Biology 120.3 Midterm Examination
Biology 120.3 Midterm Examination
October 14th, 2009 Dr. K. Wilson 1) Which of the following is not a characteristic of all living organisms? A. they must maintain a level of homeostasis B. genetic information is passed on to the next generation C. organisms store their DNA in the nucleus D. organisms must be able to respond to their environment E. populations of organisms change over generations 2) Which of the following represents an abundant element found in living organisms? A. calcium B. iron C. iodine D. hydrogen E. sodium 3) What type of bonding is likely to occur between two water molecules or strands of DNA? A. covalent B. ionic C. hydrogen D. both hydrogen and covalent E. both hydrogen and ionic 4) Which of the following pairs is not a correct monomer/polymer pairing? A. monosaccharide/polysaccharide B. amino acid/protein C. triglyceride/cellulose D. nucleotide/DNA E. nucleotide/RNA 5) Which of the following is TRUE about the structures of micelles or amphipathic molecules when placed in an aqueous (water) solution? A. the interior portion is composed of hydrophilic hydrocarbon chains B. the outside portion is composed of hydrophilic hydrocarbon chains C. the interior portion is composed of hydrophilic head groups D. the interior portion is composed of hydrophilic hydrocarbon chains and the outside portion of hydrophilic head groups E. the interior portion is composed of hydrophobic hydrocarbon chains and the outside portion of hydrophilic head groups
6) The side chain of the amino acid leucine is nonpolar. In a folded protein, where would you expect to find leucine?
A. in the interior of a cytoplasmic protein B. on the exterior of a protein embedded in a membrane C. on the exterior of a cytoplasmic protein D. either A or B E. either A or C 7) If a specimen contains 30% adenine in its DNA, then how much cytosine will there be? A. 40% B. 30% C. 20% D. 10% E. cannot be determined 8) Hydrogen bonds form because... A. oxygen is more electronegative than hydrogen B. atoms with opposite partial charges attract each other C. when covalently bonded to hydrogen, atoms such as oxygen and nitrogen do not share electrons equally D. A, B, and C are all correct E. none of the above answers are correct 9) Functional groups are important in the formation of biological molecules because... A. they introduce polarity to the molecule B. they add complexity to the molecule C. some can form hydrogen bonds D. they change the physical properties of the molecule E. all of the above answers are correct 10) Cellulose cannot be digested by most animals because... A. it is composed of fructose monomers which cannot be broken down by animal enzymes B. its highly branched alpha- 1,6 glycosidic bonds C. its highly branched beta- 1,4 glycosidic bonds D. its unbranched beta- 1,4 glycosidic bonds E. sugars made by plants cannot be digested by animals 11) A scientist suspects that the food in an ecosystem may have been contaminated with radioactive nitrogen (15N) over a period of months. Which of the following substances could be examined for radioactivity to test the hypothesis? A. the cell walls of plants growing in the ecosystem B. the DNA of rapidly growing organisms C. the sugars produced during photosynthesis by plants growing in the ecosystem D. the cholesterol in the cell membranes of organisms living in the ecosystem E. any of these choices would work well
12) Look at the picture of the fatty acid linoleic acid below. There are two carbon-carbon double bonds in the fatty acid tail. The one closest to the carboxyl group is a _________ double bond and the other is a __________ double bond. A. trans; trans B. trans; cis
C. cis; cis D. cis; trans E. none of the above are correct
13) Which of the following is not a complex biomolecule? A. glycoprotein B. lipoprotein C. glycolipid D. lipopolysaccharide E. celluloprotein 14) Which of the following statements is not part of the cell theory? A. all living things are composed of one or more cells B. cells are the smallest units of living things C. new cells only come from pre-existing cells by cell division D. new types of cells can only come about due to evolution E. all of the above statements are part of the cell theory 15) The atmosphere when life began is thought to have been composed mainly of... (OMITTED) A. H20, N2, CO, and CO2 B. H2, H2O, NH3, and CH4 C. H2O, N2, O2, and CO2 D. H2 only 16) The Miller-Urey experiment... A. used an atmosphere rich in O2 B. demonstrated that abiotic protein synthesis was possible C. did not require a source of energy D. did not require water as a reactant E. demonstrated that abiotic synthesis of simple organic molecules was possible
