Bio4A Chapter 6
plasmodesmata
channels that perforate plant cell walls Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell
17) Which of the following macromolecules leaves the nucleus of a eukaryotic cell through pores in the nuclear membrane?
A) DNA B) amino acids C) mRNA D) phospholipids Answer: C
31) What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell?
A) ER → Golgi → nucleus B) Golgi → ER → lysosome C) ER → Golgi → vesicles that fuse with plasma membrane D) ER → lysosomes → vesicles that fuse with plasma membrane Answer: C
11) 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 Answer: B
16) What is the function of the nuclear pore complex found in eukaryotes?
A) It regulates the movement of proteins and RNAs into and out of the nucleus. B) It synthesizes the proteins required to copy DNA and make mRNA. C) It selectively transports molecules out of the nucleus, but prevents all inbound molecules from entering the nucleus. D) It assembles ribosomes from raw materials that are synthesized in the nucleus. Answer: A
7) All of the following are part of a prokaryotic cell EXCEPT _____.
A) a cell wall B) a plasma membrane C) ribosomes D) an endoplasmic reticulum Answer: D
10) 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?
A) Pinch the edges of the cube into small folds. B) Flatten the cube into a pancake shape. C) Round the clay up into a sphere. D) Stretch the cube into a long, shoebox shape. Answer: C
18) Which of the following statements correctly describes some aspect of protein secretion from prokaryotic cells?
A) Prokaryotes cannot secrete proteins because they lack an endomembrane system. B) The mechanism of protein secretion in prokaryotes is probably the same as that in eukaryotes. C) Proteins secreted by prokaryotes are synthesized on ribosomes bound to the cytoplasmic surface of the plasma membrane. D) Prokaryotes cannot secrete proteins because they lack ribosomes. Answer: C
9) Which of the following is a major difference between prokaryotic cells and eukaryotic cells?
A) Prokaryotes have cells while eukaryotes do not. B) Eukaryotic cells have more intracellular organelles than prokaryotes. C) Prokaryotes are not able to carry out aerobic respiration, relying instead on anaerobic metabolism. D) Prokaryotes are generally larger than eukaryotes. Answer: B
52) Which of the following statements about the cytoskeleton is true?
A) The cytoskeleton of eukaryotes is a static structure most resembling scaffolding used at construction sites. B) Although microtubules are common within a cell, actin filaments are rarely found outside of the nucleus. 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 have little effect on a cell's response to external stimuli. Answer: C
4) What is the reason that a modern transmission electron microscope (TEM) can resolve biological images to the subnanometer level, as opposed to tens of nanometers achievable for the best super-resolution light microscope?
A) The focal length of the electron microscope is significantly longer. B) Contrast is enhanced by staining with atoms of heavy metal. C) Electron beams have much shorter wavelengths than visible light. D) The electron microscope has a much greater ratio of image size to real size. Answer: C
6) 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?
A) The toy microscope does not have the same fine control for focus of the specimen. B) The toy microscope magnifies a good deal, but has low resolution and therefore poor quality images. C) The college microscope produces greater contrast in the specimens. D) The toy microscope usually uses a different wavelength of light source. Answer: B
60) 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 the cell-cell interaction (cell 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?
A) The two species of sponge had different enzymes that functioned in the reassembly process. B) The molecules responsible for cell-cell adhesion (cell junctions) were irreversibly destroyed during the experiment. C) The molecules responsible for cell-cell adhesion (cell junctions) differed between the two species of sponge. D) One cell functioned as the nucleus for each organism, thereby attracting only cells of the same pigment. Answer: C
53) 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 is a characteristic common to all of these extracellular structures?
A) They must block water and small molecules to regulate the exchange of matter and energy with their environment. B) They must provide a rigid structure that maintains an appropriate ratio of cell surface area to volume. C) They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell. D) They are composed of a mixture of lipids and nucleotides. Answer: C
25) The Golgi apparatus has a polarity, or sidedness, to its structure and function. Which of the following statements correctly describes this polarity?
A) Transport vesicles fuse with one side of the Golgi and leave from the opposite side. B) Proteins in the membrane of the Golgi may be sorted and modified as they move from one side of the Golgi to the other. C) Lipids in the membrane of the Golgi may be sorted and modified as they move from one side of the Golgi to the other. D) All of the listed responses correctly describe polarity characteristics of the Golgi function. Answer: D
40) Suppose 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) a plant but not an animal Answer: C
14) In a bacterium, we will find DNA in _____.
A) a membrane-enclosed nucleus B) mitochondria C) the nucleoid D) ribosomes Answer: C
49) 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?
A) abnormally shaped RBCs B) an insufficient supply of ATP in the RBCs C) an insufficient supply of oxygen-transporting proteins in the RBCs D) adherence of RBCs to blood vessel walls, causing plaque formation Answer: A
58) In plant cells, the middle lamella _____.
