chapter 6
The diameter of a typical eukaryotic cell is approximately ten times the diameter of a typical prokaryote. What is the ratio of the volume of typical eukaryotic:prokaryotic cells? 1000:1 100:1 10:1
1000:1
Select the correct statement describing cellular structure or function. Plant and animal cells both carry out cellular respiration, producing ATP. Mitochondria and chloroplasts are part of the endomembrane system of the eukaryotic cell. Only plant cells contain chloroplasts, and only animal cells contain mitochondria.
Plant and animal cells both carry out cellular respiration, producing ATP.
Which of the following will have the greatest ratio of surface area to volume? A box that is 2×2×2. A box that is 1×1×1. A box that is 2×2×1. A box that is 1×1×2.
a box that is 1x1x1
The nuclear lamina is an array of intermediate filaments that line the inner side of the nuclear membrane. If a chemical treatment caused the lamina to disassemble, what would you expect to be the most likely immediate consequence? a change in the shape of the nucleus closing of nuclear pores the inability of the nucleus to divide during cell division a loss of genetic information from chromosomes
a change in the shape of the nucleus
Cilia and flagella bend because of ________. contraction by myosin a motor protein called dynein a motor protein called radial spokes conformational changes in ATP that thrust microtubules laterally
a motor protein called dynein
Which domains of life are classified as prokaryotes? Bacteria and Protista Archaea and Fungi Bacteria and Eukarya Bacteria and Archaea
bacteria and archaea
Which of the following are common traits of chloroplasts and mitochondria? Both reproduce by meiosis. Both have their own DNA. Both are found in plant and animal cells. Both are surrounded by a single membrane. Proteins for both are synthesized on ribosomes in the rough ER.
both have their own DNA
Which of the following choices correctly matches a tool and its proper application? transmission electron microscopy (TEM) to study the movement of organelles within a living cell cell fractionation to study the function of specific organelles transmission electron microscopy (TEM) to study the surfaces of preserved cells scanning electron microscopy (SEM) to study the detailed movements of living cells light microscopy to study the internal structure of cilia
cell fractionation to study the function of specific organelles
Which organelle often takes up much of the volume of a plant cell? central vacuole lysosome chloroplast Golgi apparatus
central vacuole
Which of the following correctly matches an organelle with its function? mitochondrion ... photosynthesis central vacuole ... storage nucleus ... cellular respiration lysosome ... movement ribosome ... manufacture of lipids
central vacuole ... storage
Which structure below is independent of the endomembrane system? plasma membrane nuclear envelope chloroplast Golgi apparatus
chloroplast
Which structure is not part of the endomembrane system? nuclear envelope plasma membrane chloroplast Golgi apparatus ER
chloroplast
Thylakoids, DNA, and ribosomes are all components found in _____. chloroplasts mitochondria nuclei lysosomes
chloroplasts
In a liver cell detoxifying alcohol and some other poisons, the enzymes of the peroxisome remove hydrogen from these molecules and ________. combine the hydrogen with water molecules to generate hydrogen peroxide combine the hydrogen with oxygen molecules to generate hydrogen peroxide combine the hydrogen with hydrogen peroxide to generate oxygen combine the hydrogen with hydrogen peroxide to generate oxygen and water
combine the hydrogen with oxygen molecules to generate hydrogen peroxide
One difference between eukaryotic and prokaryotic cells is that eukaryotic cells have membrane-enclosed organelles, which are lacking in prokaryotic cells. are enclosed by a membrane, which is lacking in prokaryotic cells. lack the complexity seen in prokaryotic cells. have DNA, which is lacking in prokaryotic cells.
