Quiz 1

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University of Nevada, Las Vegas *

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704

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Biology

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May 23, 2024

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Question 1 1.5 / 1.5 pts It is true that a eukaryotic cell does not contain histones. lacks a well-defined nucleus. is smaller than a prokaryotic cell. contains structures called organelles . Eukaryotic cells contain organelles and histones, they have a well-defined nucleus, and are larger than prokaryotic cells. Question 2 1.5 / 1.5 pts An organelle that is responsible for the metabolism of cellular energy is referred to as a/an mitochondrion. endoplasmic reticulum. Golgi complex. nucleolus. Mitochondria play a role in cellular metabolism, cellular respiration, and energy production. The Golgi complex is responsible for processing and packaging proteins from the endoplasmic reticulum, where they are synthesized. The nucleolus is a small, dense structure that contains the ribonucleic acid (RNA), DNA, and DNA-binding proteins.

Question 3 1.5 / 1.5 pts Which statement is correct regarding cellular energy? Oxidative phosphorylation occurs in the mitochondria. Oxidative cellular metabolism is a single reaction making adenosine triphosphate (ATP). Anaerobic glycolysis occurs in the presence of oxygen. Glycolysis is the building of sugar molecules. Oxidative phosphorylation occurs in the mitochondria. This is the mechanism by which the energy produced from carbohydrates, fats, and proteins is transferred to ATP. Glycolysis is a process that breaks down glucose molecules; it produces a net of two ATP molecules. Oxidation is a process during which a pair of electrons are removed and transferred. Oxidative cellular metabolism involves 10 biochemical reactions. Anaerobic glycolysis occurs in the absence of oxygen. Aerobic means in the presence of oxygen. Question 4 1.5 / 1.5 pts Movement of a solute molecule from an area of high concentration to an area of low concentration is called hydrostatic pressure. filtration. diffusion. osmosis. Diffusion is the movement of a solute from an area of high concentration to an area of low concentration. Osmosis is the movement of water down a concentration gradient from an area of higher water concentration to an area of lower water concentration. Filtration is the movement of water and solute through a membrane because of a greater pushing pressure on one side of

the membrane than the other. Hydrostatic pressure is the mechanical force of water pushing against a cell membrane. Question 5 1.5 / 1.5 pts Which are functions of a protein? (Select all that apply.) Cell surface markers Enzymes that drive pumps Pores or transport channels Synapses for cells Proteins may act as transport channels, pores, cell surface markers, enzymes that drive pumps, catalysts, and cell adhesion molecules (CAMs), or they may act as the key components of ATP synthesis. Synapses are the connections between two nerve cells. Question 6 1.5 / 1.5 pts Which statement best describes the cellular function of metabolic absorption? Cells can secrete digestive enzymes. Cells can take in and use nutrients. Cells can produce proteins. Cells can synthesize fats. In metabolic absorption, all cells take in and use nutrients and other substances from their surroundings. The remaining options are not inclusive in their descriptions of cellular metabolic absorption.

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Question 7 1.5 / 1.5 pts Where is most of a cell’s genetic information, including RNA and DNA, contained? Mitochondria Lysosome Nucleolus Ribosome The nucleus contains the nucleolus , a small dense structure composed largely of RNA, most of the cellular DNA, and the DNA-binding proteins, such as the histones, which regulate its activity. The mitochondria are responsible for cellular respiration and energy production. Ribosomes’ chief function is to provide sites for cellular protein synthesis. Lysosomes function as the intracellular digestive system. Question 8 1.5 / 1.5 pts Which cell component is capable of cellular autodigestion when it is released during cell injury? Lysosomes Golgi complex Smooth endoplasmic reticulum Ribosome The lysosomal membrane acts as a protective shield between the powerful digestive enzymes within the lysosome and the cytoplasm, preventing their leakage into the cytoplasmic matrix. Disruption of the membrane by various

treatments or cellular injury leads to a release of the lysosomal enzymes, which can then react with their specific substrates, causing cellular self- digestion . The chief function of a ribosome is to provide sites for cellular protein synthesis. The Golgi complex is a network of flattened, smooth vesicles and membranes often located near the cell nucleus. The smooth endoplasmic reticulum is involved in steroid hormone production and removing toxic substances from the cell. Question 9 1.5 / 1.5 pts Which mode of chemical signaling uses blood to transport communication to cells some distance away? Autocrine Neurotransmitter Paracrine Hormonal Chemical signaling can be classified into three categories: (1) local-chemical mediator, (2) hormone, and (3) neurotransmitter. Hormones are released by one set of cells and travel through tissues or the bloodstream to another set of cells where they produce a response by those cells. In paracrine signaling, cells secrete local chemical mediators that are quickly absorbed, destroyed, or immobilized. Paracrine signaling requires close membrane-to-membrane contact. Paracrine signaling usually involves different cell types; however, cells also may produce signals that they, themselves, respond to, which is called autocrine signaling. Neurotransmitters are released by neurons and cross the synaptic cleft to communicate with the cells they innervate. Question 10 1.5 / 1.5 pts How do cells receive communication from the extracellular fluid surrounding them? Plasma membrane-bound signaling molecules (involving receptors) Protein channel (gap junction)

