Unit I: The Cell
1. It is true that a eukaryotic cell:
A. Is smaller than a prokaryotic cell.
B. Contains structures called organelles.
C. Lacks a well-defined nucleus.
D. Does not contain histones.
Eukaryotic cells contain organelles and histones, they have a well-defined nucleus, and are larger than prokaryotic cells.
2. The function of a histone found in a eukaryote cell focuses on cellular:
D. Deoxyribonucleic acid (DNA) folding
The histones are binding proteins that cause the supercoiling of DNA into chromosomes and do not affect cellular division, movement, or activities.
3. An organelle that is responsible for the metabolism of cellular energy is referred to as a/an:
A. Golgi complex
C. Endoplasmic reticulum
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.
4. Which statement best describes a desmosome?
A. A desmosome is a barrier to diffusion.
B. Desmosomes hold cells together by continuous bands.
C. A desmosome is a communicating tunnel.
D. Desmosomes function as a zona occludens.
The desmosome is a type of cell junction. The other two types include tight junctions and gap junctions. Desmosomes hold cells together by forming a continuous band of epithelial tissue or belt (or button like) points of contact. They are also a source of structural stability. Tight junctions serve as barriers to diffusion and prevent the movement of substances through transport proteins. Gap junctions are clusters of communicating tunnels.
5. Which statement describes the function of a second messenger?
A. Extracellular ligand that binds with membrane-bound receptors
B. Intracellular enzyme that once will trigger a cascade of intracellular events
C. Chemical messenger that opens specific channels in the cell membrane
D. Chemical messenger that blocks a membrane-bound receptor signal
The binding of a ligand to a cell surface receptor triggers the activation of intracellular second messengers. Second messengers activate signal transduction pathways in the cell that can initiate different intracellular events. Cyclic adenosine monophosphate (cAMP) and calcium (Ca++) are the two major second-messenger pathways. First messengers are the extracellular ligands that bind to cell surface receptors. Binding of first messengers can result in the opening or closing of specific cell membrane channels or the activation of second messengers.
6. Which statement is correct regarding cellular energy?
A. Glycolysis is the building of sugar molecules.
B. Oxidative cellular metabolism is a single reaction making adenosine triphosphate (ATP).
C. Oxidative phosphorylation occurs in the mitochondria.
D. Anaerobic glycolysis occurs in the presence of oxygen.
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.
7. Movement of a solute molecule from an area of high concentration to an area of low concentration is called:
D. Hydrostatic pressure
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.
8. Which of the following is an example of an energy-releasing process?
C. Substrate-induced reaction
D. Second messenger system
Catabolism is an energy-releasing process. The energy-using process is anabolism. A substrate is a specific substance that is converted to a product in the reaction. A second messenger is a “pass-it-on signal.” This occurs when a first messenger activates a receptor that then triggers a pass-it-on signal.
9. Which of the following describes the term chemotaxis?
A. Uses the second messenger system
B. Cellular signal affecting the cell of origin
C. Movement of cells along a chemical gradient
D. Ligands bind with receptors, triggering a second reaction
Chemotaxis is cellular movement along a chemical gradient caused by chemical attraction. Autostimulation is when a cell releases a signal that actually affects the cell of origin. A pass-it-on signal is a description for a second messenger system. A second messenger system is a means by which a ligand binds with receptors of a membrane system and then triggers a second system or reaction.
10. Which of the following describes an amphipathic molecule?
A. Hydrophobic and not Hydrophilic
B. Hydrophilic and not Hydrophobic
C. Hydrophobic and Hydrophilic
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.
11. Which of the following are functions of a protein? (Select all that apply.)
A. Pores or transport channels
B. Enzymes that drive pumps
C. Cell surface markers
D. Synapses for cells
Answer: , B, & C
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.
12. Which of the following is the most common cause of cellular injury?
A. Free radical–induced injury
B. Chemical injury
D. Mechanical factors
Hypoxia is the most common cause of cellular injury and can be initiated by decreased oxygen in the environment, decreased hemoglobin, decreased red blood cells, or cardiovascular collapse. A free radical–induced injury, chemical injury, and mechanical factors are other types of cell injury but are not the most common.
