Biol 231 Exam 1 || with Perfect Answers.
Eukaryotic cells have a number of membrane-bounded organelles with specific and essential
functions in the life of the cell. For the list of organelles below, match each organelle to the best
descriptions of their properties or functions that occur there. Individual answers may apply to
more than one organelle.
1.synthesizes membrane proteins and proteins to be secreted from the cell
2.sorts proteins to many other sites in the cell
3.maintains a pH much more acidic than that of cytoplasm
4.produces molecular oxygen by splitting water
5.consumes oxygen and releases carbon dioxide
6.site of genomic DNA transcription into RNA correct answers Mitochondrion 5
Lysosome 3
Endoplasmic Reticulum 1
Nucleus 6
Golgi Apparatus 2
Chloroplast 4
You have approximately 1013 cells in your body (human cells, that is - we'll come back to the
rest in a few weeks!). If all of those human cells arose by successive divisions of your original
zygote, how many divisions did it take to produce you? Determine the integral number of
divisions that gives the closest result correct answers 43
Of course, the development of an adult organism from a zygote isn't quite that simple. In
addition, things can go awry with cell division - notably the transformation of normal cells into
cancer cells that divide in an uncontrolled way. If a single cancer cell in a tissue of the human
body divides once every day, how long will it take for that cell to produce a tumor 20 cm3 in size
(approximately equivalent to a golf ball)? Assume that the original cell has a volume of 10−9
cm3 and determine the integral number of divisions that gives the closest result. Render your
answer in days, but do not add the units, only enter a numeric value in the answer box. correct
answers 34
Cells can take up molecules from the outside world by endocytosis, through membrane channels,
or by simple diffusion. But regardless of the avenue, the rate at which the cell can acquire
material from the outside world is limited by the total surface area of the cell. On the other hand,
the amount of material that they need to take up is proportional to the cell volume - i.e., how
much biomass is in the cell. Some cells are spherical. correct answers 0.3
Using the same formula that you obtained for the previous question, calculate the surface-to-
volume ratio for a much larger spherical human oocyte (egg cell) with a radius of 300 μm correct
answers 0.01
Using the same formula calculate the surface-to-volume ratio for a spherical frog oocyte (egg
cell) with a radius of 1,300 μm correct answers 0.002308
, Cells in the body of a metazoan organism like yourself have many shapes and sizes that are
suited to their particular functions. Consider a muscle cell, which has the shape of a long
cylinder. Assume a cell in one of the tiny dorsal interosseous muscles of your hand is 14 mm
long, with a radius of 12 μm.
What is its surface-to-volume ratio in μm-1? correct answers 0.1668
Human epithelial cells can be grown in a culture dish, where they undergo many rounds of cell
division. During most of the cell cycle, they adhere tightly to the surface of the dish, spreading
out into a rectangular solid shape that approximates a White Castle burger, 65 μm x 65 μm x 1
μm thick. But during cell division they lose most of their attachment to the surface of the dish
and round up into a spherical shape with a radius of 10 μm. In both shapes the cell has about the
same volume (check it for yourself), but the surface area of the cell goes down by about 7-fold
when it rounds up (you can check this, too). How can a cell quickly decrease its S/V by
decreasing its surface area, while keeping its volume about the same?
-Endocytosis that takes up many small coated vesicles, since the cell gains the surface area of
each endosome, but loses its volume.
-Exocytosis of many small secretory vesicles, since the cell correct answers Endocytosis that
takes up many small coated vesicles, since the cell loses the surface area of each endosome, but
gains some internalized volume.
Assume that a spherical cell, with a diameter of 20 μm, has spherical mitochondria, each with a
diameter of 0.2 μm. If mitochondria occupy 10% of the volume of the cell, how many
mitochondria are there? correct answers 100,000
Number each of the following in order of its surface area, with "1" being the largest.
Total Membrane of the Er
Plasma membrane of an epithelial cell
Total membrane of a secretory vesicle
Total membrane of a mitochondrion correct answers 2
1
4
3
Number each of the following in order of its numerical value, with "1" being the largest.
