Once inside the cell, the signal continues on its way. Its ultimate destination depends on the nature of the signal, with some signals traveling to the nucleus or to other structures inside the cell. Signals most often move through the cell by passing from protein to protein, each protein modifying the next in some way. Collectively, the proteins that relay a signal to its destination make up a signaling pathway. A signaling pathway can have few or many steps. Some signaling pathways branch out in different directions, sending signals to more than one place in the cell. As a signal is transferred from protein to protein, it can also be amplified. By dividing and amplifying a signal, the cell can convert a small signal into a large response.
Asignaling pathway: the message is transferred from the receptor (1) to other proteins inside the cell. The proteins work together like runners in a relay race to carry the signal to its destination or destinations.
Signal transduction
Types of signaling molecules and the receptors they bind to on target cells. Intracellular receptors, ligand-gated ion channels, G protein-coupled receptors, and receptor tyrosine kinases.
Signal transduction
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Terms in this set (32)
Which of the following best describes the role of cell-to-cell communication during a response to an invasion of antigens?
Chemicals that are secreted from antigen-presenting cells then activate helper T cells. A
Adjacent plant cells have narrow channels
called plasmodesmata that pass through the cell walls of the connected cells and allow a cytoplasmic connection between the cells.
Which of the following statements best describes a primary function of plasmodesmata?
They allow the movement of molecules from one cell to another, enabling communication between cells. B
A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the
base of the brain. The hormone targets specific cells in many parts of the body.
Which of the following best explains a possible mechanism that would enable the hormone to efficiently reach all of the target cells in the body?
The hormone is released into the bloodstream where it can be transported to all cells with the correct receptors. C
G proteins are a family of receptor proteins that are involved in
transmitting signals from outside a cell to inside a cell. When a signaling molecule binds to a G protein, the G protein is activated. The G protein then activates an enzyme that produces a second messenger called cAMP.
Which of the following describes a critical role of cAMP during the transduction stage of a G protein signal transduction pathway?
cAMP results in the activation of an enzyme that amplifies the signal by acting on many substrate molecules. D
Which of the following best describes the component that metformin represents in a signal transduction pathway that regulates glucose production in the liver?
It is a ligand that activates the signal transduction pathway of the activation of AMPK. B
Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell?
A ligand binds to a receptor. C
During a fight-or-flight response, epinephrine is released into the body's circulatory system and transported throughout the body. Some cells exhibit a response to the epinephrine while other cells do not.
Which of the following justifies the claim that differences in components of cell signaling pathways explain the different responses to epinephrine?
Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors for epinephrine. Only cells with such receptors are capable of responding.
Signal transduction may result in changes in gene expression and cell function, which may alter phenotype in an embryo. An example is the expression of the SRY gene, which triggers the male sexual development pathway in mammals. This gene is found on the
Y chromosome.
Which statement provides the evidence to justify the claim that signal transduction may result in an altered phenotype?
If the SRY gene is absent or nonfunctional, the embryo will exhibit female sexual development. B
Which of the following statements best justifies the claim that changes in the expression of ced−9 in C. elegans can affect regulation of apoptosis in the cell?
An experiment showed that a mutation in the ced−9 gene led to excessive cell death in C. elegans. A
[figure 1. A simplified model of the insulin receptor- signaling pathway]
Which of the following statements best predicts the effect of a loss of function of the insulin receptor's intracellular domain?
The storage of GLUT4 in vesicles inside the cell will increase.
[Figure 1. A simplified model of the signal transduction cascade triggered by epinephrine binding to the beta-2 adrenergic receptor]
Which of the following outcomes will most likely result from the inactivation of the beta-2 adrenergic receptor?
The rate of glycogen synthesis in the cell will increase. D
[Figure 1. A simplified model of FGFR activation]
Which of the following changes in the FGFR signaling pathway is most likely to result in uncontrolled cell proliferation?
The irreversible association of FGFR proteins. A
[figure 1. The enzyme-substrate interactions of PFK {allosteric inhibition}]
A researcher found a mutation that resulted in the PFK enzyme being unable to bind ATP to the allosteric site. Which of the following best predicts the effect of the mutation?
Negative feedback regulation does not occur, so the enzyme will be active when glycolysis is not needed. B
[figure 1. GRAPH, Blood glucose fluctuations of an individual]
Which of the following best predicts what will happen to the blood glucose level if the person has another meal at 5 p.m?
Immediately after the meal, the blood glucose level will increase, and then insulin will be secreted to counter the increase. B
[figure 1. Simplified model of clotting cascade]
Warfarin is a drug used to treat certain blood clots. Warfarin blocks the formation of the active form of vitamin K-dependent clotting factors. Based on the model, which of the following best predicts the effects of warfarin on a patient?
Factor X will not be activated, which will prevent thrombin from forming. D
[figure 1. Typical life cycle of a eukaryotic cell]
Based on Table 1, what percent of the life cycle of yeast cells is spent in DNA replication?
25 percent C
[figure 1. BAR GRAPH Mean cell doubling times for the growing root tips of Zea mays seedlings planted in loose or compact sand]
Based on the sample means, which of the following conclusions about the cells in the growing root tips of Zea mays seedlings is best supported by the results of the experiment?