17) To experimentally test if organic molecules could be produced due to the action of deep sea-vents, your experimental set up would require... A. high pressure B. high temperature C. radioactive isotopes D. A and B are correct E. B and C are correct
18) The biggest question Dr. Wilson has regarding the idea that life originated in outer space is... A. how did life begin there? B. do little green men have chloroplasts? C. how could living organisms survive space travel? D. when are those jerks going to come back and pick him up? E. both B and D are correct 19) Protobionts are thought to be the first nonliving structure that evolved into living cells. A critical characteristic of a protobiont is... A. internal compartments that subdivide metabolic functions B. a boundary membrane that separates external from internal environments C. the ability to exclude all organic substances D. the ability to fuse with any other protobiont for reproduction E. all of the above are critical characteristics of protobionts 20) The cytoskeleton and motor proteins are important for which of the following processes? A. cell motility B. whipping motion of sperm flagella C. movement of amoeba D. muscle contraction E. all of the above choices are correct 21) Which of the following plant organelles is a colorless plastid that stores starch in roots? A. thyloplasts B. chloroplasts C. chromoplasts D. amyloplasts E. both cholorplasts and chromoplasts 22) Individual ribosomes are not visible under a light microscope but they can be seen with an electronic microscope because... A. electron beams have more energy than light beams B. electron microscopes focus light with magnets C. electron microscopes have more resolving power then light microscopes D. electrons have such high energy that they pass through biological samples E. living cells can be observed under the electron microscope
23) Which of the following is (are) found in prokaryotics? A. mitochondria B. chloroplasts C. nuclear membrane D. ribosomes E. endoplasmic reticulum
24) Tissues such as gonads that produce steroids are likely to be rich in what type of organelle? A. ribosome B. rough endoplasmic reticulum C. smooth endoplasmic reticulum D. mitochondria E. contractile vacuole 25) Animal tissues that are metabolically active and utilize large amounts of energy would be rich in... A. ribosomes B. flagella C. smooth endoplasmic reticulum D. mitochondria E. contractile vacuoles 26) The green fluorescent protein (GFP) has become an important tool in microscopy because... A. when using a TEM it allows us to see specific proteins in the cell B. it provides contrast when viewing components of living organisms C. it can be produced in specific cells or tissues of living organisms D. A and C are both correct E. B and C are both correct 27) A drug that interferes with microtubule formation is likely to be completely disrupt... A. the production of ribosomes B. the amoeboid movement of a cell C. the function of the Golgi body D. the contraction of muscle cells E. the construction of flagella in euglena cells 28) Contractile vacuoles... A. are generally found in protists that inhabit salt water B. help in the excretion of excess salt C. prevent cells from bursting as a result of the influx of excess water D. allow organisms to avoid dehydration by absorbing water from the environment E. all of the above are correct 29) Cellular membranes are... A. fluid B. solely composed of lipids C. composed of a single layer of amphipathic molecules D. selective to the transport of gases and small molecules only E. characteristic of eukaryotes but not prokaryotes 30) Which of the following is NOT true of the plasma membrane? A. it is composed of an extracellular and intracellular layer of phospholipids B. the extracellular and intracellular layers or leaflets are highly symmetrical C. the membrane contains peripheral proteins D. integral proteins span through the membrane E. the membrane contains glycolipids and glycoproteins