13. Which chemical interferes with the excretion of urate while affecting the nervous and hematopoietic systems?
A. Carbon monoxide
B. Carbon tetrachloride
Lead can interfere with the excretion of urate and thus increase an individual’s predisposition to gout; it affects the hematopoietic and nervous systems. Carbon monoxide is a gas that is an asphyxiate and interrupts respiration. Carbon tetrachloride was formerly used in dry cleaning. It damages the liver as it is converted into a highly toxic free radical. Mercury is a heavy metal and can worsen chronic conditions such as Alzheimer disease and multiple sclerosis.
14. A collection of blood that is located between the skull and the dura is called a/an:
A. Epidural hematoma
C. Subdural hematoma
D. Subarachnoid hemorrhage
Epidural hematomas are a collection of blood between the inner surface of the skull and the dura. A contusion is a bruise or bleeding into the skin and underlying tissue. A subdural hematoma is a collection of blood between the inner surface of the dura and the surface of the brain. Subarachnoid hemorrhage is a condition in which a cerebral arterial aneurysm ruptures.
15. The possible diagnosis of shaken baby syndrome is supported when an infant brought to the emergency department is found to have which type of cerebral hematoma?
A subdural hematoma is associated with blows, falls, or sudden acceleration or deceleration of the head, such as the sudden movements that occur with shaken baby syndrome. Epidural hematomas are the result of a torn artery, often associated with a skull fracture. Subarachnoid hemorrhage is a condition in which a cerebral arterial aneurysm has ruptured. An avulsion is a tear or rip in the skin, resulting when tensile strength of skin or tissue is exceeded.
16. Which term describes a tear or rip of the skin with a jagged and irregular edge?
D. Incised wound
Lacerations occur when the tensile strength of the skin is exceeded, resulting in ragged and irregular abraded edges; an extreme example is avulsion, in which a wide area of tissue is pulled away. An abrasion results from the removal of the superficial layers of the skin caused by friction between the skin and the injuring object. An incision is a precise cut with an instrument that leaves regular clean edges. An incised wound is longer than it is deep and has distinct edges without abrasion.
17. Which term describes oxygen failing to reach the blood?
Suffocation occurs when oxygen fails to reach the blood. It is a subgroup of asphyxial injuries. Strangulation is caused by compression and closure of the blood vessels and air passages by external pressure on the neck. Drowning occurs when water or fluid alters the delivery of oxygen. Petechiae are found on the neck of a victim who has been strangled. It is the result of compression of soft tissue and the breakage of blood vessels.
18. Heat exhaustion is defined as:
A. Chilling or freezing of the cells
B. Cramping of voluntary muscles
C. Hemoconcentration from salt and water loss
D. Significantly decreased blood volume
Heat exhaustion is defined by a sufficient salt and water loss that results in hemoconcentration. Hypotension occurs secondary to fluid loss and may cause a collapse. The individual may feel weak and nauseated. Chills or freezing cells are associated with hypothermic injury. Heat cramps are cramping of voluntary muscles, usually the result of vigorous exercise. Heat stroke is a life-threatening condition associated with high environmental temperatures and humidity. Generalized peripheral vasodilation and decreased circulating blood volume are significant.
19. Which statement regarding altitude and illness is true?
A. Caisson disease occurs when descending too quickly while diving.
B. Pulmonary edema as the result of hypoxia and increased pulmonary hypertension.
C. Gas emboli are caused by oxygen bubbles.
D. Altitude sickness occurs from blast injuries.
High altitude causes hypoxic injury. This hypoxia causes shunting of blood from the periphery to vital organs including the lungs and results in pulmonary hypertension. Caisson disease is often called the bends and occurs when divers ascend too quickly, resulting in a gas embolism. Gas emboli are formed when carbon dioxide and nitrogen, which are normally dissolved in blood, bubble out of solution. Blast injuries cause significant injury through the collapse of the thorax, the rupture of internal organs, and widespread hemorrhage.
