BIOL exam 2
Which of the following is FALSE?
Mitochondria contain ribosomes in the intermembrane space. The ribosomes in the mitochondria are found in the matrix of the mitochondria, not in the intermembrane space.
Which of the following pairs correctly matches a membrane transport process to its primary function?
pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane Pinocytosis is the uptake of liquid and the solutes dissolved in the liquid.
Mitochondria are found in _____.
plant and animal cells All eukaryotic cells, including plant and animal cells, contain mitochondria.
The _____ is the bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell.
plasma membrane The plasma membrane is selectively permeable.
The _____ is a selective barrier, regulating the passage of material into and out of the cell.
plasma membrane The plasma membrane regulates the passage of material into and out of the cell.
Dye injected into a plant cell might be able to enter an adjacent cell through __________.
plasmodesmata The cell walls of plant cells contain numerous channels, with strands of cytoplasm passing through them and connecting one cell's cytoplasm to that of an adjacent cell.
A cell with a predominance of rough endoplasmic reticulum is most likely ________.
producing large quantities of proteins for secretion
What is the function of a bacterium's capsule?
protection' A bacterium's capsule has a protective role.
Which of the following frequently imposes a limit on cell size?
ratios of surface area to volume
Which of the following statements about chloroplasts and mitochondria is true?
Chloroplasts and mitochondria synthesize some of their own proteins. Chloroplasts and mitochondria can synthesize some of their own proteins because they contain DNA and ribosomes
Taxol, a drug approved for the treatment of breast cancer, prevents formation of microtubules. With what cellular function might Taxol interfere
Chromosome movements in cell division
Which of the following is FALSE in respect to eukaryotic chromosomes?
Chromosomes appear only as a cell is about to divide. This is false. Although chromosomes become more compact as a cell prepares to divide, they are always present in the cell.
Which of the following would be LEAST likely to diffuse through a plasma membrane without the help of a transport protein?
a large, polar molecule The combination of being polar and large means that this molecule will be the slowest one from the choices to move across the membrane.
Which of the following particles could diffuse easily through a cell membrane?
Oxygen (O2) Small nonpolar molecules such as oxygen can diffuse across cell membranes.
Endocytosis moves materials _____ a cell via _____.
into ... membranous vesicles The prefix "endo-" means "inward."
Diffusion of ions across membranes through specific ion channels is driven by ________.
ion electrochemical gradients
According to the fluid mosaic model, a membrane ________.
is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins
Which of the following five membranes is most likely to have a lipid composition that is distinct from those of the other four?
mitochondrial outer membrane The mitochondria are not part of the endomembrane system and must synthesize their own lipids
Which structure is common to plant and animal cells?
mitochondrion
Which of these organelles carries out cellular respiration?
mitochondrion Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of ATP.
Cilia and flagella move due to the interaction of the cytoskeleton with which of the following?
motor proteins Motor proteins, such as dynein, use energy to move parts of the cytoskeleton.
Which of the following membrane activities requires energy from ATP hydrolysis?
movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid
Which type of cell is most likely to have the largest number of mitochondria?
muscle cells in the legs of a marathon runner Cellular respiration releases energy that cells need in order to carry out their functions. Active muscle cells need large amounts of energy.
What is the functional connection between the nucleolus, nuclear pores, and the nuclear membrane?
Subunits of ribosomes are assembled in the nucleolus and pass through the nuclear membrane via the nuclear pores. Proteins and ribosomal RNA are assembled into ribosomal subunits in the nucleolus.
Your intestine is lined with individual cells. No fluids leak between these cells from the gut into your body. Why?
The intestinal cells are bound together by tight junctions. The membranes of neighboring cells are actually fused at a tight junction, forming a seal that prevents the leakage of extracellular fluid across the layer of epithelial cells.
What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?
cell wall The cell wall is a rigid supporting structure.
Which of the following structures is found in animal cells but NOT in plant cells?
centrioles Although plant cells have a microtubule organizing center, they lack a pair of centrioles.
The _____ is composed of DNA and protein.
chromatin Chromatin is composed of DNA and protein.