31) Water diffuses through certain organs such as the kidneys and bladder much faster than would occur by passive diffusion through a lipid bilayer alone. What accounts for this more rapid rate of water transport in these organs? A. the composition of lipids changes to promote water transport B. presence of aquaporin channels for facilitated diffusion of water C. presence of a water pump D. presence of an ATP driven enzyme for water transport E. the presence of molecules that bind water and change its membrane permeability properties 32) In the experimental technique fluorescence recovery after photo bleaching (FRAP), cell surface molecules are labelled with a fluorescent tag and then a portion of them are bleached with a laser beam. What would one observe after the cell is incubated for a few minutes? A. the bleached molecules would disappear into the cell B. the bleached molecules would diffuse laterally though the membrane and intermix with unbleached molecules C. the bleached molecules would remain in the spot where the bleaching occurred D. all the bleached molecules would flip-flop across the cell membrane E. all of the above are correct 33) How might a plant cell compensate for the excessive membrane fluidity that occurs during prolonged exposures to elevated temperature? A. reduce membrane cholesterol content B. alter the lipid composition to have a longer fatty acyl tails and fewer double bonds C. alter the lipid composition to have shorter and more unsaturated fatty acyl tails D. alter the lipid composition to have shorter and more unsaturated fatty acyl tails E. reduce cholesterol content and alter the lipid composition to have shorter fatty acyl tails 34) An ion moving through a membrane transporter in one direction provides energy to actively transport another molecule in the opposite direction. This direction is... A. facilitated diffusion B. exchange diffusion C. symport transport D. primary active transport E. secondary active transport
35) A scientist produces an artificial membrane of phospholipids and notices that oxygen, but not glucose, readily moves through the membrane. What might account for the inability of glucose to move through the artificial membrane? A. the artificial membrane lacked a protein needed for glucose transport B. the artificial membrane lacked the appropriate types of phospholipids for glucose transport C. oxygen readily passes through the membrane so glucose should have as well D. the membrane lacked an adequate amount of amphipathic molecules for glucose transport E. thermodynamics does not allow glucose to pass through membranes produced either artificially or from living organisms
36) When a membrane is prepared by freeze-fracture and examined under the electron microscope, the exposed interior of the membrane bilayer appears to be covered with bumps. These bumps are... A. ice crystals B. integral membrane proteins C. platinum D. organelles E. vesicles 37) In the following diagram, assume that the set-up was observed for a period of several hours. Which of the following statements is correct? Inside a cell (intracellular) Outside fluids (intercellular/extracellular) Water 95%, solute 5% Water 98%, solute 2% Note: membrane is selectively permeable A. the relation of the cell to its environment is isotonic B. the cell is in a hypertonic environment C. the net flow of water is into the cell D. the cell will soon shrink E. diffusion can occur hear but not osmosis 38) Which of the following statements is true for the diagram in question 37? A. the net movement of solutes is into the cell B. there is no concentration gradient C. there is a potential for plasmolysis D. the solvent will move against its concentration gradient E. if this were a plant cell, turgor pressure would be maintained 39) Which of the following statements about diffusion is true? Diffusion... A. is a type of active transport B. requires energy C. requires a transport protein D. is the result of the random movement of molecules E. smiffusion!
40) __________ is the process through which cells can detect and respond to signals in their extracellular environment. A. cell sensation B. cell communication C. perception D. transduction E. sensory response 41) During exposure to elevated glucose, a yeast cell’s membrane glucose transporters will rapidly increase in number so the cell can import glucose. Which of the following would represent the signal for the yeast cell?
