Cellular Structures and Organelles - MCAT Biological and Biochemical Foundations of Living Systems
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In which of the following pH environments would an enzyme from the small intestine most likely be active?
In which of the following pH environments would an enzyme from the small intestine most likely be active?
Chyme from the stomach is transferred to the small intestine through the pyloric sphincter. The highly-acidic chyme is then neutralized in the duodenum of the small intestine. The majority of the small intestine has a pH between 6 and 7.
Chyme from the stomach is transferred to the small intestine through the pyloric sphincter. The highly-acidic chyme is then neutralized in the duodenum of the small intestine. The majority of the small intestine has a pH between 6 and 7.
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Which of the following is NOT a function of peroxisomes?
Which of the following is NOT a function of peroxisomes?
Peroxisomes are involved in the metabolism of hydrogen peroxide and very long chain fatty acids. They are also known to produce plasmalogen, an important phospholipid found in myelin, without which disorders of the nervous system can arise. Lysosomes, not peroxisomes, store acid hydrolases such as lipase.
Peroxisomes are involved in the metabolism of hydrogen peroxide and very long chain fatty acids. They are also known to produce plasmalogen, an important phospholipid found in myelin, without which disorders of the nervous system can arise. Lysosomes, not peroxisomes, store acid hydrolases such as lipase.
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Most scientists subscribe to the theory of endosymbiosis to explain the presence of mitochondria in eukaryotic cells. According to the theory of endosymbiosis, early pre-eukaryotic cells phagocytosed free living prokaryotes, but failed to digest them. As a result, these prokaryotes remained in residence in the pre-eukaryotes, and continued to generate energy. The host cells were able to use this energy to gain a selective advantage over their competitors, and eventually the energy-producing prokaryotes became mitochondria.
In many ways, mitochondria are different from other cellular organelles, and these differences puzzled scientists for many years. The theory of endosymbiosis concisely explains a number of these observations about mitochondria. Perhaps most of all, the theory explains why aerobic metabolism is entirely limited to this one organelle, while other kinds of metabolism are more distributed in the cellular cytosol.
The failure of phagocytosis in the initial stages of endosymbiosis could have been due to the failure of host cells to produce digestive enzymes. Most cells generate digestive enzymes into the vesicle that houses newly-phagocytosed material, or phagosome. Failure to form which of the following would be expected in a cell that was unable to digest compounds in its phagosome?
Most scientists subscribe to the theory of endosymbiosis to explain the presence of mitochondria in eukaryotic cells. According to the theory of endosymbiosis, early pre-eukaryotic cells phagocytosed free living prokaryotes, but failed to digest them. As a result, these prokaryotes remained in residence in the pre-eukaryotes, and continued to generate energy. The host cells were able to use this energy to gain a selective advantage over their competitors, and eventually the energy-producing prokaryotes became mitochondria.
In many ways, mitochondria are different from other cellular organelles, and these differences puzzled scientists for many years. The theory of endosymbiosis concisely explains a number of these observations about mitochondria. Perhaps most of all, the theory explains why aerobic metabolism is entirely limited to this one organelle, while other kinds of metabolism are more distributed in the cellular cytosol.
The failure of phagocytosis in the initial stages of endosymbiosis could have been due to the failure of host cells to produce digestive enzymes. Most cells generate digestive enzymes into the vesicle that houses newly-phagocytosed material, or phagosome. Failure to form which of the following would be expected in a cell that was unable to digest compounds in its phagosome?
Lysosomes are the cell's repository of digestive enzymes. When these merge with phagosomes, the result is a vesicle that is able to digest phagocytosed material.
Spectrin and ankyrin are structural proteins associated with the cytoskeleton, especially in muscle cells.
Lysosomes are the cell's repository of digestive enzymes. When these merge with phagosomes, the result is a vesicle that is able to digest phagocytosed material.
Spectrin and ankyrin are structural proteins associated with the cytoskeleton, especially in muscle cells.
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One component of the immune system is the neutrophil, a professional phagocyte that consumes invading cells. The neutrophil is ferried to the site of infection via the blood as pre-neutrophils, or monocytes, ready to differentiate as needed to defend their host.