have membrane-enclosed organelles, which are lacking in prokaryotic cells
Where are proteins produced other than on ribosomes free in the cytosol or ribosomes attached to the endoplasmic reticulum? in the nucleolus in the Golgi apparatus in mitochondria in lysosomes
in mitochondria
One primary advantage of light microscopy over electron microscopy is that ________. light microscopy provides higher contrast than electron microscopy light microscopy allows the visualization of dynamic processes in living cells light microscopy provides for higher resolution than electron microscopy light microscopy provides for higher magnification than electron microscopy
light microscopy allows the visualization of dynamic processes in living cells
Asbestos is a material that was once used extensively in construction. One risk from working in a building that contains asbestos is the development of asbestosis caused by the inhalation of asbestos fibers. Cells will take up asbestos by phagocytosis, but are not able to degrade it. As a result, asbestos fibers accumulate in ________. lysosomes the Golgi apparatus peroxisomes nuclei
lysosomes
Which of the following macromolecules leaves the nucleus of a eukaryotic cell through pores in the nuclear membrane? phospholipids mRNA amino acids DNA
mRNA
Suppose a young boy is always tired and fatigued, suffering from a metabolic disease. Which of the following organelles is most likely malfunctioning in this disease? smooth endoplasmic reticulum mitochondria lysosomes Golgi apparatus
mitochondria
Cyanide binds to at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the cyanide will be found within the lysosomes. mitochondria. ribosomes. endoplasmic reticulum. peroxisomes.
mitochondria.
Researchers investigating the mechanism of vesicular transport assembled a cell-free system that included microtubule tracks, vesicles, and ATP. However, they observed no movement of transport of vesicles in this system. What were they missing? an axon contractile microfilaments motor proteins intermediate filaments
motor proteins
Cytochalasin D is a drug that prevents actin polymerization. A cell treated with cytochalasin D will still be able to carry out which of the following processes? move vesicles within a cell contract muscle fibers extend pseudopodia divide in two
move vesicles within a cell
Suppose a cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from ________. nearly any eukaryotic organism a bacterium, but not a eukaryote a plant, but not an animal an animal, but not a plant
nearly any eukaryotic organism
Which cell would be best for studying lysosomes? phagocytic white blood cell nerve cell muscle cell bacterial cell
phagocytic white blood cell
Mitochondria are found in _____. animal cells only plant cells only all cells plant and animal cells animal cells and prokaryotic cells, but not plant cells
plant and animal cells
Which of the following structures form cytoplasmic channels that connect adjacent plant cells through the cell walls? tight junctions plasmodesmata desmosomes gap junctions
plasmodesmata
A cell with a predominance of rough endoplasmic reticulum is most likely ________. producing large quantities of carbohydrates for storage in the vacuole producing large quantities of proteins for secretion producing large quantities of carbohydrates to assemble an extensive cell wall matrix producing large quantities of proteins in the cytosol
producing large quantities of proteins for secretion
Which of the following frequently imposes a limit on cell size? the volume of the endomembrane system the number of mitochondria in the cytoplasm the absence of a nucleus ratios of surface area to volume
ratios of surface area to volume
Which of the following macromolecules enter the nucleus of a eukaryotic cell through pores in the nuclear membrane? ribosomal proteins phospholipids mRNA rRNA
ribosomal proteins
Which of the following is present in a prokaryotic cell? mitochondrion ER ribosome chloroplast nuclear envelope
ribosome
In the fractionation of homogenized cells using differential centrifugation, which of the following will require the greatest speed to form pellets at the bottom of the tube? nuclei ribosomes mitochondria chloroplasts
ribosomes
Which of the following are found in plant, animal, and bacterial cells? endoplasmic reticulum chloroplasts mitochondria ribosomes
ribosomes
Which of the following is the most common pathway taken by a newly synthesized protein that will be secreted by a cell? rough ER → lysosome → transport vesicle → plasma membrane Golgi → rough ER → lysosome → transport vesicle → plasma membrane rough ER → Golgi → transport vesicle → plasma membrane rough ER → Golgi → transport vesicle → nucleus
rough ER -> golgi -> transport vesicle -> plasma membrane
You have a cube of modeling clay in your hands. Which of the following changes to the shape of this cube of clay will decrease its surface area relative to its volume? Flatten the cube into a pancake shape. Round the clay up into a sphere. Pinch the edges of the cube into small folds. Stretch the cube into a long, shoebox shape.
