Cell bio final

32. Which of the following statements about apoptosis is true? (a) Cells that constitutively express Bcl2 will be more prone to undergo apoptosis. (b) The prodomain of procaspases contains the catalytic activity necessary for procaspase activation. (c) Bax and Bak promote apoptosis by binding to procaspases in the apoptosome. (d) Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria.

Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria.

8. Which of the following statements about cancer is false? a. Viruses cause some cancers b. Tobacco use is responsible for more than 20% of all cancer deaths c. A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell. d. Chemical carcinogens cause cancer by changing the nucleotide sequence of DNA

A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell.

9. Which of the following genetic changes cannot convert a proto-oncogene into an oncogene? (a) A mutation that introduces a stop codon immediately after the codon for the initiator methionine. (b) A mutation within the coding sequence that makes the protein hyperactive. (c) An amplification of the number of copies of the proto-oncogene, causing overproduction of the normal protein. (d) A mutation in the promoter of the proto-oncogene, causing the normal protein to be transcribed and translated at an abnormally high level.

A mutation that introduces a stop codon immediately after the codon for the initiator methionine.

MPF activity was discovered when cytoplasm from a Xenopus M-phase cell was injected into Xenopus oocytes, inducing the oocytes to form a mitotic spindle. In a control experiment, Xenopus interphase cytoplasm was injected into oocytes and shown not to induce the formation of a mitotic spindle. Which of the following statements is not a legitimate conclusion from the control experiment?

Components of an interphase nucleus are insufficient to cause mitotic spindle formation.

Which of the following statements about the cell cycle is false? a. Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eucaryotic cells. b. An unfavorable environment can cause cells to arrest in G1 c. A cell has more DNA during G2 than it did in G1 d. Cleavage divisions that occur in an early embryo have short G1 & G2

Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eucaryotic cells.

9. Which of the following statements is false? a. Proteoglycans can act as filters to regulate which molecules pass thorugh EC medium b. Negative charge associated w proteoglycans attracts cations, which cause water to be sucked into ECM c. Proteoglycans are a major component of compact connective tissues but are relatively unimportant in watery tissues such as the jellylike substance in the interior of the eye. d. Glycosaminoglycans are components of proteoglycan

Proteoglycans are a major component of compact connective tissues but are relatively unimportant in watery tissues such as the jellylike substance in the interior of the eye.

4. Which of the following statements about animal connective tissues is true? (a) Enzymes embedded in the plasma membrane synthesize the collagen in the extracellular matrix extracellularly. (b) In connective tissue, the intermediate filaments within the cells are important for carrying the mechanical load. (c) Cells can attach to a collagen matrix by using fibronectin, an integral membrane protein. (d) Proteoglycans can resist compression in the extracellular matrix.

Proteoglycans can resist compression in the extracellular matrix.

16. Which of the following statements is false? a. Mitotic Cdk must be phosphorylated by an activating kinase (Cak) before it is active b. Phosphorylation of mitotic Cdk by the inhibitory kinase (Wee1) makes Cdk inactive, even if it is phosphorylated by the activating kinase. c. Active M-Cdk phosphorylates the activating phosphatase (Cdc25) in a positive feedback loop. d. The activating phosphatase (Cdc25) removes all phosphates from mitotic Cdk so that M-Cdk will be active.

The activating phosphatase (Cdc25) removes all phosphates from mitotic Cdk so that M-Cdk will be active.

Which of the following is not good direct evidence that the cell-cycle control system is conserved through billions of years of divergent evolution? a. A yeast cell lacking Cdk function can use the human Cdk to substitute for its missing Cdk during the cell cycle. b. The amino acid sequences of cyclins in plants are similar to the amino acid sequences of cylins in humans. c. The Cdk proteins in humans share conserved phosphorylation sites with the Cdk proteins in yeast. d. Yeast cells have only one Cdk, whereas humans have many Cdks.

Yeast cells have only one Cdk, whereas humans have many Cdks.

