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Question 1 1 / 1 pts A cytoskeletal component requires ATP for its polymerization and contains subunits that are observed to undergo treadmilling. That cytoskeletal component is a/an: Tubulin Microtubule Keratin Actin filament Intermediate filament Actin filament is the correct answer. Acti...

Question 1 1 / 1 pts A cytoskeletal component requires ATP for its polymerization and contains subunits that are observed to undergo treadmilling. That cytoskeletal component is a/an: Tubulin Microtubule Keratin Actin filament Intermediate filament Actin filament is the correct answer. Actin filaments require ATP for polymerization, and subunits undergo treadmilling as they make their way through an F-actin polymer. Intermediate filaments have stable structures and do not undergo dynamic assembly or disassembly processes. Keratin is a type of intermediate filament. Microtubules are composed of tubulin heterodimers. They require GTP for their polymerization. Additions and subtractions of tubulins from microtubules occur from the same end of the structure. Question 2 1 / 1 pts A microtubule is observed to disassemble quickly after a period of rapid growth. Which of the following most likely occurred to this particular microtubule to stimulate its breakdown? Severing by gelsolin Formation of its ATP cap Loss of its GTP cap Binding by dynein Twisting by cofilin Loss of its GTP cap is the correct answer. Loss of the GTP cap results in rapid disassembly of microtubules. Dynein is a microtubule motor protein that enables microtubules to facilitate the movement of cilia and flagella and of intracellular cargo. ATP is not part of a microtubule structure. Gelsolin and cofilin are actin-binding proteins that stimulate the breakdown of complex actin structures. Question 3 1 / 1 pts A vesicle within a cell must be transported to another region of the cell along the microtubules. Which of the following proteins may be involved in catalyzing this transport? Dystrophin Spectrin Myosin Vimentin Kinesin Kinesin is the correct answer. Kinesin and dynein are families of microtubule motor proteins that facilitate intracellular transport along microtubules. Dystrophin, myosin, and spectrin are actin- binding proteins. Vimentin is a type of intermediate filament. Question 4 1 / 1 pts Actin polymerization may function to control or regulate: Resilience of tissue such as cartilage. Changes in the physical state of the cytosol. Chromosomal movement during cell division. Provide rigid structural stability to the cytoplasm. Strength within connective tissues The correct answer is changes in the physical state of the cytosol. Actin polymerization controls the physical state of the cytosol and the transition from gel to sol. Microtubules, composed of tubulin, regulate chromosomal movements in cell division. Intermediate filaments provide structural stability to the cytoplasm. Unlike actin and microtubules that have dynamic changes in structure, intermediate filaments are longer- lived more permanent structures and may be likened to rigid supports. Resilience is a property attributed to proteoglycans in the extracellular matrix, not to cytoskeletal components such as actin. Collagen and elastin lend strength to the ECM in connective tissues. Question 5 1 / 1 pts A 24-year-old female patient diagnosed with Hodgkin's disease is treated with combination chemotherapy. Her drug regimen includes Velban which is known to inhibit microtubule formation. Therefore, which of the following processes will be altered/impaired by Velban? Production of filamentous actin from G-actin monomers within malignant cells. Treadmilling of filamentous tubulin monomers in an ATP-dependent process. Stabilization of malignant cell membranes and protection from stretching forces. Formation of the mitotic spindle with the arrest of malignant cells in mitosis. Transformation of cytosol in malignant cells from the gel to the sol states Formation of the mitotic spindle with the arrest of malignant cells in mitosis is the correct answer. Inhibitors of microtubule formation such as Velban will prevent mitotic spindle formation with the arrest of malignant cells in mitosis. Actin is not affected so the formation of F-actin will continue and transformation from gel to sol state, regulated by actin, will also continue in the presence of the drug. Tubulin monomers are globular heterodimers, not filamentous. And GTP, not ATP, is used in the formation of microtubules. Treadmilling is usually described for actin, not for microtubules. Question 6 1 / 1 pts Which of the following properties is unique to cell adhesion mediated by cadherins? Cadherins on one cell bind to the glycosylated ligands on another cell. Cadherins are transmembrane proteins; other adhesion molecules are intracellular. Cadherins have homophilic