Q Bank Flashcards Preview

Nicole mcat > Q Bank > Flashcards

Flashcards in Q Bank Deck (45)
Loading flashcards...
1

Cystic fibrosis leads to abnormal Cl- and Na+ transport across certain epithelial membranes, leading to thick, viscous mucous. Mucous build-up limits the exocrine function of the pancreas, impairing digestion. Absorption of certain vitamins depends on proper pancreatic function. Which vitamin would likely be deficient in a patient with cystic fibrosis?

Carbohydrate and fat digestion begin in the mouth (fat digestion is minimal) with salivary amylase. Protein digestion begins in the stomach with pepsin. The majority of fat digestion occurs in the duodenum of the small intestine. Without adequate pancreatic function due to cystic fibrosis, the pancreatic lipases are not introduced in sufficient quantity to the duodenum. As a consequence, fat digestion is hindered. With malabsorption of lipids, fat soluble vitamins cannot be effectively absorbed. A, D, E, and K are the fat soluble vitamins and most likely to be deficient in a patient with cystic fibrosis

2

Acetylsalicylic acid is acidic due to the presence of a carboxyl group. Which of the following probably explains why a patient taking aspirin doesn’t typically suffer from stomach pain?

Excess acid in the stomach will cause stomach pain. Typically, aspirin will not have this effect. The stomach is maintained at a pH of 2 due to the presence of HCl. In this acidic environment, acetylsalicylic acid will remain protonated and is minimally soluble. It is only in the small intestine when the pH becomes basic that the solubility of acetylsalicylic acid dramatically increases.

3

Patients with severe acetylsalicylic acid poisoning are often given sodium bicarbonate to improve renal clearance. Which of the following could be the molar solubility of 0.1 M acetylsalicylic acid (Ka = 3 x 10-4) after the addition of bicarbonate?

Acetylsalicylic acid reacts with water in the following manner:

HA + H20 → H3O+ + A-

The equilibrium expression for this reaction is the following:

Ka = ([H3O+][A-])/[HA]

An amount ‘x’ is lost by HA (0.1 -x) and gained by H3O+ and A-. Substituting in these values gives the expression:

3 x 10-4 = x2/(0.1-x).

Because the Ka is so small, simplify the expression.

3 x 10-4 = x2/(0.1)

Solving for x (molar solubility), we determine that it is around 5.5 x 10-2.

The addition of bicarbonate will increase the solubility of acetylsalicylic acid (by removing H+ from the product side of the equilibrium reaction).

4

Gain Loss Theory of Attraction

The “gain-loss theory of attraction” states that if an individual believes that he or she gave a negative first impression to a stranger, but then wins them over, all other things equal, the individual will be more attracted to the stranger

5

Reliable Study

In order for a study to be very reliable, it must produce consistent results.

6

Aggression is probably linked to what part of the brain?

Since fear registers in the amygdala, it is likely that aggression does as well. In addition, the amygdala is part of the limbic system of the brain which is heavily involved in emotion.

7

In- Group Bias

In-Group bias is the tendency to see those in one’s own social group in a more positive light than those in any other group.

8

What is the most likely psychological justification for prescribing disulfram to an alcoholic patient?

The goal of disulfiram administration, which is described in the first passage as causing hangover like symptoms, is to reduce alcohol consumption. These unpleasant symptoms serve as an aversive effect following administration of alcohol. Adding an unpleasant result when presented with a stimulus is an example of punishment.

9

The circulatory system is a closed system with two pumps, the left side of the heart and the right side of the heart. Neglecting volume lost to the lymphatic system, which side of the heart pumps a greater volume of blood?

Both sides of the heart pump equal volumes of blood in healthy individuals.

10

A blood sample undergoes a temperature change such that all of its thermal energy is converted to potential energy. Which of the following best describes its final state?

A substance at absolute zero displays no kinetic (thermal) energy

11

If plaque buildup decreased an artery's diameter by half, what effect would this have on the average kinetic energy of blood passing through the vessel, as compared to an identically-sized vessel its normal physiologic state? (Assume cardiac output is 5 L/min in both cases, and that both vessels have negligible compliance.

In major arteries, it is reasonable to assume that there will be no significant leakage through the endothelium. Therefore the continuity equation (V1A1= V2A2) which states that the velocity of the fluid is inversely proportional to the cross sectional area holds true. This means the velocity is inversely proportional to the square of the radius (πr2 is the cross sectional area for a circular pipe). This gives v ∝ 1/r2. If the diameter is halved, then so is the radius, v ∝ 1/(1/2r)2 which simplifies to v ∝ 4r. Therefore the velocity of the fluid in the narrowed region is four times that of the fluid before the narrowed region. To get kinetic energy use KE = 1/2(ρVv2) where ρ is the density of the fluid and V is the volume and v is the velocity. This equation shows that the kinetic energy is proportional to v2. Thus, KE ∝ (4v)2 or KE ∝ 16v2. So the kinetic energy of the fluid within the narrowed region is 16 times greater than that of the fluid just before the narrowed region

12

possible explanation for why vascular flutter occurs?

