Chapter 20 - Cell Communities: Tissues, Stem Cells, and Cancer Flashcards
What is the driving force for plant cell growth?
- turgor pressure
- meiotic division
- excess sunlight
- photosynthesis
- mitotic division
Turgor pressure
(Turgor pressure, produced by the osmotic imbalance between the interior of a plant cell and its surroundings, drives plant cell growth.)
What gives the plant cell wall its tensile strength?
- myosin
- cellulose
- starch
- actin filaments
Cellulose
(Cellulose microfibrils are interwoven with other cell wall components to form a structure that resists compression and tension.)
Fibroblasts are the major cellular component in which tissues?
- muscle
- nervous
- connective
- epithelial
Connective
(Fibroblasts are the major cellular component in connective tissues. Fibroblasts manufacture and inhabit the extracellular matrix in skin, tendon, and many other connective tissues.)
Which feature of glycosaminoglycans (GAGs) allows the extracellular matrix in cartilage to resist compression?
- GAGs form stiff rods in the extracellular matrix and thereby resist compression.
- The negative charges on GAGs attract calcium phosphate, which forms a hard, resilient mesh that resists compression.
- The negative charges on GAGs attract sodium ions, which draw water into the extracellular matrix to form a water-filled gel.
- GAGs are typically attached to proteins to form proteoglycans, and both the protein and GAG chains resist compression.
The negative charges on GAGs attract sodium ions, which draw water into the extracellular matrix to form a water-filled gel.
(The negative charges on glycosaminoglycans (GAGs) attract sodium ions, which draw water into the extracellular matrix to form a water-filled gel. This feature of GAGs allows the extracellular matrix in cartilage to resist compression.)
What is the best description of connective tissue?
- All of its cells are electrically connected via gap junctions.
- All of its cells are sparsely distributed in the extracellular matrix.
- All of its cells rest on a basal lamina.
- All of its cells associate via cadherins in their plasma membrane.
All of its cells are sparsely distributed in the extracellular matrix.
(The cells of connective tissue are sparsely distributed in the extracellular matrix. Epithelial cells, not cells of connective tissue, are electrically connected via gap junctions, rest on a basal lamina, and associate via cadherins in their plasma membrane.)
Which epithelial cell junctions serve to seal neighboring cells together so that water-soluble molecules cannot easily leak between them?
- gap junctions
- tight junctions
- desmosomes
- adherens junctions
- plasmodesmata
Tight junctions
(Tight junctions seal neighboring cells together so that water-soluble molecules cannot easily leak between them. If a tracer molecule is added to one side of an epithelial sheet, it will usually not pass beyond the tight junctions.)
Which is true of cadherin proteins?
- They link epithelial cells together by binding to similar cadherins in adjacent epithelial cells.
- They allow ions and small molecules to pass from one plant cell to another.
- They create an electrical and metabolic coupling between epithelial cells.
- They anchor epithelial cells to the basal lamina.
They link epithelial cells together by binding to similar cadherins in adjacent epithelial cells.
(Cadherin proteins link epithelial cells together by binding to similar cadherins in adjacent epithelial cells. Inside the cell, cadherins are attached to the cytoskeleton.)
Which type of epithelial cell junction plays a major role in an epithelial sheet’s ability to develop tension and change its shape?
- tight junction
- desmosome
- gap junction
- adherens junction
adherens junction
(The adherens junction plays a major role in an epithelial sheet’s ability to develop tension and change its shape. In adherens junctions, cadherins are tethered to actin filaments, which can contract, giving the epithelial sheet the capacity to change its shape in various ways.)
What attaches epithelial cells to the basal lamina?
- tight junctions
- desmosomes
- hemidesmosomes
- cadherins
- adherens junctions
hemidesmosomes
(Epithelial cells are attached to the basal lamina by hemidesmosomes. The interaction is mediated by integrins in the basal plasma membrane of the epithelial cell binding to laminins in the basal lamina.)
Which of the following are the plant equivalent of a gap junction?
- desmosomes
- plasmodesmata
- tight junctions
- adherens junctions
Plasmodesmata
(Plasmodesmata are cytoplasmic channels, lined with plasma membrane, that penetrate cell walls to connect neighboring plant cells.)
In the intestine, what do Wnt proteins promote?
- apoptosis of the stem cells at the base of each intestinal crypt
- secretion of mucus at the base of each intestinal crypt
- proliferation of the stem cells and precursor cells at the base of each intestinal crypt
- apoptosis of precursor cells in each intestinal crypt
Proliferation of the stem cells and precursor cells at the base of each intestinal crypt
(In the intestine, Wnt proteins promote the proliferation of the stem cells and precursor cells at the base of each intestinal crypt. Changes in Wnt signaling can lead to a failure of intestinal development or to the formation of intestinal tumors.)
Which of the following animal cell types, under appropriate conditions, can be kept proliferating indefinitely in culture and yet retain unrestricted developmental potential?
- proliferating precursor cells
- germ cells
- embryonic stem cells
- somatic cells
embryonic stem cells
(Embryonic stem cells are animal cell types that can be kept proliferating indefinitely in culture and still retain unrestricted developmental potential. These cells can divide infinitely in culture and, if placed back into an early embryo, can give rise to all the cell types and tissues in the body.)
What is a major problem with using foreign cells grown in culture for transplantation in humans?
- The host immune system would destroy such cells.
- Such cells would not successfully integrate into host tissue.
- Such cells would die immediately upon their removal from culture.
- Such cells would tend to form cancers.
The host immune system would destroy such cells.
(For this reason, investigators are exploring the use of induced pluripotent stem cells to generate personalized ES cells, which could be induced to produce the differentiated cell types needed by the host and be genetically identical to the host’s other cells.)
