Chapter 6; A Tour of the Cell
Intermediate Filament
a component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments
Transport Vesicle
a small membranous sac in a eukaryotic cell's cytoplasm carrying molecules produced by the cell
Middle Lamella
in plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells
A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from a. a bacterium b. an animal, but not a plant c. nearly any eukaryotic organism d. any multicellular organism, like a plant or an animal e. any kind of organism
nearly any eukaryotic organism
Cytosol
the semifluid portion of the cytoplasm
Which of the following is a possible reason for grouping the peroxisomes with chloroplasts and mitochondria? a. They all contain DNA and make some of their own proteins b. They are all part of the plastid family of organelles c. They all contain two or more membranes d. They are all involved in ATP synthesis e. All of these organelles appear to increase in number by dividing
All of these organelles appear to increase in number by dividing Chloroplasts, mitochondria, and peroxisomes all increase in number by dividing within the cell.
How do microscopy and biochemistry compliment each other to reveal cell structure and function?
Cell fractionation allows biologists to identify enzymes that are not able to be seen under the microscope, while microscopy allows biologists to see what is going on in the cell and correlate biochemistry's findings to where in the cell the enzymes are.
What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell? a. Golgi --> ER --> lysosome b. nucleus --> ER --> Golgi c. ER --> Golgi --> vesicles that fuse with plasma membrane d. ER --> lysosomes --> vesicles that fuse with plasma membrane
ER --> Golgi --> vesicles that fuse with plasma membrane
What role do ribosomes play in carrying out genetic instructions?
Ribosomes in the cytoplasm translate the genetic message, carried from the DNA in the nucleus to mRNA, into a polypeptide chain.
If the function of a particular protein is a eukaryotic cell is to make up a part of the chromatin, describe the process of its synthesis. Include the cellular locations of all relevant molecules.
The information in a gene (on a chromosome in the nucleus) is used to synthesize an mRNA that is then transported through a nuclear pore to the cytoplasm. There it is translated into protein, which is transported back through a nuclear pore into the nucleus, where is joins other proteins and DNA, forming chromatin.
Describe how transport vesicles integrate the endomembrane system.
Transport vesicles move membranes and substances they enclose between other components of the endomembrane system.
Microfilament
a cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction; also called an actin filament
Pseudopodium (plural, Pseudopodia)
a cellular extension of amoeboid cells used in moving and feeding
Endoplasmic Reticulum (ER)
an extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions
Organelle
any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells
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 __________. a. be buried deep in the interior of an organism b. be involved in the rapid uptake of compounds from the cell's environment c. have a very high metabolic rate d. be a prokaryotic cell e. be nearly spherical in shape
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 is the simplest collection of matter that can live? a. molecules b. cell c. organ d. tissue e. None of these responses are correct
cell
Which of the following structures is found in animal cells but NOT in plant cells? a. mitochondria b. Golgi apparatus c. plasma membrane d. centrioles e. rough endoplasmic reticulum
centrioles Although plant cells have a microtubule organizing center, they lack a pair of centrioles.
Which organelle or structure is absent in plant cells? a. mitochondria b. Golgi vesicles c. microtubules d. centrosomes e. peroxisomes
centrosomes
As a cell begins the process of dividing, its chromosomes become shorter, thicker, and individually visible in an LM. Explain what is happening at the molecular level.
chromosomes become visible in prophase
Basal bodies are most closely associated with which of the following cell components? a. cilia b. the central vacuole c. mitochondria d. Golgi apparatus e. nucleus
cilia The microtubule assembly of a cilium or flagellum is anchored in the cell by a basal body.
Which of the following organelles is UNLIKELY to show enhanced abundance in pancreatic cells that secrete large amounts of digestive enzymes? a. free cytoplasmic ribosomes b. Golgi apparatus c. transport vesicles d. rough endoplasmic reticulum e. All of the listed organelles will show an increase in pancreatic cells secreting digestive enzymes
free cytoplasmic ribosomes Secreted proteins are not synthesized on free cytoplasmic ribosomes; therefore, these ribosomes would not show enhanced abundance.
