LS7C Week 1

In complex multicellular organisms, bulk flow is an important physiologic character. Why is bulk flow a necessary condition of complex multicellularity? a. Organisms exhibiting complex multicellularity are large and have cells/tissues that are not in contact with their environment. Systems that can overcome the limits of diffusion must occur for basic physiologic processes to occur. b. Bulk flow is necessary to move large amounts of liquid through the organism depending on physiologic needs. The tissues can all receive necessary nutrients from the environment, but bulk flow speeds the rate of diffusion. c. Complex multicellularity reflects cell adhesion between cells, and this cannot happen without bulk flow of signaling molecules from the environment. d. Complex multicellularity is related to the increase in oxygen in the environment. Because bulk flow systems are only related to the delivery of oxygen to tissues, higher environmental oxygen selected for individuals with bulk flow systems.

a. Organisms exhibiting complex multicellularity are large and have cells/tissues that are not in contact with their environment. Systems that can overcome the limits of diffusion must occur for basic physiologic processes to occur.

In many cells, the adhesion to the extracellular matrix through integrins causes the activation of kinases in the cytoplasm. This suggests that: a. integrins promote the activation of signal-transduction pathways. b. integrins are kinases. c. extracellular matrix proteins are receptors and integrins are ligands.

a. integrins promote the activation of signal-transduction pathways.

If a mutation occurred in the cadherin gene so that the cytoplasmic domain no longer attached to the cytoskeleton, which of the following would occur? a. Cadherins in adherens junctions would no longer be anchored to microtubules. b. Cadherins in desmosomes would no longer be anchored to intermediate filaments. c. Cadherins in desmosomes would no longer be anchored to microfilaments. d. Cadherins in hemidesmosomes would no longer be anchored to intermediate filaments.

b. Cadherins in desmosomes would no longer be anchored to intermediate filaments.

A decrease in cell adhesion, by the introduction of an experimental substance to a tissue, compromises the structural integrity of the tissue. Which cell junction would MOST likely be affected by this treatment causing a decrease in the strength of the tissue? a. tight junctions b. adherens junctions c. gap junctions d. hemidesmosomes

b. adherens junctions

Figure 9.15 shows how normal signaling works with a Ras protein acting downstream of a receptor kinase. You examine a cell line in which Ras is always activated even in the absence of a signaling molecule. This causes constant activation of the kinases in the MAP kinase pathway. Which of the following conditions would be MOST likely to turn off this abnormally active signaling pathway? a. the addition of a drug that prevents the phosphorylation of the receptor kinase b. the addition of a drug that prevents the final kinase from interacting with its target protein in the nucleus c. the addition of a drug that prevents the dimerization of the receptor kinase d. the addition of a drug that increases the binding affinity of Ras for MAP kinase enzymes in the cytoplasm

b. the addition of a drug that prevents the final kinase from interacting with its target protein in the nucleus

Vascular endothelial growth factor (abbreviated VEGF and pronounced "Veg-F") is a peptide signaling molecule related to platelet-derived growth factor. VEGF is important in the formation of the circulatory system because its signaling pathway causes the formation of blood vessels in developing embryos during normal development. Tumors also produce and secrete VEGF, causing the formation of new blood vessels that supply these tumors. Given what you know about the different kinds of cell signaling and VEGF, which one of the following statements is TRUE? a. VEGF is an endocrine-signaling molecule because it circulates through the bloodstream inside of platelets. b. VEGF is an endocrine-signaling molecule because it is released from platelets into the bloodstream and is carried throughout the body, causing widespread activation of platelet-derived growth factor receptors on cells in a variety of tissues. c. VEGF is a paracrine signaling molecule because it binds to receptors on cells at the site where new blood vessels are needed.

c. VEGF is a paracrine signaling molecule because it binds to receptors on cells at the site where new blood vessels are needed.

A newly discovered signaling molecule that binds to a G protein-coupled receptor is being studied by using cells maintained in cell culture. Preliminary results show that the binding of this new ligand causes the activation of adenylyl cyclase. In the next part of this study, a non-hydrolyzable version of GTP (a form of GTP that cannot be converted to GDP) is added to the cell culture dishes and is taken up by the cells. Which of the following would you expect to observe? a. decreased cAMP, decreased protein kinase A activity b. increased cAMP, decreased protein kinase A activity c. decreased cAMP, increased protein kinase A activity d. increased cAMP, increased protein kinase A activity

d. increased cAMP, increased protein kinase A activity