A. glucose transporters B. glucose receptors C. glucose D. glucose transport into the cell E. glucose kinase 42) What type of cell communication is said to occur if a cell secretes a growth factor that then acts on neighbouring cells to cause them to grow and divide more quickly? A. contract dependent signalling B. intercellular signalling C. autocrine signalling D. paracrine signalling E. endocrine signalling 43) What type of signalling occurs when insulin is secreted from the pancreas and acts on muscle cells to increase glucose uptake? A. contract dependent signalling B. intercellular signalling C. autocrine signalling D. paracrine signalling E. endocrine signalling 44) A key is placed in a keyhole then turned and the door opens. Which of the following components of cell signalling would best correspond to turning the key? A. the signal or ligand molecule B. the receptor protein C. the change in the shape of the receptor once bound to the signal molecule D. signal transduction E. the cellular responses 45) Which of the following statements about steroid molecules is FALSE? A. the receptors undergo a conformational change after binding the steroid B. the receptors are localized to the plasma membrane C. once the steroid binds to the receptor, the steroid/receptor complexes can bind to DNA D. steroid receptors regulate the expression of certain genes and the subsequent production of proteins directly E. steroid receptors are localized to either the cytoplasm or nucleus 46) As a patch of scraped skin heals, the cells fill in the injured area but do not grow beyond that point. This is an example of... A. density-dependent inhibition B. density-independent inhibition C. anchorage independence D. growth factor inhibition E. anchorage dependent inhibition 47) Cyclins and cyclin dependent kinases... A. regulate the cells advancement past checkpoints during the cell cycle B. scan the cell’s DNA to make sure there are no errors C. are steroid signals that trigger cell division D. bind to the mitotic spindle to ensure that cell division does not take place E. all of the above are roles of cyclins and cycli dependent kinase
48) Vinblastine is a standard chemotherapeutic drug used to treat cancer because it interferes with the assembly of microtubules, its effectiveness must be related to... A. disruption of mitotic spindle formation B. inhibition of regulatory protein phosphorylation C. suppression of cyclin production D. myosin denaturation and inhibition of cleavage formation E. flagella mediated cell separation 49) One difference between a cancer cell and a normal cell is that... A. the cancer cell is unable to synthesize DNA B. the cell cycle of the cancer cells is arrested at S-phase C. cancer cells continue to divide even when they are tighlt packed together D. cancer cells cannot function properly because they suffer from density-dependent inhibition E. cancer cells are always in M-phase of the cell cycle 50) In some organisms, mitosis will occur without cytokinesis. This would result in... A. cells with more than one nucleus B. cells that are unusually small C. cells lacking nuclei D. destruction of the spindle fibres E. cell cycles lacking the S-phase
October 14th, 2009 Dr. K. Wilson 1) Which of the following is not a characteristic of all living organisms? A. they must maintain a level of homeostasis B. genetic information is passed on to the next generation C. organisms store their DNA in the nucleus D. organisms must be able to respond to their environment E. populations of organisms change over generations 2) Which of the following represents an abundant element found in living organisms? A. calcium B. iron C. iodine D. hydrogen E. sodium 3) What type of bonding is likely to occur between two water molecules or strands of DNA? A. covalent B. ionic C. hydrogen D. both hydrogen and covalent E. both hydrogen and ionic 4) Which of the following pairs is not a correct monomer/polymer pairing? A. monosaccharide/polysaccharide B. amino acid/protein C. triglyceride/cellulose D. nucleotide/DNA E. nucleotide/RNA 5) Which of the following is TRUE about the structures of micelles or amphipathic molecules when placed in an aqueous (water) solution? A. the interior portion is composed of hydrophilic hydrocarbon chains B. the outside portion is composed of hydrophilic hydrocarbon chains C. the interior portion is composed of hydrophilic head groups D. the interior portion is composed of hydrophilic hydrocarbon chains and the outside portion of hydrophilic head groups E. the interior portion is composed of hydrophobic hydrocarbon chains and the outside portion of hydrophilic head groups
6) The side chain of the amino acid leucine is nonpolar. In a folded protein, where would you expect to find leucine?