Nuclear Envelope
in a eukaryotic cell, the double membrane that surrounds the nucleus, perforated with pores that regulate traffic with the cytoplasm; the outer membrane is continuous with the endoplasmic reticulum
Central Vacuole
in a mature plant cell, a large membranous sac with diverse roles in growth, storage, and sequestration of toxic substances
Integrin
in animal cells, a transmembrane receptor protein with two subunits that interconnects the extracellular matrix and the cytoskeleton
Secondary Cell Wall
in plant cells, a strong and durable matrix that is often deposited in several laminated layers around the plasma membrane and provides protection and support
Primary Cell Wall
in plants, a relatively thin and flexible layer that surrounds the plasma membrane of a young cell
Which type of cell is most likely to have the largest number of mitochondria? a. inactive yeast cells that are stored for future use b. bacterial cells that are growing on sugars c. muscle cells in the legs of a marathon runner d. photosynthetic cells in the leaves of a tree e. nondividing cells in the skin on your finger
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.
Which of the following is/are likely to limit the maximum size of a cell? a. the shape of the cell b. the time it takes a molecule to diffuse across a cell c. the cell's surface-to-volume ratio d. All of the choices are correct e. None of the choices is correct
All of the choices are correct
Explain how the compartmental organization of a eukaryotic cell contributes to its biochemical functioning.
Organelles that interact with each other regularly have means to reach one another.
Describe the characteristics of phospholipids that allow them to function as the major components of the plasma membrane.
Phospholipids are amphipathic compounds in a way that the 'head' is hydrophilic and the lipophilic 'tail' is hydrophobic. They serve as a major structural component of most biological membranes. They form the lipid bilayer in cell membranes of organisms.
How would you expect the saturation levels of membrane phospholipid fatty acids to differ in plants adapted to cold environments and plants adapted to hot environments?
Plants adapted to cold environments would be expected to have more unsaturated fatty acids in their membranes because those remain fluid at lower temperatures. Plants adapted to hot environments would be expected to have more saturated fatty acids, which would allow the fatty acids to "stack" more closely, making the membranes less fluid and therefore helping them to stay intact at higher temperatures.
How do stains used for light microscopy compare with those used for electron microscopy?
Stains used for light microscopy are colored molecules that bind to cell components, affecting the light passing through. The stains used for electron microscopy involve heavy metals that affect the beams of electrons passing through.
Your intestine is lined with individual cells. No fluids leak between these cells from the gut into your body. Why? a. The intestinal cells are fused together into one giant cell b. The intestinal cells are bound together by gap junctions c. The intestinal cells are bound together by plasmodesmata d. The intestinal cells are bound together by tight junctions e. The intestinal cells are bound together by the extracellular matrix
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.
The carbohydrates attached to some proteins and lipids of the plasma membrane are added as the membrane is made and refined in the ER and Golgi apparatus; the new membrane then forms transport vesicles that travel to the cell surface. On which side of the vesicle membrane are the carbohydrates?
They are on the inner side of the transport vesicle membrane.
Cytoplasmic Streaming
a circular flow of cytoplasm, involving interactions of myosin and actin filaments, that speeds the distribution of materials within cells
Cell Wall
a protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists; polysaccharides such as cellulose (in plants and some protists), chitin (in fungi), and peptidoglycan (in bacteria) are important structural components of cell walls
Crista (plural, Cristae)
an infolding of the inner membrane of a mitochondrion; the inner membrane houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase)
Plasmodesma (plural, Plasmodesmata)
an open channel through the cell wall that connects the cytoplasm of adjacent plant cells, allowing water, small solutes, and some larger molecules to pass between the cells
Light Microscope (LM)
an optical instrument with lenses that refract (bend) visible light to magnify images of specimens
Peroxisome
an organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen (O2), producing and then degrading hydrogen peroxide (H2 O2)
Which of the following is/are most likely to be involved in the process of producing proteins for a chloroplast or mitochondrion? a. transport vesicles b. rough endoplasmic reticulum c. the Golgi apparatus d. smooth endoplasmic reticulum e. free cytoplasmic ribosomes
free cytoplasmic ribosomes This is the only answer that is not part of the endomembrane system. Most proteins that function in chloroplasts and mitochondria are made on free cytoplasmic ribosomes and then imported into their respective organelles.
A protein that ultimately functions in the plasma membrane of a cell is most likely to have been synthesized __________. a. in the rough endoplasmic reticulum b. on free cytoplasmic ribosomes c. in the ribosomes of the mitochondria d. in the smooth endoplasmic reticulum e. in the plasma membrane
in the rough endoplasmic reticulum All of the membrane proteins of the endomembrane systems are made in the rough ER.
Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. Which of the following organelles contains these hydrolytic enzymes in animal cells? a. chloroplast b. lysosome c. central vacuole d. peroxisome e. glyoxysome
lysosome
Which structure/function pair is mismatched? a. microtubule; muscle contraction b. ribosome; protein synthesis c. Golgi apparatus; protein trafficking d. nucleolus; production of ribosomal subunits
microtubule; muscle contraction
Cilia and flagella move due to the interaction of the cytoskeleton with which of the following? a. mitochondria b. pseudopodia c. motor proteins d. tubulin e. actin
motor proteins Motor proteins, such as dynein, use energy to move parts of the cytoskeleton.
Plastid
one of a family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts; plastids are found in cells of photosynthetic eukaryotes
A cell with a predominance of free ribosomes is most likely a. producing primarily proteins for secretion b. producing primarily cytoplasmic proteins c. constructing an extensive cell wall or extracellular matrix d. digesting large food particles e. enlarging its vacuole
producing primarily cytoplasmic proteins
Cell Fractionation
the disruption of a cell and separation of its parts by centrifugation at successively higher speeds
Nucleus
(1) an atom's central core, containing protons and neutrons; (2) the organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes, made up of chromatin; (3) a cluster of neurons
Cortex
(1) the outer region of cytoplasm in a eukaryotic cell, lying just under the plasma membrane, that has a more gel-like consistency than the inner regions due to the presence of multiple microfilaments; (2) In plants, ground tissue that is between the vascular tissue and dermal tissue in a root or eudicot stem
Which type of microscope would you use to study (a) the changes in shape of a living white blood cell, (b) the details of surface texture of a hair, and (c) the detailed structure of an organelle?
(a) light microscope, (c) scanning electron microscope, and (c) transmission electron microscope
Flagellum
(plural, flagella) a long cellular appendage specialized for locomotion; like motile cilia, eukaryotic flagella have a core with nine outer doublet microtubules and two inner single microtubules (the "9 + 2" arrangement) ensheathed in an extension of the plasma membrane; prokaryotic flagella have a different structure
Prokaryotes are classified as belonging to two different domains. What are the domains? a. Bacteria and Eukarya b. Bacteria and Archaea c. Archaea and Protista d. Bacteria and Protista e. Bacteria and Fungi
Bacteria and Archaea
Which of the following statements correctly describes a common characteristic of a plant cell wall and an animal cell extracellular matrix? a. Both are permeable to water and small solutes b. Both contain large amounts of collagen c. Both are composed primarily of carbohydrates d. Both are permeable to water and small solutes, and both contain large amounts of collagen e. Both are permeable to water and small solutes, both contain large amounts of collagen, and both are composed primarily of carbohydrates
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.
Describe two common characteristics of chloroplasts and mitochondria. Consider both function and membrane structure.
Both organelles are involved in energy transformation, mitochondria in cellular respiration and chloroplasts in photosynthesis. They both have multiple membranes that separate their interiors into compartments. In both organelles, the innermost membranes - cristae, or infoldings of the inner membrane, in mitochondria, and the thylakoid membranes in chloroplasts - have large surface areas with embedded enzymes that carry out their main functions.
Describe shared features of microtubule-based motion of flagella and microfilament-based muscle contractions.
Both systems of movement involve long filaments that are moved in relation to each other by motor proteins that grip, release, and grip again adjacent polymers.
Mitochondrial Matrix
the compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle, as well as ribosomes and DNA
Which of the following statements is true about cell fractionation? a. Cell fractionation separates cells into their component parts. b. Cell fractionation is no longer used in modern cell biology. c. Cell fractionation requires the use of a scanning electron microscope. d. Cell fractionation uses strong acids to break apart cells. e. None of the listed responses is correct.
Cell fractionation separates cells into their component parts. The organelles are usually separated by centrifugation.
Which of the following statements about chloroplasts and mitochondria is true? a. Chloroplasts and mitochondria synthesize some of their own proteins b. Chloroplasts and mitochondria have three sets of membranes c. Chloroplasts, but not mitochondria, are completely independent of the cell of which they are a part d. Mitochondria, but not chloroplasts, contain a small amount of DNA e. Chloroplasts and mitochondria are components of the endomembrane system
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.