binding, with other cadherins serving as their ligands. Cadherins mediate bidirectional signaling between the cytoskeleton and the ECM. Cadherins mediate cell-to-matrix adhesion, not cell-to-cell adhesions. The correct answer is, cadherins have homophilic binding, with other cadherins serving as their ligands. Cadherins have homophilic binding, with other cadherins serving as their ligands. The unique characteristics of selectins, not cadherins, is that they bind to carbohydrate- containing ligands. All adhesion molecules are transmembrane proteins that can mediate cell-to-cell adhesions. Integrins facilitate cell-to-cell-to-ECM adhesions and have inside- out and outside-in signaling. Question 7 1 / 1 pts Fibronectin is the ligand of a particular adhesion molecule. Therefore, that adhesion molecule most likely belongs to which family? Selectins Cadherins Integrins Collagens Immunoglobulin superfamily Integrins is the correct answer. Fibronectin is a component of the ECM and integrins are the type of adhesion molecule that can mediate cell-to-ECM adhesions. Cadherins, immunoglobulin superfamily members, and selectins mediate cell-to-cell adhesion only. Collagen is not an adhesion molecule but a fibrous protein within the ECM. Question 8 1 / 1 pts Which of the following cytoskeletal components is associated with kinesin? Microfilament Microtubule Lamin A Keratin Neurofilament Question 9 1 / 1 pts Which of the following consists of globular actin monomers linked into a double helix? Neurofilament Microtubule Lamin A Microfilament Keratin Question 10 1 / 1 pts A stress fiber contains which of the following pairs of proteins? Tubulin - Kinesin Actin - Integrin Tubulin - Cadherin Tubulin - Dynein Actin - Myosin Question 11 1 / 1 pts Which kind of cytoskeletal filaments are found in microvilli and cilia? Microvilli contain actin filaments; cilia contain microtubules. Microvilli contain microtubules; cilia contain actin filaments. Microvilli contain actin filaments; cilia contain intermediate filaments. Microvilli contain microtubules; cilia contain intermediate filaments. Microvilli contain intermediate filaments; cilia contain microtubules. The correct answer is microvilli contain actin filaments; cilia contain microtubules. Microvilli contain actin, not microtubules. Question 12 1 / 1 pts What is the function of the actin cytoskeleton? Provides mechanical stability for the nuclear envelope. Creates the 3-D structure of the Golgi. Provides tracks for kinesin motors. Forms the mitotic spindle. Forms the contractile ring during cytokinesis. Question 13 1 / 1 pts Which of the substances listed below is most likely to be associated with a centriole? Histone H2A Actin Tubulin Na+/K+ -ATPase Cholesterol Question 14 1 / 1 pts What is the structure shown in the accompanying transmission electron micrograph (TEM)? This is a cross-section of an actin filament. This is a cross-section of a microtubule. This is a cross-section of a basal body. This is a cross-section of a cilium. Question 15 1 / 1 pts Each of the panels in the accompanying figure shows one of the three cytoskeletal filament networks inside the cell that has been labeled with a specific fluorescent marker. Select the row that has the correct matching of the micrograph and filament type. Filament Type Micrograph Filament Type Micrograph Filament Type Micro Intermediate Actin A Microtubules Filaments Microfilaments Actin Intermediate B Microtubules Microfilaments Filaments  Intermediate Actin C Microtubules Filaments Microfilaments A C B Row A is the correct answer. Note that the actin microfilaments are almost exclusively found under the plasma membrane and not deep in the cytoplasm or around the nucleus. Note that the microtubule network has a bright aggregation of filaments on one side of the nucleus. This is the centrosome, or microtubule organizing center. Note that the intermediate filament network runs throughout the nucleus and wraps completely around the nucleus. Question 16 1 / 1 pts The stability and arrangement of actin filaments as well as their properties and functions depend on which one of the following? Motor molecules, such as kinesin Intermediate filament proteins Microtubules The structure of the actin filaments Actin-binding proteins Actin-binding proteins is the correct answer. The stability, arrangement, and functions of actin filaments depend on the actin-binding proteins. The fundamental structure of the actin molecule is the same no matter what the function or arrangement in a cell. Acting-binding proteins have a variety of functions: 1. tropomyosin strengthens actin filaments 2. fibrin and villin are actin-bundling proteins 3. filamin and gelsolin regulate transformation from the sol to the gel state 4. members of the myosin II family are responsible for sliding filaments 5. myosin I (minimyosin) is responsible