Cell Biology - GRE Subject Test: Biochemistry, Cell, and Molecular Biology
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What is the primary function of the Golgi apparatus?
What is the primary function of the Golgi apparatus?
The Golgi apparatus is a complex organelle with many various functions. These functions are primarily dedicated to protein modification, protein packaging, and protein sorting. Some of post-translational modifications that take place in this organelle include glycosylation and phosphorylation. The Golgi apparatus is an important relay in the secretory pathway, as it produces the vesicles that contain most secreted peptides.
The Golgi apparatus is a complex organelle with many various functions. These functions are primarily dedicated to protein modification, protein packaging, and protein sorting. Some of post-translational modifications that take place in this organelle include glycosylation and phosphorylation. The Golgi apparatus is an important relay in the secretory pathway, as it produces the vesicles that contain most secreted peptides.
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Which of the following GTP-binding proteins is associated with COPI during vesicle assembly and budding in the cis-Golgi?
Which of the following GTP-binding proteins is associated with COPI during vesicle assembly and budding in the cis-Golgi?
The correct answer is ADP ribosylation factors (ARFs). ARFs are active when bound by GTP, and inactive when bound by GDP. The active GTP-bound form of ARF binds the vesicle coat protein 1 (COPI), to faciliate vesicle budding from the cis-Golgi face.
The correct answer is ADP ribosylation factors (ARFs). ARFs are active when bound by GTP, and inactive when bound by GDP. The active GTP-bound form of ARF binds the vesicle coat protein 1 (COPI), to faciliate vesicle budding from the cis-Golgi face.
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A mutation in which of the following proteins would affect the functionality of eukaryotic flagella?
I. Dynein
II. Kinesin
III. Myosin
A mutation in which of the following proteins would affect the functionality of eukaryotic flagella?
I. Dynein
II. Kinesin
III. Myosin
Eukaryotic flagella are primarily composed of microtubules and the motor protein dynein. Hydrolysis of ATP by dynein produces a sliding movement of the microtubule filaments that produces movement.
Kinesin is a motor protein that associates with microtubules, but it is not present in flagella. Myosin is a motor protein that associates with actin microfilaments.
Eukaryotic flagella are primarily composed of microtubules and the motor protein dynein. Hydrolysis of ATP by dynein produces a sliding movement of the microtubule filaments that produces movement.
Kinesin is a motor protein that associates with microtubules, but it is not present in flagella. Myosin is a motor protein that associates with actin microfilaments.
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Which of the following is true regarding microfilaments?
Which of the following is true regarding microfilaments?
Microfilaments are the smallest of the three cytoskeletal elements and are made up of actin filaments (myosin is not found in microfilaments). The 9+2 arrangement is found in microtubules, the biggest cytoskeletal elements. The third cytoskeletal element is called the intermediate filament and is made up of related proteins unique to each intermediate filament.
Microfilaments are the smallest of the three cytoskeletal elements and are made up of actin filaments (myosin is not found in microfilaments). The 9+2 arrangement is found in microtubules, the biggest cytoskeletal elements. The third cytoskeletal element is called the intermediate filament and is made up of related proteins unique to each intermediate filament.
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What are acid hydrolases?
What are acid hydrolases?
Acid hydrolases are proteins that are specifically designed to function at acidic pH, particularly at levels that would typically denature other proteins. They are commonly found in lysosomes where they aid in the digestion of various cellular wastes and materials.
Though acid hydrolases use water to break apart molecules, acids are not used as reactants, products, or catalysts in these reactions.
Acid hydrolases are proteins that are specifically designed to function at acidic pH, particularly at levels that would typically denature other proteins. They are commonly found in lysosomes where they aid in the digestion of various cellular wastes and materials.
Though acid hydrolases use water to break apart molecules, acids are not used as reactants, products, or catalysts in these reactions.
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Which of the following organelles has an acidic internal pH?
Which of the following organelles has an acidic internal pH?
An acidic environment is not suitable for the cell as a whole, so the low pH is sequestered in a specific organelle: the lysosome. This low pH in the lysosome activates the hydrolytic enzymes in the lysosome, and allows them to degrade macromolecules that enter the organelle.
An acidic environment is not suitable for the cell as a whole, so the low pH is sequestered in a specific organelle: the lysosome. This low pH in the lysosome activates the hydrolytic enzymes in the lysosome, and allows them to degrade macromolecules that enter the organelle.
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Which of the following is a common post-translational modification used to target proteins to the lysosome?
Which of the following is a common post-translational modification used to target proteins to the lysosome?
Mannose-6-phosphate is a post-translational modification found on proteins important to the functionality of the lysosome (such as acid hydrolases). Ubiquination is a signal for proteins to be brought to the proteosome and degraded. Myristoylation involves the addition of a fatty acid chain, and is often seen in proteins targeted to the plasma membrane. Acetylation is a common modification found on histones that can help make genes transcriptionally active.
Mannose-6-phosphate is a post-translational modification found on proteins important to the functionality of the lysosome (such as acid hydrolases). Ubiquination is a signal for proteins to be brought to the proteosome and degraded. Myristoylation involves the addition of a fatty acid chain, and is often seen in proteins targeted to the plasma membrane. Acetylation is a common modification found on histones that can help make genes transcriptionally active.
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An isomerase __________.
An isomerase __________.
An isomerase is an enzyme that catalyzes the rearrangement of bonds in a single molecule. For example glucose-6-phosphate isomerase catalyzes the conversion of glucose-6-phosphate into fructose-6-phosphate during glycolysis.
A hydrolase catalyzes a hydrolytic cleavage reaction, a kinase catalyzes the addition of a phosphate group, and a polymerase catalyzes polymerization reactions.
An isomerase is an enzyme that catalyzes the rearrangement of bonds in a single molecule. For example glucose-6-phosphate isomerase catalyzes the conversion of glucose-6-phosphate into fructose-6-phosphate during glycolysis.
A hydrolase catalyzes a hydrolytic cleavage reaction, a kinase catalyzes the addition of a phosphate group, and a polymerase catalyzes polymerization reactions.
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Which of the following protein coats would most likely be seen on a vesicle directed towards the plasma membrane?
Which of the following protein coats would most likely be seen on a vesicle directed towards the plasma membrane?
Clathrin coats are often seen trafficking vesicles from the Golgi apparatus to the plasma membrane. Clathrin protein is used to facilitate membrane invagination and vesicle formation, as well as direct vesicle release.
COPI coats are seen in vesicles headed from the Golgi apparatus back to the endoplasmic reticulum. COPII coats are seen in vesicles headed towards the Golgi apparatus from the endoplasmic reticulum.
Clathrin coats are often seen trafficking vesicles from the Golgi apparatus to the plasma membrane. Clathrin protein is used to facilitate membrane invagination and vesicle formation, as well as direct vesicle release.
COPI coats are seen in vesicles headed from the Golgi apparatus back to the endoplasmic reticulum. COPII coats are seen in vesicles headed towards the Golgi apparatus from the endoplasmic reticulum.
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Which of the following is an example of a multipotent stem cell differentiation into a terminal cell type?
Which of the following is an example of a multipotent stem cell differentiation into a terminal cell type?
Multipotent cell types can give rise to a small number of cell types but have a restricted fate. This is in contrast to totipotent (zygote) or pluripotent cells (germ layers, iPS (induced pluripotent cells)) which can give rise to many different cell types, some that may make up very different parts of the body.
Multipotent cell types can give rise to a small number of cell types but have a restricted fate. This is in contrast to totipotent (zygote) or pluripotent cells (germ layers, iPS (induced pluripotent cells)) which can give rise to many different cell types, some that may make up very different parts of the body.
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An unknown molecule is identified by a researcher. He notices that the structure is abundantly found in cell walls of bacteria. Upon further analysis, which of the following will be observed by the researcher?
An unknown molecule is identified by a researcher. He notices that the structure is abundantly found in cell walls of bacteria. Upon further analysis, which of the following will be observed by the researcher?
The most abundant molecule in bacterial cell walls is peptidoglycan. Recall that peptidoglycan contains repeating NAG-NAM units, which are made from glucose. In addition, peptidoglycan also has peptides attached to these oligosaccharides. These units form bonds with each other to create a strong and a robust cell wall. Peptidoglycan is synthesized in cytoplasm and on cell membrane before finally being transported to the cell wall.
Recall that phosphate head groups are found on phospholipids, which make up cell membranes (not cell walls).
The most abundant molecule in bacterial cell walls is peptidoglycan. Recall that peptidoglycan contains repeating NAG-NAM units, which are made from glucose. In addition, peptidoglycan also has peptides attached to these oligosaccharides. These units form bonds with each other to create a strong and a robust cell wall. Peptidoglycan is synthesized in cytoplasm and on cell membrane before finally being transported to the cell wall.