In order to leave the blood and migrate to the tissues, where infection is active, the monocyte undergoes a process called diapedesis. Diapedesis is a process of extravasation, where the monocyte leaves the circulation by moving in between endothelial cells, enters the tissue, and matures into a neutrophil.
Diapedesis is mediated by a class of proteins called selectins, present on the monocyte membrane and the endothelium. These selectins interact, attract the monocyte to the endothelium, and allow the monocytes to roll along the endothelium until they are able to complete diapedesis by leaving the vasculature and entering the tissues.
The image below shows monocytes moving in the blood vessel, "rolling" along the vessel wall, and eventually leaving the vessel to migrate to the site of infection.
A scientist is investigating the digestive enzymes present in a neutrophil as it digests foreign material. Where are these enzymes most likely to be stored immediately before they are used to break down phagocytosed material?
One component of the immune system is the neutrophil, a professional phagocyte that consumes invading cells. The neutrophil is ferried to the site of infection via the blood as pre-neutrophils, or monocytes, ready to differentiate as needed to defend their host.
In order to leave the blood and migrate to the tissues, where infection is active, the monocyte undergoes a process called diapedesis. Diapedesis is a process of extravasation, where the monocyte leaves the circulation by moving in between endothelial cells, enters the tissue, and matures into a neutrophil.
Diapedesis is mediated by a class of proteins called selectins, present on the monocyte membrane and the endothelium. These selectins interact, attract the monocyte to the endothelium, and allow the monocytes to roll along the endothelium until they are able to complete diapedesis by leaving the vasculature and entering the tissues.
The image below shows monocytes moving in the blood vessel, "rolling" along the vessel wall, and eventually leaving the vessel to migrate to the site of infection.
A scientist is investigating the digestive enzymes present in a neutrophil as it digests foreign material. Where are these enzymes most likely to be stored immediately before they are used to break down phagocytosed material?
The lysosome is the main storage site for digestive proteins. These digestive proteins are then released into the phagosome to form the phagolysosome. This phagolysosome is then able to digest phagocytosed material and render it harmless to the host.
The lysosome is the main storage site for digestive proteins. These digestive proteins are then released into the phagosome to form the phagolysosome. This phagolysosome is then able to digest phagocytosed material and render it harmless to the host.
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Which of the following scenarios could directly cause cell death?
Which of the following scenarios could directly cause cell death?
The lysosome contains hydrolytic enzymes that break down biological materials. If these enzymes were released, they could cause cell death by autolysis.
The inactivation of a transport protein would not be too catastrophic, and would not lead to cell death. Overstimulation of the cell cycle would lead to increased mitosis and cell proliferation, the opposite of cell death. Eventually, this overstimulation may be detected and cause apoptosis, but it will not directly cause the cell death. A silent mutation would not alter the protein created from the gene, and thus would have no effect on the cell.
The lysosome contains hydrolytic enzymes that break down biological materials. If these enzymes were released, they could cause cell death by autolysis.
The inactivation of a transport protein would not be too catastrophic, and would not lead to cell death. Overstimulation of the cell cycle would lead to increased mitosis and cell proliferation, the opposite of cell death. Eventually, this overstimulation may be detected and cause apoptosis, but it will not directly cause the cell death. A silent mutation would not alter the protein created from the gene, and thus would have no effect on the cell.
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Which of the following may be the pH inside a lysosome?
Which of the following may be the pH inside a lysosome?
Generally, a lower pH is best for lysosomal degradation. Lysosomes contain hydrolytic enzymes, which will only function in the presence of an acid catalyst. The best answer choice is a pH of 4, which is slightly acidic but not as acidic at a pH of 1. Even the stomach, which is considered extremely acidic, only has a pH of about 2.5. Lysosomal degradation at a pH of 1 would cause even the membrane integrity to be questionable.
Generally, a lower pH is best for lysosomal degradation. Lysosomes contain hydrolytic enzymes, which will only function in the presence of an acid catalyst. The best answer choice is a pH of 4, which is slightly acidic but not as acidic at a pH of 1. Even the stomach, which is considered extremely acidic, only has a pH of about 2.5. Lysosomal degradation at a pH of 1 would cause even the membrane integrity to be questionable.