for the movement of vesicles on filaments 6. spectrin cross-links the sides of actin filaments to the plasma membrane. Question 17 1 / 1 pts Inhibition of actin assembly by cytochalasins would interfere primarily with which one of the following? The structure of centrioles Separation of chromosomes in anaphase of the cell cycle Vesicular transport between the Golgi apparatus and cell membrane. Ciliary movement Phagocytic activity by macrophages Phagocytic activity by macrophages is the correct answer. Cytochalasins are potent inhibitors of cell motility and other cellular events that depend on actin assembly: cytokinesis, which is conducted by the actin-containing contractile ring; phagocytosis; and formation of lamellipodia. Cytochalasins bind to the plus end of actin filaments and prevent further polymerization. The movement of chromosomes in anaphase of the cell cycle depends on the disassembly of microtubules at the kinetochore in anaphase A and addition at the plus end of the polar microtubules in anaphase B. Ciliary movement, vesicular transport, and the structure of centrioles depend on microtubules. Question 18 1 / 1 pts A 50-year-old man attends the hottest Indianapolis 500 race in decades and sits with the sun facing him; there is no breeze. He has a history of borderline high uric acid. Dehydration during the race triggers uric acid crystal formation in his foot. The foot becomes sore, red, hot, and swollen. He drinks about 2 L of water and soda at the race and two more liters at home. However, he is anuric (complete suppression of urine formation) for 10 to 12 hours. His physician prescribes colchicine as an anti-inflammatory. Colchine acts on which intracellular structure? Intermediate filament Microtubule Microfilament Centrosome Desmosome Question 19 1 / 1 pts What family of membrane proteins does a cell most commonly use to attach itself to its non-cellular surroundings? Cadherins Integrins Importins Keratins Lamins Question 20 1 / 1 pts Which class of cellular adhesion molecule (CAM) is primarily used to link one cell to another cell of the same type? Selectins Immunoglobulin superfamily Filopodium Cadherins Integrins Question 21 1 / 1 pts A 13-year-old boy falls off his skateboard and scrapes his elbow on the concrete. To heal this wound, fibroblasts will migrate into the injured site to remodel the tissue. The accompanying micrograph shows a crawling fibroblast in tissue culture. The arrows point to the leading edge of the cell, which always acquires a particular shape in a crawling cell. What is the name of the structure that the leading edge of a crawling cell forms? Flagellum Cilium Lamellipodium Desmosome Stress fiber Cranial nerve ganglia are (i) part of what nervous system and (ii) axon fascicles in the spinal cord are part of what nervous system? Autonomic nervous system – peripheral nervous system Autonomic nervous system – central nervous system Peripheral nervous system – peripheral nervous system Central nervous system – central nervous system Central nervous system – peripheral nervous system Peripheral nervous system – central nervous system (i) The peripheral nervous system refers to parts of the nervous system outside of the brain and the spinal cord. It includes the cranial nerves, spinal nerves and their roots and branches. (ii) The central nervous system includes the brain and spinal cord. A collection of nerve fibers (axons) in the central nervous system is called "a tract". Where a collection of nerve fibers in the peripheral nervous system is simply called "a nerve". Question 2 1 / 1 pts Which of the following is true concerning a spinal nerve? It contains afferent and efferent axons It contains only efferent axons It contains only afferent axons It is part of a central nervous system tract It is also called a dorsal primary rami Spinal nerves arise from the spinal cord as rootlets which then converge to form two nerve roots: 1- An anterior (ventral) nerve root, consisting of motor (efferent) fibers. 2- A posterior (dorsal) nerve root, consisting of sensory(afferent fibers. The anterior and posterior nerve roots unite, within or just proximal to the intervertebral foramen, to form a mixed(both motor and sensory) spinal nerve. Question 3 1 / 1 pts Which of the following is true concerning somatic innervation of skeletal musculature? The efferent signal is carried through both central and peripheral parts of the nervous system Innervation requires three neuronal chain The axon modality type is called GVE Lower motor neurons are located in the dorsal horn of the spinal cord The efferent signals are only found in ventral primary rami The efferent neurons send signals from the brain to the muscles. The cell bodies of efferent neurons are located within the central nervous system. Their purpose is to take signals from the central nervous system to