Basal bodies are most closely associated with which of the following cell components?
cilia The microtubule assembly of a cilium or flagellum is anchored in the cell by a basal body.
Which of the following factors would tend to increase membrane fluidity?
a greater proportion of unsaturated phospholipids
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
Where are enzymes responsible for biosynthesis of membrane lipids located
Smooth endoplasmic reticulum
The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?
1.0 M This solution is hypertonic to the plant cell. Water will leave the cell, and eventually the plasma membrane will pull away from the cell wall, resulting in plasmolysis
1 meter = _____ centimeters.
100
Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent microorganisms from growing in the olives?
A 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis If a cell is placed in a hypertonic solution, it will lose water to its environment, shrivel, and probably die.
Which of the following would be LEAST likely to diffuse through a plasma membrane without the help of a transport protein?
A large, polar molecule
Which protein is not made at the rough ER
A protein that enters the nucleus to bind with DNA
You are studying a Na+-K pump protein in the lab. What should you order to make sure that the pump will operate
ATP
Part complete Active and passive transport of solutes across a membrane typically differ in which of the following ways?
Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy. Active and passive transport can be distinguished by whether or not they use cellular energy.
Which of the following is a correct difference between active transport and facilitated diffusion?
Active transport requires energy from ATP, and facilitated diffusion does not. Active transport can move substances against the concentration gradient, but it requires energy in the form of ATP
What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
Amphipathic nature Submit Detergents form micelles around the grease, which are then washed away because the polar head groups facing outward on the micelle are water-soluble.
Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B. and cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________.
B ... the diffusion gradient in cell B is steeper As long as a metabolically active cell converts oxygen to water during cellular respiration shortly after it enters, diffusion into the cell will continue because the concentration gradient favors movement in that direction.
Which of the following statements correctly describes a common characteristic of a plant cell wall and an animal cell extracellular matrix?
Both are permeable to water and small solutes. Both plant cell walls and the ECM of animal cells allow movement of water and small solutes
_____ is/are identical in structure to centrioles.
Basal bodies Basal bodies and centrioles have identical structures.
Seawater is hypertonic to cytoplasm in vertebrate cells and in plant cells. If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells?
Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall. Seawater will cause both cells to lose wate
Which of the following are common traits of chloroplasts and mitochondria?
Both have their own DNA.
Which of the following are common traits of chloroplasts and mitochondria?
Both have their own DNA. Mitochondria and chloroplasts contain their own DNA and ribosomes.
Which of the following statements is TRUE
Both sodium and potassium ions are transported against their concentration gradients. Both ions are transported from where their concentration is low to where their concentration is high, and the cell expends energy in the form of ATP to do it.
Which of the following statements is true about cell fractionation?
Cell fractionation separates cells into their component parts. The organelles are usually separated by centrifugation.
In what way do the membranes of a eukaryotic cell vary?
Certain proteins are unique to each membrane.
Which statement about the cytoskeleton is true?
Components of the cytoskeleton often mediate the movement of organelles within the cytoplasm. The interaction of motor proteins with the cytoskeleton is responsible for the movement of organelles in cells.
Which of the following statements about cotransport of solutes across a membrane is correct?
Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes. The electrochemical gradient created by a single ATP-dependent pump can drive the transport of many different solutes using cotransport proteins.
Which molecules do not normally cross the nuclear membrane?
DNA All processes involving DNA take place in the nucleus.
Which of the following options best depicts the flow of information when a gene directs the synthesis of a cellular component?
DNA → RNA → protein If you had trouble with this question, review the following material: The entire process by which the information in a gene directs the manufacture of a cellular product is called gene expression. The sequence of DNA nucleotides along a gene is transcribed, forming an RNA that is then translated. This results in a linked series of protein subunits called amino acids. An amino acid chain, a polypeptide, folds into a specific protein with a unique shape and function.
Which of the following correctly describes a general property of all electrogenic pumps?
Electrogenic pumps create a voltage difference across the membrane. An electrogenic pump creates a net charge difference across a membrane (a membrane potential).
If you were using compartment-specific stains and found that a stain for the nuclear envelope lightly stained another compartment as well, what would that other compartment be?
Endoplasmic reticulum
In terms of cellular function, what is the most important difference between prokaryotic and eukaryotic cells?