Which of the following is FALSE in respect to eukaryotic chromosomes? a. Chromosomes are present even when cells are not actively synthesizing proteins b. Chromosomes appear only as a cell is about to divide c. Chromosomes are present throughout a cell's reproductive cycle d. All eukaryotic cells possess one or more chromosomes e. None of the listed responses is false
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 statement about the cytoskeleton is true? a. Microtubules are chains of proteins that resist stretching b. Intermediate filaments are hollow tubes of protein that provide structural support c. Microfilaments are more permanent structures in cells compared to intermediate filaments and microtubules d. Plant cells lack a cytoskeleton because they have a rigid cell wall e. Components of the cytoskeleton often mediate the movement of organelles within the cytoplasm
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.
How do cilia and flagella bend?
Dynein arms, powered by ATP, move neighboring doublets of microtubules relative to one another. Because they are anchored within the organelle and with respect to each other, the doublets bend instead of sliding past one another.
In terms of cellular function, what is the most important difference between prokaryotic and eukaryotic cells? a. Eukaryotic cells are larger than prokaryotic cells b. Eukaryotic cells are much more successful than prokaryotic cells c. Eukaryotic cells lack many of the organelles found in prokaryotes d. Eukaryotic cells are compartmentalized, which allows for specialization e. Eukaryotic cells can synthesize proteins but prokaryotic cells cannot
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.
Green fluorescent protein (GFP) can be used to fluorescently label a specific protein in cells by genetically engineering cells to synthesize the target protein fused to GFP. What is the advantage of using GFP fusions to visualize specific proteins, instead of staining cells with fluorescently labeled probes that bind to the target protein? a. GFP fusions enable one to track changes in the location of the protein in living cells; staining usually requires preserved cells. b. GFP fusions enable higher resolution than staining with fluorescent probes. c. GFP permits the position of the protein in the cell more precisely than fluorescent probes. d. GFP permits visualization of protein-protein interactions; fluorescent probes do not. e. GFP fusions are not subject to artifacts; fluorescent probes may introduce background artifacts.
GFP fusions enable one to track changes in the location of the protein in living cells; staining usually requires preserved cells.
Microtubules and microfilaments commonly work with which of the following to perform many of their functions? a. ribosomes b. Golgi apparatus c. lysosomes d. RNA e. None of the listed responses is correct
Golgi apparatus Microtubules guide vesicles from the ER to the Golgi and from the Golgi to the plasma membrane.
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 __________. a. Golgi apparatus b. smooth endoplasmic reticulum c. plasma membrane d. rough endoplasmic reticulum e. transport vesicles
Golgi apparatus Vesicles carrying proteins from the rough ER fuse with the Golgi apparatus, where the proteins may be altered.
Which of the following sequences represents the order in which a protein made in the rough endoplasmic reticulum might move through the endomembrane system? a. nuclear envelope → lysosome b. plasma membrane → nuclear envelope c. Golgi apparatus → lysosome d. lysosome → plasma membrane e. Golgi apparatus → mitochondria
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.
Which of the following is FALSE? a. Mitochondria have more than one membrane b. Mitochondria are involved in energy metabolism c. The folds of the inner mitochondrial membrane are called cristae d. Mitochondria possess their own DNA e. Mitochondria contain ribosomes in the intermembrane space
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 statements about the cytoskeleton is true? a. The dynamic aspect of cytoskeletal function is made possible by the assembly and disassembly of a large variety of proteins into complex aggregates. b. Microfilaments are structurally rigid and resist compression, whereas microtubules resist tension (stretching). c. Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other. d. Chemicals that block the assembly of the cytoskeleton would cause little effect on the cell's response to external signals and stimuli. e. Transport vesicles among the membranes of the endomembrane system produce the cytoskeleton.
Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other.
Describe the molecular composition of nucleoli and explain their function.
Nucleoli consist of DNA & ribosomal RNA (rRNA) made according to its instructions, as well as proteins imported from the cytoplasm. Together the rRNA & proteins are assembled into large & small ribosomal subunits.
Describe the structure and function of the nucleus, the mitochondrion, the chloroplast, and the endoplasmic reticulum.
Nucleus, surrounded by nuclear envelope (double membrane). Perforated be nuclear pores. Function: Houses chromosomes, made of chromatin (DNA, genetic material, and proteins), contains nucleoli. Mitochondrion, bounded by double-membrane. Inner membrane has foldings (cristae). Function: cellular respiration. Chloroplast, two membranes around fluid stroma, which contains membranous thylakoids stacked into grana (in plants). Function: photosynthesis. Endoplasmic reticulum, extensive network of membrane-bound tubules & sacs. Membrane separates lumen from cytosol. Continuous with nuclear envelope. Function: 1) Smoother ER- synthesis of lipids, metabolism of carbohydrates, calcium storage, detoxification. 2) Rough ER- Aids in synthesis of secretory and other proteins from bound ribosome. Adds carbohydrates to glycoproteins. Produces new membrane.
