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The Optometry Admission Test (OAT) is a standardized test designed to measure general academic ability and comprehension of scientific information. The OAT test is sponsored by the Association of Schools and Colleges of Optometry (ASCO) for applicants seeking admission into an optometry program. All schools and colleges of optometry in the United States, the University of Waterloo, and Canada require the OAT.
1. Plant shoots demonstrate negative gravitropism, whereas roots demonstrate positive gravitropism. Which of the following plant hormones mediates this response?
2. Most of the CO2 in blood is converted to carbonic acid in red blood cells. When a body is active, CO2 production increases. Which of the following changes in pH would stimulate increased respiratory rate?
3. The best way to separate isotopes of the same element is to exploit:
4. Describe the correct outer shell electronic arrangement of phosphorous.
5. Alkanes increase in molecular weight
6. A specific combination of atoms that imparts common properties to a series of compounds is
Questions 7 – 8 are based on the following passage:
Cilia and flagella are tubular structures found on the surfaces of many animal cells. They are examples of organelles, sub-cellular structures that perform a particular function. By beating against the surrounding medium in a swimming motion, they may endow cells with motility or induce the medium to circulate, as in the case of gills. Ciliated cells typically each contain large numbers of cilia 2 -10 µm (micrometer) long. In contrast, flagellated cells usually have one or two flagella, and the structures can be as long as 200 µm. For both types of structure, the diameters are less than 0.5 µm.
Although they share similar structures, the motion of the two organelles is somewhat different. Flagella beat in a circular, undulating motion that is continuous. The effective stroke of a cilium’s beat, which generates the power, is followed by a more languid recovery to the original position. During the recovery stroke, they are brought in close to the membrane of the cell. Cilia usually beat in coordinated waves, so that at any given moment some are in the midst of their power stroke while others are recovering. This provides for a steady flow of fluid past gill surfaces or the epithelia lining the lungs or digestive tract.
The construction of both organelles is very similar. A portion of the cell membrane appears to be stretched over a framework made of tubulin polymers. A polymer is a long, chain-like molecule made of smaller units that are strung together. In this case, the subunits are molecules of the protein tubulin. The framework, or skeleton, of a cilium or flagellum consists of 9 pairs of tubulin polymers spaced around the periphery, and two more single polymers of tubulin that run along the center of the shaft. This is called a 9+2 pattern.
The motion of the organelles results from chemical reactions that cause the outer polymers to slide past one another. By doing so, they force the overall structure to bend. This is similar to the mechanism of contraction of skeletal muscle. In cilia and flagella, the nine outer polymer pairs of the skeleton have along their lengths molecules of a rod-shaped protein called dynein. The dynein rods can grasp, or bind to, the neighboring tubulin polymer. Energy is then used to drive a chemical reaction that causes the dynein arms to bend, causing one tubulin polymer to move along the length of the other. Through a coordinated series of thousands of such reactions, the cilium or flagellum will beat.
Cilia have also provided some of the best evidence for the inheritance of traits by a mechanism that does not involve DNA. Paramecium is a single-celled ciliated protist that lives in ponds. In one variety, the stroke cycle of the cilia is clockwise (right-handed). In another variety, it is counter-clockwise (left-handed). When the cells divide, left-handed cells give rise to more left-handed cells, and vice versa. T.M. Sonneborn of Indiana University managed to cut tiny pieces of cell membrane from a left-handed Paramecium and graft them onto a right-handed one. The cell survived, and the direction of the stroke did not change, despite the fact that cilia were now in a cell with a right-handed nucleus and surrounded by right-handed cilia, they continued to rotate to the left. A paramecium reproduces by dividing, and Sonneborn followed the transplanted patch for several generations, but it did not change direction. This suggested that the direction of rotation is a property of the cilium itself, and is not influenced by the DNA in the nucleus. In another experiment, Sonneborn transplanted the nucleus of a right-handed cell into a left-handed cell from which the original nucleus had been removed. The cell’s cilia kept their counter-clockwise direction of rotation. Further, when this cell divided, all subsequent generations maintained it as well. This proved that the direction of rotation could be inherited in a manner completely independent of the chromosomal DNA.
