Download Most eukaryotic cells are between 10 and 100 micrometers in

PROCTOR VERSION
2.9 C: Impact Cell Size Quiz
1.
Most eukaryotic cells are between 10 and 100 micrometers in diameter. Which statement is the
best justification for the small size of eukaryotic cells?
(A) Eukaryotic cells are small because the cell membranes are too weak to support the mass
and volume of a larger-sized cell.
Distractor Rationale:
This answer suggests the student may understand that cell membranes play a role in
determining cell size, but does not understand that a high surface area-to-volume ratio is
the main limitation to cell size because it affects the cell’s ability to adequately exchange
materials with the environment.
(B) Eukaryotic cells are small because they cannot synthesize the necessary macromolecules
fast enough to support cells that are large in size.
Distractor Rationale:
This answer suggests the student may understand that macromolecules are important for
cell function, but does not understand that the rate of synthesis does not affect cell size,
and that the main limitation to cell size is the surface area-to-volume ratio because it affects
the rate at which materials are exchanged with the environment.
(C) Eukaryotic cells are small in order to maintain a high ratio of surface area to volume, which
allows for rapid exchange of materials with the surroundings.
Rationale:
This answer suggests the student understands that the surface area-to-volume ratio affects
a cell’s ability to obtain necessary resources or eliminate wastes, and cells need to have a
surface area-to-volume ratio that is high enough to allow for adequate movement of
materials across the cellular membrane.
(D) Eukaryotic cells are small in order to limit the amount of resources needed for growth, which
helps reduce energy depletion.
Distractor Rationale:
This answer suggests the student may understand that a larger cell has to use more
resources to grow, but does not understand that the main limitation to cell size is the ability
to exchange materials with the environment and that large cells have a lower surface areato-volume ratio, which prevents adequate material exchange.
Aligned to: LO 2.9 CA 2.9: Represent & Model Matter Exchange
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PROCTOR VERSION
2.9 C: Impact Cell Size Quiz
2.
A typical frog egg has a diameter between 2 and 3 millimeters (mm). A eukaryotic cell is much
smaller and has a diameter between 10 and 100 micrometers (µm). Which statement best
compares the effect of cell size on the processes that occur in a frog egg and in a eukaryotic
cell?
(A) Diffusion occurs faster in a frog egg because the frog egg has a higher surface area-tovolume ratio than a eukaryotic cell.
Distractor Rationale:
This answer suggests the student may understand that the rate of diffusion and surface area
are related, but does not understand that diffusion is slower in the frog egg because the
ratio of the surface area to volume is lower than that of a eukaryotic cell.
(B) Waste is eliminated less efficiently in a eukaryotic cell because there is less surface area in
a eukaryotic cell than in a frog egg.
Distractor Rationale:
This answer suggests the student may understand that a smaller cell has less surface area
than a larger cell, but does not understand that a larger cell eliminates waste less
efficiently because it has a larger volume, which makes the surface area-to-volume ratio
lower.
(C) A eukaryotic cell is unable to obtain large molecules needed for cellular function because a
eukaryotic cell has less volume than a frog egg.
Distractor Rationale:
This answer suggests the student may understand that a smaller cell has less volume than a
larger cell, but does not understand that a smaller cell can obtain the necessary
nutrients/molecules faster than a larger cell because the smaller cell has a higher surface
area-to-volume ratio than the larger cell and that large molecules can enter small cells
because the cells are much larger than the large molecules.
(D) A frog egg is less efficient at exchanging nutrients with the environment because the frog
egg has a lower surface area-to-volume ratio than a eukaryotic cell.
Rationale:
This answer suggests the student understands that a larger cell has a lower surface areato-volume ratio and cannot exchange nutrients with the environment as efficiently as a
smaller cell, which has a higher surface area-to-volume ratio.
Aligned to: LO 2.9 CA 2.9: Represent & Model Matter Exchange
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PROCTOR VERSION
2.9 C: Impact Cell Size Quiz
3.
The diagram below shows the approximate dimensions of plant cell X and plant cell Y.
Which statement best describes the surface area-to-volume ratios of plant cell X and plant cell
Y?
(A) Plant cell Y has four times the surface area of plant cell X, but the surface area-to-volume
ratio of plant cell Y is one-half that of plant cell X.
Rationale:
This answer suggests the student understands how to calculate surface area-to-volume
ratios for 3-dimensional objects and understands that larger cells have larger membranes
but that the volume increases faster than the surface area, which reduces the surface areato-volume ratio.
(B) Since each side of plant cell Y is twice as long as the corresponding side of plant cell X, the
surface area-to-volume ratio of plant cell Y is eight times greater than that of plant cell X.
Distractor Rationale:
This answer suggests the student may understand that each side of plant cell Y is twice as
long as the corresponding sides on plant cell X, but does not understand that the surface
area of plant cell Y is only four times greater and that the surface area-to-volume ratio in
plant cell Y is half that of plant cell X.
(C) Because plant cell X and plant cell Y are the same shape, the surface area-to-volume ratio
of both plant cell X and plant cell Y is the same.
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PROCTOR VERSION
2.9 C: Impact Cell Size Quiz
Distractor Rationale:
This answer suggests the student may understand that plant cell X and plant cell Y have
similar shapes, but does not understand that the volume and surface area are affected by
doubling the dimensions, and that the surface area-to-volume ratio of plant cell Y is one-half
that of plant cell X.
(D) Plant cell Y is twice the size of plant cell X, so the surface area-to-volume ratio of plant cell Y
is twice that of plant cell X.
Distractor Rationale:
This answer suggests the student may understand that each dimension in plant cell Y is
twice as long as in plant cell X, but does not understand that because the dimensions in
plant cell Y are twice that of plant cell X, its surface area-to-volume ratio is one-half that of
plant cell X.
Aligned to: LO 2.9 CA 2.9: Represent & Model Matter Exchange
4.
Four different shapes are shown below. The shapes have approximately the same volume.
Which statement explains which shape is best suited for a cell that requires rapid exchange of
nutrients with the environment?
(A) Cell shape 1 because the volume is greatest while using the smallest space.
Distractor Rationale:
This answer suggests the student may understand that a cube is optimal for storage in
terms of the most volume in the smallest space, but does not understand that it is not the
optimal shape for nutrient exchange, which requires a large surface area and a small
volume to yield a high surface area-to-volume ratio.
(B) Cell shape 2 because it has the largest surface area per unit of volume.
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PROCTOR VERSION
2.9 C: Impact Cell Size Quiz
Rationale:
This answer suggests the student understands that the indentation in a disc-shaped object
increases the surface area-to-volume ratio, which results in increased efficiency of nutrient
exchange.
(C) Cell shape 3 because the center is equidistant to any part of the cell membrane.
Distractor Rationale:
This answer suggests the student may understand that a spherical shape allows for an
equal rate of diffusion on all sides, but does not understand that this shape does not
maximize surface area in terms of volume for the most efficient nutrient exchange.
(D) Cell shape 4 because it provides the most total surface area of any of the other shapes.
Distractor Rationale:
This answer suggests the student may understand that that a cylinder has more surface
area than any of the other shapes, but does not understand that this shape does not
maximize the surface area-to-volume ratio for the most efficient exchange of nutrients.
Aligned to: LO 2.9 CA 2.9: Represent & Model Matter Exchange
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