A. in the interior of a cytoplasmic protein B. on the exterior of a protein embedded in a membrane C. on the exterior of a cytoplasmic protein D. either A or B E. either A or C 7) If a specimen contains 30% adenine in its DNA, then how much cytosine will there be? A. 40% B. 30% C. 20% D. 10% E. cannot be determined 8) Hydrogen bonds form because... A. oxygen is more electronegative than hydrogen B. atoms with opposite partial charges attract each other C. when covalently bonded to hydrogen, atoms such as oxygen and nitrogen do not share electrons equally D. A, B, and C are all correct E. none of the above answers are correct 9) Functional groups are important in the formation of biological molecules because... A. they introduce polarity to the molecule B. they add complexity to the molecule C. some can form hydrogen bonds D. they change the physical properties of the molecule E. all of the above answers are correct 10) Cellulose cannot be digested by most animals because... A. it is composed of fructose monomers which cannot be broken down by animal enzymes B. its highly branched alpha- 1,6 glycosidic bonds C. its highly branched beta- 1,4 glycosidic bonds D. its unbranched beta- 1,4 glycosidic bonds E. sugars made by plants cannot be digested by animals 11) A scientist suspects that the food in an ecosystem may have been contaminated with radioactive nitrogen (15N) over a period of months. Which of the following substances could be examined for radioactivity to test the hypothesis? A. the cell walls of plants growing in the ecosystem B. the DNA of rapidly growing organisms C. the sugars produced during photosynthesis by plants growing in the ecosystem D. the cholesterol in the cell membranes of organisms living in the ecosystem E. any of these choices would work well
12) Look at the picture of the fatty acid linoleic acid below. There are two carbon-carbon double bonds in the fatty acid tail. The one closest to the carboxyl group is a _________ double bond and the other is a __________ double bond. A. trans; trans B. trans; cis
C. cis; cis D. cis; trans E. none of the above are correct
13) Which of the following is not a complex biomolecule? A. glycoprotein B. lipoprotein C. glycolipid D. lipopolysaccharide E. celluloprotein 14) Which of the following statements is not part of the cell theory? A. all living things are composed of one or more cells B. cells are the smallest units of living things C. new cells only come from pre-existing cells by cell division D. new types of cells can only come about due to evolution E. all of the above statements are part of the cell theory 15) The atmosphere when life began is thought to have been composed mainly of... (OMITTED) A. H20, N2, CO, and CO2 B. H2, H2O, NH3, and CH4 C. H2O, N2, O2, and CO2 D. H2 only 16) The Miller-Urey experiment... A. used an atmosphere rich in O2 B. demonstrated that abiotic protein synthesis was possible C. did not require a source of energy D. did not require water as a reactant E. demonstrated that abiotic synthesis of simple organic molecules was possible
17) To experimentally test if organic molecules could be produced due to the action of deep sea-vents, your experimental set up would require... A. high pressure B. high temperature C. radioactive isotopes D. A and B are correct E. B and C are correct
18) The biggest question Dr. Wilson has regarding the idea that life originated in outer space is... A. how did life begin there? B. do little green men have chloroplasts? C. how could living organisms survive space travel? D. when are those jerks going to come back and pick him up? E. both B and D are correct 19) Protobionts are thought to be the first nonliving structure that evolved into living cells. A critical characteristic of a protobiont is... A. internal compartments that subdivide metabolic functions B. a boundary membrane that separates external from internal environments C. the ability to exclude all organic substances D. the ability to fuse with any other protobiont for reproduction E. all of the above are critical characteristics of protobionts 20) The cytoskeleton and motor proteins are important for which of the following processes? A. cell motility B. whipping motion of sperm flagella C. movement of amoeba D. muscle contraction E. all of the above choices are correct 21) Which of the following plant organelles is a colorless plastid that stores starch in roots? A. thyloplasts B. chloroplasts C. chromoplasts D. amyloplasts E. both cholorplasts and chromoplasts 22) Individual ribosomes are not visible under a light microscope but they can be seen with an electronic microscope because... A. electron beams have more energy than light beams B. electron microscopes focus light with magnets C. electron microscopes have more resolving power then light microscopes D. electrons have such high energy that they pass through biological samples E. living cells can be observed under the electron microscope
23) Which of the following is (are) found in prokaryotics? A. mitochondria B. chloroplasts C. nuclear membrane D. ribosomes E. endoplasmic reticulum