round the clay up into a sphere
Which of the following would be most appropriate method to observe the three-dimensional structure and organization of microvilli on an intestinal cell? a hand lens (magnifying glass) standard light microscopy scanning electron microscopy transmission electron microscopy
scanning electron microscopy
Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given vinblastine would be unable to _____. maintain the shape of the nucleus form cleavage furrows during cell division migrate by amoeboid movement separate chromosomes during cell division
separate chromosomes during cell division
The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and, therefore, abundant in liver cells? nuclear envelope smooth endoplasmic reticulum Golgi apparatus rough endoplasmic reticulum
smooth endoplasmic reticulum
Which of the following would be the most appropriate method to observe the movements of condensed chromosomes during cell division? a hand lens (magnifying glass) transmission electron microscopy scanning electron microscopy standard light microscopy
standard light microscopy
A cell with a predominance of smooth endoplasmic reticulum is likely specialized to ________. actively secrete large quantities of protein store large quantities of water import and export large quantities of protein synthesize large quantities of lipids
synthesize large quantities of lipids
Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large, complex, undigested lipids. Which cellular organelle is most likely defective in this condition? the lysosome the rough endoplasmic reticulum the Golgi apparatus the smooth endoplasmic reticulum
the lysosome
In bacteria, DNA will be found in ________. a membrane-enclosed nucleus ribosomes the nucleoid mitochondria
the nucleoid
A newspaper ad for a local toy store indicates that an inexpensive toy microscope available for a small child is able to magnify specimens nearly as much as the more costly microscope available in your college lab. What is the primary reason for the price difference? The toy microscope produces less contrast in the specimens. The toy microscope usually uses a different wavelength of light source. The toy microscope does not have the same fine control for focus of the specimen. The toy microscope magnifies a good deal, but has low resolution and therefore poor quality images.
the toy microscope magnifies a good deal, but has low resolution and therefore poor quality images
A defect in which of the following intercellular junctions would allow partially digested material to leak passively between the cells of the small intestine into the abdominal cavity? gap junctions desmosomes plasmodesmata tight junctions
tight junctions
Which of the following would be most appropriate method to observe and measure the size of ribosomes in a eukaryotic cell? standard light microscopy scanning electron microscopy a hand lens (magnifying glass) transmission electron microscopy
transmission electron microscopy
What is a primary function of integrins? transmitting signals from the extracellular matrix to the cytoskeleton linking the primary and secondary cell walls in plants connecting intermediate filaments to microtubules involved in vesicular transport transmitting chemical signals from the Golgi apparatus to the plasma membrane
transmitting signals from the extracellular matrix to the cytoskeleton
Cells require which of the following to form cilia or flagella? laminin actin intermediate filaments tubulin
tubulin
Which of the following clues would tell you if a cell is prokaryotic or eukaryotic? the presence or absence of a rigid cell wall whether or not the cell contains DNA the presence or absence of ribosomes whether or not the cell carries out cellular metabolism whether or not the cell is partitioned by internal membranes
whether or not the cell is partitioned by internal membranes
Which of the following options best depicts the flow of information when a gene directs the synthesis of a cellular component? DNA → RNA → protein RNA → DNA → RNA → protein DNA → amino acid → RNA → protein protein → RNA → DNA
DNA → RNA → protein
Which of the following organelles produces and modifies polysaccharides that will be secreted? lysosome mitochondrion Golgi apparatus peroxisome
Golgi apparatus
A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in which of the following organelles or structures? mitochondria and Golgi apparatus Golgi apparatus and extracellular matrix nuclear pores and secretory vesicles nuclear matrix and extracellular matrix
Golgi apparatus and extracellular matrix
Which of the following functions is NOT associated with the cytoskeleton in eukaryotic cells? the beating of cilia or flagella maintaining the position of the nucleus in the cell the contraction of muscle cells in animals determining the shape of animal cells Movement of RNA molecules from the nucleus to the cytoplasm
Movement of RNA molecules from the nucleus to the cytoplasm
Which of the following statements about the cytoskeleton is true? Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other. Chemicals that block the assembly of the cytoskeleton would have little effect on a cell's response to external stimuli. The cytoskeleton of eukaryotes is a static structure most resembling scaffolding used at construction sites. Although microtubules are common within a cell, actin filaments are rarely found outside of the nucleus.
Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other.
Which one of the following statements about the endomembrane system is correct? Most of the phospholipids of the endomembrane system are synthesized in the mitochondria. The endoplasmic reticulum is continuous with the plasma membrane. Mitochondria function in the modification and sorting of lipids and proteins. Proteins that will be secreted from the cell are likely to be found in closed spaces bounded by membranes of the endomembrane system. Ribosomes move lipids and proteins among the different organelles of the endomembrane system.
Proteins that will be secreted from the cell are likely to be found in closed spaces bounded by membranes of the endomembrane system.
Choose the best description of the cell cytoskeleton. The cell cytoskeleton is a dynamic network of fibers that can be quickly dismantled and reassembled to change cell shape and the position of cell components. The cell cytoskeleton is similar to an animal skeleton in providing rigid internal support and structure to the cell. The cell cytoskeleton serves as permanent scaffolding to anchor cell components into position within the cell cytoplasm.
The cell cytoskeleton is a dynamic network of fibers that can be quickly dismantled and reassembled to change cell shape and the position of cell components.
H. V. Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted intercellular junctions, and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson found that the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species. How do you explain the results of Wilson's experiments? The molecules responsible for cell-cell adhesion (cell junctions) were irreversibly destroyed during the experiment. One cell functioned as an organizer for each organism, thereby attracting only cells of the same species. The molecules responsible for cell-cell adhesion (cell junctions) differed between the two species of sponge. The two species of sponge had different enzymes that functioned in the reassembly process.
The molecules responsible for cell-cell adhesion (cell junctions) differed between the two species of sponge
Identify the correct statement about differences between rough and smooth endoplasmic reticulum (ER). Rough ER consists of a network of membranous tubules and sacs called cisternae, whereas smooth ER is less complex. Smooth ER is part of the endomembrane system of the eukaryotic cell, and rough ER is not. The outer surface of smooth ER lacks ribosomes, whereas the outer surface of rough ER has ribosomes.
The outer surface of smooth ER lacks ribosomes, whereas the outer surface of rough ER has ribosomes.
Which of the following expresses the concept of emergent properties? The parts of a car, once assembled, result in a structure that can provide transportation. A cell is the basic unit of structure in living organisms. Properties emerge from a system through evolutionary mechanisms. Energy can be transformed but not created or destroyed, while matter cycles through a system.
The parts of a car, once assembled, result in a structure that can provide transportation
The cell walls of bacteria, fungi, and plant cells, and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following characteristics are common to all of these extracellular structures? They are constructed of materials that are exported from inside the cell and then transported out of the cell for assembly. They must provide a rigid structure that maintains an appropriate ratio of cell surface area to volume. They must block water and small molecules to regulate the exchange of matter and energy with their environment. They are composed of a mixture of lipids and nucleotides.
They are constructed of materials that are exported from inside the cell and then transported out of the cell for assembly.
A newly discovered unicellular organism isolated from acidic mine drainage is found to contain a cell wall, a plasma membrane, two flagella, and peroxisomes. Based just on this information, the organism is most likely ________. a nonmotile prokaryote a motile archaea a motile eukaryote a motile bacterium a nonmotile eukaryote
a motile eukaryote
Spherocytosis is a human blood disorder associated with a defective cytoskeletal protein in the red blood cells (RBCs). What do you suspect is the consequence of such a defect? an insufficient supply of ATP in the RBCs an insufficient supply of oxygen-transporting proteins in the RBCs abnormally shaped RBCs adherence of RBCs to blood vessel walls, causing plaque formation
abnormally shaped RBCs
Volume Surface Area Cell 1 9.3 μm3 26.5 μm2 Cell 2 12.2 μm3 37.1 μm2 Cell 3 17.6 μm3 40.6 μm2 Using data from the table above, select the best explanation for why that cell will be able to eliminate waste most efficiently? Cell 1, since it has the smallest volume and will not produce as much waste as the other cells. Cell 2, since it has the highest ratio of surface area to volume, which facilitates the exchange of materials between a cell and its environment. Cell 3, since it has the largest surface area, which will enable it to eliminate all of its wastes efficiently. Cell 3, because it is big enough to allow wastes to easily diffuse through the plasma membrane.
