AP Bio Essay
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During an investigation of a freshwater lake, an AP Biology student discovers a previously unknown microscopic organism. Further study shows that the unicellular organism is eukaryotic. (a) Identify FOUR organelles that should be present in the eukaryotic organism and describe the function of each organelle.
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Nucleus-Contains hereditary information/DNA/chromosomes or is the site of RNA synthesis. Ribosomes-Site of protein synthesis. ER-Internal transport or compartmentalization. Rough ER-Protein synthesis/packaging/transport. Smooth ER-Lipid synthesis or detoxification or transport. Mitochondria-ATP synthesis or aerobic/cellular respiration. Chloroplasts, plastids-Light absorption/photosynthesis/carbohydrate synthesis. Vacuole, vesicles-Storage or transport. Cilia/flagella-Motility. Basal bodies-Support cilia/flagella. Centrioles-Assist chromosome movement in mitosis. Golgi bodies-Protein modification/packaging/transport. Lysosomes-Enzymatic hydrolysis of wastes/metabolites/pathogens. Peroxisomes-Catalase/peroxidase function or detoxification.
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Prokaryotic cells lack membrane-bound organelles found in eukaryotes. However, prokaryotes must perform many of the same functions as eukaryotes. For THREE of the organelles identified in part (a), explain how prokaryotic cells carry out the associated functions.
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Nucleus-Hereditary information/DNA/chromosomes or RNA synthesis in cytosol. Ribosomes-Site of protein synthesis. ER-Diffusion of molecules in cytosol. Rough ER-Protein synthesis/transport in cytosol; may be linked to transcription. Smooth ER-Lipid synthesis or detoxification occurs in cytosol. Mitochondria-Other membranes or cytosolic molecules function in ATP synthesis. Chloroplasts-Other membranes or cytosolic molecules function in light absorption/photosynthesis/carbohydrate synthesis. Plastids-Pigments are distributed throughout cytosol or are associated with membranes. Vacuole, vesicles-Inclusion bodies/granules/large molecules in cytosol. Cilia or flagella-Motility via bacterial flagella. Basal bodies-Other structures support flagella. Centrioles-Enzyme-mediated chromosome movement. Golgi bodies-Protein modification/packaging/transport in cytosol. Lysosomes-Secreted enzymes hydrolyze wastes/metabolites/pathogens. Peroxisomes-Production/secretion of catalase or detoxification.
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According to the endosymbiotic theory, some organelles are believed to have evolved through a symbiotic relationship between eukaryotic and prokaryotic cells. Describe THREE observations that support the endosymbiotic theory.
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Mitochondria/chloroplast contain their own DNA. Mitochondria/chloroplast can self-replicate. -chromosomes are circular. -chromosomes lack histones. • Chloroplast chromosomes lack histones. -contain ribosomes that are similar to bacterial ribosomes. -Inner membrane is similar the membrane of prokaryotes.
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General description of endosymbiotic theory
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Prokaryotic cells have been engulfed by and are living within ancestral/precursor eukaryotes.
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The regulation of transpiration is an important homeostatic mechanism in plants. (a) Under controlled conditions, a transpiration experiment was conducted using two plant species. The data collected are shown in the figure below. Using the data from the experiment, calculate the rate of transpiration for species A and species B between the times of 5 and 15 minutes (show your work). Summarize the difference between the two transpiration rates.
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• Calculate transpiration rates, with units (1 point each; 2 points maximum). • Correct setups with incorrect results (1 point maximum).
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Summarize the difference between the rates
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Species A is losing water or transpiring faster than species B.
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Identify and explain THREE different structural or physiological adaptations that could account for the different transpiration rates of species A and B.
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Cuticle-Thicker cuticle decreases transpiration. Stomata number-Increased number increases transpiration. Stomata location-Underside location decreases transpiration. Stomata size-Larger stomata increase transpiration. Surface area of leaves-Increased surface area increases transpiration. Root size or structure-Affects rate of water absorption, amount of water lost.
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Pressure Potential/Solute Potential
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Water will move from the area of high pressure to the area of low pressure. Solute potential Water will move from the area of high solute potential (low solute concentration) to the area of lower solute potential (higher solute concentration).
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Ionization constant (i)
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Greater ionization decreases water potential/increases water movement, OR Decrease in ionization increases water potential/decreases water movement.
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Concentration (C)
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Increase in concentration decreases water potential/increases water movement, OR Decrease in concentration increases water potential/decreases water movement.
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Pressure Constant (R)
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No change in water potential/movement
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Temperature (T)
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Increase in temperature decreases water potential/increases water movement, OR Decrease in temperature increases water potential/decreases water movement.
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Discussion:
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Discussion stating that the formula allows osmotic potential or water movement to be calculated or predicted
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Describe cell cycle
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• Interphase (including, if specified, G1, S, G2 subphases, correctly ordered): Chromatin dispersed in nucleus; nuclear envelope and nucleoli are intact and functional; DNA is replicated here. • G1, G2: Cell growth. • S: DNA replication. • Mitosis: Nuclear division. • Prophase: Chromosomes begin to condense from chromatin; spindle apparatus assembled. • (Prometaphase): Nuclear envelope disperses, nucleoli disperse, chromosomes connect to spindle apparatus fibers and begin to show motility. • Metaphase: Chromosomes reach maximum condensation and align on metaphase plate/plane. • Anaphase: Two-chromatid chromosomes split into two daughter (one-chromatid) chromosomes; chromosomes move to opposite poles of the spindle apparatus. • Telophase: Chromosomes disperse back to chromatin form, nuclear envelope reassembles, nucleoli reassemble. • Cytokinesis: If this occurs, it is normally coordinated with telophase; cell division.
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Kinetochores • Microtubules • Motor proteins • Actin filaments
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• Kinetochores: Located in centromeres of condensed chromosomes; microtubule attachment sites necessary for chromosome positioning and movement. • Microtubules: Fundamental structural element of the spindle apparatus; framework on which chromosome motility is generated; define axis of division and cytokinesis. • Motor proteins (correct location and function must be specified): In kinetochores, move chromosomes during mitosis, including anaphase separation; involves kinesins and dyneins. OR In animal cell cleavage furrow, generate force to pinch cell in two; involves myosins. • Actin filaments: Assemble under the membrane at the cytokinesis site; interact with myosin motor proteins to generate force to pinch cell in two; also interact with astral microtubules of the spindle to position the spindle apparatus in the cell.