Eukaryotic cells are compartmentalized, which allows for specialization. The presence of membrane-bounded organelles in eukaryotes permits cellular functions to occur in specialized, isolated compartments.
Part complete Which of the following correctly describes some aspect of exocytosis or endocytosis?
Exocytosis and endocytosis temporarily change the surface area of the plasma membrane. The fusion or budding of transport vesicles at the plasma membrane either adds or removes proteins and phospholipids, thus temporarily changing the surface area.
A correct distinction between facilitated diffusion and active transport is that
Facilitated diffusion moves solutes down a concentration gradient to transport substances, while active transport moves against a gradient
Which of these statements describes some aspect of facilitated diffusion
Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane
Which of these statements describes some aspect of facilitated diffusion?
Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. The passageways for facilitated diffusion may be either protein pores or carrier proteins.
Which of the following is FALSE in regard to facilitated diffusion?
Facilitated diffusion requires the hydrolysis of ATP. This statement is false. Facilitated diffusion, like simple diffusion, needs only a concentration gradient—no energy input is required.
True or false? Large proteins containing a nuclear localization signal (NLS) bind to the nuclear pore and enter the nucleus without any expenditure of energy.
False Cytoplasmic proteins called importins bind to large proteins containing an NLS and mediate their transport across the nuclear membrane through an active transport (energy-requiring) process.
_____ are surface appendages that allow a bacterium to stick to a surface.
Fimbriae Fimbriae enable bacterial cells to stick to a surface.
_____ aid in the coordination of the activities of adjacent animal cells.
Gap (communicating) junctions Gap junctions allow for the passage of material between cells, thus facilitating communication between these cells.
If you were studying mutant cells and found that many proteins are going to the wrong compartments in these cells, where is the mutation having the greatest effect
Golgi apparatus
A researcher made an interesting observation about a protein made by the rough endoplasmic reticulum and eventually found in a cell's plasma membrane. The protein in the plasma membrane was actually slightly different from the protein made in the ER. The protein was probably altered in the __________.
Golgi apparatus Vesicles carrying proteins from the rough ER fuse with the Golgi apparatus, where the proteins may be altered.
Microtubules and microfilaments commonly work with which of the following to perform many of their functions?
Golgi apparatus Microtubules guide vesicles from the ER to the Golgi and from the Golgi to the plasma membrane
Which of the following sequences represents the order in which a protein made in the rough endoplasmic reticulum might move through the endomembrane system
Golgi apparatus to lysosome
Which of the following sequences represents the order in which a protein made in the rough endoplasmic reticulum might move through the endomembrane system?
Golgi apparatus → lysosome Proteins of the endomembrane system are synthesized in the rough ER, modified and sorted in the Golgi, and then transported to other organelles of the endomembrane system such as vacuoles.
If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?
Hypotonic The salt concentration in the solution is lower than it is in the cell, so water enters the cell, causing it to burst.
Which of the following statements correctly describes osmosis?
In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.
Which of these cannot rapidly pass directly through the phospholipids of the plasma membrane?
Ions, such as hydrogen ions, and hydrophilic molecules, such as water and glucose, cannot rapidly pass directly through the phospholipids of a plasma membrane. To move rapidly through the membrane, they must pass through membrane transport proteins.
Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane?
It exhibits specificity for a particular type of molecule.
Which of the following statements about diffusion is true
It is a passive process. Diffusion is the tendency of molecules to spread out in the available space. A substance will diffuse from an area of higher concentration to an area of lower concentration without energy input.
How can a lipid be distinguished from a sugar?
Lipids are mostly nonpolar. Lipids are nonpolar molecules, whereas sugars are polar.
Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?
Membrane carbohydrates function primarily in cell-cell recognition. Variations in carbohydrate structure distinguish one species from another, one individual from another, and even one cell type from another.
Which of the following functions of membrane proteins is important in tissue formation during embryonic development in animals?
Membrane proteins with short sugar chains form identification tags that are recognized by other cells. Cell-cell recognition is an important function of membrane proteins, and this cell-cell recognition is important in tissue formation during embryogenesis.