The continuity equation shows that the velocity of a fluid in inversely proportional to the cross sectional area. So as the artery narrows the velocity of the fluid increases. Bernoulli's equation states that when the velocity of a fluid increases, the pressure it exerts on its surroundings decreases. When the blood reaches a certain velocity due to the narrowing of the artery, the pressure on the outside of the artery becomes greater than the pressure exerted by the blood inside the artery and the walls of the artery collapse in on themselves. This stops the blood flow and then the walls snap back open. The blood then reenters the region and when it reaches the same velocity as before the walls close once again and the cycle repeats

13

What is the average combined mass of cellular structures, proteins, and other solutes in a 20 ml sample of human blood if the specific gravity of human blood is 1.06?

Specific gravity is the ratio of the density of the fluid of interest to pure water. SG = ρfluid/ρwater. The density of water is 1 g/ml. Since 1.06 = ρblood/ 1g/ml this means that ρblood = 1.06 g/ml. Comparing the density of pure water to that of whole blood shows that 0.06 g/ml or 60 mg/ml of the blood is not from water. This must be from the cells, proteins and other solutes. To solve for the combined mass of these solutes in 20 ml of blood use 60 mg/ml x 20 ml = 1200 mg or 1.2 g. Alternatively, calculate the mass of 20 ml of pure water, 1 g/ml x 20 ml = 20 g and compare it to the mass of 20 ml of whole blood, 1.06 g/ml x 20 ml = 21.2 g; 21.2 g – 20 g = 1.2 g.

14

The amount of work the heart does in one minute if the cardiac output is 6 L/min and the mean arterial pressure is 1.24 x 104 N/m2 is

Work = ΔV x P, where V is volume and P is pressure. Thus, work (joules) can have the units of volume x pressure. Power is work (joules)/time so power can have the units of (volume x pressure)/time. Looking back to the question stem, multiplying the cardiac output by the mean arterial pressure will give an answer that has the units of (volume x pressure)/time.

6 L/min x 1000 mL/L x 1 min/60s = 100 mL/s

Which is the same as 100 cm3/s. Looking at the unit of pressure, we see we need to change cm3 to m3.

100 cm3/s x 1 m3/106 cm3 = 1x 10-4 m3/s.

Now multiply this form of the cardiac output by the pressure.

1.0 x 10-4 m3/s x (1.24 x 104 N/m2) = 1.24 (N x m)/s = 1.24 J/s = 1.24 W

The question now asks for the work done in one minute so we get:

1.24 W x 60 s = 74.4 J.

15

What range of frequencies is most likely to be used for ultrasound investigation of a pregnancy?

Ultrasound uses frequencies higher than human hearing. Humans can perceive sounds in the range of 20 to 20,000 Hz. This means that ultrasound should be above these values

16

The learning theory

posits that attitudes and behaviors are developed through learning, which can be controlled through exposure and conditioning.

17

The functional attitudes theory

functional attitudes theory states that there are four functional areas of attitudes that serve individuals in life: knowledge, ego expression, adaptability, and ego defense.

18

social cognitive theory

states that attitudes are formed through observation of behavior, personal factors, and environment.

19

elaboration likelihood model

states that attitudes are formed and changed through different routes of information processing based on the degree of elaboration

20

The man has memory of a previously traumatic event. When he sees a spider, the similar event results in feelings of anxiety due to the implicit memory of the childhood experience. Implicit memory is controlled by the amygdala

explicit memory of an event is the conscious memory of the experience. This type of memory is controlled by the hippocampus.

21

amygdala and parahippocampal gyrus. These structures are both part of the limbic system, which lie within the forebrain. The dorsomedial prefrontal cortex and anterior cingulate cortex also lie within the forebrain.

midbrain consists of the inferior and superior colliculli.

hindbrain consists of the cerebellum, medulla oblongata, and reticular formation.

22

The oxygen-evolving reaction Ca(OCl)2 (s) → CaCl2 (s) + O2 (g) is initiated with 71 g of Ca(OCl)2 in a 5.5 L sealed chamber with an unknown amount of inert gas. If the resulting oxygen evolved increases the pressure of the chamber by 20%, how many moles of gas were in the chamber initially? Assume all gases are ideal and the temperature of the reaction remains constant.