20. Which form of necrosis is associated with tuberculous infections?
Caseous necrosis is normally found in the lung from tuberculosis. Tissues appear soft and granular and resemble clumped cheese (hence the name caseous) and are surrounded by a granulomatous inflammatory wall; this pulmonary infection is caused by Mycobacterium tuberculosis. It is a combination of liquefactive and coagulation necrosis. Coagulative necrosis occurs primarily in the kidneys, heart, and adrenal glands and is caused by protein degradation. Liquefactive necrosis commonly occurs in the neurons and glial cells. Fat necrosis occurs in the breast, pancreas, and other abdominal structures. It is cellular dissolution caused by powerful enzymes called lipases.
21. Which statements are true regarding apoptosis? (Select all that apply.)
A. An active process of cellular self-destruction
B. A process that deletes cells during embryonic development
C. Local cell death after severe and sudden injury
D. Nuclear and cytoplasmic shrinkage of a cell
Answer: , B, & D
Apoptosis is programmed cell death. It is an active process of cellular self-destruction that is implicated in normal embryonic development, as well as in rapidly proliferating cancer cells. Apoptosis affects single cells by causing nuclear and cytoplasmic shrinkage, followed by the fragmentation of the cell membrane. Necrosis is accidental cell death that occurs to local cells after a severe and sudden injury.
22. When considering water balance, which statement is the correct balance?
A. Isotonic fluids cause increased cellular swelling.
B. Hypertonic fluid causes increased cellular swelling.
C. Hypotonic fluid causes cellular swelling.
D. Hypernatremia causes cellular swelling.
Hypotonic extracellular fluid (ECF) causes intracellular water gain and swelling. When the ECF is hypotonic, water moves from the intravascular space to the interstitial space, across the cell membrane, and into the cell. This action causes the cell to swell. An isotonic solution is equal to the plasma in concentration of solute molecules. Therefore no net water will move because equilibrium exists. The cell size is unchanged. A hypertonic fluid has excessive solute; therefore water will leave the cell and move into the vascular space to help balance this excess. Water leaving the cell results in cell shrinkage. Hypernatremia can occur with an acute gain in sodium or a loss of water, but generally it does not cause cellular swelling.
23. It is true that hyperchloremia:
A. Occurs with a deficit of sodium.
B. Occurs with an excess of bicarbonate.
C. Has specific symptoms such as thirst.
D. Requires treatment of the underlying disorder.
Hyperchloremia (too much chloride) is usually related to an underlying disorder, and therefore treatment is centered on the underlying disorder. Because chloride usually follows sodium, this condition usually occurs with an increase in sodium and a deficit of bicarbonate. Normally, neither specific symptoms are observed nor treatments are available for chloride excess.
24. It is true that hyponatremia:
A. Is commonly caused by inadequate sodium intake.
B. Can occur with a decrease in total body water (TBW).
C. Never occurs with burns, vomiting, or diarrhea.
D. Occurs when sodium drops below 135 mEq/L.
Hyponatremia occurs when the serum sodium drops below 135 mEq/L. It is the most common electrolyte disorder in individuals who are hospitalized. Although inadequate sodium intake can cause hyponatremia, it is uncommon. It can also occur with an increase in TBW or as a result of burns, vomiting, diarrhea, or gastrointestinal suctioning.
25. Which statement is true regarding potassium balance?
A. Potassium is the major extracellular electrolyte.
B. During acidosis, potassium shifts into the cell.
C. Aldosterone is secreted when potassium is decreased.
D. Insulin causes the movement of potassium into the cell.
Insulin causes movement of potassium into the cell and is one of the treatments for hyperkalemia. Potassium balance is especially significant in the treatment of conditions requiring insulin administration, such as insulin-dependent diabetes mellitus (type 1). Potassium is the major intracellular electrolyte and maintains the osmotic balance of the intracellular fluid (ICF) space. During acidosis, potassium is shifted out of the cell in exchange for hydrogen ions. Aldosterone is secreted when potassium is elevated, resulting in the excretion of potassium by the kidneys.
