CELL BIO QUIZ's 3 & 4

BrdU and EdU are frequently used as assays to measure the number of actively proliferating cells. Why does the incorporation of these synthetic nucleotides into cellular DNA reflect active cell proliferation? BrdU and EdU are fluorescent, so cells take up the reagents when the nuclear envelope breaks down. BrdU and EdU are necessary for cells to divide. BrdU and EdU are analogs of thymidine, and are added to the new DNA strand at replication. BrdU and EdU are analogs of ATP, which is necessary for cells to proliferate.

BrdU and EdU are analogs of thymidine, and are added to the new DNA strand at replication.

Which of the following statements is true? Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior. To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol. Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response that is produced by that signal molecule on the same cell type. A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response.

Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.

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

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

Which of the following events does not usually occur during interphase? The nuclear envelope breaks down. Cells grow in size. DNA is replicated. The centrosomes are duplicated.

The nuclear envelope breaks down.

Which of the following statements is true? Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism. Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal. The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling. The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells.

The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling.

The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? a mutation that destroys the kinase activity of the receptor a mutation that prevents the binding of the normal extracellular signal to the receptor a mutation that prevents dimerization of the receptor a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor

a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor

Of the following mutations, which are likely to cause cell-cycle arrest? a mutation that inhibited the activity of Rb a mutation in a gene encoding a cell-surface mitogen receptor that makes the receptor active even in the absence of the mitogen a mutation that destroyed the kinase activity of S-Cdk a mutation that allowed G1-Cdk to be active independently of its phosphorylation status

a mutation that destroyed the kinase activity of S-Cdk

The TGFβ superfamily of receptors are membrane-bound receptor tyrosine kinases. Dimerization of TGFβ receptors causes repression of the signaling pathway via phosphorylation. activation of the signaling pathway via glycosylation. activation of the signaling pathway via phosphorylation. activation of the signaling pathway via nitrosylation.

activation of the signaling pathway via phosphorylation.

In paracrine signaling, the signaling molecule? acts on the same cells that secreted the signaling molecule. is carried to the target cells by the blood. acts on cells in close proximity to the secreting cell. acts on target cells far away from the secreting cell.

acts on cells in close proximity to the secreting cell.

Cell cycle events monitored by checkpoint pathways include cell growth. all of the other answers are correct spindle position. DNA damage.

all of the other answers are correct

Cyclins? propel the cell cycle forward by regulating the stage in which they are expressed, and set in motion the preparation events necessary for the next stage. bind and activate cyclin-dependent kinases. are present only during the cell cycle stage that they trigger. all of the other answers are correct

all of the other answers are correct

What kinds of cell behaviors could be elicited by receiving an extracellular signal? cell movement cell proliferation cell death all of the other answers are correct

all of the other answers are correct

What kinds of molecules act as extracellular signals? proteins ions lipids all of the other answers are correct

all of the other answers are correct

In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated? at the transition between G1 and S when cells enter G0 during M at the end of G2

at the end of G2

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

by means of an intracellular suicide program

Which of the following mechanisms is not directly involved in inactivating an activated RTK? dephosphorylation by serine/threonine phosphatases removal of the RTK from the plasma membrane by endocytosis dephosphorylation by protein tyrosine phosphatases digestion of the RTK in lysosomes

dephosphorylation by serine/threonine phosphatases

Mitogens are _____. transcription factors important for cyclin production. kinases that cause cells to grow in size. produced by mitotic cells to keep nearby neighboring cells from dividing. extracellular signals that stimulate cell division.

extracellular signals that stimulate cell division.

Foreign substances like nicotine, morphine, and menthol exert their initial effects by _____. diffusing through cell plasma membranes and binding to transcription factors to change gene expression. killing cells immediately, exerting their physiological effects by causing cell death. removing cell-surface receptors from the plasma membrane. interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus.

interacting with cell-surface receptors, causing the receptors to transduce signal

The creation of cells from pre-existing cells via a regulated cycle of events is known as proliferation procreation procrastination proletariat

proliferation

Progression through the cell cycle requires a cyclin to bind to a Cdk because _________. the cyclins are the molecules with the enzymatic activity in the complex. without cyclin binding, a cell-cycle checkpoint will be activated. the binding of a cyclin to Cdk is required for Cdk enzymatic activity. cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle.

the binding of a cyclin to Cdk is required for Cdk enzymatic activity.

How are signals generated by a sending cell transported over long distances to a receiving cell? via second messengers via the bloodstream via the extracellular matrix via metastasis

via the bloodstream

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

The cells produced would get smaller and smaller.

Commitment of a cell to a new cell division (referred to as "START") occurs in M S G1 G2

G1

Which of the following is the correct series of events leading to the creation of a new cell? G1 - G2 - S - M - cytokinesis G1 - M - cytokinesis - S - G2 G1 - cytokinesis - S - M - G2 G1 - S - G2 - M - cytokinesis

G1 - S - G2 - M - cytokinesis

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? The cell would pass through M phase more slowly than normal cells The cell would be unable to enter G2. The cell would be unable to enter M phase. The cell would enter M phase under conditions when normal cells would not.

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