More cells are produced per unit of time in the root tips growing in compact sand than in the root tips growing in loose sand. D
[Figure 1. LINE GRAPH Relative amounts of DNA present in the nucleus of a cell]
Based on Figure 1, which of the following statements correctly links a stage of the cell cycle with the event occurring at that stage?
Synthesis of sufficient DNA for two daughter cells occurs in stage II. B
[Figure 1. FLOW CHART Amount of DNA in picograms per cell over several rounds of cell division]
Which of the following statements is consistent with the data in Figure 1?
There is a change from 3 to 6 picograms of DNA because DNAis replicated before each round of cell division. C
[Table 1. Number of normal and infected cells found in three phases of the cell cycle]
Which of the following most accurately describes an observation and an effect of the viral infection indicated by the data in Table 1?
Seventy-five percent of the virus-infected cells are found in mitosis. The virus stimulates frequent cell division.
[Table 1. Number of cells in each of four different stages of mitosis]
Based on the data, the percent of the mitotic cells that were in metaphase is closest to which of the following?
18% C
The epidermal growth factor receptor EGFR is a cell surface receptor. When a growth factor binds to EGFR, the receptor is activated. The activated EGFR triggers a signal transduction pathway, which leads to increased frequency
of cell division.
Which of the following best predicts the effect of a mutation that causes EGFR to be active in the absence of a growth factor?
B)
Increased cell division will lead to the formation of a tumor.
The tumor suppressor protein p53 binds to DNA and activates target genes, which results in the synthesis of p21, CD95, and other proteins. The p21 protein promotes cell-cycle arrest, whereas the
CD95 protein promotes apoptosis.
Which of the following will most likely result from a loss of p53 function?
Uncontrolled cell proliferation C
[figure 1. Representation of the cell cycle and identification of the G1/S checkpoint]
Which statement best predicts why a cell's progression through the cell cycle might be halted at the G1/S checkpoint?
There are not enough nucleotides available to construct new DNA. B
FRQ 1: Growth hormone and Insulin
a) Describe the first interaction that triggers signaling to begin in a target cell.
-indicate that ligand/chemical messenger, (a hormone), binds to receptor protein in target cell
FRQ 1: Growth hormone and Insulin
b) Identify a dependent variable i the experimental design. Identify a negative for the effects of hormone addition. Identify a likely reason why the researchers continued their experiment for 240 minutes.
-dep. variable= level of phosphorylated signal protein OR level of phosphorylated STAT5 OR level of phosphorylated protein kinase B
-neg. control for effects of hormone addition= zero time point when hormone is added OR adding no hormone OR adding denatured hormone to identical culture and taking samples at same time points
-response to the hormone might take some time to start OR researchers might have wanted to see how long response to hormone lasted
FRQ 1: Growth hormone and Insulin
c) Describe the hormone and signaling protein combination that produced the greatest and most prolonged response. For the STAT5 response that reached 100% at 10 minutes in Figure 1A, calculate rate the rate of decrease (% decrease per minute) in teh detected level of phosphorylated STAT5 from 10 to 30 minutes.
-addition of insulin caused high level of phosphorylated protein kinase B (about 80% of maximum) right to end of experiment at 240 minutes
-rate of decrease= 3% to 3.5% per minute
(100% - 35%= 65% 65% / 20 = 3.25% per minute)
FRQ 1: Growth hormone and Insulin
d) The researchers claim that the similar regulation of carbohydrate metabolism by hepatocytes when the cells are treated with growth hormone or insulin results from the activation of different signaling pathways. Use the data from the researchers' experiment to support their claim.
-data shows different signaling proteins are phosphorylated by the two different hormones, which supports researchers' claim
FRQ 2: Fibroblasts
a) Based on the data for the groups of cells cultured with 0.1% serum (groups 3-7), identify which of the four proteins tested do(does) not appear to play a role in blocking cell cycle entry by fibroblasts.
-group 3 in which p16 is blocked does not appear to play role in blocking cell cycle entry
FRQ 2: Fibroblasts
b) Based on the data for the groups of cells cultured with 0.1% serum (groups 3-7), identify the group(s) most likely to include cells undergoing mitosis.
-cells undergoing mitosis are most likely found in group 7 OR in groups [paper cuts off] and 7
FRQ 2: Fibroblasts
c) Neurons (nerve cells) of the central nervous system (brain and spinal cord) and in G0 of the cell cycle and generally do not divide in response to an inquiry. The scientists predict that they can use the data from this experiment to help them treat individuals who suffer from spinal cord injuries. Provide reasoning to support the scientists' prediction.
-because blocking in some of the cyclin-dependent kinase inhibitors in experiment made fibroblasts divide, scientists might also successfully block different cyclin-dependent kinase inhibitors in neurons of spinal cord to make neurons reenter cell cycle and divide
FRQ 2: Fibroblasts
d) Interactions between cyclins and cyclin-dependent kinases control the cell cycle. Explain how the presence or absence of inhibitors of cyclin-dependent kinases might play a role in normal cells becoming cancer cells.
-lack of appropriate cyclin-dependent kinase inhibitors might let cyclins and cyclin dependent kinases continue to form active complexes that'll result in almost continuous cell cycling with DNA replication and cell division
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