16. Which type of junction involves a connection to the actin cytoskeleton? (a) adherens junctions (b) desmosomes (c) tight junctions (d) gap junctions

adherens junctions

8. Proteoglycans in the extracellular matrix of animal tissues ________________. (a) chiefly provide tensile strength (b) allow cartilage to resist compression (c) are linked to microtubules through the plasma membrane (d) are polysaccharides composed of glucose subunits

allow cartilage to resist compression

24. When introduced into mitotic cells, which of the following is expected to impair anaphase B but not anaphase A? (a) an antibody against myosin (b) ATPγS, a nonhydrolyzable ATP analog that binds to and inhibits ATPases (c) an antibody against the motor proteins that move from the plus end of microtubules to the minus end (d) an antibody against the motor proteins that move from the minus end of microtubules toward the plus end

an antibody against the motor proteins that move from the minus end of microtubules toward the plus end

6. Induced pluripotent stem (iPS) cells ______________________. (a) are created by the expression of a set of key genes in cells derived from adult tissues so that these cells can differentiate into a variety of cell types (b) require a supply of donor egg cells, such as embryonic stem cells (c) can differentiate into a greater variety of adult tissues than embryonic stem cells (d) are created by nuclear transplantation

are created by the expression of a set of key genes in cells derived from adult tissues so that these cells can differentiate into a variety of cell types

11. Tight junctions ______________________. (a) allow small water-soluble molecules to pass from cell to cell (b) interact with the intermediate filaments inside the cell (c) are formed from claudins and occludins (d) are found in cells in connective tissues

are formed from claudins and occludins

17. Condensins ________________. (a) are degraded when cells enter M-phase (b) assemble into complexes on the DNA when phosphorylated by M-Cdk (c) are involved in holding sister chromatids together (d) bind to DNA before DNA replication begins

assemble into complexes on the DNA when phosphorylated by M-Cdk

25. Which of the following precede the re-formation of the nuclear envelope during M phase in animal cells? (a) assembly of the contractile ring (b) decondensation of chromosomes (c) reassembly of the nuclear lamina (d) transcription of nuclear genes

assembly of the contractile ring

14. Hemidesmosomes are important for ______________________. (a) tubulation of epithelial sheets (b) linkages to glycosaminoglycans (c) forming the basal lamina (d) attaching epithelial cells to the extracellular matrix

attaching epithelial cells to the extracellular matrix

Programmed cell death occurs ________________. (a) by means of an intracellular suicide program (b) rarely and selectively only during animal development (c) only in unhealthy or abnormal cells (d) only during embryonic development

by means of an intracellular suicide program

12. Adherens junctions ______________________. (a) can be used to bend epithelial sheets into tubes (b) are most often found at the basal surface of cells (c) are found only in adult tissues (d) involve fibronectin and integrin interactions

can be used to bend epithelial sheets into tubes

2. An adult hemopoietic stem cell found in the bone marrow ______________________. (a) will occasionally produce epidermal cells when necessary (b) can produce only red blood cells (c) can undergo self-renewing divisions for the lifetime of a healthy animal (d) will express all the same transcription factors as those found in an unfertilized egg

can undergo self-renewing divisions for the lifetime of a healthy animal

31. Apoptosis differs from necrosis in that necrosis ________________. (a) requires the reception of an extracellular signal (b) causes DNA to fragment (c) causes cells to swell and burst, whereas apoptotic cells shrink and condense (d) involves a caspase cascade

causes cells to swell and burst, whereas apoptotic cells shrink and condense

19. The principal microtubule organizing center in animal cells is the ____________.

centrosome

12. At the end of DNA replication, the sister chromatids are held together by the (a) kinetochores (b) securins (c) cohesins (d) histones

cohesins

Which of the following molecules are not found in plants? a. cellulose b. lignin c. collagen d. pectin

collagen

3. Mouse embryonic stem (ES) cells ______________________. (a) can only be produced through therapeutic cloning (b) can give rise to all tissues and cell types in the body except germ cells (c) can be implanted in foster mothers to produce cloned cows and other animals (d) come from the inner cell mass of early embryos

come from the inner cell mass of early embryos

Levels of Cdk activity change during the cell cycle, in part, because ________________. a. the Cdks phosphorylate each other b. the Cdks activate the cyclins c. Cdk degradation precedes entry into the next phase of the cell cycle d. cyclin levels change during the cycle

cyclin levels change during the cycle

26. A cell with nuclear lamins that cannot be phosphorylated in M phase will be unable to ________________. (a) reassemble its nuclear envelope at telophase (b) disassemble its nuclear lamina at prometaphase (c) begin to assemble a mitotic spindle (d) condense its chromosomes at prophase

disassemble its nuclear lamina at prometaphase

Cells in the G0 state ________________. (a) do not divide (b) cannot re-enter the cell cycle (c) have entered this arrest state from either G1 or G2 (d) have duplicated their DNA

do not divide

The concentration of mitotic cyclin (M cyclin) ________________. (a) rises markedly during M phase (b) is activated by phosphorylation (c) falls toward the end of M phase as a result of ubiquitylation and degradation (d) is highest in G1 phase

falls toward the end of M phase as a result of ubiquitylation and degradation

11. The block on re-initiation of DNA replication ensures that the daughter cells are aneuploidy (abnormal number of chromosomes).