Two molecules that can cross a lipid bilayer without help from membrane proteins are O2 and CO2. What properties allow this to occur?
O2 and CO2 are both small nonpolar molecules that can easily pass through the hydrophobic core of a membrane.
What is the functional connection between the nucleolus, nuclear pores, and the nuclear membrane? a. Subunits of ribosomes are assembled in the nucleolus and pass through the nuclear membrane via the nuclear pores b. The nucleolus contains messenger RNA (mRNA), which crosses the nuclear envelope through the nuclear pores c. The nuclear pores are connections between the nuclear membrane and the endoplasmic reticulum that permit ribosomes to assemble on the surface of the ER d. Membrane of the endoplasmic reticulum is produced in the nucleolus and leaves the nucleus through the nuclear pores e. None of the listed responses is correct
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.
If the plant cell wall or the animal extracellular matrix were impermeable, what effect would this have on cell function?
The cell would not be able to function properly and would probably soon die, as the cell wall or ECM must be permeable to allow the exchange of matter between the cell and its external environment. Molecules involved with energy production and use must be allowed entry, as well as those that provide information about the cell's environment. Other molecules, such as products synthesized by the cell for export and the by-products of cellular respiration, must be allowed to exit.
Imagine a protein that functions in the ER but requires modification in the Golgi apparatus before it can achieve that function. Describe the protein's path through the cell, starting with the mRNA molecule that specifies the protein.
The mRNA is synthesized in the nucleus and then passes out through a nuclear pore to be translated on a bound ribosome, attached to the rough ER. The protein is synthesized into the lumen of the ER and perhaps modified there. A transport vesicle carries the protein to the Golgi apparatus. After further modification in the Golgi, another transport vesicle carries it back to the ER, where it will perform its cellular function.
Compare the structure and functions of a plant cell wall and the extracellular matrix of an animal cell.
The major structural protein of the extracellular matrix in animal cells is collagen, which is the single most abundant protein in animal tissues. The collagens are a large family of proteins. In plants, the ECM is primarily composed of cellulose. It is the major structural material of which plants are made. The result is a series of stiff, elongated fibrils — the perfect material for building the cell walls of plants.
In what way are the cells of plants and animals structurally different from single-celled eukaryotes?
The most obvious difference is the presence of direct cytoplasmic connections between cells of multicellular plants (plasmodesmata) and animal (gap junctions). These connections result in the cytoplasm being continuous between adjacent cells.
Describe the structural and functional distinctions between rough and smooth ER.
The primary distinction between rough and smooth ER is the presence of bound ribosomes on the rough ER. While both types of ER make phospholipids, membrane proteins and secretory proteins are all produced on the ribosomes of the rough ER. The smooth ER also functions in detoxification, carbohydrate metabolism, and storage of calcium ions.
Chromatin
the complex of DNA and proteins that makes up eukaryotic chromosomes; when the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope
Why would water molecules need a transport protein to move rapidly and in large quantities across a membrane?
Water is a polar molecule, so it cannot pass very rapidly through the hydrophobic region in the middle of the phospholipid bilayer.
Do plant cells have mitochondria?
Yes, plants have mitochondria. All living cells need mitochondria carry out the usual steps of respiration.
Scanning Electron Microscope (SEM)
a microscope that uses an electron beam to scan the surface of a sample, coated with metal atoms, to study details of its topography
Cytoplasm
the contents of the cell bounded by the plasma membrane; in eukaryotes, the portion exclusive of the nucleus
Chromosome
a cellular structure consisting of one DNA molecule and associated protein molecules; (in some contexts, such as genome sequencing, the term may refer to the DNA alone.); a eukaryotic cell typically has multiple, linear chromosomes, which are located in the nucleus; a prokaryotic cell often has a single, circular chromosome, which is found in the nucleoid, a region that is not enclosed by a membrane; see also chromatin
Ribosome
a complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus, see also nucleolus
Basal Body
a eukaryotic cell structure consisting of a "9 + 0" arrangement of microtubule triplets; the basal body may organize the microtubule assembly of a cilium or flagellum and is structurally very similar to a centriole
Thylakoid
a flattened, membranous sac inside a chloroplast; thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular "machinery" used to convert light energy to chemical energy
Actin
a globular protein that links into chains, two of which twist helically about each other, forming microfilaments (actin filaments) in muscle and other kinds of cells
Collagen
a glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom
Microtubule
a hollow rod composed of tubulin proteins that makes up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella
Proteoglycan
a large molecule consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells; a proteoglycan may consist of up to 95% carbohydrate
Vacuole
a membrane-bounded vesicle whose specialized function varies in different kinds of cells
Lysosome
a membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists
Food Vacuole
a membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell
Vesicle
a membranous sac in the cytoplasm of a eukaryotic cell
Contractile Vacuole
a membranous sac that helps move excess water out of certain freshwater protists
Transmission Electron Microscope (TEM)
a microscope that passes an electron beam through very thin sections stained with metal atoms and is primarily used to study the internal ultrastructure of cells
Electron Microscope (EM)
a microscope that uses magnets to focus an electron beam on or through a specimen, resulting in a practical resolution that is 100-fold greater than that of a light microscope using standard techniques; a transmission electron microscope (TEM) is used to study the internal structure of thin sections of cells; a scanning electron microscope (SEM) is used to study the fine details of cell surfaces
Nuclear Lamina
a net-like array of protein filaments that lines the inner surface of the nuclear envelope and helps maintain the shape of the nucleus
Cytoskeleton
a network of microtubules, microfilaments, and intermediate filaments that extend throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions
Nucleoid
a non-membrane-enclosed region in a prokaryotic cell where its chromosome is located
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. a bacterium b. a yeast (fungus) cell c. a cell from the intestinal lining of a cow d. a cell from a pine tree e. a photosynthetic protist cell or a plant cell
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.
Motor Protein
a protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell
Glycoprotein
a protein with one or more covalently attached carbohydrates
Cilium
a short appendage containing microtubules in eukaryotic cells; a motile cilium is specialized for locomotion or moving fluid past the cell; it is formed from a core of nine outer doublet microtubules and two inner single microtubules (the "9 + 2" arrangement) ensheathed in an extension of the plasma membrane; a primary cilium is usually nonmotile and plays a sensory and signaling role; it lacks the two inner microtubules (the "9 + 0" arrangement)
Organ
a specialized center of body function composed of several different types of tissues
Nucleolus (plural, Nucleoli)
a specialized structure in the nucleus, consisting of chromosomal regions containing ribosomal RNA (rRNA) genes along with ribosomal proteins imported from the cytoplasm; site of rRNA synthesis and ribosomal subunit assembly; see also ribosome
Granum (plural, Grana)
a stack of membrane-bounded thylakoids in the chloroplast; grana function in the light reactions of photosynthesis
Centriole
a structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a "9 + 0" pattern; a centrosome has a pair of centrioles
Centrosome
a structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division; a centrosome has two centrioles
When biologists wish to study the internal ultra-structure of cells, they can achieve their finest resolution by using a. a phase-contrast light microscope b. a scanning electron microscope c. a transmission electron microscope d. a confocal fluorescence microscope e. a super-resolution fluorescence microscope
a transmission electron microscope
Eukaryotic Cell
a type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles; organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotes
Phagocytosis
a type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells)
Tight Junction
a type of intercellular junction between animal cells that prevents the leakage of material through the space between cells
Desmosome
a type of intercellular junction in animal cells that functions as a rivet, fastening cells together
Gap Junction
a type of intercellular junction in animal cells, consisting of proteins surrounding a pore that allows the passage of materials between cells
Myosin
a type of motor protein that associates into filaments that interact with actin filaments to cause cell contraction
Which statement about extracellular structures (plant cell walls and the extracellular matrix of animal cells) is correct? a. some extracellular structures provide for cytoplasmic connections between adjacent cells b. information can be transmitted from these extracellular structures to the cytoplasm c. proteins and carbohydrates are common components of extracellular structures d. extracellular Structures can play a role in determining the cell shape e. all of the choices are correct
all of the choices are correct
Fibronectin
an extracellular glycoprotein secreted by animal cells that helps them attach to the extracellular matrix
Chloroplast
an organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water
Golgi Apparatus
an organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates
Mitochondrion (plural, Mitochondria)
an organelle in eukaryotic cells that serves as the site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP
Which of the following contain the 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules? a. both motile cilia and primary (nonmotile) cilia b. centrioles only c. both flagella and motile cilia d. both basal bodies and primary (nonmotile) cilia e. both centrioles and basal bodies
both flagella and motile cilia
Which structure is NOT part of the endomembrane system? a. nuclear envelope b. chloroplast c. Golgi apparatus d. plasma membrane
chloroplast
Thylakoids, DNA, and ribosomes are all components found in a. vacuoles b. chloroplasts c. mitochondria d. lysosomes e. nuclei
chloroplasts
Where would you expect to find proteins involved with movement of structures within a cell? a. transport vesicles moving from the ER to the Golgi b. cytoskeleton c. plasma membrane d. muscles e. nucleus
cytoskeleton Movement of organelles and vesicles within cells is accomplished by motor proteins moving along the cytoskeleton.
