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Transcript
Cell Biology Sample Free Response Questions The following data were collected by observing subcellular structures of three different types of eukaryotic cells. RELATIVE AMOUNTS OF ORGANELLES IN THREE CELL TYPES Based on an analysis of the data, identify a likely primary function of each cell type and explain how the data support the identification. (3) Cell Type Smooth ER Rough ER Mitochondria Cilia Golgi Bodies X Small amount Small amount Large number Present Small amount Y Large amount Large amount Moderate number Absent Large amount Z Absent Absent Absent Absent Absent This was a 3 point question on last year’s exam… Cell Type X Identify function • Locomotion • Movement / surface transport • Secretion / exocytosis • Protein synthesis Y • • Lipid/hormone synthesis Detoxification Explain how data support identification (1 point each correct pair). NOTE: No points for identification without explanation. Has cilia for movement and large amounts of mitochondria to provide energy for locomotion of cell itself AND (ciliated protist) or movement of particles (mucus /oocyte) along cell surface AND Has large amounts of rough ER and Golgi to produce and package proteins AND Has large amounts of smooth ER to produce lipids / hormones Cell Z Oxygen transport in animal cells AND • Water transport in plant cells • Epidermal cells (stratum AND corneum, cork, nails) • Ground tissue (schlerenchyma) AND • Vascular tissue (xylem) • Maximizes volume / AND space available (hemoglobin, oxygen) • Is a dead cell/is AND undergoing apoptosis • • Transport OR • Protection OR • Support OR • Storage OR • No function OR Does not require these organelles The membranes of the rough endoplasmic reticulum have a very large surface area. In one or two sentences, describe how a large surface area aids the activities of the structure. (2) • Large amounts of surface area provide ample areas for membrane bound enzymes to carry out catalytic functions. • These enzymes can modify and package proteins for export. Glycoproteins produced in the rough endoplasmic reticulum may ultimately be exported from the cell. • In two or three sentences, describe the pathway of the glycoprotein from the ER to the outside of the cell. (3) • Glycoproteins are placed in vesicles, which are actively transported to the Golgi apparatus for further processing. • In the Golgi, the glycoproteins are readied for leaving the cell, then transported to the cell membrane by vesicles which bud off the trans side of the Golgi body. • The vesicles fuse with cell membrane, releasing the glycoprotein into the intercellular matrix. Living cells are highly organized and regulated. Describe the structure of the plasma membrane. • Plasma membranes are composed of a lipid bilayer. Phospholipids are amphipathic; the phosphate head faces the interior and exterior of the cell, and the non-polar tail forms a hydrophobic barrier that keeps out ions and large polar molecules. Explain how the plasma membrane contributes to the regulation of the cell. • Membrane proteins allow for large polar molecules and ions to enter the cell via specific channels. • Non-polar molecules are free to diffuse into the cell. • Pump proteins are able to “grab” substances using active transport (ATP) to pump substances in or out of the cell, as needed. What evidence supports the theory that chloroplasts and mitochondria are evolved from prokaryotic cells? • Chloroplasts and mitochondria have their own circular pieces of DNA, like prokaryotes. • Their ribosomes, which are produced by the organelles themselves, are similar to prokaryotes and different from the rest of the ribosomes in the cell. • Chloroplasts and mitochondria divide by binary fission, like prokaryotes. The idea of surface area is an important concept in biology. • Explain how surface area plays a critical role in the digestive system. • Large amounts of surface area allow for maximum nutrient absorption in the stomach and small intestine. In 1941, Daveson and Danielli proposed a trilaminar structure of the cell membrane. The model consisted of a layer of lipid with a layer of protein on either side. Describe the current model for the cell membrane. The fluid mosaic model consists of a lipid bilayer with proteins embedded throughout. Polysaccharides (glycogen in animals) are often attached to phospholipids and proteins, and have regulatory functions, acting as receptors for incoming messages and recognition markers for immune cells. Membrane proteins can also be enzymes, portals for entry of molecules that do not pass easily, and pumps that can import or export substances. Describe and discuss THREE differences between prokaryotic and eukaryotic cells. • Eukaryotes contain organelles, which perform specialized functions within cells. Prokaryotes do not have organelles. • Eukaryotes have chromosomes contained within a nuclear membrane. Prokaryotes have a single circular chromosome that is not bound within a membrane. • Eukaryotic cells are 10-100 times larger than prokaryotic cells, grow more slowly, and have a lower surface area/volume ratio. Eukaryotes use oxygen for respiration, which prokaryotes do not. Identify the cell organelle shown in the micrograph below. • Mitochondrion Identify the structure labeled A and explain how it is adapted for the organelle to function efficiently. • Cristae (inner membrane) provide additional surface area for the enzymatic reactions of respiration.