Question 1

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 is the physical boundary structure that surrounds and defines a cell. It is composed of a phospholipid bilayer and various proteins that regulate the movement of molecules in and out of the cell. The hydrophilic layer and phospholipid side chains are components of the plasma membrane, but they do not physically define the cell structure in the same way that the plasma membrane does. Protein channels are also components of the plasma membrane, but they are not the boundary structure itself.

Question 2

Which of the following statements is false?
A)Eukaryotes use RNA as the hereditary genetic material.
B)Eukaryotes can be multicellular.
C)Eukaryotes have a membrane-enclosed nucleus.
D)Eukaryotes have membrane-enclosed organelles.

Accepted Answer

Eukaryotes use DNA as the hereditary genetic material, not RNA. RNA is involved in the process of gene expression, but it is not the primary hereditary material in eukaryotes.

Question 3

Volvox, the multicellular green alga shown below, has flagellated cells on its surface cells but not on interior cells. How might this condition develop? 
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 development of flagella on surface cells of Volvox and not on interior cells may be due to signals from surface cells or the absence of signals from the environment to the plasma membranes of the interior cells suppressing the growth of flagella. The signaling pathway may involve molecules or proteins that activate or inhibit the expression of genes involved in flagellar development. Thus, the surface cells being exposed to the environment may have different signal inputs compared to the interior cells, leading to the differential development of flagella.

Question 4

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

Question 5

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 freely move around.
D)the membrane assembles and disassembles as necessary for cell function.

Accepted Answer

The word fluid in the term fluid mosaic model refers to the movement and fluidity of the proteins within a membrane. The proteins are not fixed in place, but rather have the ability to move around within the lipid bilayer. This movement is important for various cellular processes, such as cell signaling and membrane transport.

Question 6

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 plasma membrane is a selectively permeable barrier that allows certain substances to enter or exit while keeping others out. It functions like a screen door in that it permits the passage of gases, small molecules, and water while preventing the entry of larger molecules, toxins, and pathogens.

Question 7

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

While there is not a single universally accepted definition of life, the generally agreed upon characteristics of living organisms include structural organization (cells or tissues), energy-dependence (metabolism), and self-replication (can reproduce and pass on genetic information). Nucleic acids and proteins are important components of living cells, but they alone do not necessarily define life. Similarly, size and the presence of specific organelles are not necessary for life. Therefore, option A is the most appropriate choice.

Question 8

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 both the plasma membrane and the membranes of organelles is to keep reactants close together to speed up biological reactions. This is achieved through the selective permeability of the membrane, which allows certain substances to pass through while keeping others out. The close proximity of enzymes and substrates at the membrane also helps to facilitate reactions.

Question 9

A cell you view under a microscope has a cell wall and chromosomes but no nucleus. The cell you are viewing could be a
A)human muscle cell.
B)cell from the leaf of a maple tree.
C)bacterium recovered from the large intestine of a mammal.
D)cell from the skin of a potato.

Accepted Answer

The presence of a cell wall and chromosomes but no nucleus suggests that the cell being viewed is a prokaryotic cell. The only option that fits this description is a bacterium recovered from the large intestine of a mammal. Human muscle cells, cells from the leaf of a maple tree, and cells from the skin of a potato are all eukaryotic cells and therefore have a nucleus.

Question 10

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, specifically algae, and fungi both have unicellular representatives. While plants also have unicellular representatives (such as algae), they are not the only eukaryotic kingdom to retain unicellular organisms as there are unicellular representatives in both protists and fungi. Animals, on the other hand, do not have any unicellular representatives as all animals are multicellular.

Question 11

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 is directly exposed to the cytoplasm, and it is composed of phospholipid heads and proteins. The hydrophilic heads of the phospholipids face the cytoplasm, while the hydrophobic tails are facing each other to form the bilayer. Proteins are embedded or attached to the membrane and play important roles in various cellular processes such as transport, signaling, and enzymatic activity. There are no nucleic acids found in the plasma membrane.

