein subunits organized into double-stranded rods. Microfilaments help determine the overall shape of a cell and assist in some cellular locomotion. They also are responsible for muscular contractions and forming the cleavage furrow during cytokinesis. Therefore, reduced ability of a cell to undergo cytokinesis would be a result of the cell's being deficient in microfilaments, not intermediate filaments. (Choice B) Microtubules are made of alternating α- and β-tubulin subunits organized into hollow tubes. Microtubules form the mitotic spindle during the cell division process. They also are involved in movement within the cell; for example, they facilitate intracellular vesicular transport. Therefore, reduced intracellular transport of substances would be a result of a deficiency in microtubules, not intermediate filaments, in the cell. (Choice D) Microtubules form the cores of both cilia and flagella. A cell having a reduced number of cilia on its surface would be a result of a microtubule, not intermediate filament, deficiency. Educational objective:The cytoskeleton consists of three types of fibers: microfilaments, microtubules, and intermediate filaments. Intermediate filaments are i

Atpenins are succinate-ubiquinone reductase inhibitors with antifungal properties. Atpenins illustrate the fact that: A. succinate oxidation at Complex II decreases the pH of the intermembrane space. B. protons from FADH2 flow back into the matrix against their concentration gradient. C. electron transfer from Complex II to III is facilitated by ubiquinol in the inner membrane. D. ubiquinone has a higher reduction potential than cytochrome c in the cell membrane.

C. electron transfer from Complex II to III is facilitated by ubiquinol in the inner membrane. (Choices A and B) Although Complex I, III, and IV pump protons into the intermembrane space against their concentration gradient, Complex II does not pump protons, and therefore does not directly contribute to the decrease in pH in the intermembrane space. (Choice D) In the electron transport chain, carriers with a higher reduction potential have a stronger tendency to be reduced (gain electrons). Therefore, electrons are transferred to carriers with higher reduction potentials at each step. Because electrons are transferred from ubiquinol to cytochrome c, this indicates that ubiquinone has a lower reduction potential whereas cytochrome c has a higher reduction potential. Educational objective:Complex II (succinate-ubiquinone reductase, or succinate dehydrogenase) oxidizes succinate to fumarate and transfers electrons to Complex III. Electrons are transferred from flavin adenine dinucleotide (FADH2) to iron-sulfur centers in Complex II, then to ubiquinone (coenzyme Q), which carries them to Complex III through the inner membrane in the form of ubiquinol.

If thin-layer chromatography shows that a distillation of molecules with boiling points above 150 °C results in an impure compound, one can conclude that a possible error made during the distillation was: A. reducing the pressure of the distillation system. B. using a tall fractionating column. C. heating the mixture too quickly. D. placing boiling chips in the mixture

C. heating the mixture too quickly. (Choice A) Compounds with boiling points above 150 °C must be distilled under reduced pressure using vacuum distillation. This decreases the boiling points, preventing decomposition of the compounds. (Choice B) Fractional distillation uses a column to improve separation of compounds by increasing the length of the path the vapor must travel before condensing and dripping into the receiving flask. (Choice D) Boiling chips are used to evenly heat a liquid and prevent superheating. Their use in the distillation would prevent the mixture from abruptly forming large bubbles that could spill over into the receiving flask. Educational objective:Distillation is a technique that separates molecules based on their boiling points, and there are three main types: simple, fractional, and vacuum. The molecule with the lowest boiling point distills before the molecules with higher boiling points. The mixture must be heated slowly to ensure that a lower boiling-point compound evaporates before a higher boiling-point compound and that the molecules are separated.

A student analyzing dividing cells of a certain type under the microscope finds that each daughter cell produced contains half the number of chromosomes as its parent cell. Given this, cells of this type would most likely contain all of the following EXCEPT: A. peroxisomes. B. nuclear pore proteins. C. single-stranded genomes. D. microtubules.

C. single-stranded genomes. Single-stranded genomes, however, can be found in certain viruses but not in eukaryotic cells. Eukaryotic cells instead contain double-stranded DNA genomes. Educational objective:Eukaryotic cells can be distinguished by their unique characteristics. They have a genome with multiple linear chromosomes (double-stranded DNA). They also use meiosis as one mechanism of cell division (sexual reproduction), and they have membrane-bound organelle

The graph below shows the redox titration curve of a 0.05 M Sn2+ solution titrated with 0.1 M Ce4+. The equivalence point indicates the volume of 0.1 M Ce4+ required to fully oxidize all of the Sn2+ in solution. If more than 100 mL of 0.1 M Ce4+ is required to titrate an equal volume of another 0.05 M Sn2+ solution, which of the following could be used to explain the inaccurate equivalence point? A. The volume of the Sn2+ solution has increased. B. The concentration of Sn2+ in solution has increased. C. An impurity that can oxidize Ce3+ back to Ce4+ is present in the Sn2+ solution. D. A metal salt impurity that can also be oxidized by Ce4+ is present in the Sn2+ solution.

