Concept explainers
The sheet of cells that form the gut epithelium folds into peaks called villi and valleys called crypts. The cells within the crypt region secrete a protein, Netrin-1, that becomes concentrated within the crypts. Netrin-1 is the ligand for a receptor protein that is found on the surface of all gut epithelial cells. Netrin-1 binding triggers a signal pathway that promotes cell growth. Gut epithelial cells undergo apoptosis (cell death) in the absence of Netrin-1 ligand binding.
a. How would you characterize the type of signaling (autocrine, paracrine, endocrine) found in this system?
b. Predict where the greatest amount of cell growth and cell death would occur in the epithelium.
c. The loss of the Netrin-1 receptor is associated with some types of colon cancer. Suggest an explanation for the link between this signaling pathway and tumor formation.
Want to see the full answer?
Check out a sample textbook solutionChapter 9 Solutions
BIOLOGY VOL. II
- Cytokine receptors and tyrosine kinase receptors are similar in all of the following ways EXCEPT one. Which one is the exception? O They are both down-regulated by lysosomal degradation They both involve receptor exoplasmic domain dimerization They both result in an effector protein entering the nucleus O They both involve cytosolic domain phosphorylationarrow_forwardGLUT4 is a protein channel that facilitates the transport of glucose into the cell. Under nor- mal conditions, some of the GLUT4 proteins that are synthesized by the cell do not become active and are instead stored within the membranes of vesicles. The insulin receptor tyrosine kinase (TRK) is a receptor protein that facilitates the decrease of glucose concentration in the bloodstream by increasing the uptake of glucose by cells. When the insulin hormone binds the insulin TRK receptor, a signal transduction pathway causes the activation and addition of GLUT4 to the cell membrane. A model of this signal transduction pathway is illustrated in the figure below. insulin insulin receptor cytoplasm A model of the insulin TRK receptor signal-transduction pathway. Which of the following best predicts the effect of a loss of function of the insulin TRK2 A B C D The stimulation of the signal transduction pathway will increase. The storage of GLUT4 inside the cell will increase. The concentration…arrow_forwardWould an antibody response against the B subunit protect against the effects of the toxin?arrow_forward
- urgntarrow_forwardBinding of talin induces a separation of α and β subunits and induces conformational changes that results in the Integrin to bind extracellular matrix ligands. This is an example of Question options: Fibronectin Inside-out signaling Outside-in signaling All of the abovearrow_forwardCholera toxins, produced by the pathogenic bacteria Vibrio cholerae, disrupt G Protein Coupled Receptor (GPCR) signaling pathways. They interfere with... the ability of the beta subunit of a G protein to bind to the GPCR the ability of the gamma subunit of a G protein to exchange GDP for GTP the ability of the beta subunit of a G protein to bind to an effector protein the ability of the alpha subunit of a G protein to hydrolyze GTP to GDParrow_forward
- Below is a diagram of the canonical Wnt signalling pathway. Numbers 1-7 refer to different molecules involved in the pathway. Numbers 1-7 on the diagram indicate molecules that are involved in the Wnt signalling pathway, but their names have not been given. Identify the missing components and write their names against the numbers 1-7 given below: 1. 2. 3. 4. 5. 6.arrow_forwardMolecule X is a soluble protein that is secreted in response to extracellular signal Y. Which sorting signal must molecule X have?arrow_forwardGap junctions and tunneling nanotubes are two distinct types of direct intracellular communication. In comparing and contrasting gap junctions and tunneling nanotubes, which of the following statements is true? gap junctions provide a portal for small molecules, proteins and small organelles to move from cell to cell, tunneling nanotubes only permit small molecules to pass between cells typically, there are only two gap junctions that exist between adjacent cells that are communicating via this mechanism; on the other hand, there are many tunneling nanotubes between communicating cells both gap junctions and tunneling nanotubes can pass small molecules between cells none of the above is truearrow_forward
- a) b) d) You, a Jojo's Bizzare Adventures fan, hear about the upcoming part 6 as an anime. You get very excited to the point where your heart just stops beating and you almost die. You are taken into the hospital and the doctor tells you that Ca2+ is not being released intracellularly, causing your heart to stop contracting. This may be due to which protein? Adenylyl Cyclase Intracellular Docking protein Protein Kinase A Phospholipase Carrow_forwardYou perform a competition study on a GPCR. You have isolated the plasma membrane from cells which contains the GPCR of interest. If an agonist and an inverse agonist are at equal concentrations in your study but the inverse agonist has a 10 x higher affinity for the receptor than the agonist, what would you expect to be the overall outcome to be? More of the agonist is bound and so most of the receptor is in its active conformation and is stimulated More of the inverse agonist is bound and so most of the receptor is in its inactive conformation and is unstimulated.arrow_forwardThe figure below illustrates a model of a signal transduction cascade, initiated by the bind- ing of a ligand to a membrane-bound receptor. ligand A partial model of a signal transduction pathway A inactivated molecules B -receptor protein A D activated molecule 1 Based on the figure, which of the following describes the most likely outcome of a mutation that changes the intracellular region of receptor protein A? activated molecule 2 activated molecule 3 The receptor will not activate molecule 1, but the activation of molecules 2 and 3 will continue at lower rates. Molecule 1 will not become activated, preventing the activation of molecules 2 and 3 and the subsequent cellular response. с The ligand will not be able to bind the membrane-bound receptor, preventing the signal transduction pathway from initiating. The ligand that binds to protein A will not enter the cell, preventing the cellular response from occurring.arrow_forward
- Biology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStax