Plant Biology - GRE
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Double fertilization in angiosperms results in a zygote and a triploid .
Double fertilization in angiosperms results in a zygote and a triploid .
Double fertilization is the process by which two sperm cells are introduced to the ovule. One sperm (
) fertilizes the egg (
), creating a zygote(
). The other sperm combines with the two polar nuclei (
), forming the endosperm (
) that will nourish the embryo.
Double fertilization is the process by which two sperm cells are introduced to the ovule. One sperm (
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Which of the following structures is unique to plant cells?
Which of the following structures is unique to plant cells?
Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.
Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.
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Which of the following can be found in plant cells, but not animal cells?
Which of the following can be found in plant cells, but not animal cells?
Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.
The other structure that may be found in plant cells, but not animal cells, is a cell wall.
Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.
The other structure that may be found in plant cells, but not animal cells, is a cell wall.
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The Calvin cycle takes place in the and occurs .
The Calvin cycle takes place in the and occurs .
The Calvin cycle takes place in the stroma of the chloroplast, which is the region in the chloroplast lumen outside of the thylakoids. It does not actually matter whether or not light is present for the reactions of the Calvin cycle to take place. They are light independent, but light will not prevent the reactions from occurring, similar to how glycolysis is independent of oxygen. As long as the appropriate nutrients and reactants are present, including ATP and NADPH generated from the light reactions, the Calvin cycle will occur.
The Calvin cycle takes place in the stroma of the chloroplast, which is the region in the chloroplast lumen outside of the thylakoids. It does not actually matter whether or not light is present for the reactions of the Calvin cycle to take place. They are light independent, but light will not prevent the reactions from occurring, similar to how glycolysis is independent of oxygen. As long as the appropriate nutrients and reactants are present, including ATP and NADPH generated from the light reactions, the Calvin cycle will occur.
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Where in the chloroplasts does the Calvin Cycle of photosynthesis take place?
Where in the chloroplasts does the Calvin Cycle of photosynthesis take place?
The Calvin Cycle occurs in the stroma, the aqueous fluid-filled area of the chloroplast. The stroma can be seen as analogous to the cytoplasm of a cell, in that it is the liquid in which all other substructures reside. The other processes of photosynthesis, the light-dependent reactions, take place in the thylakoid, a membrane-bound substructure within the chloroplast.
The Calvin Cycle occurs in the stroma, the aqueous fluid-filled area of the chloroplast. The stroma can be seen as analogous to the cytoplasm of a cell, in that it is the liquid in which all other substructures reside. The other processes of photosynthesis, the light-dependent reactions, take place in the thylakoid, a membrane-bound substructure within the chloroplast.
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What is the purpose of photosystem II in photosynthesis?
What is the purpose of photosystem II in photosynthesis?
Photosystem II splits water into hydrogen and oxygen. Hydrogen ions accumulate in the thylakoid space, creating an electrochemical concentration gradient. Due to this gradient, hydrogen ions pass through ATP sythase, powering the synthesis of ATP from ADP + Pi.
Photosystem II splits water into hydrogen and oxygen. Hydrogen ions accumulate in the thylakoid space, creating an electrochemical concentration gradient. Due to this gradient, hydrogen ions pass through ATP sythase, powering the synthesis of ATP from ADP + Pi.
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In plants, leaves contain specialized pores used for gas exchange. Each pore is formed by a pair of cells that control its closing and opening. What are these cells called?
In plants, leaves contain specialized pores used for gas exchange. Each pore is formed by a pair of cells that control its closing and opening. What are these cells called?
For proper functioning, plants must take in carbon dioxide, expel oxygen, and limit the loss of water vapor. This gas exchange takes place via pores called stomata. These pores are formed by a pair of adjacent cells that can open and close in response to a number of factors. These cells are called guard cells.
The cuticle and epidermis are layers of leaf structure, and do not correspond to specific cell types. The stoma is the name of a single pore itself, not its surrounding cells.
For proper functioning, plants must take in carbon dioxide, expel oxygen, and limit the loss of water vapor. This gas exchange takes place via pores called stomata. These pores are formed by a pair of adjacent cells that can open and close in response to a number of factors. These cells are called guard cells.
The cuticle and epidermis are layers of leaf structure, and do not correspond to specific cell types. The stoma is the name of a single pore itself, not its surrounding cells.
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Plant cells differentiate to perform different functions and enable the plant to grow. One cell type is present in young stems and petioles and functions to provide flexible support. This cell type is less resistant to bending forces because it lacks a secondary cell wall and the protein lignin, which causes rigidity in other plant cells.
What differentiated plant cell is being described?
Plant cells differentiate to perform different functions and enable the plant to grow. One cell type is present in young stems and petioles and functions to provide flexible support. This cell type is less resistant to bending forces because it lacks a secondary cell wall and the protein lignin, which causes rigidity in other plant cells.
What differentiated plant cell is being described?
As described in the beginning of this question, collenchyma cells are found in young stems and petioles (leaves) and function to provide flexible support to the plant. This is because chollenchyma cells lack secondary cell walls and do not produce lignin to harden them—this protein is characteristic of sclerenchyma cells, which are also used to provide support/strength to the plant.