This question appears to be asking about many things at once, so let's break it down step by step. First, it's not helpful to work with mass of starting reactant when we'll need moles later on, so let's convert that. We find the molecular weight of Ca(OCl)2 is 143 g/mol meaning we start the reaction with roughly 0.5 moles. The oxygen evolved is in a 1:1 ratio, so we know we also produce 0.5 moles of oxygen. The question then essentially relies on answering the following question: if 0.5 moles of gas increase the pressure by 20%, how much was there to start? This is a ratio problem, not a chemistry problem, and can be solved by simply dividing 0.5 by 20% (or 0.2) which gives us 2.5. Said another way: 3 (0.5 + 2.5) is 20% greater 2.5. Therefore the beginning number of moles must have been 2.5 or (B).

23

Which of the following are responsible for the hardening of arteries (atherosclerosis)

LDL, or low-density lipoproteins, are protein-lipid assemblies used in the transport of lipids through the body through blood vessels. Low-density lipoproteins have a higher concentration of lipids than proteins (vice versa for high-density lipoproteins) and contribute to plaque building up on the walls of blood vessels. Erythrocytes are red blood cells. Gastrin is a large, peptide hormone that regulates the secretion of HCl from the parietal cells of the stomach.

24

What is the molecular geometry of the ion AlCl63-

The optimal distribution of 6 substituent groups (and no lone pairs) would be along each axis (x, y, and z); there are four groups on a plane, one up, and one down. This way, all groups are 90° from each other. This means the ion would be octahedral.

25

Transferring a protein from a 1 M electrolyte solution to a 0.1 M electrolyte solution would most likely have which of the following consequences for the protein?

Reducing the ion content of the buffer effectively eliminates the ability of the buffer to stabilize charges on residues (e.g. -COO-Na+). This would cause a reduction in the stability of charged species in solution, resulting in protonation of acidic residues and the deprotonation of basic residues. These two events together neutralize the charges on the compounds in accord with the decreased stability of charges in the new solution.

26

A researcher wishes to conduct an experiment on classical conditioning in rats. Which of the following must happen in the experiment?

Classical conditioning works by pairing neutral stimuli with an unconditioned stimuli, so that during conditioning the neutral stimuli becomes the conditioned stimuli and produces a conditioned response.

27

A ball of weight 20N sits at the bottom of a 100m pool. Buoyancy force is calculated and is determined to be 30N. Approximately how long will it take for the ball to rise to the surface?

We first need to calculate the mass of the object. We know that weight is 20N, which is equal to m*a, with a=9.8 m/s2, thus mass is approximately 2 kg. We can calculate the net force, which is 10N in the upward direction. From this, we know F=ma, thus 10N = 2*a, thus acceleration is 5 m/s2. Because initial velocity is zero, we can use the kinematics equation d=at2/2, thus 100 = 5t2/2. Thus t2=40, thus t is approximately 6 seconds. Thus (B) is the correct answer.

28

Terminal Velocity of an Object

Terminal velocity is the speed at which an object experiences zero acceleration through the medium in which it is moving whereby the restraining force is generated solely by the medium itself. For example, a free-falling object will reach terminal velocity once the drag force of the air is equal to the gravitation pull of the earth. Once the two are in equilibrium, the object will cease to accelerate due to the canceling of the two forces.

29

You are given the following reaction:
A + 2B → C

Three experiments were done to determine the rate law for this reaction. The following results were obtained:
Trial 1: [A] = 0.1, [B] = 0.05, Initial Rate = 1 x 10-4
Trial 2: [A] = 0.1, [B] = 0.1, Initial Rate = 2 x 10-4
Trial 3: [A] = 0.2, [B] = 0.1, Initial Rate = 5 x 10-5

What is the rate law for this reaction?

To solve rate law problems in a systematic fashion by comparing two experiment trials in which the concentration of one reactant is held constant. This can be repeated again to determine the rate law of the other reactant. Thus in this problem, we can first compare trials 1 and 2 since [A] is the same. We see that when [B] doubles from 0.05 to 0.1 M, the rate also doubles. Thus, the rate law for B is 1. Comparing trials 2 and 3 (since [B] is the same), we see that if [A] doubles from 0.1 to 0.2 M, then the rate decreases by a factor of 4. This means the rate law for A is -2. Hence, the rate law is Rate = [A]-2[B]

30

During vacuum distillation, what is the purpose of decreasing the pressure?

Decreasing the pressure of a system decreases the boiling point. This in turn speeds up the distillation and eliminates the need for higher temperatures.