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AP Labs 1-4

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Ashley Duffy

on 28 April 2011

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Transcript of AP Labs 1-4

Water potential in potato cells was determined in the following manner. The initial masses of six groups of potato cores were measured. The potato cores were placed in sucrose solutions of various molarities. The masses of the cores were measured again after 24 hours. Percent changes in mass were calculated. Components of water potential:
1. Solute Potential (measure of the free energy of water)
2. Pressure Potential (maximum osmotic pressure that could develop in a solution if it were separated from distilled water by a selectively permeable membrane)
3. Matrix Potential (magnitude of matrix potential depends on the distances between solid particles, the width of the menisci, and the chemical composition of the solid matrix)
A. B. Water potential is important for the movement of water in plants because it is required to move water from areas of high water potential such as the roots, to areas of low water potential like the leaves. C. In a 0.0 M sucrose solution a typical animal cell would take in water and expand because the animal cell would have a higher solute concentration than the sucrose solution. (Hypertonic) In a 0.1 M sucrose solution a typical animal cell would lose water and shrivel up because the animal cell would have a lower solute concentration than the sucrose solution. (Hypotonic) AP Lab 1 Molarity of Sucrose in beaker Percent Change in Mass AP Lab 2 An experiment was conducted to measure the reaction rate of the human salivary enzyme -amylase. Ten mL of
a concentrated starch solution and 1.0 mL of -amylase solution were placed in a test tube. The test tube was
inverted several times to mix the solution and then incubated at 25°C. The amount of product (maltose) present
was measured every 10 minutes for an hour. The results are given in the table below. A. Time in minutes Maltose Concentration Rate of reaction:
0-10 minutes 0.51 micrometers/ minutes
10-20 minutes 0.35 micrometers/ minutes
20-30 minutes 0.18 micrometers/ minutes B. A change in reaction rate was observed after 30 minutes because as the enzyme was used up the rate of reaction began to slow down since there was less of the enzyme remaining to react. C. I would predict these results because doubling the enzyme concentration allows the reaction to occur twice as fast because there is double the amount of enzyme available to react with the substrate. D. Two environmental factors that can change the rate of an enzyme-mediated reaction are temperature and pH. Increasing the temperature will increase the rate of reaction because the heat provides extra energy and speeds up the enzyme particles. Decreasing temperature decreases the rate of reaction because the enzyme particles begin to move slower. Changing pH changes the rate of reaction depending on the original pH of the solution. If the solution is basic, then increasing the pH would speed up the reaction, but if the solution is acidic then decreasing the pH would speed up the reaction. Changes in pH change the rate of reaction based on the solution pH by increasing the concentration of the acid or the base. AP Lab 3 Meiosis reduces chromosome number and rearranges genetic information. A. B. C. Trisomy 21 (down syndrome) is when a person has an extra copy of chromosome 21. Some effects on the phenotype of a person with down syndrome are:
•Decreased muscle tone at birth
•Flattened nose
•Separated joints between the bones of the skull (sutures)
•Small ears and mouth
•Upward slanting eyes
•Wide, short hands with short fingers
•White spots on the colored part of the eye (Brushfield spots)
•Impulsive behavior
•Poor judgment
•Short attention span
•Slow learning
This abnormality could result from a defect in meiosis because humans are supposed to receive one copy of each chromosome from both parents, but if a person receives three copies of chromosome 21, then they will develop Trisomy 21.
Rearrangement of genetic information begins in Prophase 1 of meiosis because this is when the chromosomes group in pairs of identical chromosomes called homologous pairs that come from the two parents. The homologous pairs then break apart and switch places during crossing over.
Reduction occurs during Anaphase 1 because that is when the chromosomes move to opposite sides of the cell and the cell begins to pull apart so that two new cells will be formed and will inherit identical genetic information and have half the original number of chromosomes . Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occurs without fertilization by a male. The genomes of the offspring are exactly the same as that of the parent because they receive the diploid number of chromosomes from the parent, and because they are only receiving genes from one parent instead of two. AP Lab 4 Biological molecules can be separated by using chromatographic techniques. The diagram above shows the separation of several spinich leaf pigments by paper chromatography. A. B. C. R=distance of pigment travelled/distance solvent travelled
Paper chromatography can be used to separate pigments based on their chemical and physical
properties because when a colored chemical sample is placed on a filter paper, the colors separate from the sample by placing one end of the paper in a solvent. As the solvent diffuses up the paper it dissolves the various molecules in the sample based on the polarities of the molecules and the solvent. The various solubilities cause the different color molecules to leave solution at different places as the solvent continues to move up the paper. The more soluble a molecule is, the higher it will migrate up the paper. The size of the molecule also affects the distance a pigment travels because smaller molecules move further up the paper than the larger molecules.
Pigments absorb light, and their color comes from the wavelengths of light that are reflected and not absorbed. Accessory pigments absorb energy that chlorophyll a does not absorb, and include chlorophyll b, xanthophylls, and carotenoids. During light dependent reactions, light strikes chlorophyll a to excite the electrons to a higher energy state. This energy is used in photosynthesis and is converted to ATP and NADPH in Photosystem I and Photosystem II.
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