Chemical messengers such as ligands Hormone secretion such as neurotransmitters Signal transduction involves incoming signals or instructions from extracellular chemical messengers (ligands) that are conveyed to the cell’s interior for execution. The other options do not correctly describe how cells receive communication from the surrounding extracellular fluid. Question 11 1.5 / 1.5 pts What does the loss of the adenosine triphosphate (ATP) during ischemia cause cells to do? Swell because of the influx of nitric oxide (NO) Shrink because of the influx of calcium (Ca) Shrink because of the influx of potassium chloride (KCl) Swell because of the influx of sodium chloride (NaCl) A reduction in ATP levels causes the plasma membrane’s sodium–potassium (Na+–K+) pump and sodium–calcium exchange to fail, which leads to an intracellular accumulation of sodium and calcium and diffusion of potassium out of the cell. (The Na+–K+ pump is discussed in Chapter 1.) Sodium and water can then freely enter the cell, and cellular swelling results. The other options do not accurately describe the result of ATP at the cellular level. Question 12 1.5 / 1.5 pts How do free radicals cause cell damage? Stimulating the release of lysosomal enzymes that digest the cell membranes Giving up an electron, which causes injury to the chemical bonds of the cell membrane

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Transferring one of its charged, stabilized atoms to the cell membrane, which causes lysis Stealing the cell’s oxygen to stabilize the electron, thus causing hypoxia A free radical is an electrically uncharged atom or group of atoms having an unpaired electron. Having one unpaired electron makes the molecule unstable; thus to stabilize, the molecule gives up an electron to another molecule or steals one. Therefore it is capable of forming injurious chemical bonds with proteins, lipids, or carbohydrates—key molecules in membranes and nucleic acids. Free radical damage is not caused by hypoxia, lysosomal enzymes, or transferring atoms. Question 13 1.5 / 1.5 pts What is a consequence of leakage of lysosomal enzymes during chemical injury? Edema of the Golgi body prevents the transport of proteins out of the cell. Shift of calcium out of the plasma membrane occurs, destroying the cytoskeleton. Enzymatic digestion of the nucleus and nucleolus occurs, halting DNA synthesis. Influx of potassium ions into the mitochondria occurs, halting the ATP production. Acid hydrolases from leaking lysosomes are activated in the reduced pH of the injured cell and they digest cytoplasmic and nuclear components. Influx of potassium ions into the mitochondria, edema of Golgi bodies, and calcium destruction of the cytoskeleton are not a consequence of leakage of lysosomal enzymes during chemical injury. Question 14 1.5 / 1.5 pts A healthcare professional is assessing a child whose parents report poor grades in school, trouble paying attention, and “naughty” behaviors that

have become so frequent the child is always in trouble. For which health condition should the professional facilitate testing? Hypoxic injury Lead poisoning Mercury exposure Cadmium injection Decreased academic achievement, IQ, and specific cognitive measures; increased incidence of attention-related behaviors and problem behaviors are related to lead exposure. Hypoxic injury is usually caused by ischemia, which is not apparent in this child. Exposure to mercury poisoning in utero can lead to deafness, blindness, intellectual disability, cerebral palsy, and central nervous system (CNS) defects. The main effects of cadmium poisoning are renal tubular disease and obstructive lung disease. Question 15 1.5 / 1.5 pts In hypoxic injury, why does sodium enter the cell and cause swelling? The lactic acid produced by the hypoxia binds with sodium in the cell. The cell membrane permeability increases for sodium during periods of hypoxia. Sodium cannot be transported to the cell membrane during hypoxia. ATP is insufficient to maintain the pump that keeps sodium out of the cell. In hypoxic injury, movement of fluid and ions into the cell is associated with acute failure of metabolism and a loss of ATP production. Normally, the presence of ATP and ATPase, the active transport enzyme, maintains the pump that transports sodium ions out of the cell. In metabolic failure caused by hypoxia, reduced ATP and ATPase levels permit sodium to accumulate in the cell, whereas potassium diffuses outward. The other options do not accurately describe the cause of the swelling caused by hypoxia.

Question 16 1.5 / 1.5 pts A patient experienced multiple traumatic injuries and received many blood transfusions within a few days of the injuries. For which medical condition should the healthcare professional monitor the patient for? Hemosiderosis Kidney damage HIV infection High blood pressure Hemosiderosis is a condition that occurs only when excess iron is stored as hemosiderin in the cells of many organs and tissues. This condition is common in individuals who have received repeated blood transfusions or prolonged parenteral administration of iron. While blood transfusions can expose a person to infectious diseases, this is not as likely to be a problem since blood products are tested. Kidney damage may occur in patients with traumatic injuries, but is not directly related to the multiple blood transfusions. Question 17 1.5 / 1.5 pts What is the cause of free calcium in the cytosol that damages cell membranes by uncontrolled enzyme activation? Activation of endonuclease interferes with the binding of calcium to protein. Activation of phospholipases, to which calcium normally binds, degrades the proteins. Depletion of ATP normally pumps calcium from the cell. An influx of phosphate ions competes with calcium for binding to proteins.

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If abnormal direct damage occurs to membranes or ATP is depleted, then calcium increases in the cytosol. The other options do not accurately describe the cause of free calcium in cytosol to damage cell membranes. Partial Question 18 1 / 1.5 pts Which statements are true regarding apoptosis? (Select all that apply.) Local cell death after severe and sudden injury A process that deletes cells during embryonic development An active process of cellular self-destruction Causes cell loss in proliferating cell populations Question 19 1.5 / 1.5 pts The function of a histone found in a eukaryote cell focuses on cellular deoxyribonucleic acid (DNA) folding. movement. division. activities. The histones are binding proteins that cause the supercoiling of DNA into chromosomes and do not affect cellular division, movement, or activities. Question 20 1.5 / 1.5 pts Which describes an amphipathic molecule? It is a nonpolar molecule. It is both hydrophobic and hydrophilic.

It is permeable to water only. It is a one-layered structure. The amphipathic molecule is both hydrophobic and hydrophilic. A hydrophilic molecule is a charged, water-loving molecule. A hydrophobic molecule is an uncharged or water-hating molecule. A polar molecule is another name for an amphipathic molecule.

Quiz 1

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