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There are two models for the operation of the Golgi apparatus in eukaryotic cells. As it is difficult to visualize the operation of cells at the molecular level in real time, scientists typically rely on static electron micrographs to see the morphology of organelles. As a result, the dynamic operation of these organelles can sometimes be unclear.
Cisternal Maturation Hypothesis
In the cisternal maturation hypothesis, the cisternae of the Golgi apparatus evolve. Proteins leave the endoplasmic reticulum, and enter the cis-Golgi. The cisterna of the cis-Golgi then matures, with its enzymatic contents and internal environment changing as it becomes the medial-Golgi, and, eventually, the trans-Golgi.
In this model, the proteins never physically leave their membrane-bound cisternae during their transit across the Golgi. Instead, the entire unit of contents remains within the evolving cisternae.
Vesicular Transport Hypothesis
In contrast to the cisternal maturation hypothesis, the vesicular transport hypothesis posits that the cis-, medial-, and trans-Golgi cisternae are more static structures. Instead of evolving around their contents, the contents are physically shuttled via vesicular intermediates from each cisterna to the next.
In the case of vesicular transport, vesicles are shuttled along microtubules. Motor proteins facilitate this movement, with unique proteins being used for each direction of movement along a microtubule.
Microtubules are closely associated not only with vesicular transport, but also with cilia and flagella physiology. Which statement is true regarding cilia and flagella?
I. Most ciliated cells have many cilia structures
II. Most flagellated cells have only one flagellum
III. Only flagella have a 9+2 microtubule arrangement
IV. Both cilia and flagella move via the action of dynein
There are two models for the operation of the Golgi apparatus in eukaryotic cells. As it is difficult to visualize the operation of cells at the molecular level in real time, scientists typically rely on static electron micrographs to see the morphology of organelles. As a result, the dynamic operation of these organelles can sometimes be unclear.
Cisternal Maturation Hypothesis
In the cisternal maturation hypothesis, the cisternae of the Golgi apparatus evolve. Proteins leave the endoplasmic reticulum, and enter the cis-Golgi. The cisterna of the cis-Golgi then matures, with its enzymatic contents and internal environment changing as it becomes the medial-Golgi, and, eventually, the trans-Golgi.
In this model, the proteins never physically leave their membrane-bound cisternae during their transit across the Golgi. Instead, the entire unit of contents remains within the evolving cisternae.
Vesicular Transport Hypothesis
In contrast to the cisternal maturation hypothesis, the vesicular transport hypothesis posits that the cis-, medial-, and trans-Golgi cisternae are more static structures. Instead of evolving around their contents, the contents are physically shuttled via vesicular intermediates from each cisterna to the next.
In the case of vesicular transport, vesicles are shuttled along microtubules. Motor proteins facilitate this movement, with unique proteins being used for each direction of movement along a microtubule.
Microtubules are closely associated not only with vesicular transport, but also with cilia and flagella physiology. Which statement is true regarding cilia and flagella?
I. Most ciliated cells have many cilia structures
II. Most flagellated cells have only one flagellum
III. Only flagella have a 9+2 microtubule arrangement
IV. Both cilia and flagella move via the action of dynein
Most ciliated cells have many cilia, as their role is important in such efforts as moving mucous in the respiratory tract. Flagellated cells, in contrast, typically have one flagellum that is used for locomotion. Dynein is important in both structures, as is the 9+2 microtubule structure.
Most ciliated cells have many cilia, as their role is important in such efforts as moving mucous in the respiratory tract. Flagellated cells, in contrast, typically have one flagellum that is used for locomotion. Dynein is important in both structures, as is the 9+2 microtubule structure.
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There are two models for the operation of the Golgi apparatus in eukaryotic cells. As it is difficult to visualize the operation of cells at the molecular level in real time, scientists typically rely on static electron micrographs to see the morphology of organelles. As a result, the dynamic operation of these organelles can sometimes be unclear.
Cisternal Maturation Hypothesis
In the cisternal maturation hypothesis, the cisternae of the Golgi apparatus evolve. Proteins leave the endoplasmic reticulum, and enter the cis-Golgi. The cisterna of the cis-Golgi then matures, with its enzymatic contents and internal environment changing as it becomes the medial-Golgi, and, eventually, the trans-Golgi.
In this model, the proteins never physically leave their membrane-bound cisternae during their transit across the Golgi. Instead, the entire unit of contents remains within the evolving cisternae.
Vesicular Transport Hypothesis
In contrast to the cisternal maturation hypothesis, the vesicular transport hypothesis posits that the cis-, medial-, and trans-Golgi cisternae are more static structures. Instead of evolving around their contents, the contents are physically shuttled via vesicular intermediates from each cisterna to the next.
In the case of vesicular transport, vesicles are shuttled along microtubules. Motor proteins facilitate this movement, with unique proteins being used for each direction of movement along a microtubule.
In the Golgi apparatus, mannose-6-phosphate is often added to proteins to mark them for delivery to lysosomes. Which membrane-bound structure fuses with lysosomes following uptake of large and small extra-cellular particles, respectively?
There are two models for the operation of the Golgi apparatus in eukaryotic cells. As it is difficult to visualize the operation of cells at the molecular level in real time, scientists typically rely on static electron micrographs to see the morphology of organelles. As a result, the dynamic operation of these organelles can sometimes be unclear.
Cisternal Maturation Hypothesis
In the cisternal maturation hypothesis, the cisternae of the Golgi apparatus evolve. Proteins leave the endoplasmic reticulum, and enter the cis-Golgi. The cisterna of the cis-Golgi then matures, with its enzymatic contents and internal environment changing as it becomes the medial-Golgi, and, eventually, the trans-Golgi.
In this model, the proteins never physically leave their membrane-bound cisternae during their transit across the Golgi. Instead, the entire unit of contents remains within the evolving cisternae.
Vesicular Transport Hypothesis
In contrast to the cisternal maturation hypothesis, the vesicular transport hypothesis posits that the cis-, medial-, and trans-Golgi cisternae are more static structures. Instead of evolving around their contents, the contents are physically shuttled via vesicular intermediates from each cisterna to the next.
In the case of vesicular transport, vesicles are shuttled along microtubules. Motor proteins facilitate this movement, with unique proteins being used for each direction of movement along a microtubule.
In the Golgi apparatus, mannose-6-phosphate is often added to proteins to mark them for delivery to lysosomes. Which membrane-bound structure fuses with lysosomes following uptake of large and small extra-cellular particles, respectively?
An endosome is a specific type of intracellular vesicle formed from the uptake of large particles from the extracellular environment. Similarly, a pinosome is an intracellular vesicle formed from the uptake of small particles or fluids. Endosomes result from endocytosis; pinosomes result from pinocytosis.
These vesicles are transported to the lysosomes in the cell, where they fuse and deposit their contents into the lysosome structure for degradation by hydrolytic enzymes.
An endosome is a specific type of intracellular vesicle formed from the uptake of large particles from the extracellular environment. Similarly, a pinosome is an intracellular vesicle formed from the uptake of small particles or fluids. Endosomes result from endocytosis; pinosomes result from pinocytosis.
These vesicles are transported to the lysosomes in the cell, where they fuse and deposit their contents into the lysosome structure for degradation by hydrolytic enzymes.
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Which organelles contain genetic material?
Which organelles contain genetic material?
The nucleus contains the genetic code of each individual, and the mitochondria is a semiautonomous organelle that contains mitochondrial DNA (passed through the maternal line). mDNA codes specifically for the proteins involved in the electron transport chain, allowing for their implantation in the inner mitochondrial membrane without having to be synthesized elsewhere in the cell.
The nucleus contains the genetic code of each individual, and the mitochondria is a semiautonomous organelle that contains mitochondrial DNA (passed through the maternal line). mDNA codes specifically for the proteins involved in the electron transport chain, allowing for their implantation in the inner mitochondrial membrane without having to be synthesized elsewhere in the cell.
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What is the direct role of the nucleolus in the cell?
What is the direct role of the nucleolus in the cell?
The nucleolus, which is located in the nucleus, is directly involved in the production of rRNA. The rRNA composes the ribosome structure, and is directly involved in synthesis of protein.
The nucleolus, which is located in the nucleus, is directly involved in the production of rRNA. The rRNA composes the ribosome structure, and is directly involved in synthesis of protein.
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Where is ribosomal RNA synthesized in eukaryotic cells?
Where is ribosomal RNA synthesized in eukaryotic cells?
The nucleolus is a structure within the nucleus, and is the site of rRNA synthesis. The individual subunits of the ribosome assemble in the nucleus, are exported through the nuclear pores, and are finally brought together into function units in the cytosol.
The nucleus contains DNA, the lysosome has enzymes that break down molecules, and the mitochondria are the site of ATP production. The rough endoplasmic reticulum has a surface that is studded with ribosomes, and works in coordination with these ribosomes to modify proteins after synthesis.
The nucleolus is a structure within the nucleus, and is the site of rRNA synthesis. The individual subunits of the ribosome assemble in the nucleus, are exported through the nuclear pores, and are finally brought together into function units in the cytosol.
The nucleus contains DNA, the lysosome has enzymes that break down molecules, and the mitochondria are the site of ATP production. The rough endoplasmic reticulum has a surface that is studded with ribosomes, and works in coordination with these ribosomes to modify proteins after synthesis.
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The construction of ribosomal subunits is accomplished by which cellular structure?
The construction of ribosomal subunits is accomplished by which cellular structure?
The nucleolus is located inside of the eukaryotic nucleus. It is responsible for the creation of the ribosomal subunits, as well as the rRNA that will be incorporated into the ribosomes. Ribosomal subunits are synthesized in the nucleolus and exported to the cytoplasm, where they can be assembled into functional translation complexes.
The rough endoplasmic reticulum contains ribosomes embedded in its membrane and is responsible for synthesizing certain proteins. The smooth endoplasmic reticulum is responsible for metabolizing toxins and synthesizing lipids. The Golgi apparatus plays a key role in protein sorting, packaging, and transport within vesicles.
The nucleolus is located inside of the eukaryotic nucleus. It is responsible for the creation of the ribosomal subunits, as well as the rRNA that will be incorporated into the ribosomes. Ribosomal subunits are synthesized in the nucleolus and exported to the cytoplasm, where they can be assembled into functional translation complexes.
The rough endoplasmic reticulum contains ribosomes embedded in its membrane and is responsible for synthesizing certain proteins. The smooth endoplasmic reticulum is responsible for metabolizing toxins and synthesizing lipids. The Golgi apparatus plays a key role in protein sorting, packaging, and transport within vesicles.
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The                      is a structure where ribosomes are formed and the site where                      is transcribed.
The                      is a structure where ribosomes are formed and the site where                      is transcribed.
The nucleolus is a special structure within the nucleus that is responsible for the transcription of rRNA genes and the formation of ribosomal subunits. Transcription of mRNA, tRNA, and miRNA occurs in other regions of the nucleus. Nuclear pores are highly regulated structures that allow for import and export of materials in the nucleus.
The nucleolus is a special structure within the nucleus that is responsible for the transcription of rRNA genes and the formation of ribosomal subunits. Transcription of mRNA, tRNA, and miRNA occurs in other regions of the nucleus. Nuclear pores are highly regulated structures that allow for import and export of materials in the nucleus.
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Which of the following choices can be passed through a nuclear pore complex?
I. pre-mRNA
II. Ribosomal subunits
III. Transcription factors
IV. Mitochondria
Which of the following choices can be passed through a nuclear pore complex?
I. pre-mRNA
II. Ribosomal subunits
III. Transcription factors
IV. Mitochondria
The only option that cannot pass the nuclear envelope from the nucleus is mitochondria. Mitochondria range from 0.5-1.0 micrometers, while nuclear pore complexes are about 120 nanometers in diameter. That being said, mitochondria are too large to fit through a nuclear pore complex.
Ribosomes, pre-mRNA, and proteins (such as transcription factors) are all perfectly capable of moving through the nuclear pore complexes, given the appropriate environment.
The only option that cannot pass the nuclear envelope from the nucleus is mitochondria. Mitochondria range from 0.5-1.0 micrometers, while nuclear pore complexes are about 120 nanometers in diameter. That being said, mitochondria are too large to fit through a nuclear pore complex.