false

8. Collagen Provides Tensile Strength in Plant Tissues. A yeast cell that enters mitosis prematurely before reaching normal size in G2 will appear as elongated cells.

false

12. Integrins are unable to relay signals between the cell and their external environment.

false ABLE

3. Activation of APC/C leads to the degradation of B-type cyclins which arrests the cell in the G0 stage.

false degradation of securin

4. The APC/C polyubiquinates the protein securin in order to stitch epithelial cells together.

false in order to inhibit activity of separase

10. Aggrecans are the core protein that are responsible for folding the collagen trimmers in the endoplasmic reticulum.

false responsible for withstanding compression in cartilage

5. Plant cells communicate with other plant cells via gap junctions composed of connexin proteins.

false via plasmodesmata

15. Which of the following does not occur during M phase in animal cells? (a) growth of the cell (b) condensation of chromosomes (c) breakdown of nuclear envelope (d) attachment of chromosomes to microtubules

growth of the cell

13. At desmosomes, cadherin molecules are connected to ________________. (a) actin filaments (b) intermediate filaments (c) microtubules (d) gap junctions

intermediate filaments

13.The G1 DNA damage checkpoint ________________. (a) causes cells to proceed through S phase more quickly (b) involves the degradation of p53 (c) is activated by errors caused during DNA replication (d) involves the inhibition of cyclin-Cdk complexes by p21

involves the inhibition of cyclin-Cdk complexes by p21

10. A basal lamina ______________________. (a) is a thin layer of connective tissue cells and matrix underlying an epithelium (b) is a thin layer of extracellular matrix underlying an epithelium (c) is attached to the apical surface of an epithelium (d) separates epithelial cells from each other

is a thin layer of extracellular matrix underlying an epithelium

7. A malignant tumor is more dangerous than a benign tumor because ______________________. (a) its cells are proliferating faster (b) it causes neighboring cells to mutate (c) its cells attack and phagocytose neighboring normal tissue cells (d) its cells invade other tissues

its cells invade other tissues

18. Cadherins ______________________. (a) are used to transfer proteins from one cell to another (b) mediate cell-cell attachments through homophilic interactions (c) are abundant in the plant cell wall (d) bind to collagen fibrils

mediate cell-cell attachments through homophilic interactions

19. Plasmodesmata ______________________. (a) permit small molecules to pass from one cell to another (b) are found only in animal cells (c) are closed by the neurotransmitter dopamine (d) provide tensile strength

permit small molecules to pass from one cell to another

6. Fibroblasts organize the collagen of the extracellular matrix by ______________. (a) cutting and rejoining the fibrils (b) processing procollagen into collagen (c) twisting fibrils together to make ropelike fibers (d) pulling the collagen into sheets or cables after it has been secreted

pulling the collagen into sheets or cables after it has been secreted

27. Cytokinesis in animal cells ________________. (a) requires ATP (b) leaves a small circular 'scar' of actin filaments on the inner surface of the plasma membrane (c) is often followed by phosphorylation of integrins in the plasma membrane (d) is assisted by motor proteins that pull on microtubules attached to the cell cortex

requires ATP

5. A major distinction between the connective tissues in an animal and other main tissue types such as epithelium, nervous tissue, or muscle is _______________. (a) the ability of connective tissue cells such as fibroblasts to change shape (b) the amount of extracellular matrix in connective tissues (c) the ability of connective tissues to withstand mechanical stresses (d) the numerous connections that connective tissue cells make with each other

the amount of extracellular matrix in connective tissues

21. A friend declares that chromosomes are held at the metaphase plate by microtubules that push on each chromosome from opposite sides. Which of the following observations does not support your belief that the microtubules are pulling on the chromosomes?

