Question 1

The boundary structure that physically defines a cell is the

Accepted Answer

The plasma membrane is the physical boundary structure that defines a cell. It is composed of a bilayer of phospholipids, with hydrophilic heads facing outward and hydrophobic tails facing inward. The membrane also contains various proteins and channels that regulate the passage of molecules into and out of the cell.

Question 2

Which of the following statements is FALSE?

Accepted Answer

The plasma membrane is not the storehouse for each cell's genetic information. Genetic information is stored in the cell's nucleus (or in prokaryotes, in the nucleoid region).

Question 3

Which of the following statements is true?

Accepted Answer

Different eukaryotic cells, such as muscle cells, nerve cells, or skin cells, have different specialized functions, and thus they contain different numbers and types of organelles. For example, muscle cells contain many mitochondria that produce energy for muscle contraction, while nerve cells have more elaborate networks of endoplasmic reticulum for protein synthesis and cell signaling.

Question 4

The definition of life is somewhat arbitrary; the critical aspect(s)that currently define(s)cells as living structures is (are)

Accepted Answer

The current consensus among biologists is that living things exhibit structural organization, demonstrate energy dependence, and are capable of self-replication. These are the critical aspects that define cells as living structures. While the other options have some relevance to the definition of life, they do not capture the essential features of living organisms.

Question 5

Multicellularity offers a variety of advantages to an organism; among the most important is

Accepted Answer

Adaptive size is one of the most important advantages of multicellularity because, as a larger organism with many cells, an organism can have a larger surface area to volume ratio, which is important for exchange of nutrients and gases with the environment. Single cells are limited in their size because the larger they become, the more difficult it is for them to exchange materials with the environment. By being multicellular, the organism can become large without sacrificing the ability to exchange materials with the environment efficiently.

Question 6

Which statement best describes the relationship between cell size (surface area,volume,and average width or radius)and cell function?

Accepted Answer

As a cell increases in size, its volume increases at a faster rate than its surface area. This means that the surface area to volume ratio decreases, making it more difficult for nutrients and waste to be transported across the cell membrane efficiently. This has implications for cell function, as the cell may struggle to meet its metabolic needs and maintain homeostasis. Therefore, C is the best choice as it accurately describes the relationship between cell size and function.

Question 7

The part of the plasma membrane that is in contact with the external environment of the cell consists of ________ molecules.

Accepted Answer

The hydrophilic portions of the lipid and protein molecules in the plasma membrane are in contact with the external environment of the cell, as they are attracted to water and other polar molecules. The hydrophobic portions of these molecules face inward, away from the aqueous environment, and form the interior of the membrane. Neutral and nonpolar molecules may also be present, but they do not make up the part of the membrane in contact with the external environment.

Question 8

Advancement in biology was hindered by the concept of spontaneous generation,the belief that nonliving objects could spontaneously come to life.What aspect of the cell theory specifically refutes this idea?

Accepted Answer

The aspect of the cell theory that specifically refutes the idea of spontaneous generation is that all living cells come from preexisting cells. This means that life does not spontaneously arise from nonliving matter, but rather comes from other living organisms.

Question 9

Which of the following molecules is NOT found associated with the plasma membrane?

Accepted Answer

Nucleic acids are not typically found associated with the plasma membrane. Phospholipids, proteins, and carbohydrates are all major components of the plasma membrane.

Question 10

Multicellularity does not characterize all types of organisms living today; which eukaryotic kingdoms retain unicellular representatives?

Accepted Answer

Protists and fungi retain unicellular representatives in their respective kingdoms. Algae within the protist kingdom can be unicellular, while yeast is a unicellular fungus. Animals and plants have only multicellular representatives in their respective kingdoms.

Question 11

Volvox,the multicellular green alga shown here,has flagellated cells on its surface cells,but not on interior cells.Which of the following is the most likely explanation for the development of this condition?