Question 12

That multicellularity _____ provides strong evidence of its adaptive value.
A)evolved independently within various eukaryotic groups
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

The fact that multicellularity evolved independently within various eukaryotic groups suggests that it provides significant adaptive advantages, as different lineages found similar solutions to environmental challenges.

Question 13

Imagine examining a cell using a light microscope; a prokarotye could be distinguished from a eukaryote by the absence of
A)DNA.
B)a plasma membrane.
C)a nucleus.
D)a cell wall.

Accepted Answer

Prokaryotes do not have a nucleus, while eukaryotes do. All other options (DNA, plasma membrane, and cell wall) are present in both prokaryotes and eukaryotes.

Question 14

The sizes of several biological structures are indicated in the figure below. 
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 most bacteria, with a length of about 0.5 to 5 micrometers. Viruses and ribosomes are much smaller and cannot be seen with a light microscope, while frog eggs are much larger than bacteria.

Question 15

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 surface area-volume relationships, 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 an organism to grow larger than a single cell, which is limited by the constraints of surface area-to-volume ratios. Adaptive size is one of the significant advantages of multicellularity.

Answer: D
 Multicellularity provides more significant protection against predators as the organism can replenish missing cells. This advantage is absent in single-celled organisms.

A) and B) are incorrect because they do not adequately describe the advantages of multicellularity. While reproductive potential and genetic specialization are essential characteristics of multicellular organisms, they are not the most significant advantages.

Question 16

Which of the following structures in not found in all types of cells?
A)cytoplasm
B)ribosomes
C)a nucleus
D)a plasma membrane

Accepted Answer

Not all cells have a nucleus. This includes prokaryotic cells and some types of eukaryotic cells, such as red blood cells.

Question 17

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 primarily involved in regulating the transport of molecules into and out of the cell and in receiving signals from the external environment. However, the storehouse for each cell's genetic information is the nucleus, not the plasma membrane.

Question 18

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 aspect of the cell theory that specifically refutes spontaneous generation is the principle that all living cells come from preexisting cells. This means that life does not arise spontaneously, but rather is passed down from previous generations of living cells. This refutes the idea that nonliving objects can generate life on their own, as there must be a preexisting living cell to give rise to new life.

Question 19

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

Accepted Answer

The hydrophilic portions of the constituent molecules in the plasma membrane, such as the phospholipid head groups and membrane proteins, face the external environment of the cell, which is typically aqueous in nature. This allows for interactions with water and other polar molecules outside the cell. The hydrophobic portions of the membrane face toward the interior of the cell, away from the external environment.

Question 20

Which statement best describes the relationship between cell surface area, volume, and average width or radius?
A)Bigger cells have more surface area, more volume, more storage capacity, and are adaptively superior.
B)Spherical cells have a more favorable relationship between surface area and volume, which explains why red blood cells and most bacteria are spherical.
C)The rate of increase of volume exceeds that of surface area; membrane transport becomes progressively inefficient as cell size increases.
D)Since each feature is determined geometrically, the ratios for any two measurements remains constant regardless of overall cell size.

Accepted Answer

As the cell grows in size, the volume increases much more rapidly than the surface area. This means that the surface area to volume ratio decreases, and it becomes increasingly difficult for the cell to exchange materials with its environment. This can limit the cell's ability to survive and function efficiently.

Quiz 6: Cell Structure and Internal Compartments

The boundary structure that physically defines a cell is the

Which of the following statements is false?

Volvox, the multicellular green alga shown below, has flagellated cells on its surface cells but not on interior cells. How might this condition develop?

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

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

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

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

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 cell you view under a microscope has a cell wall and chromosomes but no nucleus. The cell you are viewing could be a

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

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

That multicellularity _____ provides strong evidence of its adaptive value.

Imagine examining a cell using a light microscope; a prokarotye could be distinguished from a eukaryote by the absence of

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

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

Which of the following structures in not found in all types of cells?

Which of the following statements is false?

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?

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

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