A) allows adjacent cells to adhere to one another B) prevents dehydration of adjacent cells C) maintains the plant's circulatory system D) allows for gas and nutrient exchange among adjacent cells Answer: A
47) Researchers tried to explain how vesicular transport occurs in cells by attempting to assemble the transport components. They set up microtubular tracks along which vesicles could be transported, and they added vesicles and ATP (because they knew the transport process requires energy). Yet, when they put everything together, there was no movement or transport of vesicles. What were they missing?
A) an axon B) contractile microfilaments C) endoplasmic reticulum D) motor proteins Answer: D
12) Which structure is common to plant and animal cells?
A) chloroplast B) central vacuole C) mitochondrion D) centriole Answer: C
35) Thylakoids, DNA, and ribosomes are all components found in _____.
A) chloroplasts B) mitochondria C) lysosomes D) nuclei Answer: A
37) In a liver cell detoxifying alcohol and some other poisons, the enzymes of the peroxisome remove hydrogen from these molecules and _____.
A) combine the hydrogen with water molecules to generate hydrogen peroxide B) use the hydrogen to break down hydrogen peroxide C) transfer the hydrogen to the mitochondria D) transfer the hydrogen to oxygen molecules to generate hydrogen peroxide Answer: D
48) Cilia and flagella bend because of _____.
A) conformational changes in ATP that thrust microtubules laterally B) a motor protein called radial spokes C) the quick inward movements of water by osmosis. D) a motor protein called dynein Answer: D
56) Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells?
A) desmosomes B) gap junctions C) extracellular matrix D) tight junctions Answer: B
50) Cytochalasin D is a drug that prevents actin polymerization. A cell treated with cytochalasin D will still be able to _____.
A) divide in two B) contract muscle fibers C) extend pseudopodia D) move vesicles within a cell Answer: D
38) The evolution of eukaryotic cells most likely involved _____.
A) endosymbiosis of an aerobic bacterium in a larger host cell—the endosymbiont evolved into mitochondria B) anaerobic archaea taking up residence inside a larger bacterial host cell to escape toxic oxygen—the anaerobic bacterium evolved into chloroplasts C) an endosymbiotic fungal cell evolving into the nucleus D) acquisition of an endomembrane system and subsequent evolution of mitochondria from a portion of the Golgi Answer: A
45) 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) maintain the shape of the nucleus Answer: C
55) The extracellular matrix is thought to participate in the regulation of animal cell behavior by communicating information from the outside to the inside of the cell via which of the following?
A) gap junctions B) the nucleus C) DNA and RNA D) integrins Answer: D
46) Amoebae move by crawling over a surface (cell crawling), which involves _____.
A) growth of actin filaments to form bulges in the plasma membrane B) setting up microtubule extensions that vesicles can follow in the movement of cytoplasm C) reinforcing the pseudopod with intermediate filaments D) cytoplasmic streaming Answer: A
33) Which of the following is NOT true? Both chloroplasts and mitochondria _____.
A) have their own DNA B) have multiple membranes C) are part of the endomembrane system D) are capable of reproducing themselves Answer: C
59) Where would you expect to find tight junctions?
A) in the epithelium of an animal's stomach B) between the smooth endoplasmic reticulum and the rough endoplasmic reticulum C) between plant cells in a woody plant D) in the plasma membrane of prokaryotes Answer: A
39) Where are proteins produced other than on ribosomes free in the cytosol or ribosomes attached to the ER?
A) in the extracellular matrix B) in the Golgi apparatus C) in mitochondria D) in the nucleolus Answer: C
2) 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 Answer: C
19) Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
A) lipids B) glycogen C) proteins D) nucleic acids Answer: C
34) Which organelle is the primary site of ATP synthesis in eukaryotic cells?
A) lysosome B) mitochondrion C) Golgi apparatus D) peroxisome Answer: B
30) Which of the following produces and modifies polysaccharides that will be secreted?
A) lysosome B) mitochondrion C) Golgi apparatus D) peroxisome Answer: C
22) Which organelle often takes up much of the volume of a plant cell?
A) lysosome B) vacuole C) Golgi apparatus D) peroxisome Answer: B
42) Suppose a young boy is always tired and fatigued, suffering from a metabolic disease. Which of the following organelles is most likely involved in this disease?
A) lysosomes B) Golgi apparatus C) ribosomes D) mitochondria Answer: D
43) Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures?
A) membrane proteins of the inner nuclear envelope B) free ribosomes and ribosomes attached to the ER C) components of the cytoskeleton D) cellulose fibers in the cell wall Answer: C
15) Which organelle or structure is absent in plant cells?