Accepted Answer

The most likely explanation for the development of this condition is that signals from surface cells or the absence of signals from the environment to the plasma membranes of the interior cells suppresses the growth of flagella. This explanation is supported by the fact that the surface cells have flagella and are exposed to the environment, while the interior cells lack flagella and are shielded from the environment by the surface cells. Signals from the surface cells or the absence of signals from the environment could influence the plasma membrane of the interior cells, preventing them from growing flagella.

Question 12

Prokaryotes and eukaryotes are primarily distinguished by the absence or presence of internal,membrane-bound organelles.Are prokaryotic cells at an evolutionary disadvantage because they lack organelles?

Accepted Answer

Prokaryotic cells are not at an evolutionary disadvantage because they lack organelles. Although eukaryotic cells are more efficient at carrying out processes such as photosynthesis and respiration, prokaryotic cells are still able to survive and reproduce without these organelles. Prokaryotic cells have evolved to carry out these processes through different mechanisms, such as using the cell membrane to generate energy. Therefore, prokaryotic cells are not at a disadvantage simply because they lack organelles.

Question 13

Which of the following structures is found in all types of cells?

Accepted Answer

The plasma membrane, also known as the cell membrane, encloses all types of cells and regulates the movement of substances into and out of the cell. Chloroplasts are only found in plant cells, cilia are only found in some animal and protist cells, and a cell wall is only found in plant, fungi, and some bacterial cells.

Question 14

The plasma membrane of a cell and the membrane boundaries of organelles,such as mitochondria and chloroplasts,serve similar functions.What is one of the main functions of the membranes of both cells and organelles?

Accepted Answer

Both cell and organelle membranes compartmentalize the cell and organelles, keeping reactants near each other to speed up biological reactions. This is essential for efficient cellular and metabolic processes. Option B is incorrect because membranes control the movement of molecules in and out of the cell or organelle, not allowing them to freely diffuse. Option C is incorrect because while mitochondrial membranes are important for cellular respiration, chloroplast membranes are important for photosynthesis rather than respiration. Option D is incorrect because membranes are selectively permeable, allowing water and other necessary molecules to pass through them.

Question 15

What components of the plasma membrane of an animal cell would you find at its innermost surface,directly exposed to the cytoplasm?

Accepted Answer

The innermost surface of the plasma membrane is directly exposed to the cytoplasm. This region contains the hydrophilic heads of the phospholipid bilayer as well as various types of proteins that are embedded within or attached to the membrane. These proteins include enzymes, transporters, receptors, and structural proteins. Nucleic acids are not normally found in the plasma membrane. Therefore, option C is the correct answer.

Question 16

A screen door allows breezes to enter and aromas to exit,but keeps out insects.Its function most resembles

Accepted Answer

The plasma membrane of a cell serves as a barrier, allowing certain substances to enter and exit while keeping out others. The screen door works in a similar way, allowing air and smells to pass through while keeping insects out. The cytosol and ER lumen are not analogous to a screen door, and a ribosome is involved in protein synthesis, which is not relevant to the function of a screen door.

Question 17

Strong evidence that multicellularity conveys adaptive value to multicellular organisms is provided by the fact that it

Accepted Answer

The independent evolution of multicellularity in various eukaryotic groups suggests that it provides significant adaptive advantages, as it has been naturally selected multiple times across different lineages.

Question 18

The sizes of several biological structures are indicated in the following figure.  Which of the following is the smallest structure you could see with a light microscope?

Accepted Answer

The answer of The sizes of several biological structures are...

Question 19

The magnification of a specimen by a light microscope is a result of

Accepted Answer

The answer of The magnification of a specimen by a...

Question 20

The word "fluid" in the term fluid mosaic model refers to the fact that

Accepted Answer

The word "fluid" in the fluid mosaic model refers to the ability of proteins within the membrane to move around freely, giving the membrane a fluid quality. A refers to the patchwork nature of the membrane's composition, B refers to the selective permeability of the membrane, and D implies a level of assembly and disassembly that is not consistent with the fluidity of the model.

Quiz 3: Cell Structure and Internal Compartments