5. Cell Components

Microtubules and microfilaments commonly work with which of the following to perform many of their functions?

What component of the cytoskeletons do motor proteins use to transport vesicles?

In human cells, ___________________ are used to move a cell within its environment while ___________________ are used to move objects in the environment relative to the cell.

969

Which statement about the cytoskeleton is true?

1866

Which of the following structures is found in animal cells but not in plant cells?

999

Cilia and flagella move due to the interaction of the cytoskeleton with which of the following?

1259

Basal bodies are most closely associated with which of the following cell components?

1002

Describe two different ways in which cilia can function in organisms.

706

Cilia are found on cells in almost every organ of the human body, and the malfunction of cilia is involved in several human disorders. During embryological development, for example, cilia generate a leftward flow of fluid that initiates the left-right organization of the body organs. Some individuals with primary ciliary dyskinesia exhibit a condition (situs inversus) in which internal organs such as the heart are on the wrong side of the body. Explain why this reversed arrangement may be a symptom of PCD.

1107

The figure below illustrates the results they observed as the chromosomes moved toward the opposite poles of the cell. Describe these results. What would you conclude about where the microtubules depolymerize from comparing the length of the microtubules on either side of the mark? How could the experimenters determine whether this is the mechanism of chromosome movement in all cells?

622

Microtubules often produce movement through their interaction with motor proteins. But in some cases, microtubules move cell components when the length of the microtubule changes. Through a series of experiments, researchers determined that microtubules grow and shorten as tubulin proteins are added or removed from their ends. Other experiments showed that microtubules make up the spindle apparatus that 'pulls' chromosomes toward opposite ends (poles) of a dividing cell. The figures below describe a clever experiment done in 1987 to determine whether a spindle microtubule shortens (depolymerizes) at the end holding a chromosome or at the pole end of a dividing cell. Experimenters labeled the microtubules of a dividing cell from a pig kidney with a yellow fluorescent dye. As shown on the left half of the diagram below, they then marked a region halfway along the microtubules by using a laser to eliminate the fluorescence from that region. They did not mark the other side of the spindle (right side of the figure).

901