Ribosomes, pre-mRNA, and proteins (such as transcription factors) are all perfectly capable of moving through the nuclear pore complexes, given the appropriate environment.
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Which of the following is not true of eukaryotic nuclei?
Which of the following is not true of eukaryotic nuclei?
Ribosomal subunits are synthesized in the nucleolus, which is located inside the nucleus. The nucleus is surrounded by two membranes, known as the nuclear envelope, studded with large nuclear pore complexes. Import and export of substances through the pore complexes is highly regulated. Nuclei are supported by what is known as a nuclear lamina. This nuclear lamina is composed of intermediate filaments that provide support and structure for the nucleus.
It has recently been shown that chromosomes are not randomly distributed through the nucleus. Chromosomes occupy specific regions of the nucleus, which are currently referred to as "nuclear territories".
Ribosomal subunits are synthesized in the nucleolus, which is located inside the nucleus. The nucleus is surrounded by two membranes, known as the nuclear envelope, studded with large nuclear pore complexes. Import and export of substances through the pore complexes is highly regulated. Nuclei are supported by what is known as a nuclear lamina. This nuclear lamina is composed of intermediate filaments that provide support and structure for the nucleus.
It has recently been shown that chromosomes are not randomly distributed through the nucleus. Chromosomes occupy specific regions of the nucleus, which are currently referred to as "nuclear territories".
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A pharmaceutical company develops a drug that attacks lamins inside the nucleus. What can you conclude about this drug?
A pharmaceutical company develops a drug that attacks lamins inside the nucleus. What can you conclude about this drug?
Lamins are intermediate filaments found inside the nucleus. Lamins attach to nuclear proteins and form a layer underneath the nuclear envelope (nuclear membrane) called the nuclear lamina. The nuclear lamina functions to position nuclear pores to let molecules pass between the cytoplasm and the nucleoplasm. It also functions to break and resynthesize the nuclear envelope during mitosis. Recall that the nuclear envelope is broken down during the prophase of mitosis; therefore, lack of lamins will directly affect this phase of mitosis.
In addition to the aforementioned functions, lamins are also involved in maintaining the integrity of chromosomes. Lack of lamins will decrease the stability of chromosomes. Cholesterol and most other lipids are synthesized in the smooth endoplasmic reticulum; therefore, lamins are irrelevant to cholesterol synthesis. Since they are involved in positioning nuclear pores, lamins are important for exchanging molecules between the nucleus and cytoplasm. Lack of lamins will decrease this trafficking.
Lamins are intermediate filaments found inside the nucleus. Lamins attach to nuclear proteins and form a layer underneath the nuclear envelope (nuclear membrane) called the nuclear lamina. The nuclear lamina functions to position nuclear pores to let molecules pass between the cytoplasm and the nucleoplasm. It also functions to break and resynthesize the nuclear envelope during mitosis. Recall that the nuclear envelope is broken down during the prophase of mitosis; therefore, lack of lamins will directly affect this phase of mitosis.
In addition to the aforementioned functions, lamins are also involved in maintaining the integrity of chromosomes. Lack of lamins will decrease the stability of chromosomes. Cholesterol and most other lipids are synthesized in the smooth endoplasmic reticulum; therefore, lamins are irrelevant to cholesterol synthesis. Since they are involved in positioning nuclear pores, lamins are important for exchanging molecules between the nucleus and cytoplasm. Lack of lamins will decrease this trafficking.
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Which of the following processes occurs only in the nucleus?
I. Transcription
II. DNA replication
III. Translation
Which of the following processes occurs only in the nucleus?
I. Transcription
II. DNA replication
III. Translation
The central dogma of molecular biology states that genetic information flows from DNA to RNA to protein. The first step is the replication of the genetic material, DNA, during the S phase of the cell cycle. The second step is the conversion of DNA to RNA. This process is called transcription and involves several enzymes that convert the DNA to mRNA. The final step is called translation, which involves the conversion of mRNA to protein.