Which statement is true about stem cells?
- They are usually present in large numbers, especially in tissues that undergo rapid renewal.
- They can divide for the lifetime of the organism.
- They always divide asymmetrically, giving rise to two different daughter cells.
- They are terminally differentiated.
They can divide for the lifetime of the organism.
(Correct. Stem cells can divide without limit—or at least for the life of the organism. Stem cells replenish epithelial cells and blood cells, among others.)
Which of these human cells undergoes the most rapid turnover?
- intestinal epithelial cells
- skin epidermal cells
- bone-forming cells
- red blood cells
- nerve cells
intestinal epithelial cells
(Compared to the other four human cell types, intestinal epithelial cells are the ones that undergo the most rapid turnover. Cells in the intestinal epithelium are replaced every three to six days.)
Cancer is fundamentally which type of disease?
- a genetic disease
- a human disease
- an environmental disease
- an infectious disease
- a disease of obesity
A genetic disease
(Cancer is best described as a genetic disease. Cancer arises as a consequence of changes to DNA. These changes to the DNA nucleotide sequence are collectively referred to as mutations.)
Which of the following can give rise to cancer-promoting mutations?
Choose one or more:
- DNA replication errors
- exposure to ionizing radiation
- inhalation of tobacco smoke
- exposure to excess sunlight
- DNA replication errors
- exposure to ionizing radiation
- inhalation of tobacco smoke
- exposure to excess sunlight
(Cancer-promoting mutations can be generated by a variety of mutagens. They can also occur spontaneously, due to limitations in the accuracy of DNA replication and repair. Thus, DNA replication errors, exposure to excess sunlight and ionizing radiation, and the inhalation of tobacco smoke can all promote genetic mutations that can lead to cancer.)
Many of the genes mutated in individual tumors are involved with which of the following regulatory pathways?
Choose one or more:
- pathways controlling the catabolism of lactose
- pathways governing the initiation of cell division
- pathways regulating the cell’s response to DNA damage or stress
- pathways governing the initiation of cell division
- pathways regulating the cell’s response to DNA damage or stress
(Many of the genes mutated in individual tumors are involved with pathways governing the initiation of cell division and those regulating the cell’s response to DNA damage or stress.)
Which of the following is most consistent with the data contained within these karyotypes?
- The karyotype on the left is not likely that of human and the karyotype on the right is from a normal human male.
- The karyotype on the right is most likely from an advanced tumor due to its significant evidence of genetic instability.
- The karyotype on the right is most likely from a young tumor because it is still demonstrating genetic stability.
- The karyotype on the left is most likely from an advanced tumor due to its significant evidence of genetic instability.
The karyotype on the right is most likely from an advanced tumor due to its significant evidence of genetic instability.
(The karyotype on the right is most likely from an advanced tumor. Note the significant evidence of genetic instability. Cancer cells often have highly abnormal chromosomes, reflecting genetic instability.)
Based on the information that is depicted in the illustration, this tumor would most likely be considered ______ because the cells ________ expressing cadherin proteins.
Malignant
Are not
(Correct. Based on the information that is depicted in the illustration, this tumor would most likely be considered malignant because the cells have broken through the basement membrane and have entered the vasculature.
Correct. Based on the information that is depicted in the illustration, these cells are motile and therefore have stopped expressing their anchoring cadherins.)
For both clinical and cosmetic reasons, plastic surgeons inject substances into connective tissue underlying the skin epidermis. This plumps up areas deficient in soft tissue, and is used to reduce surgical scars or wrinkles, for example. Which normal connective tissue components are good candidates to be injected as fillers in this type of procedure?
Choose one or more:
- cadherin
- hemidesmosome
- glycosaminoglycan
- collagen
- Collagen
- Glycosaminoglycan
(Both collagen, a protein that provides tensile strength, and glycosaminoglycans, polysaccharides that resist compression, are components of the extracellular matrix and employed as fillers in soft tissue augmentation.)
Which of the following determines the direction that cellulose microfibrils are laid down in the extracellular space of a plant cell?
- orientation of microtubules in the cell wall
- amount of turgor pressure within a cell
- availability of sugar monomers for cellulose microfibril elongation
- orientation of microtubules on the cytoplasmic side of the plasma membrane
- orientation of cellulite on the cytoplasmic side of the plasma membrane
orientation of microtubules on the cytoplasmic side of the plasma membrane
(Microtubules beneath the cell wall serve as tracks that guide the movement of the enzyme complexes that synthesize the cellulose microfibrils.)
Which of the following is not true of integrin?
- Certain intracellular chemical signals can activate integrins from inside the cell, causing them to reach out and grab hold of extracellular structures.
- Integrins undergo extensive conformational changes on binding to molecules on either side of the plasma membrane.
- When integrin binds to the extracellular matrix, it stretches into an extended, activated state to attach to molecules on the inside of the cell.
- Integrin molecules serve as stable, permanent anchors that anchor a cell to the extracellular matrix.
Integrin molecules serve as stable, permanent anchors that anchor a cell to the extracellular matrix.
(Integrin molecules do not serve as stable, permanent anchors that anchor a cell to the extracellular matrix. Rather, integrins are conformationally dynamic, which allows a cell to crawl along the extracellular matrix by forming connections at the front end of the cell while letting go at the rear.)
Compared to plant cell walls, what is true of the extracellular matrix of most animal tissues?
- It contains more nitrogen.
- It is generally thicker and stronger.
- It contains more carbon.
- It contains cellulose that is produced inside the cell in a precursor form, rather than synthesized extracellularly.
It contains more nitrogen.
(Compared to plant cell walls, the extracellular matrix of animal tissues contains more protein (collagen, elastin, fibronectin, proteoglycans) than the plant cell wall, and thus more nitrogen.)