cell 2, since it has the highest ratio of surface area to volume, which facilitates the exchange of materials between a cell and its environment
Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures? free ribosomes and ribosomes attached to the ER components of the cytoskeleton membrane proteins of the inner nuclear envelope cellulose fibers in the cell wall
components of the cytoskeleton
A cell has formed a food vacuole as it ingested a food particle. Which of the following events is associated with the breakdown of that food particle? Proteins for digestion of the food particle were initially processed in mitochondria. Proteins for digestion of the food are made by ribosomes in the Golgi apparatus. Digestion of the food particle occurs in a vesicle enclosed by a membrane that separates the digestion from the cytoplasm. Enzymes for the breakdown of the food are delivered to the food vacuole from the cytosol. The membrane of the food vacuole is derived from the cell wall.
digestion of the food particle occurs in a vesicle enclosed by a membrane that separates the digestion from the cytoplasm
What is the explanation for how a modern transmission electron microscope (TEM) can achieve a resolution of about 0.2 nanometers, whereas a standard light microscope has a maximum resolution of about 200 nanometers? Glass lenses in light microscopes refract light, which reduces resolution. Electron beams have much shorter wavelengths than visible light. Contrast is enhanced by staining with atoms of heavy metal. The electron microscope has a much greater ratio of image size to real size.
electron beams have much shorter wavelengths than visible light
The evolution of eukaryotic cells most likely involved ________. endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into mitochondria endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into chloroplasts endosymbiosis of a photosynthetic archaeal cell in a larger bacterial host cell to escape toxic oxygen-the anaerobic archaea evolved into chloroplasts evolution of an endomembrane system and subsequent evolution of mitochondria from a portion of the smooth endoplasmic reticulum
endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into mitochondria
Which of the following is a major difference between prokaryotic cells and eukaryotic cells? Prokaryotic cells are generally larger than eukaryotic cells. Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not. Eukaryotic cells have flagella, while prokaryotic cells do not. Prokaryotic cells have cell walls, while eukaryotic cells do not.
eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not
A characteristic 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules is associated with ________. bacterial flagella eukaryotic flagella, motile cilia, and nonmotile cilia centrioles and basal bodies eukaryotic flagella and motile cilia
eukaryotic flagella and motile cilia
Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through _____. gap junctions desmosomes plasmodesmata tight junctions
gap junctions
In plant cells, the middle lamella ________. glues adjacent cells together connects the cytoplasm of adjacent cells prevents excessive uptake of water by plant cells prevents dehydration of adjacent cells
glues adjacent cells together
Amoebae move by crawling over a surface (cell crawling), which involves ________. growth of actin filaments to form bulges in the plasma membrane localized contractions driven by myosin and microtubules reinforcement of the pseudopod with intermediate filaments assembly of microtubule extensions that vesicles can follow in the direction of movement
growth of actin filaments to form bulges in the plasma membrane
If plant cells are grown on media containing radioactively labeled thymine for one generation, radioactively labeled macromolecules will be detected in which of the following? only in the nucleus only in the nucleus and chloroplasts only in the nucleus and mitochondria in the nucleus, mitochondria, and chloroplasts
in the nucleus, mitochondria, and chloroplasts
Which statement about extracellular structures (plant cell walls and the extracellular matrix of animal cells) is correct? Proteins and lipids are common components of extracellular structures. Information can be transmitted from these extracellular structures to the cytoplasm. All extracellular structures form barriers to separate adjacent cells. Extracellular structures store energy in the form of polysaccharides for subsequent metabolism by the cell. Extracellular structures regulate the passage of water molecules across the cell membrane.