Recall that phosphate head groups are found on phospholipids, which make up cell membranes (not cell walls).
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Gram positive bacteria have __________ cell wall(s) and Gram negative bacteria have __________ cell wall(s).
Gram positive bacteria have __________ cell wall(s) and Gram negative bacteria have __________ cell wall(s).
Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.
Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.
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Which polymer is the primary component of plant cell walls?
Which polymer is the primary component of plant cell walls?
Cell walls can vary in composition based on what organism is being discussed. In the case of plant cells, cellulose is the primary component. Bacteria use peptidolgycan in their cell walls, and fungi use chitin.
Cell walls can vary in composition based on what organism is being discussed. In the case of plant cells, cellulose is the primary component. Bacteria use peptidolgycan in their cell walls, and fungi use chitin.
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Which of the following encloses a plant cell in a rigid framework and cannot be digested by humans?
Which of the following encloses a plant cell in a rigid framework and cannot be digested by humans?
The cell wall is composed of cellulose and encloses a plant cell in a rigid framework. Plant cells have both cell membranes and cell walls. Plant cell walls cannot be digested by humans due to the beta glycosidic bond in its structure. The cell membrane forms the outer boundary of a cell and isolates cell contents from the environment. The cell membrane regulates movement of materials into and out of the cell. The cell membrane is also referred to as the plasma membrane. The nuclear envelope regulates movement into and out of the nucleus. The cytoskeleton gives shape and support to cells and is typically involved in cell movement.
The cell wall is composed of cellulose and encloses a plant cell in a rigid framework. Plant cells have both cell membranes and cell walls. Plant cell walls cannot be digested by humans due to the beta glycosidic bond in its structure. The cell membrane forms the outer boundary of a cell and isolates cell contents from the environment. The cell membrane regulates movement of materials into and out of the cell. The cell membrane is also referred to as the plasma membrane. The nuclear envelope regulates movement into and out of the nucleus. The cytoskeleton gives shape and support to cells and is typically involved in cell movement.
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Which of the following is true regarding cell walls?
I. They are only found in bacteria that can be Gram stained
II. Some organisms that have cell walls can undergo photosynthesis
III. They expand when a cell is placed in a hypoosmolar environment
Which of the following is true regarding cell walls?
I. They are only found in bacteria that can be Gram stained
II. Some organisms that have cell walls can undergo photosynthesis
III. They expand when a cell is placed in a hypoosmolar environment
Cell walls are robust structures found in most bacteria, fungi, and plants. Gram stain depends on the properties of the cell wall. Some bacteria don’t stain well with Gram stain (such as Mycobacterium that causes tuberculosis) because of unique cell walls (not lack thereof). Fungal and plant cell walls are also made up of polysaccharides. Fungal cell walls contain a special molecule called chitin whereas plant cell walls contain cellulose. Recall that plants obtain energy from sunlight via photosynthesis; therefore, photosynthetic organisms do contain cell walls.
One of the biggest function of a cell wall is to prevent cellular swelling. Recall that a cell placed in a hypoosmolar solution will swell due to the influx of water; however, this cellular swelling will not occur in a cell containing cell wall because the robust cell wall prevents contents of the cell from expanding, thereby preventing cellular lysis.
Cell walls are robust structures found in most bacteria, fungi, and plants. Gram stain depends on the properties of the cell wall. Some bacteria don’t stain well with Gram stain (such as Mycobacterium that causes tuberculosis) because of unique cell walls (not lack thereof). Fungal and plant cell walls are also made up of polysaccharides. Fungal cell walls contain a special molecule called chitin whereas plant cell walls contain cellulose. Recall that plants obtain energy from sunlight via photosynthesis; therefore, photosynthetic organisms do contain cell walls.
One of the biggest function of a cell wall is to prevent cellular swelling. Recall that a cell placed in a hypoosmolar solution will swell due to the influx of water; however, this cellular swelling will not occur in a cell containing cell wall because the robust cell wall prevents contents of the cell from expanding, thereby preventing cellular lysis.
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How are glucose monomers linked in the cellulose polymers present in a plant cell wall?
How are glucose monomers linked in the cellulose polymers present in a plant cell wall?