DNA replication and transcription occur inside the nucleus because the enzymes required to carry out these processes are found in the nucleoplasm. Translation, on the other hand, occurs on ribosomes in the cytoplasm or on ribosomes on the rough endoplasmic reticulum.
The central dogma of molecular biology states that genetic information flows from DNA to RNA to protein. The first step is the replication of the genetic material, DNA, during the S phase of the cell cycle. The second step is the conversion of DNA to RNA. This process is called transcription and involves several enzymes that convert the DNA to mRNA. The final step is called translation, which involves the conversion of mRNA to protein.
DNA replication and transcription occur inside the nucleus because the enzymes required to carry out these processes are found in the nucleoplasm. Translation, on the other hand, occurs on ribosomes in the cytoplasm or on ribosomes on the rough endoplasmic reticulum.
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After performing a genetic study, a physician finds that a patient has a defect in the genetic material that codes for ribosomes. Where in the cell is this genetic material found?
After performing a genetic study, a physician finds that a patient has a defect in the genetic material that codes for ribosomes. Where in the cell is this genetic material found?
Genetic information that codes for ribosomes is found on the nucleolus. Recall that the nucleolus is a specialized structure found inside the nucleus that functions to assemble ribosomes from proteins and ribosomal RNA (rRNA). The DNA that encodes for rRNA is on the nucleolus or in the vicinity of the nucleolus.
The periplasm is the space between the inner and outer cell membrane in gram-negative bacteria; it is irrelevant to this question. The nuclear envelope is the phospholipid bilayer that covers the nucleus. It does not contain any genetic information. Histones are proteins that organize and structure DNA strands; they don’t have any genetic information.
Genetic information that codes for ribosomes is found on the nucleolus. Recall that the nucleolus is a specialized structure found inside the nucleus that functions to assemble ribosomes from proteins and ribosomal RNA (rRNA). The DNA that encodes for rRNA is on the nucleolus or in the vicinity of the nucleolus.
The periplasm is the space between the inner and outer cell membrane in gram-negative bacteria; it is irrelevant to this question. The nuclear envelope is the phospholipid bilayer that covers the nucleus. It does not contain any genetic information. Histones are proteins that organize and structure DNA strands; they don’t have any genetic information.
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Which of the following is true of the RNA transcripts in the nucleolus and nucleus?
Which of the following is true of the RNA transcripts in the nucleolus and nucleus?
In the nucleolus, the transcripts synthesized are rRNA molecules. The unique aspect of rRNA molecules is that they are never converted to proteins; therefore, they never undergo translation. The rRNA molecules synthesized by the nucleolus are assembled with other proteins to create ribosomes; they themselves never undergo translation.
Transcription in the rest of the nucleus produces mRNA molecules that enter the cytoplasm and undergo translation to create proteins.
In the nucleolus, the transcripts synthesized are rRNA molecules. The unique aspect of rRNA molecules is that they are never converted to proteins; therefore, they never undergo translation. The rRNA molecules synthesized by the nucleolus are assembled with other proteins to create ribosomes; they themselves never undergo translation.
Transcription in the rest of the nucleus produces mRNA molecules that enter the cytoplasm and undergo translation to create proteins.
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The nucleolus is responsible for synthesis of which of the following compounds?
The nucleolus is responsible for synthesis of which of the following compounds?
The nucleolus has genes for transcribing ribosomal RNA. RNA polymerase I in the nucleolus transcribes the gene for ribosomal RNA and causes formation of ribosomal complexes. mRNA and tRNA are transcribed elsewhere in the nucleus and use RNA polymerase II and III, respectively. Arachidonic acid is an omega-6 polyunsaturated fatty acid, which plays roles in cell-signaling, prostaglandin synthesis, and the immune response, and is synthesized in the cytosol.
The nucleolus has genes for transcribing ribosomal RNA. RNA polymerase I in the nucleolus transcribes the gene for ribosomal RNA and causes formation of ribosomal complexes. mRNA and tRNA are transcribed elsewhere in the nucleus and use RNA polymerase II and III, respectively. Arachidonic acid is an omega-6 polyunsaturated fatty acid, which plays roles in cell-signaling, prostaglandin synthesis, and the immune response, and is synthesized in the cytosol.
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