the jiggling movement of chromosomes at the metaphase plate

17. Which type of junction contributes the most to the polarization of epithelial cells? (a) adherens junctions (b) desmosomes (c) tight junctions (d) gap junctions

tight junctions

1. Both multicellular plants and animals have _____________________. (a) cells capable of locomotion (b) cells with cell walls (c) a cytoskeleton composed of actin filaments, microtubules, and intermediate filaments (d) tissues composed of multiple different cell types

tissues composed of multiple different cell types

1. Cellulose microfibrils give the plant cell wall its tensile strength.

true

10. Small molecules and ions can pass through gap junctions.

true

12. Procollagen chains are synthesized on the endoplasmic reticulum.

true

13. Passage through the cell cycle is controlled by heterodimeric protein kinases.

true

14. The cdc25 phosphatase removes a phosphate from the CDK kinase yielding highly active MPF.

true

15. Initiation of DNA replication occurs at each origin, but only once, until a cell proceeds through anaphase.

true

15. Integrins couple the matrix outside a cell to the cytoskeleton inside It.

true

16. Mitotic CDK kinases are activated by an increase in mitotic cyclins.

true

16. Proteoglycan core proteins are synthesized on the endoplasmic reticulum.

true

19. Regulation of integrin-mediated adhesion can regulate cell movement.

true

2. N-acetylglucosamine is a repeating disaccharide found in the extracellular matrix.

true

6. The staggering of the collagen trimmers gives the fibrils a striated appearance in the electron microscope.

true

7. Large proteoglycan aggregates may contain a hyaluronin molecule bound to the core protein of multiple proteoglycan molecules.

true

9. Connective tissue such a tendon and cartilage differs from other solid tissues in that most of its volume is made up of extracellular matrix rather than cells.

true

1. Cells that are terminally differentiated ______________________. (a) will undergo apoptosis within a few days (b) usually can no longer undergo cell division (c) are unable to move (d) no longer produce RNAs

usually can no longer undergo cell division

15. Which of the following statements about gap junctions is false? a. Gap junctions are made of connexons b. Molecules are up to 100 daltons in MW can move across gap junctions c. Because gap junctions do not allow ions to pass through, they are not used for electrically coupling cells. d. Gap junctions can close in response to EC signals

Because gap junctions do not allow ions to pass through, they are not used for electrically coupling cells.

You create cells with a version of Cdc6 that cannot be phosphorylated and thus cannot be degraded. Which of the following statements describes the likely consequence of this change in Cdc6? (a) Cells will enter S phase prematurely. (b) Cells will be unable to complete DNA synthesis. (c) The origin recognition complex (ORC) will be unable to bind to DNA. (d) Cdc6 will be produced inappropriately during M phase.

Cells will be unable to complete DNA synthesis.

10. Which of the following statements about tumor suppressor genes is false? a. Gene amplification of a tumor supressor gene is less dangerous than gene amplification of a proto-oncogene b. Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells. c. Inactivation of tumor supressor genes leads to enhanced cell survival & proliferation d. Individuals w only 1 functional copy of a tumor supressor gene are more prone to cancer than individuals w 2 functional copies of a tumor suppressor gene

Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells.

5. How do reproductive cloning and therapeutic cloning differ? (a) The DNA in the nucleus of cells produced for therapeutic cloning is genetically identical to the donor genome, whereas in cells produced for reproductive cloning it is not. (b) Reproductive cloning requires a supply of fertilized donor egg cells, whereas therapeutic cloning requires unfertilized egg cells. (c) Therapeutic cloning requires nuclear transplantation, whereas reproductive cloning does not. (d) Embryos are placed into foster mothers during reproductive cloning but not during therapeutic cloning.

Embryos are placed into foster mothers during reproductive cloning but not during therapeutic cloning.

13. A loss of cdc2 function results in the premature entry into mitosis.

FALSE

17. Cadherins are responsible for Ca++-dependent interactions between connexin proteins.

FALSE

18. Checkpoint mechanisms can determine whether DNA has been properly regulated but whether DNA is segregated to the daughter cells.

FALSE

19. Cyclin-CDK complexes are composed of a regulatory subunit CDK and a catalytic subunit, cyclin.

FALSE

20. Fibronectin is a multidomain extracellular matrix protein that forms the core of a proteoglycan aggregate.

FALSE

11. Animal Epithelial Cells Consist Largely of Extracellular Matrix.

FALSE ANIMAL CONNECTIVE TISSUE

17. Unlike proteins, polysaccharide gels can not resist compression.

FALSE CAN!!!

