©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
BOT 331 Exam 1 Questions and Answers
100% Solved
There are two types of nucleic acids: DNA and RNA. There is both DNA
and RNA inside the nucleus, mitochondria and plastids.
Is there both DNA and RNA in the cytosol? Explain your answer - ✔✔No,
not both. DNA remains in the nucleus. RNA copies of genes are
synthesized in the nucleus, but then moved out pores into the cytosol,
where ribosomes (also containing RNA) bind RNA and use the RNA to
direct synthesis of proteins.
In the case of plastids and mitochondria, RNA copies of the organelle's
genes remain in the organelle, and are translated into protein by ribosomes
in the plastid stroma or mitochondrial matrix.
The conducting cells of the xylem experience negative water pressures that
could cause the cell's walls to collapse, but the walls typically resist
collapsing.
, ©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
State two properties of a conducting cell's wall that resists collapse. -
✔✔The walls resist collapse because the walls are very thick. Most of the
thickness is secondary wall that is dense with cellulose microfibrils and the
phenolic polymer lignin, which is very rigid. The phenols of lignin also
cross-link to microfibrils, strengthening the wall.
the tension is what potentially could cause collapse and the thick, lignified
walls resist the collapse.
What is stress relaxation AND how does a cell cause stress relaxation? -
✔✔Stress relaxation is when microfibrils slide relative to each other, which
relieves the tension that is otherwise pulling on microfibrils. Tension in the
wall is due to the cell's turgor pressure.
A cell causes relaxation by breaking the bonds between hemicellulose and
cellulose, which allows the fibers to slide. A cell breaks the bonds by
pumping protons into the wall (acidification), which activates a protein
called Expansin. Expansin catalyzes breaking of the hemicelluose cross-
links.
Be sure to answer all of the following 3 questions about water potential
before moving to the next question.
For each, explain your answer.
BOT 331 Exam 1 Questions and Answers
100% Solved
There are two types of nucleic acids: DNA and RNA. There is both DNA
and RNA inside the nucleus, mitochondria and plastids.
Is there both DNA and RNA in the cytosol? Explain your answer - ✔✔No,
not both. DNA remains in the nucleus. RNA copies of genes are
synthesized in the nucleus, but then moved out pores into the cytosol,
where ribosomes (also containing RNA) bind RNA and use the RNA to
direct synthesis of proteins.
In the case of plastids and mitochondria, RNA copies of the organelle's
genes remain in the organelle, and are translated into protein by ribosomes
in the plastid stroma or mitochondrial matrix.
The conducting cells of the xylem experience negative water pressures that
could cause the cell's walls to collapse, but the walls typically resist
collapsing.
, ©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
State two properties of a conducting cell's wall that resists collapse. -
✔✔The walls resist collapse because the walls are very thick. Most of the
thickness is secondary wall that is dense with cellulose microfibrils and the
phenolic polymer lignin, which is very rigid. The phenols of lignin also
cross-link to microfibrils, strengthening the wall.
the tension is what potentially could cause collapse and the thick, lignified
walls resist the collapse.
What is stress relaxation AND how does a cell cause stress relaxation? -
✔✔Stress relaxation is when microfibrils slide relative to each other, which
relieves the tension that is otherwise pulling on microfibrils. Tension in the
wall is due to the cell's turgor pressure.
A cell causes relaxation by breaking the bonds between hemicellulose and
cellulose, which allows the fibers to slide. A cell breaks the bonds by
pumping protons into the wall (acidification), which activates a protein
called Expansin. Expansin catalyzes breaking of the hemicelluose cross-
links.
Be sure to answer all of the following 3 questions about water potential
before moving to the next question.
For each, explain your answer.
