BIOL 150 – Quiz 9 – Flashcards

A chemical that binds to a cell to cause its activity to change is an example of which of the following elements of cellular communication? - A receptor molecule - A signaling molecule - A responding cell - Non of these choices are correct. - A signaling cell

Which of the following types of cellular activities can be a response to cell signaling? - Cell division is triggered. - All of these choices are correct. - Gene expression patterns are changed. - Cell signals are released to communicate with other cells. - Enzyme activity patterns are changed.

Which of the following statements about communication among bacteria is correct? (Select all correct choices.) - Small peptides can stimulate a DNA-uptake response. - Cellular communication in bacteria is based on the same principles as communication within multicellular organisms. - Unlike eukaryotes, in bacterial communication no receptor molecule is required. - At lower population density, a higher concentration of signaling molecules is typically observed.

Many mutations in receptor kinases that lead to cancer allow the dimerization and activation of the receptor, even in the absence of signaling molecule. An example of this is a mutant form of the EGF receptor kinase called Her2/neu. An antibody that prevents dimerization of Her2/neu receptor kinases is being tested for its effectiveness in stopping cancer. At which stage would this drug work? - It would prevent the receptor from binding to the signal. - It would prevent the receptor from becoming activated. - It would prevent the termination of the signal. - It would prevent the signaling cell from producing the signal.

Kohler and Lipton first discovered a growth factor (PDGF) by : - Observing that fibroblasts could not grow in cell culture without the addition of purified red blood cells. - Observing that fibroblasts could not grow and repair wounding without the action of platelets. - Observing that fibroblasts could not grow in cell culture without adding PDGF to the growth medium. - Observing that fibroblasts could not grow in cell culture without adding bovine blood serum to the growth medium. - Observing that fibroblasts grew better in cell culture when blood serum was added to the growth medium instead of blood plasma.

Communication between cells always involves four components, including a signaling cell, a signaling molecule, a receptor, and a target responding cell. True or false: A specific signaling molecule may bind to receptors on more than one kind of cell.

Communication between cells always involves four components, including a signaling cell, a signaling molecule, a receptor, and a target responding cell. True or false: Receptors for signaling molecules are always integral membrane proteins on the surface of responding cells.

Communication between cells always involves four components, including a signaling cell, a signaling molecule, a receptor, and a target responding cell. True or false: Signaling molecules involved in endocrine signaling are always hydrophobic hormones like testosterone.

According to Fig. 9.6, what is a key difference between cell signaling mediated by a surface receptor, compared to that mediated by an intracellular receptor? - Signaling molecules that bind to cell-surface receptors lead to cellular responses restricted to the cytoplasm; signaling molecules that bind to intracellular receptors lead to cellular responses restricted to the nucleus. - Cell-surface receptors bind to specific signaling molecules; intracellular receptors bind any signaling molecule. - Cell-surface receptors bind polar signaling molecules; intracellular receptors bind nonpolar signaling molecules. - None of these statements about cell signaling differences is correct. - Cell-surface receptors typically bind to smaller signaling molecules than those bound by intracellular receptors.

Types of steroids include: - Insect molting hormones. - Lipid-soluble hormones derived from cholesterol. - Glucocorticoids that regulate blood glucose levels. - Sex hormones such as estrogen and testosterone. - All of these choices are correct.

In spite of their heterogeneity, steroid hormones: - Bind intracellular receptors to form complexes that migrate to the nucleus. - Bind to cell-surface receptors. - Have the same effect on different types of cells. - Are hydrophilic small molecules that bind to intracellular receptors. - Facilitate the initiation of translation by ribosomes.

Which of the following would NOT be considered a cell-surface receptor? - A receptor that allows ions to enter the cell when a ligand binds - A receptor that binds a non polar steroid hormone and activates transcription - A receptor that causes GDP to be exchanged for GTP in a G protein - A receptor that must form a dimer after binding the ligand to transmit a signal

How are steroid hormone receptors and cell-surface receptors similar? - When activated the signals of both types are transducer across the plasma membrane. - Both types causes GDP to be exchanged for GTP in a G protein. - Both types undergo a conformational change when they bind to their ligand. - When bound to their ligand, both types enter the nucleus to activate transcription.

A G protein: - All of these choices are correct. - Is a component of a signal-transduction pathway that is coupled to a G protein-coupled receptor. - Becomes deactivated when bound GTP is dephosphorylated to GDP. - Releases GDP and binds to GTP when associated with an activated receptor. - Is composed of three subunits and is inactive when bound to GDP.

Second messengers: - Play a role in activation of intracellular signal transduction. - All of these choices are correct. - Are small intracellular molecules that participate in signal transduction. - Amplify the effects of the signal. - Are removed in order to terminate a cellular signaling response.

According to Fig 9.10, which of the following is NOT responsible for amplifying the signal in a cell responding to adrenaline signaling? - The production of cAMP by adenylyl cyclase - The binding of the receptor by adrenaline - The phosphorylation of proteins by protein kinase A - All of these choices amplify the adrenaline signal. - The activation of protein kinase A by cAMP

A cellular response to a signal can be terminated by: - Depletion of a second messenger. - All of these choices are correct. - Inactivation of intracellular signal-transduction proteins. - Automatic inactivation of proteins in the signal pathway over time. - Depletion of the signal that activates the receptor.

Why do the functions of many receptor kinases depend on the fluid nature of the plasma membrane? - The generation of cAMP requires a fluid membrane. - The receptor monomers must move together and dimerize to be activated. - Phosphorylation requires a fluid membrane. - Binding of ligand to the receptor requires a fluid membrane.