Which of the following is a major difference between prokaryotic and eukaryotic cells?
Most prokaryotic cells have no internal membranes; eukaryotic cells do. If you had trouble with this question, review the following material: All cells are enclosed by a plasma membrane, a selective barrier that forms a boundary between the cell and the external environment. The existence of cells depends on the properties of phospholipids that make up the plasma membrane. Eukaryotic cells have extensive, elaborately arranged internal membranes as well that divide the cell into compartments called organelles, but most prokaryotic cells do not have internal membranes. All cells have DNA that stores the genetic information of the cell.
A selectively permeable membrane separates two solutions. Water is able to pass through this membrane; however, sucrose (a disaccharide) and glucose (a monosaccharide) cannot pass. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solutions change?
Nothing will happen, because the two solutions are isotonic to one another. Osmotic pressure is produced by the concentration of dissolved substances and is not influenced by the relative sizes of the solutes.
Which molecule will diffuse most quickly across a lipid bilayer membrane
O2
In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?
On the inside surface of the vesicle
Where in the membrane would carbohydrates most likely be found
On the outside of the plasma membrane
Nucleoplasmin is a nuclear protein. This protein was divided into two segments and linked to the same large cytoplasmic protein, generating two fusion proteins. After injecting these fusion proteins into a cell, one of the proteins was found in the nucleus and the other in the cytoplasm. Which of the following conclusions can be drawn from these results?
Only one of the two fusion proteins possesses a nuclear localization signal. The nuclear localization signal is only present in the fusion protein that enters the nucleus.
Which statements about the sidedness of the plasma membrane is correct?
Parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane. Every integral membrane protein has a specific orientation in the plasma membrane. The two lipid layers may differ in specific lipid composition. The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed
A small protein (molecular weight = 25,000 daltons) is injected into a cell and observed in the nucleus a short time later. What type of transport has taken place?
Passive transport A 25,000-dalton protein is small enough to diffuse through nuclear pores without any expenditure of energy.
Which of the following statements about passive transport is correct?
Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule Passive transport can occur in either direction, but the direction of net diffusion is down the concentration gradient of the solute.
Alcohol is destroyed in the cell by the removal of hydrogen atoms. Where does this occur
Peroxisome
Cells such as bacteria are taken up by other cells such as white blood cells by which mechanism
Phagocytosis
Which structure is common to all cells
Phospholipid bilayer cell membrane
Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?
Phospholipids form a selectively permeable structure Their structure allows some substances to penetrate easily and blocks others.
Which of the following pairs correctly matches a membrane transport process to its primary function?
Pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane
You viewed a TEM image of a plant cell, and found a large structure that dominated the interior of the cell, and pushed other organelles against the cell wall. What organelle is this likely to be
Plant Vacuole
Which of the following organelles is UNLIKELY to show enhanced abundance in pancreatic cells that secrete large amounts of digestive enzymes?
Ribosomes
_____ are the sites of protein synthesis.
Ribosomes
The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true?
The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect. This is what the term "fluid mosaic" refers to.
Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, do protons not move back into the cell through the sucrose-proton cotransport protein
The movement of protons through the cotransport protein cannot occur unless sucrose moves at the same time. The obligate coupling of proton movement to sucrose movement prevents the energy of the proton gradient from being lost if sucrose is not present.
Which of the following statements about the nuclear envelope is false?
The nuclear envelope is continuous with the Golgi apparatus. This statement is false; the nuclear envelope is continuous with the endoplasmic reticulum.
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. If you had trouble with this question, review the following material: The study of life on Earth extends from the molecular scale to the microscopic scale of the cells that make up organisms to the global scale of the entire living planet. We can divide this enormous range into different levels of biological organization. Starting at the molecular level and zooming out, novel properties emerge at each level that are absent from the preceding one. These emergent properties are due to the arrangement and interactions of parts as complexity increases.
How do membrane phospholipids interact with water?
The polar heads interact with water; the nonpolar tails do not. If you had trouble with this question, review the following material: A phospholipid is similar to a fat molecule but has only two fatty acids attached to glycerol rather than three. The third hydroxyl group of glycerol is joined to a phosphate group, which has a negative electrical charge in the cell. The fatty acids, referred to as the "tails" of the phospholipid, are hydrocarbons that are hydrophobic and therefore do not interact with water. The phosphate group and its attachments form a hydrophilic "head" that has an affinity for water.
