5. Cell Components

Introduction to the Cytoskeleton

Microtubules | Cells | MCAT | Khan Academy

Microfilaments and intermediate filaments | Cells | MCAT | Khan Academy

What is the Cytoskeleton?

Which of the following best characterizes an adaptive radiation?

a. Descendant species occupy a large geographic area.
b. A single lineage diversifies rapidly, and descendant species occupy many habitats and ecological roles.
c. Natural selection is particularly intense, because disruptive selection occurs.
d. Species recover after a mass extinction.

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). <img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/e8703f92447b00dc-1677714421797.jpg" style="width: 300px;">

Short Video: Flagellum in Sperm

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?<img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/266770e4aee89a70-1677714454648.jpg" style="width: 300px;">

No. The lysosomes are involved in degradation, and this is not a function shared with the cytoskeleton.

No. The cytoskeleton does not have a role in protein synthesis.

No. RNA has nothing to do with the functioning of the cytoskeleton.

Consider the function of the cytoskeleton.

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

Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allows species to exploit more resources and frees them from the need to hide in small refuges.

The graph shown here compares the average carapace (shell) length of mainland and island tortoises. Summarize the results, then use the data to predict whether the surface area to volume ratio is higher in mainland or island tortoises. <IMAGE>

No. Both mitochondria and chloroplasts are found in plant cells.

No. This is a feature common to all cells, so it must be found in both animal and plant cells.

No. All plant cells and animal cells have at least one Golgi apparatus.

No. Plant and animal cells both have rough endoplasmic reticulum.

Compare and contrast the structures found in animal and plant cells.

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

No. Actin is a protein that is a major component of microfilaments.

No. Pseudopodia are transient cell structures involved in amoeboid movement.

No. Mitochondria supply the energy for motion in the cytoskeleton, but they do not cause the motion.

No. Tubulin is the major protein component of microtubules.

Consider how motion is accomplished in the cytoskeleton.

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

USMLE Step 1 - Lesson 20 - Elements of the Cytoskeleton

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

Short Video: Sperm Flagellum

Cilia & Flagella

Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allows species to exploit more resources and frees them from the need to hide in small refuges.

Which tortoises, mainland or island, need to eat more food per gram of their body mass?

Intermediate filaments are hollow tubes of protein that provide structural support.

No. Microtubules are relatively rigid tubular structures that provide support in the cell.

Microtubules are chains of proteins that resist stretching.

No. Microfilaments are polymers of the protein actin that are quite strong and resist stretching.

Microfilaments are more permanent structures in cells compared to intermediate filaments and microtubules.

No. Intermediate filaments are more permanent in their structure than microfilaments and microtubules are in theirs.

Plant cells lack a cytoskeleton because they have a rigid cell wall.

No. The cytoskeleton is important in many other processes besides maintaining cell shape.

Components of the cytoskeleton often mediate the movement of organelles within the cytoplasm.

Consider the structures and functions of the different types of cytoskeleton.

Which statement about the cytoskeleton is true?

The cytoskeleton | Structure of a cell | Biology | Khan Academy

No. Basal bodies are made up of components of the cytoskeleton and are not associated with the nucleus.

No. Basal bodies are made up of components of the cytoskeleton and are not associated with the mitochondria.

No. Basal bodies are made up of components of the cytoskeleton and are not associated with the vacuole.

No. Basal bodies are made up of components of the cytoskeleton and are not associated with the Golgi.

Centrioles are structurally similar to basal bodies.

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

Animation: Cilia and Flagella

BioFlix: Cytoskeleton

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

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.

Cell Organelles 2 Cytoskeleton

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.

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1. Introduction to Biology

2. Chemistry

3. Water

4. Biomolecules

6. The Membrane

7. Energy and Metabolism

8. Respiration

9. Photosynthesis

10. Cell Signaling

11. Cell Division

12. Meiosis

13. Mendelian Genetics

14. DNA Synthesis

15. Gene Expression

16. Regulation of Expression

17. Viruses

18. Biotechnology

19. Genomics

20. Development

21. Evolution by Natural Selection

22. Evolution of Populations

23. Speciation

24. History of Life on Earth

25. Phylogeny

26. Prokaryotes

27. Protists

28. Plants

29. Fungi

30. Overview of Animals

31. Invertebrates