26. Which statement is true regarding hypokalemia?
A. Hypokalemia occurs when the serum level is below 135 mEq/L.
B. One cause of hypokalemia is diabetic ketoacidosis.
C. Dietary causes of hypokalemia are common.
D. Diuretics do not cause hypokalemia.
Hypokalemia is low potassium. Therefore hypokalemia is defined as a serum level less than 3.5 mEq/L. It is often caused by diuretics. Diabetic ketoacidosis does cause hypokalemia. Potassium is shifted out of the cell in exchange for hydrogen and then excreted. The serum level may remain within a normal range, but then when insulin is administered, potassium is shifted back into the cells and a deficit occurs. Potassium balance is especially significant in the treatment of conditions requiring insulin administration, such as insulin-dependent diabetes mellitus (type 1). Dietary causes are uncommon.
27. Hypernatremia is defined as levels above:
A. 147 mEq/L
B. 5.5 mEq/L
C. 105 mEq/L
D. 8.5 mg/dl
Hypernatremia is defined as serum levels above 147 mEq/L. Hyperkalemia is defined as serum levels above 5.5 mEq/L, and hyperchloremia is defined as serum levels above 105 mEq/L. Hypocalcemia occurs when serum calcium concentrations are less than 8.5 mg/dl.
28. Which statement is true regarding magnesium?
A. Hypomagnesemia occurs with a concentration less than 2.5 mEq/L.
B. Magnesium is a major extracellular cation.
C. Thirty percent is stored in the muscle and bone.
D. Symptoms of hypomagnesemia include weakness and depression.
Symptoms of low magnesium include weakness, tetany, increased reflexes, depression, ataxia, convulsions, and irritability. Magnesium level is normal when between 1.8 and 2.4 mEq/L and is a major intracellular cation. Thirty percent is stored in the cells, with 40% to 60% stored in the bones and muscle.
29. Which statement describes acidemia?
A. State in which the pH of arterial blood is greater than 7.45
B. State in which the pH of arterial blood is less than 7.35
C. Systemic decrease in hydrogen ion concentration
D. Systemic excess of base
Acidemia is a state in which the pH of arterial blood is less than 7.35. Alkalemia is a state in which the pH of arterial blood is greater than 7.45. A systemic increase in hydrogen ion concentration or loss of base is termed acidosis. A systemic decrease in hydrogen ion concentration or an excess of base is termed alkalosis.
30. Common causes of edema formation (increased filtration of fluid from capillaries and lymph into surrounding tissues) include which of the following? (Select all that apply.)
A. Decreased hydrostatic pressure
B. Decreased plasma oncotic pressure
C. Increased capillary membrane permeability
D. Lymphatic obstruction
E. Sodium retention
Answer: , C, D, & E
The five common causes of increased edema are: (1) increased hydrostatic pressure, (2) decreased plasma oncotic pressure, (3) increased capillary membrane permeability, (4) lymphatic obstruction, and (5) sodium retention.
31. Which of the following are clinical manifestations of hypokalemia? (Select all that apply.)
A. Carbohydrate metabolism is affected as a result of decreased insulin secretion.
B. Renal function is impaired.
C. Neuromuscular excitability is decreased.
D. Skeletal muscle is affected with increased contractility.
Answer: , B, & C
Carbohydrate metabolism is affected by depressing insulin secretion and alters hepatic and skeletal muscle glycogen synthesis. Renal function may be impaired with a decreased ability to concentrate urine, and renal tubular atrophy and fibrosis may occur. Neuromuscular excitability is decreased causing skeletal muscle weakness, smooth muscle atony, and cardiac dysrhythmias. Hypokalemia causes the skeletal muscle to be weak.
32. Which treatments are appropriate for hyperkalemia? (Select all that apply.)
A. Calcium gluconate
B. Treating the contributing cause
C. Administering glucagon
D. Sodium bicarbonate
Answer: , B, & D
Calcium gluconate, treating the contributing cause, and sodium bicarbonate are all appropriate treatments. Calcium gluconate can be administered to restore normal neuromuscular irritability when serum potassium levels are dangerously high. Glucose, which readily stimulates insulin secretion, or the administration of glucose and insulin for those with diabetes, facilitates cellular entry of potassium. Sodium bicarbonate corrects metabolic acidosis and lowers serum potassium. Glucagon is administered to treat beta-blocker overdose or hypoglycemia.