Which of the following factors does not affect membrane permeability?
The polarity of membrane phospholipids Phospholipids contain both a polar head and a nonpolar hydrocarbon tail, both of which are necessary for their ability to form membrane bilayers.
Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true?
The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane. This is how the sodium-potassium pump generates voltage across the cell membrane.
Why are lipids and proteins free to move laterally in membranes?
There are only weak hydrophobic interactions in the interior of the membrane.
In experiments to test whether a protein can enter the nucleus, why would proteins be labeled with fluorescent molecules?
To make the proteins easy to see Fluorescent tags make the location of the proteins easy to visualize.
Glucose can be moved into cells via an active transport mechanism when the concentration of glucose inside the cell is higher than the concentration of glucose outside of the cell. This active transport mechanism moves glucose and sodium into the cell at the same time. The glucose moves up its gradient and the sodium moves down its gradient. Which of the following statements about this mechanism is accurate
To pump glucose up its concentration gradient, sodium moves down its concentration gradient, and the distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism. The movement of sodium down its gradient drives glucose up its gradient, and because sodium is at different concentrations on either side of the membrane and as sodium has a +1 charge, an electrochemical gradient also exists.
In facilitated diffusion, what is the role of the transport protein?
Transport proteins provide a hydrophilic route for the solute to cross the membrane. This is the most general description of facilitated diffusion by membrane transport proteins.
True or false? Osmosis is a type of diffusion.
True Osmosis is the diffusion of water across a selectively permeable membrane.
True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.
True The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail
Which statement best describes a biological membrane
Two layers of phospholipids with proteins either spanning the layers or on the surface of the layers
A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition
Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. The added salt makes the solution hypertonic compared to the cell. Water will leave the cell by osmosis.
The force driving simple diffusion is ________, while the energy source for active transport is ________.
a concentration gradient; ATP hydrolysis
The concentration of solutes in a red blood cell is about 2%, but red blood cells contain almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions?
a hypertonic sucrose solution When a cell is placed in a hypertonic environment, water will leave the cell, causing it to shrink.
A particular cell has a nucleus and chloroplasts in addition to the fundamental structures required by all cells. Based on this information, this cell could be __________.
a photosynthetic protist cell or a plant cell Some protists (such as algae) can photosynthesize, and so can plants. As both the protists and plants are eukaryotes, they contain organelles.
For a protein to be an integral membrane protein, it would have to be _____.
amphipathic, with at least one hydrophobic region
Consider two cells with the same volume but with very different surface areas due to differences in their shapes. The cell with the larger surface area is likely to
be involved in the rapid uptake of compounds from the cell's environment The high surface area is likely to be associated with high transport rates of compounds across the plasma membrane. The greater the surface area, the greater the potential for transport.
Which of the following molecules is most likely to passively diffuse across the plasma membrane?
carbon dioxide Hydrophobic molecules, such as hydrocarbons, carbon dioxide, and oxygen, can dissolve in the membrane and cross it with ease.
Which of the following is the simplest collection of matter that can live
cell
Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures?
components of the cytoskeleton
The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following
cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis Movement of most solutes against their concentration gradient couples the movement of one solute down its concentration gradient to the movement of another (glucose in this case) against its concentration gradient.
The primary role of _____ is to bind animal cells together.
desmosomes The primary role of desmosomes (anchoring junctions) is to bind cells together.
Consider a protein that is made in the rough endoplasmic reticulum. You observe that when the synthesis of the protein is completed, the protein is located in the ER membrane. Where else in the cell might this protein be found?
embedded in the plasma membrane, functioning in the transport of molecules into the cell This is the only answer in which the protein is a membrane protein
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?
endocytosis Endocytosis is the procedure that cells use to import large molecules across their plasma membrane
Which of the following is NOT a function of membrane proteins
energy, carbon, and nitrogen storage Proteins are not present in biological membranes to act as stores of energy, carbon, and nitrogen.
