Question 1

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?
A) They keep reactants near each other to speed biological reactions.
B) They allow external chemicals to diffuse freely into and out of the cell.
C) They encourage cellular respiration at the membrane boundaries.
D) They keep water out of the cell and organelle interiors.

Accepted Answer

The main function of the plasma membrane and the membrane boundaries of organelles is to regulate the movement of molecules in and out of cells and organelles. This is achieved through selective permeability, which allows certain molecules to pass through while restricting others. Additionally, by keeping reactants near each other, the membranes increase the efficiency of biological reactions. Therefore, choice A is the best answer. Choices B, C, and D are incorrect because they do not accurately reflect the main function of these membranes.

Question 2

Which of the following structures is found in all types of cells?
A) chloroplasts
B) cilia
C) a cell wall
D) a plasma membrane

Accepted Answer

A plasma membrane is found in all cells and is the outermost boundary that separates the internal environment of the cell from the external environment. Chloroplasts, cilia, and a cell wall are only found in specific types of cells. Chloroplasts are only found in plant cells, cilia are only found in certain animal cells, and a cell wall is found in bacteria, fungi, and plant cells but not in animal cells.

Question 3

The part of the plasma membrane that is in contact with the external environment of the cell consists of ________ molecules.
A) hydrophobic portions of the constituent
B) hydrophilic portions of the constituent
C) neutral (uncharged)
D) nonpolar ends of the constituent

Accepted Answer

The hydrophilic portions of the constituent (such as phospholipid head groups) face the external environment of the cell and interact with water molecules, while the hydrophobic portions face the interior of the membrane and interact with each other to form the membrane's lipid bilayer.

Question 4

Strong evidence that multicellularity conveys adaptive value to multicellular organisms is provided by the fact that it
A) evolved within various eukaryotic groups independently.
B) first emerged about 1.5 billion years ago.
C) reduces the potential for predation.
D) allows an organism with relatively small cells to develop a large body.

Accepted Answer

Multicellularity evolving independently in various eukaryotic groups suggests it confers significant adaptive advantages, leading to its repeated emergence across different lineages.

Question 5

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?
A) viruses
B) frog egg
C) most bacteria
D) ribosomes

Accepted Answer

The smallest structure visible with a light microscope is bacteria, with a size ranging from 0.2 to 2 micrometers. Viruses, ribosomes, and other subcellular structures are much smaller than bacteria and require more powerful microscopes to be observed. The frog egg is much larger than all of these structures, measuring several millimeters in diameter.

Question 6

Which statement best describes the relationship between cell size (surface area,volume,and average width or radius)and cell function?
A) Bigger cells have more surface area,more volume,more storage capacity,and are adaptively superior in many ways because of their greater size.
B) Spherical cells function best because they have a more favorable surface area : volume ratio,which explains why red blood cells and most bacteria are spherical.
C) The rate of increase of volume exceeds that of surface area,causing membrane transport of nutrients and waste to become progressively inefficient as cell size increases.
D) Since each feature is determined geometrically,the ratios for any two measurements and cell function capabilities remains constant regardless of overall cell size.

Accepted Answer

As cell size increases, the volume increases at a faster rate than the surface area, causing membrane transport of nutrients and waste to become progressively inefficient. This limits the cell's ability to function properly. Therefore, smaller cells have a greater surface area to volume ratio and are more efficient in nutrient exchange and waste removal.

Question 7

What components of the plasma membrane of an animal cell would you find at its innermost surface,directly exposed to the cytoplasm?
A) phospholipid tails only
B) proteins only
C) phospholipid heads and proteins
D) phospholipid heads and nucleic acids

Accepted Answer

The innermost surface of the plasma membrane of an animal cell is directly exposed to the cytoplasm. This surface is composed of phospholipids heads and proteins, forming a dynamic and selectively permeable barrier that regulates the exchange of molecules between the cell and its environment. The hydrophilic heads of the phospholipids face the cytoplasm, while the hydrophobic tails face towards the interior of the membrane. The proteins embedded in the membrane serve various functions, such as transporters, receptors, enzymes, and structural components.