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? a. embedded in the plasma membrane, functioning in the transport of molecules into the cell b. n a mitochondrion, functioning in ATP synthesis c. in the internal space of the Golgi apparatus, being modified before the protein is excreted d. in the cytoplasm, functioning as an enzyme in carbohydrate synthesis e. in the aqueous interior of a lysosome, functioning as a digestive enzyme
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.
Bacterial cells are prokaryotic. Unlike a typical eukaryotic cell, they __________. a. have a smaller nucleus b. have no membrane-bounded organelles in their cytoplasm c. have no ribosomes d. lack a plasma membrane e. lack chromosomes
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 __________. a. free in the cytoplasm of eukaryotes b. on the rough ER c. in bacterial cells d. free in the cytoplasm of eukaryotes and on the rough ER e. free in the cytoplasm of eukaryotes, on the rough ER, and in bacterial cells
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.
Dynein
in cilia and flagella, a large motor protein extending from one microtubule doublet to the adjacent doublet: ATP hydrolysis drives changes in dynein shape that lead to bending of cilia and flagella
Dye injected into a plant cell might be able to enter an adjacent cell through __________. a. plasmodesmata b. a cell wall c. a gap junction d. a microtubule e. a tight junction
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 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? a. transmission electron microscope, because of its high magnifying power b. light microscope, because of its high resolving power c. scanning electron microscope, because of its ability to visualize the surface of subcellular objects d. light microscope, because the specimen is alive e. transmission electron microscope, because of its high resolving power
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.
What technique would be most appropriate to use to observe the movements of condensed chromosomes during cell division? a. light microscopy b. scanning electron microscopy c. transmission electron microscopy d. confocal fluorescence microscopy e. super-resolution fluorescence microscopy
light microscopy
The advantage of light microscopy over electron microscopy is that a. light microscopy provides for higher magnification than electron microscopy b. light microscopy provides for higher resolving power than electron microscopy c. light microscopy allows one to view dynamic processes in living cells d. light microscopy provides higher contrast than electron microscopy specimen preparation for light microscopy does not produce artifacts
light microscopy allows one to view dynamic processes in living cells
Which of the following contains hydrolytic enzymes? a. lysosome b. vacuole c. mitochondrion d. Golgi apparatus e. Peroxisome
lysosome
Which of the following categories best describes the function of the rough endoplasmic reticulum? a. breakdown of complex foods b. energy processing c. information storage d. structural support of cells e. manufacturing
manufacturing The rough endoplasmic reticulum is involved in the manufacture of proteins for the endomembrane system.
Movement of vesicles within the cell depends on what cellular structures? a. microtubules and motor proteins b. actin filaments and microtubules c. actin filaments and ribosomes d. centrioles and motor proteins e. actin filaments and motor proteins
microtubules and motor proteins
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 a. mitochondria b. ribosomes c. peroxisomes d. lysosomes
mitochondria
Which of the following structures is found in eukaryotic but NOT prokaryotic cells? a. cytosol b. mitochondria c. plasma membrane d. DNA e. ribosomes
mitochondria Only eukaryotic cells have membrane-bound organelles such as mitochondria.
Which of the following five membranes is most likely to have a lipid composition that is distinct from those of the other four? a. lysosome membrane b. mitochondrial outer membrane c. endoplasmic reticulum d. Golgi apparatus e. plasma membrane
mitochondrial outer membrane The mitochondria are not part of the endomembrane system and must synthesize their own lipids.