A characteristic 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules is associated with ________.
eukaryotic flagella and motile cilia
Which of the following processes and organelles account for the replacement of lipids and proteins lost from the plasma membrane?
exocytosis and smooth ER and rough ER In exocytosis, vesicles derived from the endomembrane system fuse with the plasma membrane, thus increasing the number of phospholipids in the plasma membrane and increasing its surface area. The smooth ER is largely responsible for production of lipids destined for the membrane, and the rough ER produces proteins destined for the plasma membrane.
A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which of the following best describes a mechanism by which Ca2+ enters the cell?
facilitated diffusion of Ca2+ into the cell down its electrochemical gradient Both the electrical and chemical (concentration) gradients contribute the energy to move Ca2+ into the cells by facilitated diffusion as long as there is a channel or carrier that is specific for Ca2+.
Which of the following organelles is UNLIKELY to show enhanced abundance in pancreatic cells that secrete large amounts of digestive enzymes?
free cytoplasmic ribosomes Secreted proteins are not synthesized on free cytoplasmic ribosomes; therefore, these ribosomes would not show enhanced abundance.
Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through _____.
gap junctions
One difference between eukaryotic and prokaryotic cells is that eukaryotic cells
have membrane-enclosed organelles, which are lacking in prokaryotic cells. If you had trouble with this question, review the following material: All cells share certain characteristics that allow cells to perform all activities required for life. All cells have both a membrane (the plasma membrane) that acts as a selective barrier and DNA, which is the cell's genetic material. Eukaryotic cells have added complexity with extensive, elaborately arranged internal membranes that divide the cell into compartments called organelles.
Bacterial cells are prokaryotic. Unlike a typical eukaryotic cell, they _
have no membrane-bounded organelles in their cytoplasm Prokaryotic cells have no membrane-bounded organelles
Chloroplasts and mitochondria are thought to be of prokaryotic origin. One piece of evidence that supports this hypothesis is that these organelles contain prokaryotic-like ribosomes. These ribosomes are probably most similar to ribosomes found __________.
in bacterial cells Like the ribosomes in bacteria, the ribosomes in the mitochondria are smaller than those found free in the cytoplasm or bound to endoplasmic reticulum in the eukaryotes.
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?
in the interior of the membrane The steroid cholesterol, wedged between phospholipid molecules in the plasma membranes of animals, helps stabilize the membrane.
A protein that ultimately functions in the plasma membrane of a cell is most likely to have been synthesized __________.
in the rough endoplasmic reticulum All of the membrane proteins of the endomembrane systems are made in the rough ER.
A researcher wants to film the movement of chromosomes during cell division. Which type of microscope should she choose and why is it the best choice?
light microscope, because the specimen is alive Although the resolution of the light microscope is far less than that of electron microscopes, light microscopy is the only technique that permits one to observe living cells.
Which organelle plays a role in intracellular digestion?
lysosome The prefix "lyso-" means decomposition.
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in _____.
lysosomes
Which of the following categories best describes the function of the rough endoplasmic reticulum?
manufacturing The rough endoplasmic reticulum is involved in the manufacture of proteins for the endomembrane system.
The cilia and flagella of eukaryotic cells are composed of _____.
microtubules Eukaryotic cilia and flagella are composed of microtubules.
Which of these are hollow rods that shape and support the cell?
microtubules Microtubules are rods that also play a role in organelle movement.
Which of the following structures is found in eukaryotic but NOT prokaryotic cells
mitochondria Only eukaryotic cells have membrane-bound organelles such as mitochondria.
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
Hydrophobic substances like salad oil are
nonpolar molecules that repel water molecules. If you had trouble with this question, review the following material: Salad oil is predominantly made up of carbon and hydrogen atoms, which share electrons almost equally, forming nonpolar covalent bonds. Substances that are nonpolar due to their large number of nonpolar bonds do not have an affinity for water and are termed hydrophobic ("water-fearing"). Substances that contain polar bonds are hydrophilic ("water-loving") because they contain atoms with partial charges due to those polar bonds. For example, a hydrogen atom with a partial positive charge can form a hydrogen bond with a partial negative charge on the oxygen atom of a water molecule.