Question 8

The word "fluid" in the term fluid mosaic model refers to the fact that
A) membranes are a patchwork of lipids and proteins.
B) membranes are selectively permeable.
C) the proteins within a membrane move around freely.
D) the membrane assembles and disassembles as necessary for cell function.

Accepted Answer

The term "fluid" in the fluid mosaic model refers to the fact that the proteins within a membrane move around freely, allowing for membrane flexibility and fluidity. The term "mosaic" refers to the patchwork nature of the lipids and proteins within the membrane. This is best explained by choice C.

Question 9

The definition of life is somewhat arbitrary;the critical aspect(s)that currently define(s)cells as living structures is (are)
A) structural organization,energy dependence,and self-replication.
B) nucleic acid housed within a protective,protein-based container.
C) size: any carbon-based molecular assembly between 0.1 and 1 µm.
D) the presence of at least two classically recognized organelles.

Accepted Answer

A is the best choice as it encompasses the three critical aspects that are currently used to define cells as living structures. Structural organization refers to the complex organization of cells, which distinguishes them from non-living structures. Energy dependence refers to the fact that all living cells require energy to maintain their organization and perform their functions. Self-replication refers to the ability of cells to reproduce and produce offspring that are similar to the parent cell, which is a key characteristic of living organisms. B, C, and D are not comprehensive enough to define living cells. B only refers to the presence of nucleic acids and does not include other important aspects of living cells. C is too narrow and excludes many organisms that are larger or smaller than the specified size range. D is too specific and excludes many cells that do not have classically recognized organelles.

Question 10

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?
A) Every living organism is composed of one or more cells.
B) All living cells come from preexisting cells.
C) Cells are the smallest unit of life possible on Earth.
D) The components of a cell do not individually retain the distinctive characteristics of life.

Accepted Answer

The concept of spontaneous generation suggests that living cells can arise from nonliving matter, but the Cell Theory specifically states that all living cells come from preexisting cells, refuting the idea of spontaneous generation.

Question 11

Which of the following statements is FALSE?
A) The plasma membrane prevents some molecules from entering the cell.
B) The plasma membrane prevents some molecules from leaving the cell.
C) The plasma membrane receives signals from the outside environment.
D) The plasma membrane is the storehouse for each cell's genetic information.

Accepted Answer

The plasma membrane is not the storehouse for each cell's genetic information, that is the role of the nucleus. The plasma membrane is responsible for controlling what enters and exits the cell and receiving signals from the outside environment.

Question 12

Multicellularity offers a variety of advantages to an organism;among the most important is
A) reproductive potential-when separated,each individual cell is capable of independent survival.
B) genetic specialization-each cell can eliminate unnecessary genetic material and produce replicate (backup)copies of essential genetic material.
C) adaptive size-single cells remain constrained by the relationship of surface area to volume,but collectively,the organism can enlarge to the extent that is most advantageous.
D) protective-if partially consumed by predators,the remainder of the organism can replenish the missing cells.

Accepted Answer

Multicellularity allows organisms to reach larger sizes that cannot be attained by single cells due to the limitations of surface area to volume ratio. This increased size provides many advantages such as better nutrient absorption, greater access to resources, and increased efficiency in locomotion. Therefore, the advantage of adaptive size is the most important benefit of multicellularity. The other options do not accurately describe the benefits of multicellularity.

Question 13

Which of the following molecules is NOT found associated with the plasma membrane?
A) phospholipids
B) nucleic acids
C) proteins
D) carbohydrates

Accepted Answer

Nucleic acids, such as DNA and RNA, are not typically found associated with the plasma membrane. They are found in the nucleus or cytoplasm of the cell.

Question 14

A screen door allows breezes to enter and aromas to exit,but keeps out insects.Its function most resembles
A) the cytosol.
B) the plasma membrane.
C) the ER lumen.
D) a ribosome.

Accepted Answer

The function of a screen door to allow certain molecules to pass through while keeping others out is similar to the function of the plasma membrane in a cell, which selectively allows certain substances to enter and exit the cell while keeping others out. The cytosol, ER lumen, and ribosome do not have the same function or analogy to a screen door.

Question 15

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?