information can be transmitted from these extracellular structures to the cytoplasm
What is the function of the nuclear pore complex found in eukaryotes? It assembles ribosomes from raw materials that are synthesized in the nucleus. It synthesizes secreted proteins. It regulates the movement of proteins and RNAs into and out of the nucleus. It synthesizes the proteins required to copy DNA and make mRNA.
it regulates the movement of proteins and RNAs into and oout of the nucleus
Membrane phospholipids form impermeable layers for cells. may have ʺkinksʺ in their tails, each caused by the presence of a double bond between carbons. have hydrophilic tails that face outward and are exposed to water and hydrophobic heads that face the center of the membrane and are shielded from water. remain fluid because they are tightly packed against one another.
may have "kinks" in their tails, each caused b the presence of a double bond between carbons
Cyanide binds with at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the bound cyanide is likely to be localized within the ________. smooth endoplasmic reticulum peroxisomes mitochondria lysosomes
mitochondria
Which of the following is the smallest structure that would most likely be visible with a standard (not super-resolution) research-grade light microscope? mitochondrion ribosome virus microtubule
mitochondrion
Which organelle is the primary site of ATP synthesis in eukaryotic cells? Golgi apparatus lysosome peroxisome mitochondrion
mitochondrion
Which structure is common to plant and animal cells? central vacuole mitochondrion chloroplast wall made of cellulose centriole
mitochondrion
Which structure is common to plant and animal cells? mitochondrion chloroplast central vacuole centriole
mitochondrion
Which statement correctly describes an endomembrane function? Products of the ER are usually modified during their transit from the cis to the trans region of the Golgi apparatus. Secretory proteins in transit from one part of the cell to another are carried in lysosomes. The lumen of the endoplasmic reticulum (ER) is continuous with the cell nucleus.
products of the ER are usually modified during their transit from the cis to the trans region of the golgi apparatus
Examination of a cell by transmission electron microscopy reveals a high density of ribosomes in the cytoplasm. This observation suggests that this cell is actively producing large amounts of which of the following molecules? proteins lipids polysaccharides nucleic acids
proteins
Which of the following statements correctly describes some aspect of protein secretion from prokaryotic cells? Prokaryotes cannot secrete proteins because they lack an endomembrane system. Proteins secreted by prokaryotes are likely synthesized on ribosomes bound to the cytoplasmic surface of the plasma membrane. The mechanism of protein secretion in prokaryotes is probably the same as that in eukaryotes. Prokaryotes cannot secrete proteins because they lack rough endoplasmic reticulum.
proteins secretes by prokaryotes are likely synthesized on ribosomes bound to the cytoplasmic surface of the plasma membrane
Gaucher disease is the most common of lipid storage diseases in humans. It is caused by a deficiency of an enzyme necessary for the breakdown of lipids. This leads to the accumulation of fatty material in organs of the body including the spleen, liver, kidneys, lungs, brain, and bone marrow. Using your knowledge of the structure of eukaryotic cells, identify the statement below that best explains how internal membranes and the organelles of cells may be involved in Gaucher disease. The lysosomes lack sufficient amounts of enzymes necessary for the metabolism of lipids. The mitochondria are most likely defective and do not produce adequate amounts of ATP needed for cellular energy. The Golgi apparatus produces vesicles with faulty membranes, which fail to be transported to the plasma membrane for secretion. The rough endoplasmic reticulum contains too many ribosomes, which results in an overproduction of the enzyme involved in lipid breakdown.
the lysosomes lack sufficient amounts of enzymes necessary for the metabolism of lipids
Which statement correctly describes the nuclear envelope of a eukaryotic cell? The nuclear envelope is a single membrane, consisting of a phospholipid bilayer. Plasmadesmosomes in the nuclear envelope permit the exchange of macromolecules between the nucleus and the cytoplasm. All of the proteins of the cell are synthesized on ribosomes bound on the nuclear envelope. The nuclear envelope is continuous with the endoplasmic reticulum. The outer layer of the nuclear envelope is coated with laminin.
the nuclear envelope is continuous with the endoplasmic reticulum