Where is a bacterial cell's DNA found?
nucleoid region Bacteria lack a nucleus; their DNA is found in the nucleoid region.
Ribosomal subunits are manufactured by the _____.
nucleolus Ribosomes are manufactured by the nucleolus.
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found?
on the outside (external) surface of the membrane Membrane carbohydrates are covalently bonded to lipids or proteins and extend out from the external side of the plasma membrane as a means of cell identification.
Facilitated diffusion is a type of _______.
passive transport During facilitated diffusion, the cell is not expending energy to move the particles across the membrane; therefore, facilitated diffusion is a form of passive transport.
Which of these organelles produces H2O2 as a by-product?
peroxisome Peroxisomes produce hydrogen peroxide as a by-product of their metabolic processes.
A white blood cell engulfing a bacterium is an example of _____.
phagocytosis Phagocytosis occurs when a cell engulfs a large particle.
Which of the following enables a cell to pick up and concentrate a specific kind of molecule?
receptor-mediated endocytosis In receptor-mediated endocytosis, only a specific molecule, called a ligand, can bind to the receptor. Without receptor binding occurring first, endocytosis does not proceed.
Which of the following groups is primarily involved in synthesizing molecules needed by the cell?
ribosome, rough endoplasmic reticulum, smooth endoplasmic reticulum Each of these structures is capable of synthesizing molecules needed by cells.
Which of the following organelles might be found inside other organelles?
ribosomes Ribosomes are nonmembranous organelles that are found in the cytoplasm but also in mitochondria and chloroplasts.
In a bacterium, where are proteins synthesized?
ribosomes Ribosomes are involved in the manufacture of polypeptides (proteins).
Which of the following features do prokaryotes and eukaryotes have in common?
ribosomes, plasma membrane, and cytoplasm
What is the correct order of the exocytosis
rough ER, Golgi apparatus, transport vesicle, plasma membrane
Which of these organelles manufactures proteins bound for secretion out of the cell?
rough endoplasmic reticulum The ribosomes associated with the rough ER synthesize secretory proteins bound for the exterior of the cell. Further processing and packaging occurs in the Golgi apparatus.
Which of the following would be most appropriate method to observe the three-dimensional structure and organization of microvilli on an intestinal cell?
scanning electron microscopy
You would expect a cell with an extensive Golgi apparatus to
secrete large amounts of protein The Golgi apparatus modifies and sorts the lipids and proteins produced in the ER. Cells that secrete large amounts of material require an extensive Golgi apparatus.
Where is calcium stored?
smooth endoplasmic reticulum In addition to storing calcium, the smooth ER also plays a role in detoxification and lipid synthesis.
You can recognize the process of pinocytosis when _____.
the cell is engulfing extracellular fluid Pinocytosis is "cell drinking."
A dish of animal cells was grown in the presence of radioactive phosphorous. The phosphorous largely ended up in nucleotides inside the actively growing animal cells. In which cellular structure or structures would you predict the majority of the radioactive phosphorous to accumulate
the nucleus Large numbers of nucleotides would be used to make new DNA as the cells grew, and the DNA is housed in the nucleus.
A substance moving from outside the cell into the cytoplasm must pass through
the plasma membrane The plasma membrane defines the boundary between the cytoplasm and the outside of the cell.
Which of the following is/are likely to limit the maximum size of a cell?
the shape of the cell the time it takes a molecule to diffuse across a cell the cell's surface-to-volume ratio
Which of these cell junctions form a barrier to the passage of materials?
tight junctions Tight junctions form a barrier that prevents fluids from moving between cells.
Beginning within the nucleus, the first step leading to the synthesis of a polypeptide is _____.
transferring of information from DNA to messenger RNA Transcription is the first of the two main steps of protein synthesis.
Which of the following would be most appropriate method to observe and measure the size of ribosomes in a eukaryotic cell?
transmission electron microscopy
Cells require which of the following to form cilia or flagella?
tubulin
Which of the following best describes the structure of a biological membrane
two layers of phospholipids with proteins either crossing the layers or on the surface of the layers The membrane proteins can be found either embedded in or attached to the surface of the phospholipid bilayer.