A) mitochondria B) microtubules C) centrosomes D) peroxisomes Answer: C
41) Cyanide binds with 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) peroxisomes C) lysosomes D) endoplasmic reticulum Answer: A
32) 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 phagocytize asbestos, but are not able to degrade it. As a result, asbestos fibers accumulate in _____.
A) mitochondria B) ribosomes C) peroxisomes D) lysosomes Answer: D
1) The smallest cell structure that would most likely be visible with a standard (not super- resolution) research-grade light microscope is a _____.
A) mitochondrion B) microtubule C) ribosome D) microfilament Answer: A
13) Which of the following is present in a prokaryotic cell?
A) mitochondrion B) ribosome C) chloroplast D) ER Answer: B
44) Which of the following contain the 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules?
A) motile cilia and primary (nonmotile) cilia B) flagella and motile cilia C) basal bodies and primary (nonmotile) cilia D) centrioles and basal bodies Answer: B
24) Which structure is NOT part of the endomembrane system?
A) nuclear envelope B) chloroplast C) Golgi apparatus D) plasma membrane Answer: B
54) A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in its _____.
A) nuclear matrix and extracellular matrix B) mitochondria and Golgi apparatus C) Golgi apparatus and extracellular matrix D) nuclear pores and secretory vesicles Answer: C
36) In a plant cell, DNA may be found _____.
A) only in the nucleus B) only in the nucleus and chloroplasts C) in the nucleus, mitochondria, and chloroplasts D) in the nucleus, mitochondria, chloroplasts, and peroxisomes Answer: C
57) Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through _____.
A) plasmodesmata B) tight junctions C) desmosomes D) gap junctions Answer: D
23) A cell with an extensive area of smooth endoplasmic reticulum is specialized to _____.
A) play a role in storage B) synthesize large quantities of lipids C) actively export protein molecules D) import and export protein molecules Answer: B
21) A cell with a predominance of free ribosomes is most likely _____.
A) primarily producing proteins for secretion B) primarily producing proteins in the cytosol C) constructing an extensive cell wall or extracellular matrix D) enlarging its vacuole Answer: B
3) In the fractionation of homogenized cells using centrifugation, the primary factor that determines whether a specific cellular component ends up in the supernatant or the pellet is the _____.
A) relative solubility of the component B) size and weight of the component C) percentage of carbohydrates in the component D) presence or absence of lipids in the component Answer: B
27) Which structure is the site of the synthesis of proteins that may be exported from the cell?
A) rough ER B) plasmodesmata C) Golgi vesicles D) free cytoplasmic ribosomes Answer: A
29) 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?
A) rough ER B) smooth ER C) Golgi apparatus D) nuclear envelope Answer: B
5) What technique would be most appropriate to use to observe the movements of condensed chromosomes during cell division?
A) standard light microscopy B) scanning electron microscopy C) transmission electron microscopy Answer: A
28) 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 must be involved in this condition?
A) the endoplasmic reticulum B) the Golgi apparatus C) the lysosome D) mitochondrion Answer: C
20) The nuclear lamina is an array of filaments on the inner side of the nuclear membrane. If a method were found that could cause the lamina to fall into disarray, what would you most likely expect to be the immediate consequence?
A) the loss of all nuclear function B) the inability of the nucleus to divide during cell division C) a change in the shape of the nucleus D) failure of chromosomes to carry genetic information Answer: C
8) Cell size is limited by _____.
A) the number of proteins within the plasma membrane B) the surface area of mitochondria in the cytoplasm C) surface to volume ratios D) the size of the endomembrane system Answer: C
26) The difference in lipid and protein composition between the membranes of the endomembrane system is largely determined by the _____.
A) transportation of membrane lipids among the membranes of the endomembrane system by small membrane vesicles B) function of the Golgi apparatus in sorting and directing membrane components C) modification of the membrane components once they reach their final destination D) synthesis of different lipids and proteins in each of the organelles of the endomembrane system Answer: B
51) Cells require which of the following to form cilia or flagella?
