Question 1

Which of the following statements concerning cells of bacteria and archaea is correct?

Accepted Answer

Both archaea and bacteria contain DNA. However, neither archaea nor bacteria contain a membrane-bound nucleus or mitochondria with DNA. Additionally, while some archaea may contain small membrane-enclosed organelles (such as gas vacuoles), these are not considered true organelles like those found in eukaryotic cells.

Question 2

When disrupted cells are spun in a centrifuge at increasingly higher speeds, which of the following correctly lists the order in which cellular components will pellet?

Accepted Answer

Typically, when disrupted cells are spun in a centrifuge at increasingly higher speeds, the order in which cellular components pellet is based on their size and density. The largest and heaviest components will generally pellet first, followed by smaller and lighter components. Therefore, the correct order in this case would be nucleus (the largest and heaviest component), followed by mitochondria (which are smaller and denser than ribosomes), and then ribosomes. Thus, the best choice is D.

Question 3

Which of the following statements correctly describes some aspect of protein secretion from prokaryotic cells?

Accepted Answer

Prokaryotes lack an endomembrane system, which is necessary for the process of protein secretion in eukaryotic cells. However, prokaryotic cells can still secrete proteins by using specialized secretion systems. The proteins that are secreted by prokaryotes are synthesized on ribosomes that are bound to the cytoplasmic surface of the plasma membrane. These ribosomes are usually associated with the bacterial cytoskeleton, which helps to direct the newly synthesized proteins to the secretion system. Once the protein is targeted to the secretion system, it is transported across the plasma membrane and released into the external environment. Therefore, option C is the correct statement.

Question 4

When subcellular components from disrupted cells are separated using centrifugation, the primary factor that determines whether a specific cellular component remains in the liquid solution or ends up in the pellet is

Accepted Answer

Centrifugation separates subcellular components based on their size and weight. Therefore, the primary factor that determines whether a specific component will stay in the liquid or end up in the pellet is its relative size and weight. Generally, larger and heavier components will pellet at a lower speed than smaller and lighter components.

Question 5

What is the primary reason that a modern transmission electron microscope (TEM) can resolve biological images as small as 2 nm, whereas 200 nm is the limit of resolution for a light microscope?

Accepted Answer

Electron beams have much shorter wavelengths than visible light, which allows for higher resolution imaging in a TEM compared to a light microscope.

Question 6

The volume enclosed by the plasma membrane of plant cells is often much larger than the corresponding volume in animal cells. The most reasonable explanation for this observation is that

Accepted Answer

Plant cells contain a large central vacuole that can occupy up to 90% of the cell's volume, reducing the volume of the cytoplasm. This results in a larger overall volume for the cell compared to animal cells, which have smaller vacuoles or none at all.

Question 7

Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?

Accepted Answer

Ribosomes are responsible for protein synthesis, therefore cells that specialize in producing proteins will have large numbers of ribosomes.

Question 8

Prokaryotes are classified as belonging to two different domains. What are the domains?

Accepted Answer

Prokaryotes are classified into two domains, Bacteria and Archaea. Eukarya is the third domain that includes all eukaryotic organisms. Protista is a kingdom within the domain Eukarya, and it includes unicellular eukaryotes that do not fit into other kingdoms, such as plants, animals, and fungi. Therefore, options A, B, and C are incorrect.

Question 9

The nuclear lamina is a netlike array of filaments on the inner side of the nuclear membrane. If a method were found that could cause the lamina to fall into disarray, what would you expect to be the most likely immediate consequence?

Accepted Answer

The nuclear lamina provides structural support to the nucleus and helps maintain its shape. If the lamina were to fall into disarray, the nucleus would lose its shape, which is likely to affect various nuclear functions, such as DNA replication and transcription, but it is unlikely to cause an immediate loss of all nuclear function, the inability of the nucleus to divide, or disruption of the nuclear pore complex. The lamina also does not play a direct role in keeping out destructive chemicals, so choice (E) is also incorrect.

Question 10

What technique would be most appropriate to use to observe the movements of condensed chromosomes during cell division?

Accepted Answer

The answer of What technique would be most appropriate to...

Question 11

When biologists wish to study the internal ultrastructure of cells, they can achieve the finest resolution by using a

Accepted Answer

Transmission electron microscopes (TEMs) can achieve the finest resolution among the given choices, allowing biologists to study the internal ultrastructure of cells at the nanometer scale. The high-energy electron beam in TEMs can pass through very thin samples, allowing for detailed imaging of cellular organelles and molecular structures. In contrast, phase-contrast light microscopes and confocal fluorescence microscopes have lower resolution capabilities, while scanning electron microscopes are primarily used for surface imaging.

Question 12

Which structure is the site of the synthesis of proteins destined for export from the cell?

Accepted Answer

Rough ER is studded with ribosomes and is responsible for the synthesis of proteins that are destined for secretion or for incorporation into the plasma membrane or into lysosomes.

Question 13

One advantage of light microscopy over transmission electron microscopy is that

Accepted Answer

Light microscopy allows for live cells to be observed, whereas transmission electron microscopy requires the cells to be fixed and sectioned, preventing observation of dynamic processes.

Question 14

Extracellular matrix proteins are produced by ribosomes in which part of a eukaryotic cell?

Accepted Answer

Extracellular matrix proteins are secreted by the cell and therefore must be synthesized on the rough endoplasmic reticulum (ER), where proteins are synthesized and processed for secretion. Ribosomes are located on the surface of the rough ER, so the correct answer is E, rough ER.

Question 15

A cell with an abundance of free ribosomes is most likely

Accepted Answer

Free ribosomes are not attached to the endoplasmic reticulum and are found in the cytoplasm. Cells with an abundance of free ribosomes are likely producing proteins that function within the cytoplasm, such as enzymes and structural components. Therefore, choice B is the best answer. Choices A and C are incorrect because proteins for secretion or extracellular matrix components are typically produced on ribosomes attached to the endoplasmic reticulum. Choice D is incorrect because new membranes would be produced on ribosomes attached to the endoplasmic reticulum. Choice E is incorrect because vacuoles are not typically proteins and thus would not require an abundance of free ribosomes.

Question 16

Biologists commonly use cell fractionation to

Accepted Answer

Cell fractionation involves breaking open cells and separating out their components. Biologists use it to isolate organelles, such as mitochondria or chloroplasts, for further study of their biological functions.

Question 17

The smallest cell structures that would most likely be visible with a standard (not super-resolution) research-grade light microscope is

Accepted Answer

Chloroplasts are large enough to be seen with a standard light microscope, whereas microtubules, ribosomes, and nuclear pores are too small to be resolved by this type of microscope.

Question 18

The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and therefore abundant in liver cells?

Accepted Answer

Smooth ER is primarily involved in detoxification and is abundant in liver cells.

Question 19

Which of the following will be found in nearly all eukaryotic cells?

Accepted Answer

Mitochondria are found in nearly all eukaryotic cells and are responsible for energy production through cellular respiration. Choice A (cell wall) is only found in plant cells and some prokaryotic cells. Choice C (chloroplasts) are only found in plant cells and some protists. Choice D (nucleoid) is only found in prokaryotic cells. Choice E (capsule) is only found in some bacteria.

Question 20

Which of the following may be found in eukaryotic cells, but not in bacteria?

Accepted Answer

Endoplasmic reticulum is a membrane-bound organelle found in eukaryotic cells that is responsible for protein and lipid synthesis, as well as calcium storage and detoxification. Bacteria lack these organelles.

Quiz 4: A Tour of the Cell