Due to their lack of rigidity, collenchyma cells a also capable of elongating with the stems and leaves they support, allowing them to remain alive at maturity. Sclerenchymal cells lack this ability.
As described in the beginning of this question, collenchyma cells are found in young stems and petioles (leaves) and function to provide flexible support to the plant. This is because chollenchyma cells lack secondary cell walls and do not produce lignin to harden them—this protein is characteristic of sclerenchyma cells, which are also used to provide support/strength to the plant.
Due to their lack of rigidity, collenchyma cells a also capable of elongating with the stems and leaves they support, allowing them to remain alive at maturity. Sclerenchymal cells lack this ability.
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Plant cells differentiate to be able to perform different functions and enable it to grow. One cell type has a critical job in supporting the plant. These cells have secondary walls that are further strengthened by a glue-like substance called lignin, which increases the cell's rigidity. At maturity, these cells cannot elongate and are found in regions of the plant that have stopped growing, forming a "skeleton" for the plant.
What type of differentiated plant cell is described?
Plant cells differentiate to be able to perform different functions and enable it to grow. One cell type has a critical job in supporting the plant. These cells have secondary walls that are further strengthened by a glue-like substance called lignin, which increases the cell's rigidity. At maturity, these cells cannot elongate and are found in regions of the plant that have stopped growing, forming a "skeleton" for the plant.
What type of differentiated plant cell is described?
As described in the background to the question, sclerenchyma cells are specialized to support the plant as it grows. These cells have thick secondary walls that are further strengthened by the hardening agent called lignin. As a result, these cells are highly rigid and inflexible.
At maturity, these cells cannot elongate and are found in regions of the plant that have stopped growing. In some parts of the plant, the sclerenchyma cells may even be dead; however, the rigid walls remain and act like a skeleteon that supports the remainder of the plaint over its lifetime.
Sclerenchyma cells can also further differentiate into two types called sclereids and fibers. Sclerids can provide hardness to nut shells. Fibers, as their name suggests, are usually arranged in long threads and have commercial uses, such as being made into rope.
As described in the background to the question, sclerenchyma cells are specialized to support the plant as it grows. These cells have thick secondary walls that are further strengthened by the hardening agent called lignin. As a result, these cells are highly rigid and inflexible.
At maturity, these cells cannot elongate and are found in regions of the plant that have stopped growing. In some parts of the plant, the sclerenchyma cells may even be dead; however, the rigid walls remain and act like a skeleteon that supports the remainder of the plaint over its lifetime.
Sclerenchyma cells can also further differentiate into two types called sclereids and fibers. Sclerids can provide hardness to nut shells. Fibers, as their name suggests, are usually arranged in long threads and have commercial uses, such as being made into rope.
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What is the main structural component of a plant cell wall?
What is the main structural component of a plant cell wall?
Cellulose, a polymer of glucose, is the main component of plant cell walls.
Collagen is found in the connective tissues of animals. Chitin is found in the cell walls of fungi. Actin and myosin are the proteins responsible for contraction in muscle cells; actin is also a microfilament in the cytoskeleton. Peptidoglycan is found in the cell walls of bacteria.
Cellulose, a polymer of glucose, is the main component of plant cell walls.
Collagen is found in the connective tissues of animals. Chitin is found in the cell walls of fungi. Actin and myosin are the proteins responsible for contraction in muscle cells; actin is also a microfilament in the cytoskeleton. Peptidoglycan is found in the cell walls of bacteria.
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What are the protein channels in plants that allow high rates of water flow through the membrane via passive transport?
What are the protein channels in plants that allow high rates of water flow through the membrane via passive transport?
The correct answer is aquaporins. While water can move across a membrane via simple diffusion, these transmembrane proteins increase the flow of water. Remember that water is a polar molecule, and is thus relatively impermeable to the plasma membrane despite its small size.
The correct answer is aquaporins. While water can move across a membrane via simple diffusion, these transmembrane proteins increase the flow of water. Remember that water is a polar molecule, and is thus relatively impermeable to the plasma membrane despite its small size.
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Which of the following structures is unique to plant cells?
Which of the following structures is unique to plant cells?
Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.
Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.
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Which of the following can be found in plant cells, but not animal cells?
Which of the following can be found in plant cells, but not animal cells?
Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.
The other structure that may be found in plant cells, but not animal cells, is a cell wall.
Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.
The other structure that may be found in plant cells, but not animal cells, is a cell wall.
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The Calvin cycle takes place in the and occurs .
The Calvin cycle takes place in the and occurs .
The Calvin cycle takes place in the stroma of the chloroplast, which is the region in the chloroplast lumen outside of the thylakoids. It does not actually matter whether or not light is present for the reactions of the Calvin cycle to take place. They are light independent, but light will not prevent the reactions from occurring, similar to how glycolysis is independent of oxygen. As long as the appropriate nutrients and reactants are present, including ATP and NADPH generated from the light reactions, the Calvin cycle will occur.