-log(10^-1)
-log(10^-14
10^3
log(10^3)
-log(10^-7) correct answers 5
2
1
4
3
If a solution is at pH 5, what is the concentration of protons in mol/L (M)? correct answers
0.00001
Eukaryotic cells have a number of membrane-bounded organelles with specific and essential
functions in the life of the cell. For the list of organelles below, match each organelle to the best
descriptions of their properties or functions that occur there. Individual answers may apply to
more than one organelle.
1.synthesizes membrane proteins and proteins to be secreted from the cell
2.sorts proteins to many other sites in the cell
3.maintains a pH much more acidic than that of cytoplasm
4.produces molecular oxygen by splitting water
5.consumes oxygen and releases carbon dioxide
6.site of genomic DNA transcription into RNA correct answers Mitochondrion 5
Lysosome 3
Endoplasmic Reticulum 1
Nucleus 6
Golgi Apparatus 2
Chloroplast 4
You have approximately 1013 cells in your body (human cells, that is - we'll come back to the
rest in a few weeks!). If all of those human cells arose by successive divisions of your original
zygote, how many divisions did it take to produce you? Determine the integral number of
divisions that gives the closest result correct answers 43
Of course, the development of an adult organism from a zygote isn't quite that simple. In
addition, things can go awry with cell division - notably the transformation of normal cells into
cancer cells that divide in an uncontrolled way. If a single cancer cell in a tissue of the human
body divides once every day, how long will it take for that cell to produce a tumor 20 cm3 in size
(approximately equivalent to a golf ball)? Assume that the original cell has a volume of 10−9
cm3 and determine the integral number of divisions that gives the closest result. Render your
answer in days, but do not add the units, only enter a numeric value in the answer box. correct
answers 34
Cells can take up molecules from the outside world by endocytosis, through membrane channels,
or by simple diffusion. But regardless of the avenue, the rate at which the cell can acquire
material from the outside world is limited by the total surface area of the cell. On the other hand,
the amount of material that they need to take up is proportional to the cell volume - i.e., how
much biomass is in the cell. Some cells are spherical. correct answers 0.3
Using the same formula that you obtained for the previous question, calculate the surface-to-
volume ratio for a much larger spherical human oocyte (egg cell) with a radius of 300 μm correct
answers 0.01
Using the same formula calculate the surface-to-volume ratio for a spherical frog oocyte (egg
cell) with a radius of 1,300 μm correct answers 0.002308
, Cells in the body of a metazoan organism like yourself have many shapes and sizes that are
suited to their particular functions. Consider a muscle cell, which has the shape of a long
cylinder. Assume a cell in one of the tiny dorsal interosseous muscles of your hand is 14 mm
long, with a radius of 12 μm.
What is its surface-to-volume ratio in μm-1? correct answers 0.1668
Human epithelial cells can be grown in a culture dish, where they undergo many rounds of cell
division. During most of the cell cycle, they adhere tightly to the surface of the dish, spreading
out into a rectangular solid shape that approximates a White Castle burger, 65 μm x 65 μm x 1
μm thick. But during cell division they lose most of their attachment to the surface of the dish
and round up into a spherical shape with a radius of 10 μm. In both shapes the cell has about the
same volume (check it for yourself), but the surface area of the cell goes down by about 7-fold
when it rounds up (you can check this, too). How can a cell quickly decrease its S/V by
decreasing its surface area, while keeping its volume about the same?
-Endocytosis that takes up many small coated vesicles, since the cell gains the surface area of
each endosome, but loses its volume.
-Exocytosis of many small secretory vesicles, since the cell correct answers Endocytosis that
takes up many small coated vesicles, since the cell loses the surface area of each endosome, but
gains some internalized volume.
Assume that a spherical cell, with a diameter of 20 μm, has spherical mitochondria, each with a
diameter of 0.2 μm. If mitochondria occupy 10% of the volume of the cell, how many
mitochondria are there? correct answers 100,000
Number each of the following in order of its surface area, with "1" being the largest.
Total Membrane of the Er
Plasma membrane of an epithelial cell
Total membrane of a secretory vesicle
Total membrane of a mitochondrion correct answers 2
1
4
3
Number each of the following in order of its numerical value, with "1" being the largest.
-log(10^-1)
-log(10^-14
10^3
log(10^3)
-log(10^-7) correct answers 5
2
1
4
3
If a solution is at pH 5, what is the concentration of protons in mol/L (M)? correct answers
0.00001
