AP BIOLOGY EXAM FREE RESPONSE
QUESTIONS AND ANSWERS
An organism is heterozygous at two gene loci on different chromosomes.
a. explain how these alleles are transmitted by the process of mitosis to daughter cells.
b. explain how these alleles are distributed to gametes by meiosis - Answer-a. mitotic
cell division produces daughter cells that are genetically identical to the parent cell.
Mitosis is the division of the nucleus and consists of the following stages: prophases,
metaphase, anaphase, telophase. In preparation for mitosis, the DNA replicates itself.
Cytokinesis, the actual division of the cytoplasm, almost always follows mitosis but it not
part of mitosis. During prohase, the nuclear membrane begins to break apart and the
nucleolus disappears as the chromosomes condense and become visible under a light
microscope. In metaphase, chromosomes line up single file on the metaphase plate.
Sister chromatids begin to separate during anaphase. They are pulled apart by spindle
fibers connected at one end of the centrioles and at the other end to the kinetochore
within the centromere of the chromosome. In telophase, chromosomes reform into a
circle as the nuclear membrane begins to reform. The two daughter cells that will result
from this mitotic cell division each contain the same chromosomes, T, t, Y, y.
b. Meiosis is a form of cell division that produces gametes, sex cells, with the haploid
chromosome number, n. Two stages that occur in meiosis: meiosis I, reduction division,
in which sister chromatids separate, The two stages of meiosis are further divided into
phases. Each meiotic cell division consists of the same four stages as mitosis:
prophase, metaphase, anaphase, telophase. In meiosis I, the homologous pairs line up
double file on the metaphase plate. One homologue comes from the mother, and one
comes from the father. During anaphase I, the homologues are pulled apart by spindle
fibers and migrate to the poles; one homologue goes to each daughter cell. How the
homologues separate or segregate is determined by how they line up on the metaphase
plate; and how they line up on the metaphase plate
predict what would happen to the level of ATP production if you made the cristae
membrane permable to protons across its entire length and why. - Answer-production of
ATP would cease. The produciton of ATP depends on the maintenance of a proton
gradient across the cristae membrane. Normally ATP is formed as protons flow through
the ATP synthase channels just as water flowing over a dam in a hydroelectric plant
creates electricity. The potential energy from the flow of electrons us used to
phosphorylate ADP into ATP
if chloroplasts and mitochondria were once free-living prokaryotes, what structures
would you expect to find in the plasma membranes of living prokaryotes, and explain
your answer - Answer-*several answers would be accepted*
since mitochondria and chloroplasts evolved from free-living prokaryotes, one would
expect to find ATP synthases in the living prokaryotic membrane. They would produce
ATP by the same or similar mechanism, oxidative phosphorylation, as mitochondria and
chloroplasts do.
, Membranes are important structural features of cells.
a. describe the structure of a membrane
b. discuss the role of membranes in ATP synthesis - Answer-a. the structure of the
plasma membrane was eludicated by SJ Singer in 1972, who described the membrane
as a fluid mosaic, meaning it is made of small pieces that move. The plasma membrane
consists of a phospholipid bilayer with the hydrophillic head of the phospholipid end
facing outward and the hydrophobictail facing inward. Protein molecules are dispersed
throughout the membrane. Some proteins, integral proteins, completely span the
membrane. The average membrane has the consistency of olive oil and is about 40%
lipid and 60% protein, The membrane is selectively premeable and therefore controls
what enters and leaves the cell. In general only small, uncharged, hydrophobic
molecules can diffuse freely through the membrane. Large, polar molecules cannot
diffuse freely through the membrane; they must pass through special protein channels.
b.cristae membranes in the mitochondria play a special role in ATP synthesis. The
cristae membrane is highly folded to increase surface area to allow for more reactions.
It contains electron transport chains, collections of molecules embedded within the
membrane. Most of these molecules are proteins that carry electrons from higher to
lower energy levels. The ETC uses the exergonic flow of electrons to pump protons
across the cristae membrane to the outer compartment of the mitochondria to create an
electrochemical or proton gradient. the key here is that the cristae membrane does not
allow protons to diffuse through the membrane. protons can pass through only special
protein channels, large enzyme complexes called ATP synthases channels. as protons
flow through the ATP synthase channels, like water flowing through a dam, energy is
generated to produce ATP by a process known as chemiosmosis
isolated chloroplasts are placed in an illuminated solution with the appropriate
chemicals to carry out ATP production. Predict what would happen to the rate of
glucose production is a compound is added to the solution that makes membranes
permeable to protons. explain your answer - Answer-photosynthesis would cease
because no ATP would be produced during the light dependent reactions. The reason
no ATP would be produced is that the process of chemiosmosis that produces ATP
depends on the maintenance of a proton gradient within the grana. If grana membranes
were to become permeable to protons, no gradient could form and no ATP would be
produced. Therefore, no sugar could be manufactured in the Calvin cycle
You prepare a slide of living elodea leaf and look at the cells under 40x magnification.
You see many rectangular shaped cells filled with green chloroplasts. While you are
observing the tissue, you carefully place three drops of 4% salt solution next to the right
side of the cover slip and draw the slution acrss the slide by holding a piece of paper
towel on the left edge of the cover slip. You notice that suddenly the chlroplasts have
clustered into the middle of every cell and are surrounded by a membrane. The cell
walls remain unchanged. Explain what has occurred and the mechanism behind it. -
Answer-Because the salt water solution is hypertonic to the elodea cells, water from
inside the cells diffuses rapidly out of the cells. The water moves from the region of a
high concentration of water to a low concentration of water. The chloroplasts are
QUESTIONS AND ANSWERS
An organism is heterozygous at two gene loci on different chromosomes.
a. explain how these alleles are transmitted by the process of mitosis to daughter cells.
b. explain how these alleles are distributed to gametes by meiosis - Answer-a. mitotic
cell division produces daughter cells that are genetically identical to the parent cell.
