Question 1

A new protein with a molecular weight of 25,000 Da is discovered and found to reside only in the nucleus.For this to happen, the protein must

Accepted Answer

Proteins that reside in the nucleus are generally transported across the nuclear envelope, which consists of the inner and outer membranes. Small molecules (less than 60 kDa) can pass through nuclear pores, but larger proteins must be actively transported across the envelope through the nuclear pore complex. Therefore, option B is the correct answer. Options A, C, D, and E are not relevant to the localization of the protein in the nucleus.

Question 2

Lysosomes are important to eukaryotic cells because they contain

Accepted Answer

Lysosomes contain digestive enzymes that break down cell waste materials as well as foreign substances that are taken into the cell.

Question 3

The membrane surrounding each organelle

Accepted Answer

The membrane surrounding each organelle regulates traffic into and out of the organelle. This is important for maintaining the unique environment and functions of each organelle within the cell.

Answer: E
 The membrane surrounding each organelle is perforated with pores to allow for the exchange of molecules and communication between organelles. This is important for coordinating cellular processes and maintaining homeostasis. However, not all organelles have pores in their membranes.

Question 4

Although plant and animal cells are both classified as eukaryotic, they do have some differences.Which pair correctly names an animal and a plant cell structure that serve some of the same functions?

Accepted Answer

Both animal lysosomes and plant vacuoles are involved in cellular digestion and waste management. Lysosomes contain hydrolytic enzymes that break down macromolecules, while vacuoles store and sequester waste products, among other functions.

Question 5

While using electron microscopy to examine the cell membrane of a bacterium, you have discovered the presence of a complex motor protein assembly.You do not find any evidence of a proper flagellum.You can conclude that the bacterium most likely has lost its ability to make

Accepted Answer

The presence of a complex motor protein assembly suggests that the bacterium may have been capable of locomotion using a flagellum. However, the absence of a proper flagellum suggests that the bacterium has lost its ability to synthesize flagellin, the protein component of the flagellum. Therefore, choice A is the best answer. The other choices (B, C, D, and E) are not directly related to flagellum synthesis.

Question 6

Specialized cellular appendages of prokaryotes that help bacteria adhere to one another when they exchange genetic material are called

Accepted Answer

Pili are specialized cellular appendages of prokaryotes that are used to facilitate bacterial adhesion to each other and to exchange genetic material, a process known as conjugation. Capsules are protective coatings that surround the bacterial cell and help to resist the host's immune system. Cilia and flagella are motile appendages that aid in bacterial locomotion. The Golgi apparatus is only found in eukaryotic cells and is involved in processing and sorting of cellular products.

Question 7

Chloroplasts are a type of

Accepted Answer

Chloroplasts are a type of plastid, which are organelles found in plant cells involved in processes such as photosynthesis and storage of pigments. Leucoplasts and chromoplasts are also types of plastids but do not have the ability to carry out photosynthesis like chloroplasts. The endoplasmic reticulum and Golgi apparatus are other organelles found in cells but are not related to plastids.

Question 8

You discover what looks to be a new organelle that is smaller than a mitochondrion, but you need to do further testing to best determine its cellular function.What would be your best plan of action?

Accepted Answer

Isolating the organelle using cell fractionation and followed by biochemical analysis would be the best plan of action to determine its cellular function. This approach allows for the purification and identification of the organelle and its specific components, which can then be analyzed to determine its function. This method is commonly used in organelle research and is the most efficient way to determine the function of an unknown organelle. Observing movement, using electron microscopy, or disrupting organelle transport or membrane are not likely to provide sufficient information about the function of the organelle.

Question 9

Ribosomes are not found in

Accepted Answer

Ribosomes are found in mitochondria, chloroplasts, the rough endoplasmic reticulum, and prokaryotic cells, where they are involved in protein synthesis. They are not found in the Golgi apparatus, which is involved in modifying, sorting, and packaging proteins and lipids for secretion or use within the cell.

Question 10

A moss cell is placed in culture with an unknown chemical substance.It is found that the cell appears able to "divide," because the cell is observed to grow and replicate its internal organelles and nuclei, but it does not form primary cell walls.It appears that the substance has affected the synthesis of the polysaccharides that compose the cell wall.Which organelle is possibly targeted by the unknown chemical?

Accepted Answer

The Golgi apparatus is responsible for synthesizing and modifying polysaccharides that make up the cell wall. Therefore, if the substance has affected the synthesis of these polysaccharides, then it is likely targeting the Golgi apparatus. The nucleus, plasmodesmata, mitochondrion, and chloroplasts are not directly involved in synthesizing the cell wall, so they are less likely to be targeted by the substance.