the peripheral nervous system. The efferent neurons within the peripheral nervous system synapse with the muscle at the neuromuscular junction to cause muscle to contract. Question 4 1 / 1 pts The term central nervous system refers to the: Brain and cranial nerves Brain and spinal cord Spinal nerves, spinal cord and brain Spinal cord and spinal nerves Question 5 1 / 1 pts The peripheral nervous system consist of: the brain and spinal cord The spinal and cranial nerves the brain only cranial nerves only spinal nerves only Question 6 1 / 1 pts Collections of nerve cell bodies inside the Peripheral nervous system are called: Nuclei Tracts Axons Ganglia A ganglion is a cluster of interconnecting nerve cell bodies found in the peripheral nervous system. Which of the following lipid motions is the slowest? Rotational diffusion Protrusion Flip-flop Lateral diffusion Flip-flop of particular lipids is required to distribute lipids among the two leaflets. This is carried out by proteins called flippases, floppases, and scramblases. They also help preserve the sidedness of some of the lipids. Question 2 1 / 1 pts What is the type of bond that connects fatty acids to the glycerol backbone in fat? Ionic Ester Ether Peptide Amide Covalent Ester bond is correct. Question 3 1 / 1 pts Which of the following lipid headgroups is not found in glycerol-phospholipids: Galactose Choline Inositol Serine Ethanolamine Galactose is a headgroup for galactocerebroside, but not for any of the four canonical glycerol-phospholipids. Question 4 1 / 1 pts Which type of phospholipase cleaves phosphatidylinositol 4,5 bisphosphate to generate Inositol trisphosphate? Type B Type C Type A1 Type A2 Type D Type C is correct. Question 5 1 / 1 pts The glycocalyx is principally made of which of the following? Carbohydrates Hemes Nucleic acids Proteins Lipids The glycocalyx is mainly formed from glycolipids and glycoproteins, where the dense area outside the membrane per se, is the carbohydrate chains. Question 6 1 / 1 pts The core of phospholipid bilayers is best described as which of the following: Water filled Polar Amphipathic Charged Hydrophobic Hydrophobic is correct. Question 7 1 / 1 pts Which of the following lipid motions is the fastest? Flip-flop Lateral diffusion Rotational diffusion Protrusion Protrusion is correct. Question 8 1 / 1 pts The major normal role of cholesterol in the human body is to do which of the following: Form intracellular inclusions Make bile Stiffen arteries Moderate membrane fluidity Cause dietary restrictions Moderating membrane fluidity is considered the most important role for cholesterol in most mammalian membranes. PartialQuestion 9 0.67 / 1 pts Which of the following lipids are found only on the interior (cytoplasmic) leaflet. Select all that apply. Phosphatidyl choline Phosphatidyl serine Cholesterol Sphingomyelin Galactocerebroside Phosphatidyl Inositol Phosphatidyl Ethanolamine Question 10 1 / 1 pts Which of the following bonds is found in sphingolipids and not in glycerophospholipids: Amide Peptide Ester Ether Covalent Amide bonds is correct. Question 11 1 / 1 pts A plasma membrane is rich in poly-unsaturated fatty acids. What would you expect the effect of cholesterol in such membranes to be? Cholesterol will cause atherosclerotic plaques Cholesterol prevents lipid flip-flop Cholesterol will make the membrane more fluid Cholesterol will stiffen the membrane Cholesterol just takes up space in the membrane A membrane with lipids with a high percentage of poly-unsaturated fatty acids will be highly fluid. The presence of cholesterol will somewhat lessen the fluidity. Question 12 1 / 1 pts Which of the following enzymes could convert phosphatidylcholine into a detergent? Select all that apply Phospholipase A2 Phospholipase A1 Phospholipase B Phospholipase C Phospholipase D Phospholipase A1 and Phospholipase A2 are the best answers. Phospholipase B is also a possible answer. Cleaving one of the fatty acid groups will reduce the size of the hydrophobic parts and the headgroup will remain the same size. These enzymes, phospholipase A1 and A2, generate lyso-phosphatidyl choline, which can act as a detergent. Typically lyso-PC is present in low quantities in membranes and serves signaling functions rather than act as a detergent. Question 13 1 / 1 pts Sphingolipids differ from glycerol-phospholipids by which of the following characteristics? Sphingolipids have a glycerol basis structure Sphingolipids have a glycerol basis structure Sphingolipids have amide bonds Sphingolipids are only located on the outer leaflet of the membrane Sphingolipids are only located on the outer leaflet of the membrane Sphingolipids have amide bonds is correct Question 14 1 / 1 pts Which variety of lipids contains ether bonds? Sphingolipids Glycolipids Plasmalogens Cardiolipins Glycerophospholipids Cholesterol esters