A) Interior cells attempt to grow flagella,but the lack of open space suppresses the effort.
B) Interior cells discard the genetic instructions for flagella once their interior position is established.
C) The commitment of resources for photosynthesis reduces the availability of protein and other biomolecules needed to produce flagella.
D) 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.

Accepted Answer

The most likely explanation for the development of flagellated cells only on the surface of Volvox is that signals from the surface cells or the lack of signals from the environment to the plasma membranes of the interior cells suppress the growth of flagella. This suggests that there is some sort of cell-cell communication or environmental cue that determines where flagella are grown, rather than a lack of resources or physical space.

Question 16

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?
A) Yes;without organelles,prokaryotic cells cannot photosynthesize or respire.
B) Yes;without organelles,prokaryotes are unable to bring together the reactants needed for biological reactions.
C) No;although prokaryotic cells are comparatively less efficient than eukaryotic cells,they are still able to carry out the processes necessary for survival and reproduction.
D) No;eukaryotic organelles are expelled each time the cell divides.

Accepted Answer

Prokaryotic cells have been able to survive and thrive for billions of years without the presence of membrane-bound organelles. Although eukaryotic cells are able to perform some functions more efficiently due to the presence of specialized organelles, prokaryotic cells are still capable of carrying out essential biological processes such as metabolism, reproduction, and response to stimuli. Therefore, prokaryotic cells are not at an evolutionary disadvantage because they lack organelles.

Question 17

Multicellularity does not characterize all types of organisms living today;which eukaryotic kingdoms retain unicellular representatives?
A) protists (slime mold),plants (algae),and fungi (yeast)
B) animals (plasmodium),plants (algae),and fungi (yeast)
C) protists (algae)and fungi (yeast)
D) animals (plasmodium),protists (algae),and fungi (yeast)

Accepted Answer

- Protists kingdom retains unicellular representatives such as some algae.
- Fungi kingdom retains unicellular representatives such as yeast.
- Plants kingdom mostly consists of multicellular organisms, but some algae are unicellular. However, not all types of plants have unicellular representatives.
- Animals kingdom mostly consists of multicellular organisms, but some protists such as plasmodium are unicellular. However, not all types of animals have unicellular representatives.

Question 18

The magnification of a specimen by a light microscope is a result of
A) the bending of light as it passes through glass lenses.
B) the focusing of electron beams by magnets.
C) the reflection of light off a specimen.
D) using chemicals to physically enlarge cells.

Accepted Answer

The magnification of a light microscope is achieved through the bending of light as it passes through the glass lenses. This bending of light allows for the specimen to appear larger and more detailed under the microscope. Option B refers to electron microscopes, which use electron beams instead of light, and Option C is not accurate as reflection does not cause magnification. Option D is also not accurate as chemicals cannot physically enlarge cells to a visible extent.

Question 19

The boundary structure that physically defines a cell is the
A) plasma membrane.
B) protein channel.
C) hydrophilic layer.
D) phospholipid side chain.

Accepted Answer

The plasma membrane physically defines the boundary of a cell. It is composed of phospholipids, proteins, and carbohydrates and is selectively permeable, allowing certain substances to move in and out of the cell. Protein channels and phospholipid side chains are components of the plasma membrane, but they do not define the entire boundary structure. The hydrophilic layer is also a component of the plasma membrane but is not what physically defines the cell's boundary.

Question 20

Which of the following statements is true?
A) All types of eukaryotic cells have the same structure,appearance,and function.
B) Different eukaryotic cells contain different numbers and types of organelles,depending on the specific tasks they must perform.
C) Bacterial cells contain membrane-bound organelles.
D) Plant and animal cells have the same structure and organelles.

Accepted Answer

Different eukaryotic cells have different structures and functions based on the tasks they must perform. This includes differences in the number and types of organelles present. Option A is false because different types of eukaryotic cells have different structures and functions. Option C is false because bacterial cells do not contain membrane-bound organelles. Option D is false because plant and animal cells have different structures and organelles.

Quiz 3: Cell Structure and Internal Compartments

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?

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

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

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

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?

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

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

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

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

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?

Which of the following statements is FALSE?

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

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

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

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?

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?

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

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

The boundary structure that physically defines a cell is the

Which of the following statements is true?