One theory to explain this is the concept of nucleation. According to this idea, the tubulin proteins in left- and right-handed Paramecia are the same, so that the genes that give rise to them are also identical. However, once they begin to chain together in a left- or right-handed manner, they continue to do so. Therefore the direction of rotation does not depend upon the genes, but rather on some basal structure that is passed on to the cell’s offspring when it divides.
7. Cilia and flagella are both
8. According to the passage, where would you expect to find cilia?
9. Which of the following measurements has the most significant digits?
10. A person walks 4 meters in a single direction. He or she then changes directions and walks an additional 9 meters. What is the total magnitude of the displacement of the person?
11. Which of the following expressions is equivalent to the equation 3x2 + 4x - 15?
12. Prizes are to be awarded to the best pupils in each class of an elementary school. The number of students in each grade is shown in the table, and the school principal wants the number of prizes awarded in each grade to be proportional to the number of students. If there are twenty prizes, how many should go to fifth grade students?
1. E: Auxin controls cell wall plasticity and is produced at root and shoot tips. It controls the responses of these structures to light and gravity.
2. A: When the CO2 concentration is high, more carbonic acid is formed, and the body needs to increase respiration to remove it from the blood. Thus, a drop in pH causes an increase in the respiratory rate.
3. D: Isotopes of the same element must have the same chemical behavior, so A, B, and C all represent, in one form or another, chemical behavior. Isotopes differ in mass, and this can be used to separate them by some appropriate physical property.
4. B: Phosphorus is in the third period, so the outermost levels must be 3s, 3p. Phosphorus is in Group 5A, which indicates that it has 5 valence electrons. To fill the 3s and 3p, 2 electrons first fill the s orbital, and then the remaining 3 electrons enter the p orbitals. So, 3s2 3p3.
5. C: Molecular weights are expressed as grams per mole. Each additional carbon atom to the alkane requires two additional hydrogen atoms. The molecular formula of the alkane will therefore increase by -CH2-, which incrementally increases the molecular weight by 14g per mole.
6. A: This is the definition of a functional group. "Substituent" refers to an atom or group of atoms attached to a specific carbon atom within a molecule and describes the structure of the molecule rather than its chemical behavior. A “diluent” is a solvent used to dilute the concentration of a solution. An “eluent” is a solvent used to elute materials in a chromatographic separation process.
9. B: Significant digits indicate the precision of the measurement. Answer B has 5 significant figures. A and C each have 4. D has 3. The leading zeros in Answers A and D and are not counted as significant digits, but zeros at the end of the number (as in Answers A and B) do count. In answer D, the zero in between 2 and 9 is significant.
10. C: Displacement is a vector that indicates the change in the location of an object. Answer A would be correct if the question asked for the total distance the person walked or if the person didn’t change direction. If the person turned around 1800, the displacement could be as small as 5 meters. If the person changed directions only a fraction of a degree, its magnitude would be less than 13 meters, not as large as 13 meters.
11. D: Each term of each expression in parentheses must be multiplied by each term in the other. Thus for D, (x+3)(3x-5) = 3x2+9x-5x-15 = 3x2+4x-15
A. (x-3)(x+5) = x2-3x+5x-15 = x2+2x-15 ≠ 3x2 +4x - 15
B. (x+5)(3+x2) = 3x+15+x3+5x2≠ 3x2+4x-15
C. x(3x+4-15) = 3x2+4x-15x = 3x2-11x ≠ 3x2+4x-15
12. B: First determine the proportion of students in Grade 5. Since the total number of students is 180, this proportion is =0.2, or 20%. Then determine the same proportion of the total prizes, which is 20% of twenty, or 0.2 x 20 = 4.
A. 5 ≠ 0.2 x 20
C. 7 ≠ 0.2 x 20
D. 3 ≠ 0.2 x 20
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