chapter 11 ap bio
What are the functions of signal transduction pathways?
-Signal transduction pathways allow different types of cells to respond differently to the same signal molecule.-Signal transduction pathways convert a signal on a cell's surface to a specific cellular response.-Signal transduction pathways amplify the effect of a signal molecule.
FRQ 1: Growth hormone and Insulinc) 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 2: Fibroblastsc) 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: Fibroblastsb) 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 1: Growth hormone and Insulind) 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 1: Growth hormone and Insulinb) 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 2: Fibroblastsa) 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 1: Growth hormone and Insulina) 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 2: Fibroblastsd) 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
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.
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.
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.
Notch is a receptor protein displayed on the surface of certain cells in developing fruit fly embryos. Notch's ligand is a membrane-bound protein called Delta that is displayed on the surface of adjacent cells. When Notch is activated by its ligand, the intracellular tail of the Notch protein becomes separated from the rest of the protein. This allows the intracellular tail to move to the cell's nucleus and alter the expression of specific genes.Which of the following statements best explains Delta's role in regulating cell communication through the Notch signaling pathway?
Delta restricts cell communication to short distances within a developing embryo.
The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1.A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statements best helps justify the researcher's claim?
Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate.
Cyclic AMP phosphodiesterase is an enzyme that catalyzes the conversion of cyclic AMP to a different molecule. Which of the following best predicts the effect of inhibiting cyclic AMP phosphodiesterase in a muscle cell stimulated by epinephrine?
Glycolysis will stop because epinephrine will no longer stimulate glycogen breakdown
Which of the following statements best describes the role of cyclic AMP in the signal transduction pathway?
It acts as a second messenger that helps relay and amplify the signal within the cell.
Metformin is a drug used to treat type 2 diabetes by decreasing glucose production in the liver. AMP-activated protein kinase (AMPK) is a major cellular regulator of glucose metabolism. Metformin activates AMPK in liver cells but cannot cross the plasma membrane. By blocking AMPK with an inhibitor, researchers found that AMPK activation is required for metformin to produce an inhibitory effect on glucose production by liver cells.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
Ethylene causes fruits to ripen. In a signaling pathway, receptors activate transcription factors, which ultimately leads to ripening.Which of the following best supports the claim that ethylene initiates the signal transduction pathway that leads to ripening of fruit?
Loss-of-function mutations in ethylene receptors result in changes to the ripening process
Figure 1 is a proposed model of the feedback system controlling erythrocyte (red blood cell) production.Air is less dense at very high elevations, so less oxygen is available than in the denser air at sea level. Based on the model in Figure 1, if a person travels from sea level to a high elevation location, which of the following correctly predicts the response to the decreased blood oxygen level?
More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes.
The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1.Cyclic AMP phosphodiesterase is an enzyme that catalyzes the conversion of cyclic AMP to a different molecule. Which of the following best predicts the effect of inhibiting cyclic AMP phosphodiesterase in a muscle cell stimulated by epinephrine?
Phosphorylase kinase will remain active because protein kinase A will no longer be deactivated.
A student claims that the Y chromosome contains the sex-determining region gene, known as the SRY gene, which causes male fetuses to develop testes.Which of the following provides correct information about cell signaling that supports the claim?
The SRY gene produces a protein that binds to specific regions of DNA in certain tissues, which affects the development of these tissues.
Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances?
The proteins interact directly with proteins on the surfaces of other cells.
The coagulation cascade controls blood clot formation in response to blood vessel injury. Thrombin is an enzyme that plays a key role in regulating the coagulation cascade. A simplified model of thrombin's role in regulating the coagulation cascade is represented in Figure 1.Argatroban is a competitive inhibitor of thrombin. Which of the following effects on the coagulation cascade is most likely to result from inhibiting thrombin activity with argatroban?
The rate of fibrin formation will decrease.
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.
In flowering plants, plasmodesmata are narrow channels through cell walls that connect the cytoplasms of adjacent cells. An explanation of how plant cells communicate across cell walls will most likely refer to the diffusion through plasmodesmata of which of the following?
small, water-soluble molecules