Download Answers to End-of-Chapter Questions – Brooker et al ARIS site

Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 10
Test Yourself Questions
1. The function of the extracellular matrix (ECM) in most multicellular organisms is
a. to provide strength.
b. to provide structural support.
c. to organize cells and other body parts.
d. cell signaling.
e. all of the above.
Answer: e. The ECM serves all of these functions.
2. The protein found in the ECM of animals that provides strength and resistance to tearing when
stretched is
a. elastin.
b. cellulose.
c. collagen.
d. laminin.
e. fibronectin.
Answer: c. Collagen provides tensile strength to animal tissues.
3. The polysaccharide that forms the hard outer covering of many invertebrates is
a. collagen.
b. chitin.
c. chondroitin sulfate.
d. pectin.
e. cellulose.
Answer: b. Chitin is a polysaccharide found in the hard outer covering of many invertebrates.
4. The single most abundant organic molecule of Earth is __________ and it is the main
macromolecule of the _______________.
a. collagen, connective tissue of animals
b. chitin, muscle tissue of animals
c. cellulose, primary cell wall of plants
d. integrins, cell junctions in plants
e. pectin, secondary cell wall of plants
Answer: c. Cellulose is the main macromolecule of the primary cell wall of plants and is very likely the
most abundant organic molecule on Earth.
5. __________________ are proteins that attach animal cells to the ECM.
a. Cadherins
b. Integrins
c. Occludins
d. Tight junctions
e. Desmosomes
Answer: b. Integrins, a type of CAM, are proteins that attach animal cells to the ECM.
6. The gap junctions of animal cells differ from the plasmodesmata of plant cells in that
a. gap junctions serve as communicating junctions and plasmodesmata serve as adhesion
junctions.
b. gap junctions prevent extracellular material from moving between adjacent cells but the
plasmodesmata do not.
c. gap junctions allow for direct exchange of cellular material between cells, but plasmodesmata
cannot allow the same type of exchange.
d. gap junctions are formed by specialized proteins that form channels through the membranes
of adjacent cells, but plasmodesmata are not formed by specialized proteins.
e. all of the above
Answer: d. The plasmodesmata of plant cells are channels between cells but the channel is formed
because the plasma membrane of one cell is continuous with the plasma membrane of an adjacent cell.
Gap junctions of animal cells, however, are formed by specialized proteins that connect the two
membranes and create a channel between the two cells.
7. Which of the following is involved in the process of tissue and organ formation in multicellular
organisms?
a. cell division
b. cell differentiation
c. cell connections
d. cell growth
e. All of the above
Answer: e. All of these processes are needed for tissue and organ formation. Migration and apoptosis
also are important in tissue and organ formation in animals.
8. The tissue type common to animals that functions in the conduction of electrical signals is
a. epithelial.
b. dermal.
c. muscle.
d. nervous.
e. ground.
Answer: d. Nervous tissue is specialized for conducting electrical signals.
9. Photosynthesis occurs mainly in the ______________ tissue of plants.
a. vascular
b. dermal
c. parenchyma
d. collenchyma
e. sclerenchyma
Answer: c. Parenchyma is the primary site for photosynthesis.
10. Which of the following is not a correct statement in the comparison of plant tissues to animal
tissues?
a. Nervous tissue of animals plays the same role as vascular tissue in plants.
b. The dermal tissue of plants is similar to epithelial tissue of animals in that both provide a
covering for the organism.
c. The epithelial tissue of animals and the dermal tissue of plants have special characteristics
that limit the movement of extracellular material between cell layers.
d. The ground tissue of plants and the connective tissue of animals provide structural support
for the organism.
e. All of the above are correct comparisons between plant and animal tissues.
Answer: a. Nervous tissue in animals is involved in cell signaling, while vascular tissue in plants is
involved in the transport of materials throughout the plant.
Conceptual Questions
1.
List and explain the four characteristics of the extracellular matrix.
Answer:




2.
Strength – Provides toughness and prevents tearing.
Structural support – The skeleton provides support and facilitates movement.
Organization – The ECM holds cells together in proper arrangements.
Cell signaling – Facilitates communication among cells in response to changes in the environment.
Distinguish between the primary cell wall and the secondary cell wall.
Answer: The primary cell wall is synthesized first between the two newly made daughter cells. The
secondary cell wall is made in layers by the deposition of cellulose fibrils and other components.
3.
List and explain the four types of animal tissues.
Answer:




Epithelial tissue is composed of cells that are joined together via tight junctions and form continuous
sheets that function as linings in different parts of the body.
Connective tissue provides support to the body and helps to connect different tissues to each other.
Muscle tissue can generate a force that facilitates movement.
Nervous tissue receives, generates, and conducts electrical signals throughout the body.
Experimental Questions
1. What was the purpose of the study conducted by Loewenstein and colleagues?
Answer: The researchers were aware of the function of gap junctions that allow the direct exchange of
materials between adjacent cells. However, the researchers did not know the size range of molecules
that could move through the gap junctions. The purpose of the study was to determine the limit of the
molecular mass that could pass through gap junctions.
2. Explain the experimental procedure used by Loewenstein to determine the size of gap-junction
channels.
Answer: The researchers used fluorescent dyes to visibly monitor the movement of material from one
cell to an adjacent cell through the gap junctions. First, monolayers of rat liver cells were cultured. Next,
fluorescent dyes with molecules of various masses were injected into particular cells. The researchers
then used fluorescence microscopy to determine whether or not the dyes were transferred from one cell
to the next.
3. What did the results of Figure 10.13 indicate about the size of gap-junction channels?
Answer: The researchers found that molecules of masses less than 1,000 daltons could pass through
the gap junction channels. Molecules of masses larger than 1,000 daltons could not pass through the
gap junctions. Further experimentation revealed variation in gap junction channel size of different cell
types. However, the upper limit to the gap junction channel size was determined to usually be around
1,000 daltons.
Collaborative Questions
1. What role does the extracellular matrix play in animals?
Answer: Unlike the cells of bacteria, fungi, and plants, the cells of animals are not surrounded by a rigid
cell wall that provides structure and support. In animal cells, this function is achieved through the
extracellular matrix (ECM) that surrounds the cells. In joints, this ECM, which is found in cartilage, acts
to strengthen and protect the joints. In skeletons, the ECM not only provides structural support, but also
facilitates movement by helping muscles attach to bone. The ECM also plays a key role in the proper
arrangement of cells throughout the body and helps bind many body parts together, such as tendons to
bones. Last, the ECM plays a role in cell signaling and helps the cell sense changes in their surrounding
environment.
2. What are the six basic cell processes required to create tissues and organs?
Answer: To create tissues and organs, cells must undergo six basic processes that influence their
shape, arrangement and number:
Cell division  Many cells are needed to make tissues and organs. These arise via cell division.
Cell growth  After a cell divides it needs to grow to reach its correct size.
Differentiation  Due to the expression of different genes, cells can differentiate into specialized cells
based on what cells are needed at that particular time in the tissue or organ.
Migration  During embryonic development in animals, cells migrate to their appropriate position within
the body. This event doesn't occur in plants.
Apoptosis  Apoptosis is also known as programmed cell death. During development, organs and
tissues need to be shaped to form their correct structure. For example, during the development of
fingers and toes, the cells between the digits must be removed. This cell removal is done through the
process of apoptosis.
Cell connections  For tissues and organs to work properly, the cells must be held together in a specific
arrangement. This is achieved through the different types of cell-to-cell connections.