A) tubulin B) laminin C) actin D) intermediate filaments Answer: A
cells
All organisms are made of cells The cell is the simplest collection of matter that can be alive All cells are related by their descent from earlier cells Cells can differ substantially from one another but share common features
ECM
Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin ECM proteins bind to receptor proteins in the plasma membrane called integrins The ECM has an influential role in the lives of cells ECM can regulate a cell's behavior by communicating with a cell through integrins The ECM around a cell can influence the activity of gene in the nucleus Mechanical signaling may occur through cytoskeletal changes, that trigger chemical signals in the cell Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact
junctions in epithelial cells
At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid Desmosomes (anchoring junctions) fasten cells together into strong sheets Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells
chromosomes
Each chromosome is composed of a single DNA molecule associated with proteins The DNA and proteins of chromosomes are together called chromatin Chromatin condenses to form discrete chromosomes as a cell prepares to divide The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis
mitochondria and chloroplast similarities with bacteria
Enveloped by a double membrane Contain free ribosomes and circular DNA molecules Grow and reproduce somewhat independently in cells These similarities led to the endosymbiont theory
rough er
Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles, secretory proteins surrounded by membranes Is a membrane factory for the cell
centrosomes and centrioles
In animal cells, microtubules grow out from a centrosome near the nucleus In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring
three main fibers making up cytoskeleton
Microtubules are the thickest of the three components of the cytoskeleton Microfilaments, also called actin filaments, are the thinnest components Intermediate filaments are fibers with diameters in a middle range
cilia and flagella
Microtubules control the beating of flagella and cilia, microtubule-containing extensions that project from some cells Cilia and flagella differ in their beating patterns Cilia and flagella share a common structure A core of microtubules sheathed by the plasma membrane A basal body that anchors the cilium or flagellum A motor protein called dynein, which drives the bending movements of a cilium or flagellum
endomembrane system
Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane These components are either continuous or connected via transfer by vesicles
eukaryotic
Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells DNA in a nucleus that is bounded by a membranous nuclear envelope Membrane-bound organelles Cytoplasm in the region between the plasma membrane and nucleus Eukaryotic cells are generally much larger than prokaryotic cells
basic features of cells
Plasma membrane Semifluid substance called cytosol Chromosomes (carry genes) Ribosomes (make proteins)
multiple layers of cell walls
Primary cell wall: Relatively thin and flexible Middle lamella: Thin layer between primary walls of adjacent cells Secondary cell wall (in some cells): Added between the plasma membrane and the primary cell wall Plasmodesmata are channels between adjacent plant cells
prokaryotic
Protists, fungi, animals, and plants all consist of eukaryotic cells No nucleus DNA in an unbound region called the nucleoid No membrane-bound organelles Cytoplasm bound by the plasma membrane
smooth er
Synthesizes lipids Metabolizes carbohydrates Detoxifies drugs and poisons Stores calcium ions
cytoskeleton
The cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell's structures and activities, anchoring many organelles It is composed of three types of molecular structures Microtubules Microfilaments Intermediate filaments The cytoskeleton helps to support the cell and maintain its shape It interacts with motor proteins to produce motility Inside the cell, vesicles can travel along tracks provided by the cytoskeleton
nucleus
The nucleus contains most of the DNA in a eukaryotic cell Ribosomes use the information from the DNA to make proteins The nucleus contains most of the cell's genes and is usually the most conspicuous organelle The nuclear envelope encloses the nucleus, separating it from the cytoplasm The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer
cystoplasmic streaming
a circular flow of cytoplasm within cells This streaming speeds distribution of materials within the cell In plant cells, actin-myosin interactions and sol-gel transformations drive cytoplasmic streaming
lysosome
a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes work best in the acidic environment inside the lysosome Hydrolytic enzymes and lysosomal membranes are made by rough ER and then transferred to the Golgi apparatus for further processing Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell's own organelles and macromolecules, a process called autophagy
plasma membrane
a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell
endoplasmic reticulum
accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER Smooth ER, which lacks ribosomes Rough ER, whose surface is studded with ribosomes
cell wall of plants
an extracellular structure that distinguishes plant cells from animal cells Prokaryotes, fungi, and some unicellular eukaryotes also have cell walls The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein
ribosomes
complexes made of ribosomal RNA and protein Ribosomes carry out protein synthesis in two locations In the cytosol (free ribosomes) On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)
golgi apparatus
consists of flattened membranous sacs called cisternae Functions of the Golgi apparatus Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles
chloroplasts
found in plants and algae, are the sites of photosynthesis Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae Chloroplast structure includes Thylakoids, membranous sacs, stacked to form a granum Stroma, the internal fluid The chloroplast is one of a group of plant organelles, called plastids
microtubules
hollow rods about 25 nm in diameter and about 200 nm to 25 microns long Functions of microtubules Shaping the cell Guiding movement of organelles Separating chromosomes during cell division
vacuoles
large vesicles derived from the ER and Golgi apparatus Vacuoles perform a variety of functions in different kinds of cells Food vacuoles are formed by phagocytosis Contractile vacuoles, found in many freshwater protists, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water
intermediate filaments
range in diameter from 8-12 nanometers, larger than microfilaments but smaller than microtubules They support cell shape and fix organelles in place Intermediate filaments are more permanent cytoskeleton fixtures than the other two classes
perixomes
specialized metabolic compartments bounded by a single membrane Peroxisomes produce hydrogen peroxide and convert it to water Peroxisomes perform reactions with many different functions How peroxisomes are related to other organelles is still unknown
mitochondria
the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP Mitochondria are in nearly all eukaryotic cells They have a smooth outer membrane and an inner membrane folded into cristae The inner membrane creates two compartments: intermembrane space and mitochondrial matrix Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesize ATP
