Homework set 4

_____ aid in the coordination of the activities of adjacent animal cells. Keratin fibers Desmosomes Gap (communicating) junctions Tight junctions Plasmodesmata

Gap junctions

H. V. Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted the cell—cell interaction (cell junctions), and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson found that the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species. How do you explain the results of Wilson's experiments? The two species of sponge had different enzymes that functioned in the reassembly process. The molecules responsible for cell—cell adhesion (cell junctions) were irreversibly destroyed during the experiment. The molecules responsible for cell—cell adhesion (cell junctions) differed between the two species of sponge. One cell functioned as the nucleus for each organism, thereby attracting only cells of the same pigment.

The molecules responsible for cell—cell adhesion (cell junctions) were irreversibly destroyed during the experiment.

An elephant and a mouse are running in full sunlight, and both overheat by the same amount above their normal body temperatures. When they move into the shade and rest, which animal will cool down faster? The elephant will because it has the higher surface-area-to-volume ratio. The elephant will because it has the lower surface-area-to-volume ratio. The mouse will because it has the higher surface-area-to-volume ratio. They will cool at the same rate because they overheated by the same amount. The mouse will because it has the lower surface-area-to-volume ratio.

The mouse will because it has the higher surface-area-to-volume ratio.

The large surface area in the small intestine directly facilitates ________. absorption filtration secretion elimination temperature regulation

absorption

Which of the following is an example of a connective tissue? smooth muscles cuboidal epithelium blood nerves the surface of the skin

blood

The surface area of a plant's root system is substantially larger than the surface area of its shoot system. The extensive surface area of roots is an adaptation associated with ________. the internal structure of the vascular tissue in roots the release of carbon dioxide generated by photosynthesis the fact that roots absorb materials while shoots do not the storage of nutrients within the root system contact with soil particles for mineral and water absorption

contact with soil particles for mineral and water absorption

Integrins are integral membrane proteins. They are often attached to _____. the membranes of intracellular organelles the outside of the plasma membrane cytoskeletal proteins and proteins in the extracellular matrix glycogen molecules and other types of cellular inclusions

cytoskeletal proteins and proteins in the extracellular matrix

The primary role of _____ is to bind animal cells together. gap (communicating) junctions tight junctions desmosomes the cytoskeleton plasmodesmata

desmosomes

You are looking through a microscope at a slide of animal tissue and see a single layer of flat, closely packed cells that cover a surface. This specific tissue is most likely _____. epithelial cardiac muscle of the heart a tendon adipose a neuron

epithelial

Blood is a type of connective tissue because blood _____. has an extensive extracellular matrix can be both liquid and solid has multiple cell types functions in transportation

has an extensive extracellular matrix

Which of these cell junctions form a barrier to the passage of materials? tight junctions keratin fibers desmosomes (anchoring junctions) plasmodesmata gap (communicating) junctions

tight junctions

Intercalated discs are cell-cell junctions found between cardiac muscle cells. One feature of these intercalated discs is that they contain a large number of gap junctions, which means that ________. water ions and small molecules can readily pass from one cardiac muscle cell to the next an extension of smooth endoplasmic reticulum goes through the gap junction, making it continuous from one cardiac muscle cell to the next RNA from one cardiac muscle cell can be transported into an adjacent cell through the gap junction cardiac cells can function independently when necessary

water ions and small molecules can readily pass from one cardiac muscle cell to the next