Mitosis is the division of the nucleus and consists of the following stages: prophases,
metaphase, anaphase, telophase. In preparation for mitosis, the DNA replicates itself.
Cytokinesis, the actual division of the cytoplasm, almost always follows mitosis but it not
part of mitosis. During prohase, the nuclear membrane begins to break apart and the
nucleolus disappears as the chromosomes condense and become visible under a light
microscope. In metaphase, chromosomes line up single file on the metaphase plate.
Sister chromatids begin to separate during anaphase. They are pulled apart by spindle
fibers connected at one end of the centrioles and at the other end to the kinetochore
within the centromere of the chromosome. In telophase, chromosomes reform into a
circle as the nuclear membrane begins to reform. The two daughter cells that will result
from this mitotic cell division each contain the same chromosomes, T, t, Y, y.
b. Meiosis is a form of cell division that produces gametes, sex cells, with the haploid
chromosome number, n. Two stages that occur in meiosis: meiosis I, reduction division,
in which sister chromatids separate, The two stages of meiosis are further divided into
phases. Each meiotic cell division consists of the same four stages as mitosis:
prophase, metaphase, anaphase, telophase. In meiosis I, the homologous pairs line up
double file on the metaphase plate. One homologue comes from the mother, and one
comes from the father. During anaphase I, the homologues are pulled apart by spindle
fibers and migrate to the poles; one homologue goes to each daughter cell. How the
homologues separate or segregate is determined by how they line up on the metaphase
plate; and how they line up on the metaphase plate
predict what would happen to the level of ATP production if you made the cristae
membrane permable to protons across its entire length and why. - Answer-production of
ATP would cease. The produciton of ATP depends on the maintenance of a proton
gradient across the cristae membrane. Normally ATP is formed as protons flow through
the ATP synthase channels just as water flowing over a dam in a hydroelectric plant
creates electricity. The potential energy from the flow of electrons us used to
phosphorylate ADP into ATP
if chloroplasts and mitochondria were once free-living prokaryotes, what structures
would you expect to find in the plasma membranes of living prokaryotes, and explain
your answer - Answer-*several answers would be accepted*
since mitochondria and chloroplasts evolved from free-living prokaryotes, one would
expect to find ATP synthases in the living prokaryotic membrane. They would produce
ATP by the same or similar mechanism, oxidative phosphorylation, as mitochondria and
chloroplasts do.
, Membranes are important structural features of cells.
a. describe the structure of a membrane
b. discuss the role of membranes in ATP synthesis - Answer-a. the structure of the
plasma membrane was eludicated by SJ Singer in 1972, who described the membrane
as a fluid mosaic, meaning it is made of small pieces that move. The plasma membrane
consists of a phospholipid bilayer with the hydrophillic head of the phospholipid end
facing outward and the hydrophobictail facing inward. Protein molecules are dispersed
throughout the membrane. Some proteins, integral proteins, completely span the
membrane. The average membrane has the consistency of olive oil and is about 40%
lipid and 60% protein, The membrane is selectively premeable and therefore controls
what enters and leaves the cell. In general only small, uncharged, hydrophobic
molecules can diffuse freely through the membrane. Large, polar molecules cannot
diffuse freely through the membrane; they must pass through special protein channels.
b.cristae membranes in the mitochondria play a special role in ATP synthesis. The
cristae membrane is highly folded to increase surface area to allow for more reactions.
It contains electron transport chains, collections of molecules embedded within the
membrane. Most of these molecules are proteins that carry electrons from higher to
lower energy levels. The ETC uses the exergonic flow of electrons to pump protons
across the cristae membrane to the outer compartment of the mitochondria to create an
electrochemical or proton gradient. the key here is that the cristae membrane does not
allow protons to diffuse through the membrane. protons can pass through only special
protein channels, large enzyme complexes called ATP synthases channels. as protons
flow through the ATP synthase channels, like water flowing through a dam, energy is
generated to produce ATP by a process known as chemiosmosis
isolated chloroplasts are placed in an illuminated solution with the appropriate
chemicals to carry out ATP production. Predict what would happen to the rate of
glucose production is a compound is added to the solution that makes membranes
permeable to protons. explain your answer - Answer-photosynthesis would cease
because no ATP would be produced during the light dependent reactions. The reason
no ATP would be produced is that the process of chemiosmosis that produces ATP
depends on the maintenance of a proton gradient within the grana. If grana membranes
were to become permeable to protons, no gradient could form and no ATP would be
produced. Therefore, no sugar could be manufactured in the Calvin cycle
You prepare a slide of living elodea leaf and look at the cells under 40x magnification.
You see many rectangular shaped cells filled with green chloroplasts. While you are
observing the tissue, you carefully place three drops of 4% salt solution next to the right
side of the cover slip and draw the slution acrss the slide by holding a piece of paper
towel on the left edge of the cover slip. You notice that suddenly the chlroplasts have
clustered into the middle of every cell and are surrounded by a membrane. The cell
walls remain unchanged. Explain what has occurred and the mechanism behind it. -
Answer-Because the salt water solution is hypertonic to the elodea cells, water from
inside the cells diffuses rapidly out of the cells. The water moves from the region of a
high concentration of water to a low concentration of water. The chloroplasts are