18. The maturation promoting factor stimulates meiotic maturation in oocytes and in doing so inhibits mitosis in somatic cells.

FALSE DRIVES MITOSIS IN SOMATIC CELLS

14. Cells grow in size and synthesize proteins and RNA at the interface of G2/M period of the cell cycle.

FALSE interphase

29. Which organelle fragments during mitosis?

Golgi apparatus

23. Which of the following statements is true? a. Anaphse A must be completed before anaphse B can take place b. In cells which anaphse B predominates, the spindle will elongate much less than in cells in which anaphse A dominates c. In anaphse A, both kinetochore & interpolar MTs shorten. d In anaphase B, microtubules associated w cell cortex shorten

In anaphase B, microtubules associated with the cell cortex shorten.

Which of the following statements about integrins is false? a. Integrins use adaptor proteins to interact with the microtubule cytoskeleton b. Integrins can switch to an activated state by binding to an ECM matrix molecule c. Integrins can switch to an activated state by binding to an intracellular protein d. Activated integrin molecules takes on an extended conformation

Integrins use adaptor proteins to interact with the microtubule cytoskeleton.

22. Which of the following statements about the anaphase-promoting complex (APC) is false? a. It promotes degradation of proteins that regulate M phase b. It inhibits M-Cdk activity c. It is continuously active throughout the cell cycle d.M-Cdk stimulates its activity

It is continuously active throughout the cell cycle.

20. Which of the following statements about kinetochores is true?

Kinetochores assemble onto chromosomes during late prophase.

28. Which of the following statements is false? a. Cytokinesis in plant cells is mediated by the microtubule cytoskeleton. b. Small membrane vesicles derived from the Golgi apparatus deliver new cell wall material for the new wall of the dividing cell. c.The phragmoplast forms from the remains of interpolar microtubules of the mitotic spindle. d. Motor proteins walking along the cytoskeleton are important for the contractile ring that guides formation of the new cell wall.

Motor proteins walking along the cytoskeleton are important for the contractile ring that guides formation of the new cell wall.

Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G2? a. The cell would be unable to enter M phase. b. The cell would be unable to enter G2. c. The cell would enter M phase under conditions when normal cells would not. d. The cell would pass through M phase more slowly than normal cells.

The cell would enter M phase under conditions when normal cells would not.

What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only? a. Cells would not be able to replicate their DNA. b. The mitotic spindle could not assemble. c. Cells would get larger and larger. d. The cells produced would get smaller and smaller.

The cells produced would get smaller and smaller.

28. Which of the following statements is false? a. The cleavage furrow is a puckering of the plasma membrane caused by the constriction of a ring of filaments attached to the plasma membrane. b. The cleavage furrow will not begin to form in the absence of a mitotic spindle. c. The cleavage furrow always forms perpendicular to the interpolar microtubules. d. The cleavage furrow always forms in the middle of the cell.

The cleavage furrow always forms in the middle of the cell.

Which of the following statements is false? a. DNA synthesis begins at the origin of replication b. Loading of the origin recognition complexes (ORCs) is triggered by S-Cdk. c. Phosphorylation & degradation of Cdc6 help to ensure that DNA is replicated only once in each cell cycle. d. DNA synthesis can only begin after pre-replicative complexes assembles on the ORCs

The loading of the origin recognition complexes (ORCs) is triggered by S-Cdk.

2. Which of the following statements about plant cell walls is true? a. MT cytoskeleton directs the orientation in which cellulose is deposited in the cell wall b. Molecular components of cell wall are the same in all plant tissues c. Bc plant cell walls are rigid, they are not deposited until cell has stopped growing d. Cellulose in cell walls is produced as precursor molecule in the cell & delivered to extracellular space by exocytosis

The microtubule cytoskeleton directs the orientation in which cellulose is deposited in the cell wall.

18. Which of the following statements is true? (a) The mitotic spindle is largely made of intermediate filaments. (b) The contractile ring is made largely of microtubules and actin filaments. (c) The contractile ring divides the nucleus in two. (d) The mitotic spindle helps segregate the chromosomes to the two daughter cells.

The mitotic spindle helps segregate the chromosomes to the two daughter cells.

Which of the following events does not usually occur during interphase? a. Cells grow in size b. Nuclear envelope breaks down c. DNA is replicated d. Centrosomes are duplicated

The nuclear envelope breaks down.