The Calvin cycle takes place in the stroma of the chloroplast, which is the region in the chloroplast lumen outside of the thylakoids. It does not actually matter whether or not light is present for the reactions of the Calvin cycle to take place. They are light independent, but light will not prevent the reactions from occurring, similar to how glycolysis is independent of oxygen. As long as the appropriate nutrients and reactants are present, including ATP and NADPH generated from the light reactions, the Calvin cycle will occur.
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Where in the chloroplasts does the Calvin Cycle of photosynthesis take place?
Where in the chloroplasts does the Calvin Cycle of photosynthesis take place?
The Calvin Cycle occurs in the stroma, the aqueous fluid-filled area of the chloroplast. The stroma can be seen as analogous to the cytoplasm of a cell, in that it is the liquid in which all other substructures reside. The other processes of photosynthesis, the light-dependent reactions, take place in the thylakoid, a membrane-bound substructure within the chloroplast.
The Calvin Cycle occurs in the stroma, the aqueous fluid-filled area of the chloroplast. The stroma can be seen as analogous to the cytoplasm of a cell, in that it is the liquid in which all other substructures reside. The other processes of photosynthesis, the light-dependent reactions, take place in the thylakoid, a membrane-bound substructure within the chloroplast.
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What is the purpose of photosystem II in photosynthesis?
What is the purpose of photosystem II in photosynthesis?
Photosystem II splits water into hydrogen and oxygen. Hydrogen ions accumulate in the thylakoid space, creating an electrochemical concentration gradient. Due to this gradient, hydrogen ions pass through ATP sythase, powering the synthesis of ATP from ADP + Pi.
Photosystem II splits water into hydrogen and oxygen. Hydrogen ions accumulate in the thylakoid space, creating an electrochemical concentration gradient. Due to this gradient, hydrogen ions pass through ATP sythase, powering the synthesis of ATP from ADP + Pi.
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How do plants transport water against gravity?
How do plants transport water against gravity?
Plants do not have the ability to actively transport water to their respective cells. Instead, water undergoes capillary action, which allows it to flow upward against gravity. When the water is located in a very narrow chamber, such as the xylem of a plant, it creates intermolecular interactions with the walls of the chamber. These interactions allow small amounts of the water to "climb" the chamber walls. Due to the cohesion of water, whereby it is attracted to itself, more water molecules follow the "climbing" adhesion molecules. This subsequently allows the adhering molecules to climb higher, and the joint interaction of the adhesion and cohesion eventually allow the water to reach the topmost region of the plant (the leaves). Water is then released from the stomata, furthering the pull of water to the region of low pressure.
Plants do not have the ability to actively transport water to their respective cells. Instead, water undergoes capillary action, which allows it to flow upward against gravity. When the water is located in a very narrow chamber, such as the xylem of a plant, it creates intermolecular interactions with the walls of the chamber. These interactions allow small amounts of the water to "climb" the chamber walls. Due to the cohesion of water, whereby it is attracted to itself, more water molecules follow the "climbing" adhesion molecules. This subsequently allows the adhering molecules to climb higher, and the joint interaction of the adhesion and cohesion eventually allow the water to reach the topmost region of the plant (the leaves). Water is then released from the stomata, furthering the pull of water to the region of low pressure.
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Which of the following best describes how water is transported from the roots of a tree to the tallest branches?
Which of the following best describes how water is transported from the roots of a tree to the tallest branches?
One of water's most distinctive properties is cohesion—that is, the tendency of water molecules to "stick" to one another. In plants, this cohesion results in columns of water that stretch through the plant's xylem (the vascular tissue responsible for transport of water), from the roots all the way to the leaves. During transpiration, water evaporates from plants' leaves. Because of the cohesion of water, whenever water evaporates, more molecules are "pulled" into the roots to maintain the column of water. This is the transpirational pull-cohesion tension theory.
In contrast, adhesion is the tendency of water molecules to "stick" to other substances, such as the walls of a glass. Adhesion is responsible for the curved meniscus of water in a graduated cylinder. Phloem is responsible for sugar and carbohydrate transport in plants, while xylem transports water.
One of water's most distinctive properties is cohesion—that is, the tendency of water molecules to "stick" to one another. In plants, this cohesion results in columns of water that stretch through the plant's xylem (the vascular tissue responsible for transport of water), from the roots all the way to the leaves. During transpiration, water evaporates from plants' leaves. Because of the cohesion of water, whenever water evaporates, more molecules are "pulled" into the roots to maintain the column of water. This is the transpirational pull-cohesion tension theory.
In contrast, adhesion is the tendency of water molecules to "stick" to other substances, such as the walls of a glass. Adhesion is responsible for the curved meniscus of water in a graduated cylinder. Phloem is responsible for sugar and carbohydrate transport in plants, while xylem transports water.
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Which of the following structures is unique to plant cells?
Which of the following structures is unique to plant cells?
Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.
Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.
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Which of the following can be found in plant cells, but not animal cells?
Which of the following can be found in plant cells, but not animal cells?
Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.
The other structure that may be found in plant cells, but not animal cells, is a cell wall.
Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.
The other structure that may be found in plant cells, but not animal cells, is a cell wall.
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