24) Tissues such as gonads that produce steroids are likely to be rich in what type of organelle? A. ribosome B. rough endoplasmic reticulum C. smooth endoplasmic reticulum D. mitochondria E. contractile vacuole 25) Animal tissues that are metabolically active and utilize large amounts of energy would be rich in... A. ribosomes B. flagella C. smooth endoplasmic reticulum D. mitochondria E. contractile vacuoles 26) The green fluorescent protein (GFP) has become an important tool in microscopy because... A. when using a TEM it allows us to see specific proteins in the cell B. it provides contrast when viewing components of living organisms C. it can be produced in specific cells or tissues of living organisms D. A and C are both correct E. B and C are both correct 27) A drug that interferes with microtubule formation is likely to be completely disrupt... A. the production of ribosomes B. the amoeboid movement of a cell C. the function of the Golgi body D. the contraction of muscle cells E. the construction of flagella in euglena cells 28) Contractile vacuoles... A. are generally found in protists that inhabit salt water B. help in the excretion of excess salt C. prevent cells from bursting as a result of the influx of excess water D. allow organisms to avoid dehydration by absorbing water from the environment E. all of the above are correct 29) Cellular membranes are... A. fluid B. solely composed of lipids C. composed of a single layer of amphipathic molecules D. selective to the transport of gases and small molecules only E. characteristic of eukaryotes but not prokaryotes 30) Which of the following is NOT true of the plasma membrane? A. it is composed of an extracellular and intracellular layer of phospholipids B. the extracellular and intracellular layers or leaflets are highly symmetrical C. the membrane contains peripheral proteins D. integral proteins span through the membrane E. the membrane contains glycolipids and glycoproteins
31) Water diffuses through certain organs such as the kidneys and bladder much faster than would occur by passive diffusion through a lipid bilayer alone. What accounts for this more rapid rate of water transport in these organs? A. the composition of lipids changes to promote water transport B. presence of aquaporin channels for facilitated diffusion of water C. presence of a water pump D. presence of an ATP driven enzyme for water transport E. the presence of molecules that bind water and change its membrane permeability properties 32) In the experimental technique fluorescence recovery after photo bleaching (FRAP), cell surface molecules are labelled with a fluorescent tag and then a portion of them are bleached with a laser beam. What would one observe after the cell is incubated for a few minutes? A. the bleached molecules would disappear into the cell B. the bleached molecules would diffuse laterally though the membrane and intermix with unbleached molecules C. the bleached molecules would remain in the spot where the bleaching occurred D. all the bleached molecules would flip-flop across the cell membrane E. all of the above are correct 33) How might a plant cell compensate for the excessive membrane fluidity that occurs during prolonged exposures to elevated temperature? A. reduce membrane cholesterol content B. alter the lipid composition to have a longer fatty acyl tails and fewer double bonds C. alter the lipid composition to have shorter and more unsaturated fatty acyl tails D. alter the lipid composition to have shorter and more unsaturated fatty acyl tails E. reduce cholesterol content and alter the lipid composition to have shorter fatty acyl tails 34) An ion moving through a membrane transporter in one direction provides energy to actively transport another molecule in the opposite direction. This direction is... A. facilitated diffusion B. exchange diffusion C. symport transport D. primary active transport E. secondary active transport
35) A scientist produces an artificial membrane of phospholipids and notices that oxygen, but not glucose, readily moves through the membrane. What might account for the inability of glucose to move through the artificial membrane? A. the artificial membrane lacked a protein needed for glucose transport B. the artificial membrane lacked the appropriate types of phospholipids for glucose transport C. oxygen readily passes through the membrane so glucose should have as well D. the membrane lacked an adequate amount of amphipathic molecules for glucose transport E. thermodynamics does not allow glucose to pass through membranes produced either artificially or from living organisms
36) When a membrane is prepared by freeze-fracture and examined under the electron microscope, the exposed interior of the membrane bilayer appears to be covered with bumps. These bumps are... A. ice crystals B. integral membrane proteins C. platinum D. organelles E. vesicles 37) In the following diagram, assume that the set-up was observed for a period of several hours. Which of the following statements is correct? Inside a cell (intracellular) Outside fluids (intercellular/extracellular) Water 95%, solute 5% Water 98%, solute 2% Note: membrane is selectively permeable A. the relation of the cell to its environment is isotonic B. the cell is in a hypertonic environment C. the net flow of water is into the cell D. the cell will soon shrink E. diffusion can occur hear but not osmosis 38) Which of the following statements is true for the diagram in question 37? A. the net movement of solutes is into the cell B. there is no concentration gradient C. there is a potential for plasmolysis D. the solvent will move against its concentration gradient E. if this were a plant cell, turgor pressure would be maintained 39) Which of the following statements about diffusion is true? Diffusion... A. is a type of active transport B. requires energy C. requires a transport protein D. is the result of the random movement of molecules E. smiffusion!