D. A metal salt impurity that can also be oxidized by Ce4+ is present in the Sn2+ solution. Choices A and B) The question states that the volume and Sn2+ concentration is the same in both of the titrated solutions. (Choice C) An impurity that could oxidize Ce3+ back to Ce4+ would regenerate some of the added titrant, and this would mean that less than 100 mL (not more) would be needed to reach the equivalence point. Educational objective:Impurities that undergo the same oxidation-reduction behavior as the analyte cannot be distinguished from the analyte and decrease the accuracy of the measured equivalence point in a redox titration.

Researchers hypothesized that administration of canagliflozin reduces blood pressure in patients with T2DM by increasing urine output and reducing total blood volume. A decrease in which of the following would also result in lowered blood pressure? Activation of the renin-angiotensin system Production of aldosterone Secretion of antidiuretic hormone A. II only B. III only C. I and III only D. I, II, and III

D. I, II, and III The renin-angiotensin system (RAS) is a multiorgan molecular cascade activated when BP (or blood volume) falls. A drop in BP causes the juxtaglomerular cells in the kidney to release renin, an enzyme that cleaves the plasma protein angiotensinogen to form angiotensin I. Angiotensin-converting enzyme then cleaves angiotensin I to form angiotensin II. Angiotensin II ultimately raises BP by inducing both the release of aldosterone from the adrenal cortex (increasing BP by increasing blood volume through water retention) and the constriction of arterioles (increasing BP without changing blood volume). Aldosterone is released in response to RAS activation or to an increased serum level of K+. Aldosterone acts on the distal tubules and collecting ducts of nephrons to promote the reabsorption of Na+ and the secretion of K+. Increased reabsorption of Na+ increases the osmolarity, or solute concentration, of the renal interstitial fluid. Elevated osmolarity promotes water reabsorption, which ultimately causes blood volume and BP to increase. ADH is released by the posterior pituitary when BP falls or when blood osmolarity rises. ADH promotes water reabsorption by increasing the permeability of the distal tubule and collecting duct to water. It also induces vasoconstriction, the narrowing of blood vessels. Both of these effects increase BP. Angiotensin II of the RAS pathway, aldosterone, and ADH are hormones that cause BP to increase. Accordingly, a decrease in RAS activation, ADH secretion, or aldosterone production would cause BP to fall (Numbers I, II, and III). Educational objective:Angiotensin II, antidiuretic hormone, and aldosterone all regulate blood pressure. The effect of these hormones on blood pressure can be explained wholly or in part by the modulation of water and salt reabsorption in the kidney

Which statement best describes the function of the nodes of Ranvier? The nodes of Ranvier: A. prevent depolarization from spreading toward the axon soma. B. promote entry of extracellular K+ into unmyelinated axons. C. prevent entry of extracellular Na+ into myelinated axons. D. increase the rate of depolarization toward the axon terminal.

D. increase the rate of depolarization toward the axon terminal.

The refractive indices of the glass optical fiber, polymer lens, and liquid crystal lens described in the passage are denoted as n1, n2, and n3, respectively. The refractive indices of the glass optical fiber and the two focusing lenses are related by which of the following? The incident angle of the laser in the glass fiber was held constant at 45°. The refracted angles for a polymer lens and a liquid crystal lens were 55° and 35°, respectively. A. n1 < n2 and n1 < n3 B. n1 > n2 and n1 > n3 C. n1 < n2 and n1 > n3 D. n1 > n2 and n1 < n3

D. n1 > n2 and n1 < n3 Going from a high n to low n the angle of refraction will get larger-bends away from normal Going from a low n to high n the angle of refraction will get smaller- bends towards normal more Snell's law governs the refraction of light when crossing a boundary of two media with different refractive indices. Light traveling from a medium with a higher refractive index into one with a lower refractive index will have a refracted angle that is greater than the incident angle.

The solutes in an aqueous reaction mixture are separated by extraction. The function of the nonpolar organic solvent is to: A. transfer hydrophilic molecules to the organic layer. B. combine the components of a reaction mixture. C. increase the volume of the solvent. D. remove hydrophobic molecules from the aqueous layer.

D. remove hydrophobic molecules from the aqueous layer.