ACCURATE & COMPREHENSIVE ANSWERS
What is the most common site of lipid accumulation?
Liver
Although lipids sometimes accumulate in heart and kidney cells, the most common site of intracellular
lipid accumulation, or fatty change, is liver cells. Subcutaneous tissue is not a common site of lipid
accumulation.
What occurs during exocytosis?
Macromolecules can be secreted across eukaryotic cell membranes.
In eukaryotic cells, secretion of macromolecules almost always occurs by exocytosis. The remaining
options do not correctly describe exocytosis.
Which form of cell communication is used to communicate within the cell itself and with other cells in
direct physical contact?
Plasma membrane-bound signaling molecules
Cells communicate in three main ways; they display plasma membrane-bound signaling molecules that
affect the cell itself and other cells in direct physical contact with it, they affect receptor proteins inside
the target cell, and they form protein channels (gap junctions) that directly coordinate the activities of
adjacent cells. Neurotransmitters are released by neurons and cross the synaptic cleft to communicate
with the cells they innervate. Ligands are involved in binding processes.
Which is the best example of active transport?
Movement requiring the expenditure of metabolic energy
Active transport requires a life, biologic activity, and the expenditure of metabolic energy. Movement
due simply to differences in concentration gradients is called passive transport. Movement of two
molecules in the same direction is called symport, while moving two molecules in opposite directions is
called antiport.
During cell injury caused by hypoxia, why does an increase in the osmotic pressure within the cell
occur?
b.Sodium chloride enters 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 pump that transports sodium ions out of the cell is
maintained by the presence of ATP and ATPase, the active transport enzyme. In metabolic failure caused
by hypoxia, reduced ATP and ATPase levels permit sodium to accumulate in the cell, whereas potassium
diffuses outward. The increase of intracellular sodium increases osmotic pressure, which draws more
water into the cell. (Transport mechanisms are described in Chapter 1.) The remaining options do not
accurately describe the cell injury that results in increased osmotic pressure caused by hypoxia.
The action of which hormone helps explain increases in affective anxiety and eating disorders, mood
cycles, and vulnerability to autoimmune and inflammatory diseases in women as a result of
stimulation of the CRH gene promoter and central norepinephrine system?
, Estrogen
Of the options provided, only estrogen directly stimulates the CRH gene promoter and the central
noradrenergic (norepinephrine) system, which may help explain adult women's slight hypercortisolism,
increases in affective anxiety and eating disorders, mood cycles, and vulnerability to autoimmune and
inflammatory disease, all of which follow estradiol fluctuations.
What area in the body may act as a reservoir in which HIV can be relatively protected from antiviral
drugs?
Central nervous system (including the brain)
HIV may persist in regions where the antiviral drugs are not as effective, such as the central nervous
system (CNS). The bone marrow, thymus gland, and lungs are not as protected from antiviral drugs.
What characteristic do atopic individuals have that make them genetically predisposed to develop
allergies?
Greater quantities of IgE
Atopic individuals tend to produce higher quantities of IgE and to have more crystalline fragment (Fc)
receptors for IgE on their mast cells. Greater quantities of histamine, more histamine receptors, and a
deficiency in epinephrine do not lead to a genetic predisposition to allergies.
What is the term for the process during which lymphoid stem cells migrate and change into either
immunocompetent T cells or immunocompetent B cells?
Clonal diversity
The process is called the generation of clonal diversity and occurs in specialized (primary)lymphoid
organs-the thymus gland for T cells and the bone marrow for B cells. Clonal differentiation, selection,
and competence do not describe this process.
When antibodies are formed against red blood cell antigens of the Rh system, how are the blood cells
destroyed?
Phagocytosis in the spleen
Antibodies against platelet-specific antigens or against red blood cell antigens of the Rh system coat
those cells at low density, resulting in their preferential removal by phagocytosis in the spleen, rather
than by complement-mediated lysis. These blood cells are not destroyed by complement-mediated cell
lysis, phagocytosis by macrophages, neutrophil granules, or toxic oxygen products.
Which disease is an example of a rickettsial infection?
Rocky Mountain spotted fever is a result of rickettsiae. Cholera is a bacterial infection, candida is a
fungal infection, and sleeping sickness is a protozoal infection.
What does the loss of the adenosine triphosphate (ATP) during ischemia cause cells to do?
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