40) __________ is the process through which cells can detect and respond to signals in their extracellular environment. A. cell sensation B. cell communication C. perception D. transduction E. sensory response 41) During exposure to elevated glucose, a yeast cell’s membrane glucose transporters will rapidly increase in number so the cell can import glucose. Which of the following would represent the signal for the yeast cell?
A. glucose transporters B. glucose receptors C. glucose D. glucose transport into the cell E. glucose kinase 42) What type of cell communication is said to occur if a cell secretes a growth factor that then acts on neighbouring cells to cause them to grow and divide more quickly? A. contract dependent signalling B. intercellular signalling C. autocrine signalling D. paracrine signalling E. endocrine signalling 43) What type of signalling occurs when insulin is secreted from the pancreas and acts on muscle cells to increase glucose uptake? A. contract dependent signalling B. intercellular signalling C. autocrine signalling D. paracrine signalling E. endocrine signalling 44) A key is placed in a keyhole then turned and the door opens. Which of the following components of cell signalling would best correspond to turning the key? A. the signal or ligand molecule B. the receptor protein C. the change in the shape of the receptor once bound to the signal molecule D. signal transduction E. the cellular responses 45) Which of the following statements about steroid molecules is FALSE? A. the receptors undergo a conformational change after binding the steroid B. the receptors are localized to the plasma membrane C. once the steroid binds to the receptor, the steroid/receptor complexes can bind to DNA D. steroid receptors regulate the expression of certain genes and the subsequent production of proteins directly E. steroid receptors are localized to either the cytoplasm or nucleus 46) As a patch of scraped skin heals, the cells fill in the injured area but do not grow beyond that point. This is an example of... A. density-dependent inhibition B. density-independent inhibition C. anchorage independence D. growth factor inhibition E. anchorage dependent inhibition 47) Cyclins and cyclin dependent kinases... A. regulate the cells advancement past checkpoints during the cell cycle B. scan the cell’s DNA to make sure there are no errors C. are steroid signals that trigger cell division D. bind to the mitotic spindle to ensure that cell division does not take place E. all of the above are roles of cyclins and cycli dependent kinase
48) Vinblastine is a standard chemotherapeutic drug used to treat cancer because it interferes with the assembly of microtubules, its effectiveness must be related to... A. disruption of mitotic spindle formation B. inhibition of regulatory protein phosphorylation C. suppression of cyclin production D. myosin denaturation and inhibition of cleavage formation E. flagella mediated cell separation 49) One difference between a cancer cell and a normal cell is that... A. the cancer cell is unable to synthesize DNA B. the cell cycle of the cancer cells is arrested at S-phase C. cancer cells continue to divide even when they are tighlt packed together D. cancer cells cannot function properly because they suffer from density-dependent inhibition E. cancer cells are always in M-phase of the cell cycle 50) In some organisms, mitosis will occur without cytokinesis. This would result in... A. cells with more than one nucleus B. cells that are unusually small C. cells lacking nuclei D. destruction of the spindle fibres E. cell cycles lacking the S-phase