Which plant cell organelle contains its own DNA and ribosomes? a. glyoxysome b. vacuole c. mitochondrion d. Golgi apparatus e. peroxisome
mitochondrion
Which structure is common to plant and animal cells? a. chloroplast b. central vacuole c. mitochondrion d. centriole
mitochondrion
Cytochalasin D is a drug that prevents actin polymerization. A cell treated with cytochalasin D will still be able to a. perform amoeboid movement b. form cleavage furrows c. contract muscle fibers d. extend pseudopodia e. move vesicles around the cell
move vesicles around the cell
Which of the following LACK membranes as part of their structure? a. endoplasmic reticulum b. peroxisomes c. ribosomes d. mitochondria e. Golgi apparatus
peroxisomes
Which cell would be best for studying lysosomes? a. muscular cell b. nerve cell c. phagocytic white blood cell d. bacterial cell
phagocytic white blood cell
Which of the following is present in a prokaryotic cell? a. mitochondrion b. ribosome c. nuclear envelope d. chloroplast
ribosome
Which of the following groups is primarily involved in synthesizing molecules needed by the cell? a. ribosome, rough endoplasmic reticulum, smooth endoplasmic reticulum b. smooth endoplasmic reticulum, ribosome, vacuole c. rough endoplasmic reticulum, lysosome, vacuole d. lysosome, vacuole, ribosome e. vacuole, rough endoplasmic reticulum, smooth endoplasmic reticulum
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? a. mitochondria b. ribosomes c. transport vesicles d. the nucleolus e. No organelles are found inside of other organelles
ribosomes Ribosomes are nonmembranous organelles that are found in the cytoplasm but also in mitochondria and chloroplasts.
Which of the following features do prokaryotes and eukaryotes have in common? a. mitochondria, cytoplasm, and plasma membrane b. nucleus, plasma membrane, and ribosomes c. ribosomes, plasma membrane, and cytoplasm d. mitochondria, ribosomes, and cytoplasm e. ribosomes, nucleus, and plasma membrane
ribosomes, plasma membrane, and cytoplasm
You would expect a cell with an extensive Golgi apparatus to __________. a. make large amounts of ATP b. move rapidly c. absorb nutrients in the GI tract d. store large quantities of ions e. secrete large amounts of protein
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.
Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given vinblastine would be unable to a. form cleavage furrows during cell division b. migrate by amoeboid movement c. separate chromosomes during cell division d. extend pseudopods e. maintain the shape of the nucleus
separate chromosomes during cell division
A primary objective of cell fractionation is to a. view the structure of cell membranes b. sort cells based on their size and weight c. determine the size of various organelles d. separate the major organelles so that their particular function can be determined e. separate lipid-soluble from water-soluble molecules
separate the major organelles so that their particular function can be determined
Smooth ER
that portion of the endoplasmic reticulum that is free of ribosomes
Rough ER
that portion of the endoplasmic reticulum with ribosomes attached
Endomembrane System
the collection of membranes inside and surrounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the plasma membrane, the nuclear envelope, the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, and vacuoles
In which of the following sites might protein synthesis occur in a typical eukaryotic cell? a. the cytoplasm b. the mitochondria c. the rough endoplasmic reticulum d. the cytoplasm and the rough endoplasmic reticulum e. the cytoplasm, the rough endoplasmic reticulum, and the mitochondria
the cytoplasm, the rough endoplasmic reticulum, and the mitochondria Ribosomes are present in the cytoplasm, on the rough ER, and in mitochondria (and chloroplasts).
Passive Transport
the diffusion of a substance across a biological membrane with no expenditure of energy
Plasma Membrane
the membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition
Extracellular Matrix (ECM)
the meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides, and proteoglycans synthesized and secreted by cells
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? a. the nucleus b. rough endoplasmic reticulum c. the Golgi apparatus d. rough endoplasmic reticulum and Golgi apparatus e. the Golgi apparatus and the nucleus
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 __________. a. the plasma membrane b. the endomembrane system c. a microtubule d. a ribosome e. the nucleus
the plasma membrane The plasma membrane defines the boundary between the cytoplasm and the outside of the cell.
Genomics
the systematic study of whole sets of genes (or other DNA) and their interactions within a species, as well as genome comparisons between species
Endosymbiont Theory
the theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by a host cell; the engulfed cell and its host cell then evolved into a single organism; see also endosymbiosis