Question 1

One difference between plant cells and animal cells is that

Accepted Answer

Animal cells lack a large central vacuole, whereas plant cells have a large central vacuole that takes up most of the space in the cell.

Question 2

A mutant cell line is compared with a nonmutant cell line of the same type.The nonmutant cells secrete the steroid estrogen, but the mutant cells do not.Where should a researcher look to determine whether the mutant cells' defect is in the excretion of the hormone or in its synthesis?

Accepted Answer

The smooth ER is involved in the synthesis of lipids and steroids, including estrogen. If the defect is in synthesis, it would be evident in the smooth ER.

Question 3

You are given an unknown organism to classify.The presence of which cell structure would eliminate the possibility that the organism is an animal?

Accepted Answer

Amyloplasts are typically found in plant cells, therefore the presence of amyloplasts would eliminate the possibility that the organism is an animal.

Question 4

Which structure is involved in the breakdown of food particles by the cell?

Accepted Answer

The phagosome is a specialized structure in the cell that is involved in the engulfing and breakdown of food particles. It is formed when a cell engulfs a solid particle, such as a bacterium, and brings it into the cell in a membrane-bound compartment called the phagosome. The phagosome then fuses with lysosomes, which contain digestive enzymes, and the food particle is broken down into its component parts, which the cell can use for energy and other metabolic functions.

Question 5

A cancer drug is being tested, and it is found that although the cancer cells can divide, the nuclear envelope cannot re-form.It is determined that a protein substance is sequestered so that it cannot be polymerized into the necessary structure.What is the most likely protein target of the drug?

Accepted Answer

Lamin is a protein that plays a critical role in the formation and maintenance of the nuclear envelope. If this protein is sequestered and cannot be polymerized into the necessary structure, the nuclear envelope cannot reform properly. Therefore, inhibition of lamin could be the protein target of the cancer drug being tested. Keratin is a structural protein present in cells, but it is not directly involved in nuclear envelope formation. α-tubulin, β-tubulin, and actin are all involved in cytoskeleton formation and are not directly involved with nuclear envelope formation.

Question 6

Which statement about lysosomes is true?

Accepted Answer

Lysosomes are organelles that contain hydrolytic enzymes that can break down various types of biomolecules. They are involved in the degradation of worn-out organelles and macromolecules in a process called autophagy.

Answer: None of the above 
 Options B, C, and D are incorrect as lysosomes do not provide storage of starch in plant cells or contain anthocyanins that aid in pollination. Lysosomes are found in both plant and animal cells, and there is no evidence that they arose through endosymbiosis.

Question 7

Microvilli are supported by a network of which type of structure?

Accepted Answer

Microvilli are supported by a network of microfilaments (actin filaments), which provide structural support and help with the movement of the microvilli. Microtubules, intermediate filaments, and chromatin do not play a significant role in supporting microvilli. Myosin is a motor protein that is involved in muscle contraction and not in microvilli support.

Question 8

A patient is admitted to the hospital for dehydration and malnutrition.On close observation of the intestine, it appears that the cells lining the intestine have fully formed microvilli.However, these microvilli are not uniformly standing upright and protruding into the lumen of the intestine, but are lying down so that full exposure to the contents of the intestine cannot be obtained.The doctors conclude that the patient may have a defect in what cellular component?

Accepted Answer

Actin is responsible for the formation and contraction of microvilli. If there is a defect in actin, the microvilli may not stand upright and protrude into the lumen of the intestine, leading to malabsorption of nutrients and dehydration.

Question 9

Microtubules are made of

Accepted Answer

Microtubules are made of tubulin protein and are essential in chromosome movement during mitosis.

Question 10

What type of agent would be most likely to disrupt the structures of microvilli?

Accepted Answer

Microvilli are supported by actin filaments, so an actin depolymerizing agent would disrupt their structure by breaking down the actin filaments.

Question 11

An unknown animal is discovered preserved in ice.In its cells is an unknown type of cytoskeletal component that is ropelike in structure and has a diameter of 11 nm.How would a scientist classify this component?

Accepted Answer

The ropelike structure and diameter of 11 nm suggest that this component is an intermediate filament. Microfilaments, microvilli, cilia, and microtubules all have different structures and diameters.

Question 12

Microtubules are composed of

Accepted Answer

Microtubules are made up of two types of globular proteins called α-tubulin and β-tubulin. These proteins bind together to form protofilaments, which are then arranged in a cylindrical structure to form the microtubule.

Question 13

Cytoskeletal components with a 7 nm diameter are discovered in the cultured cells of an animal.Which would be a good experiment to check your hypothesis about the identity of these cytoskeletal components?

Accepted Answer

CActin filaments, which are part of the cytoskeleton, have a diameter of about 7 nm. To test if the structures are actin filaments, depolymerizing actin (choice B) would cause the structures to collapse if they are indeed actin. Injecting a tubulin binding protein (choice C) would affect microtubules, which have a larger diameter, and thus serves as a control to confirm that the structures are not microtubules.

Question 14

If you wanted to stop the movement of a ciliated protist in culture, you could incubate it in a substance that inhibits

Accepted Answer

Dynein is responsible for the movement of cilia and flagella in eukaryotic cells. Incubation of a ciliated protist in a substance that inhibits dynein would result in the cessation of its movement. Inhibiting the other options (flagellin, myosin, actin, and kinesin) would not affect the movement of cilia, as they are not involved in this process.

Question 15

Which is the correct order of structures that a macromolecule and its monomers will encounter in the time period between when the macromolecule is engulfed into a cell and when its monomers are used as an energy source?

Accepted Answer

The correct order starts with the macromolecule being engulfed into a phagosome, then it is digested into monomers in a secondary lysosome. These monomers are released into the cytoplasm, where they can be used in various processes, including being further broken down in the mitochondria for energy.

Question 16

A cultured cell line appears to be having trouble surviving.Upon closer examination, you find that the cells do not appear to have normal chromosome separation.Based on this observation, you decide to check for the presence of a mutated protein.You will be sure to analyze the gene for which protein?

Accepted Answer

Tubulin is a protein that plays a critical role in the separation of chromosomes during cell division. Mutations in tubulin can lead to problems with chromosome segregation and cell survival. Therefore, checking for the presence of a mutated tubulin protein would be the best choice in this scenario.

Question 17

Which type of cell structure is found in plants but not in animals?

Accepted Answer

Glyoxysomes are specialized plant cell structures that are involved in lipid metabolism in germinating seeds. They are not found in animal cells. Ribosomes, mitochondria, nuclei, and lysosomes are all found in both plant and animal cells.

Question 18

Which structure is involved with maintaining the position of the organelles within a cell?

Accepted Answer

Intermediate filaments, a type of cytoskeleton, are responsible for maintaining the position and shape of organelles within a cell.

Question 19

Hair and some intermediate filaments are composed of

Accepted Answer

Hair and intermediate filaments are composed of keratin.

Question 20

Muscle cells need large amounts of calcium and ATP for contraction.Based on these requirements, you would expect that muscle cells would have an increased number of what type of organelles (per unit volume)?

Accepted Answer

Mitochondria are crucial for ATP production, providing the energy required for muscle contraction. The smooth endoplasmic reticulum (SER) plays a key role in calcium storage and release, which is essential for muscle cell contraction.

Quiz 5: Cells: the Working Units of Life