Question 11

You examine an unknown organism using freeze-fracture electron microscopy and discover ribosomes in its cytoplasm.You also find that it has inner membranes, but it is difficult to tell whether they are contiguous with the cell membrane or not.Finding which of the following would allow you to classify this organism as a prokaryote?

Accepted Answer

Finding a capsule would allow you to classify the organism as a prokaryote, as capsules are commonly found in bacteria, which are prokaryotic organisms. Prokaryotes do not have a distinct nucleus or organelles such as mitochondria or plastids, which are features of eukaryotes.

Question 12

Which is a function of a plant cell vacuole?

Accepted Answer

The plant cell vacuole functions to provide physical support as it takes up a significant portion of the cell's volume and helps maintain turgor pressure, which keeps the cell firm and upright.

Other answer choices are incorrect: 
A) Energy metabolism occurs primarily in the mitochondria and chloroplasts, not the vacuole
C) Information storage is not a primary function of the vacuole; genetic material is stored in the nucleus
D) Metabolic regulation is not a primary function of the vacuole; this is primarily carried out by organelles such as the endoplasmic reticulum and Golgi apparatus
E) Protein transport is carried out by organelles such as the endoplasmic reticulum and Golgi apparatus, not the vacuole.

Question 13

Suppose you are given an unknown single-celled organism with a flagellum and asked to classify it as either prokaryote or eukaryote.Compilation of all the following characteristics of your cell can help you, except the

Accepted Answer

The presence or absence of ribosomes cannot help in distinguishing between prokaryotes and eukaryotes because both cell types contain ribosomes, albeit of slightly different sizes and structures.

Question 14

A secondary lysosome is a lysosome that

Accepted Answer

A secondary lysosome is a primary lysosome that has fused with a phagosome, forming a larger and more active digestive compartment. It contains hydrolytic enzymes that help break down the engulfed material.

Question 15

Scientists have observed that in prokaryotes, translation of messenger RNAs begins before transcription has completed.In contrast, translation is completely separate from transcription in eukaryotes because DNA is isolated in the nucleus away from ribosomes, which carry out protein synthesis in the cytoplasm.What advantage does this compartmentalization provide eukaryotes?

Accepted Answer

Compartmentalization of DNA and protein synthesis allows for more opportunities to regulate gene expression. Eukaryotes can control when and where specific genes are transcribed, processed, and translated into proteins. This allows for greater complexity in gene expression and more finely tuned control over cellular processes.

Question 16

In order for an organism to be classified as eukaryotic, it must contain

Accepted Answer

Eukaryotic cells have membrane-bound organelles, such as the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus, which are not present in prokaryotic cells.

Answer: B 
 All living organisms contain DNA, both prokaryotic and eukaryotic. However, the presence of DNA alone cannot determine if an organism is eukaryotic or not.

Therefore, the best choice is C.

Question 17

It is found that a particular type of cell isolated and growing in culture secretes a much larger amount of protein than human liver cells grown under the same conditions.From this, you hypothesize that these cells must have a large number or amount of

Accepted Answer

Protein synthesis is one of the primary functions of the rough endoplasmic reticulum (ER) in eukaryotic cells. If a particular type of cell secretes a much larger amount of protein than other cells grown under the same conditions, it suggests that this cell type has a greater abundance of rough ER, which is responsible for the translation and secretion of proteins. The smooth ER is not directly involved in protein synthesis and would not account for the increased protein secretion observed in this cell culture. Chromosomes, nuclear pores, and peptidoglycan are not directly related to protein synthesis and secretion in eukaryotic cells.

Question 18

Galactose-substituted diglycerides and sulfolipids are the most abundant lipids in the biosphere because of their presence in _______, which are highly abundant in plant cells.

Accepted Answer

Galactose-substituted diglycerides and sulfolipids are present in thylakoids, the membrane-bound compartments within chloroplasts that carry out photosynthesis in plant cells. Thylakoids are highly abundant in plant cells and contain large amounts of these types of lipids.

Question 19

The membranes of the endoplasmic reticulum are continuous with the membranes of the

Accepted Answer

The endoplasmic reticulum (ER) is directly connected to the nuclear envelope, meaning that the membranes of the ER and the nuclear envelope are continuous. The ER is also connected to the Golgi apparatus and the cell membrane, but not in a continuous manner. The nucleolus is not a membrane-bound organelle and is not connected to the ER. The mitochondria have their own distinct membranes and are not continuous with the ER. Therefore, the best choice is A) nuclear envelope.

Question 20

Which technique could you use to determine whether the flagellum-like structure you are observing is made of the protein flagellin or the protein tubulin?

Accepted Answer

Biochemical analysis would involve isolating the flagellum-like structure and performing tests to determine the presence of specific proteins, like flagellin or tubulin, through methods like Western blotting or immunoprecipitation.

Quiz 5: Cells: the Working Units of Life