Question 1

Which of the following statements describes a primary function of integrins?

Accepted Answer

Integrins are transmembrane proteins that play a crucial role in cell adhesion, connecting the extracellular matrix to the cytoskeleton. They transmit signals from the extracellular environment into the cell, influencing cell behavior, migration, and survival.

Question 2

Movement of amoebae across a surface requires which of the following activities by components of the cytoskeleton?

Accepted Answer

Amoebae move by extending parts of their cell in a process called pseudopodia, which involves the assembly of actin filaments at the leading edge to form bulges in the plasma membrane. This actin polymerization pushes the membrane outwards, creating the movement.

Question 3

Which of the following statements describes a primary function of the middle lamella associated with plant cells?

Accepted Answer

The middle lamella, rich in pectins, acts as a cementing layer between plant cells, effectively gluing them together.

Question 4

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through which of the following structures?

Accepted Answer

Gap junctions are specialized structures that allow ions and small molecules to pass directly from the cytoplasm of one cell to the cytoplasm of an adjacent cell, facilitating intercellular communication.

Question 5

Passive leakage of partially digested material from the small intestine into the human abdominal cavity may result from defects in which of the following type of intercellular junction?

Accepted Answer

Tight junctions are specialized structures in cell membranes that create a watertight seal between adjacent cells, preventing the leakage of materials between cells. In the context of the small intestine, they prevent the leakage of partially digested material into the abdominal cavity. Defects in tight junctions can lead to such leakage, highlighting their critical role in maintaining the integrity of barriers within the body.

Question 6

A characteristic 9 + 2 arrangement of microtubules, consisting of nine doublet microtubules surrounding a pair of single microtubules describes the ultrastructure of which of the following cellular structures?

Accepted Answer

The 9 + 2 arrangement of microtubules is characteristic of eukaryotic flagella and motile cilia, which are structures involved in cell movement or the movement of fluids over cell surfaces.

Question 7

Certain animal cells normally have well-defined spherical nuclei when observed by light microscopy. Cells with a genetic defect have irregularly-shaped nuclei. Which of the following cytoskeletal elements is most likely affected by this genetic defect?

Accepted Answer

Intermediate filaments, including nuclear lamins, provide structural support and shape to the nucleus. A defect in these filaments can lead to irregularly-shaped nuclei.

Question 8

Bending of cilia and flagella results from which of the following activities?

Accepted Answer

The bending of cilia and flagella is caused by conformational changes in a motor protein called dynein, which is attached to microtubules. Dynein uses ATP to change shape and move, causing the microtubules to slide against each other, resulting in the bending motion.

Question 9

Which of the following structures form cytoplasmic channels that connect adjacent plant cells through the cell walls?

Accepted Answer

Plasmodesmata are cytoplasmic channels that penetrate the cell walls of plant cells and allow direct communication between adjacent cells.

Question 10

The cell walls of bacteria, fungi, and plant cells, and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following characteristics is common to all of these extracellular structures?

Accepted Answer

These extracellular structures are indeed constructed from materials that are synthesized within the cytoplasm and then transported outside of the cell, where they are assembled into their final forms.

Question 11

Cyanide binds with at least one protein complex involved in producing ATP. If a cell is exposed to cyanide, most of the bound cyanide is likely to be localized within which of the following organelles?

Accepted Answer

Cyanide inhibits the cytochrome c oxidase complex (Complex IV) in the electron transport chain within mitochondria, preventing ATP production.

Question 12

Motor proteins provide for molecular motion in cells by interacting with which of the following cellular structures?

Accepted Answer

Motor proteins interact with components of the cytoskeleton, such as microtubules and actin filaments, to facilitate movement within cells. This includes the transport of vesicles, organelles, and other cellular components, as well as the movement of the cell itself in some cases.

Question 13

Researchers investigating the mechanism of vesicle transport assembled a cell-free system that included microtubules, vesicles, and ATP. However, they observed no movement of transport of vesicles because the mixture was missing which of the following components?

Accepted Answer

Motor proteins are essential for the movement of vesicles along microtubules in cells. Without motor proteins, such as kinesin or dynein, vesicles cannot be transported, even if ATP is present for energy.

Question 14

A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in which of the following structural elements?

Accepted Answer

The extracellular matrix (ECM) is rich in glycoproteins, which are proteins modified with polysaccharides (sugar chains). A mutation that disrupts polysaccharide modifications would directly affect the structure and function of the ECM, as these modifications are crucial for the proper organization, strength, and signaling functions of the ECM.

Question 15

Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells treated with vinblastine would most likely be unable to perform which of the following cellular functions?

Accepted Answer

Vinblastine inhibits microtubule polymerization, which is crucial for the separation of chromosomes during cell division. Microtubules form the mitotic spindle that separates chromosomes, so inhibiting their formation would directly affect this process.

Question 16

A young child who suffers from a metabolic disease is always tired and fatigued. Which of the following organelles is most likely malfunctioning in this disease?

Accepted Answer

Mitochondria are known as the powerhouses of the cell because they produce ATP, the energy currency of the cell. A malfunction in mitochondria would lead to decreased energy production, explaining the symptoms of tiredness and fatigue in the child.

Question 17

Cytochalasin D is a drug that prevents actin polymerization. Which of the following processes will be unaffected in cells treated with cytochalasin D?

Accepted Answer

Movement of transport vesicles in the cytosol is primarily dependent on microtubules and motor proteins like kinesin and dynein, not actin filaments. Therefore, cytochalasin D, which affects actin polymerization, would not affect this process.

Question 18

Which of the following statements best describes some aspect of cytoskeleton structure or function in eukaryotic cells?

Accepted Answer

Cilia and flagella movement is indeed facilitated by motor proteins that cause microtubules to slide past each other, a process essential for the mobility of cells and the movement of fluids across cell surfaces.

Question 19

A particular cell contains the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. Based on this composition, it could be a cell from which of the following organisms?

Accepted Answer

The presence of DNA, ribosomes, a plasma membrane, and mitochondria indicates a eukaryotic cell, as mitochondria are organelles specific to eukaryotes. Both plant and animal cells, as well as other eukaryotic cells, contain these components.

Question 20

Which of the following molecules is required by cells to assemble cilia or flagella?

Accepted Answer

Tubulin is the protein that polymerizes to form microtubules, which are essential components of the structure of cilia and flagella. These microtubules provide the scaffolding that gives cilia and flagella their shape and are involved in their movement.

Quiz 7: Cell Structure and Function