Cellulose is a polymer of glucose linked by beta (1-4) linkages. Humans lack the enzyme that catalyzes the cleavage of this bond; thus cellulose (dietary fiber) is indigestible and passes through the digestive system unchanged.
Cellulose is a polymer of glucose linked by beta (1-4) linkages. Humans lack the enzyme that catalyzes the cleavage of this bond; thus cellulose (dietary fiber) is indigestible and passes through the digestive system unchanged.
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Which of the following typically describes molecules that easily diffuse through the plasma membrane (lipid bilayer) of animal cells?
Which of the following typically describes molecules that easily diffuse through the plasma membrane (lipid bilayer) of animal cells?
The correct answer is nonpolar, small in size, and have a large lipid solubility coefficient. The center of the lipid bilayer is nonpolar and composed of fatty acid chains; therefore, nonpolar molecules diffuse through more easily. Diffusion does not use transport proteins to shuttle molecules through the lipid bilayer, so smaller molecules are able to diffuse more easily between the phospholipids that comprise the bilayer. Finally, a higher lipid solubility coefficient means that the molecule is more soluble in lipids and less soluble in aqueous solutions. A low lipid solubility means that the molecule is more aqueous-soluble than lipid-soluble.
The correct answer is nonpolar, small in size, and have a large lipid solubility coefficient. The center of the lipid bilayer is nonpolar and composed of fatty acid chains; therefore, nonpolar molecules diffuse through more easily. Diffusion does not use transport proteins to shuttle molecules through the lipid bilayer, so smaller molecules are able to diffuse more easily between the phospholipids that comprise the bilayer. Finally, a higher lipid solubility coefficient means that the molecule is more soluble in lipids and less soluble in aqueous solutions. A low lipid solubility means that the molecule is more aqueous-soluble than lipid-soluble.
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Dense specialized plasma membrane microdomains that cluster cholesterol, sphingolipids, and protein receptors, and are also sites of receptor trafficking and assembly of signal molecules, are called __________.
Dense specialized plasma membrane microdomains that cluster cholesterol, sphingolipids, and protein receptors, and are also sites of receptor trafficking and assembly of signal molecules, are called __________.
The correct answer is lipid rafts. Lipid rafts are more dense, less fluid domains of the plasma membrane. In addition to clustering cholesterol and sphingolipids, large transmembrane-domain proteins also localize here.
Integrins are transmembrane receptors, micelles are small lipid spheres, and phosphoinositides are a family of lipid molecules.
The correct answer is lipid rafts. Lipid rafts are more dense, less fluid domains of the plasma membrane. In addition to clustering cholesterol and sphingolipids, large transmembrane-domain proteins also localize here.
Integrins are transmembrane receptors, micelles are small lipid spheres, and phosphoinositides are a family of lipid molecules.
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Which type of membrane protein spans the entire width of the membrane?
Which type of membrane protein spans the entire width of the membrane?
Integral proteins are proteins that connect the inside of the cell to the outside by traversing the phospholipid bilayer. Carrier proteins, for example, allow substances to pass the membrane by letting them cross through channels.
Integral proteins are proteins that connect the inside of the cell to the outside by traversing the phospholipid bilayer. Carrier proteins, for example, allow substances to pass the membrane by letting them cross through channels.
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Many retroviruses, including (human immunodeficiency virus) HIV and other lentiviruses, generally bind what structure on the plasma membrane of vertebrate cells?
Many retroviruses, including (human immunodeficiency virus) HIV and other lentiviruses, generally bind what structure on the plasma membrane of vertebrate cells?
The correct answer is glycoprotein. HIV and many lentiviruses, which are also retroviruses, bind the CD4 glycoprotein. Lipopolysaccharides are found in bacteria, not vertebrates. Oligosaccharides are sugar polymers and generally function in cell-cell signaling. Cholesterol and phosphatidylcholine are components of the plasma membrane, not necessarily extracellularly exposed. The latter two help define the shape and rigidity of the plasma membrane.
The correct answer is glycoprotein. HIV and many lentiviruses, which are also retroviruses, bind the CD4 glycoprotein. Lipopolysaccharides are found in bacteria, not vertebrates. Oligosaccharides are sugar polymers and generally function in cell-cell signaling. Cholesterol and phosphatidylcholine are components of the plasma membrane, not necessarily extracellularly exposed. The latter two help define the shape and rigidity of the plasma membrane.
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