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Chapter 4

Self-Study Quiz

Self-Study Quiz

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This activity contains 20 questions.

	___________are specialized protein complexes that create an aqueous pore between the cytoplasms of two adjacent cells.   Hormones Receptors Gap junctions Ion channels

	How do most hydrophobic chemical messengers get transported to a target cell?   They dissolve easily in the circulatory fluids. They bind to hormones in the blood. They move from cell to cell through gap junctions. They bind to carrier proteins in the blood.

	When a chemical messenger (or ligand) reaches a target cell, it binds to a receptor. A hydrophobic ligand binds to a(n)________, whereas a hydrophilic ligand binds to a(n) ___________.   intracellular receptor; transmembrane receptor transmembrane receptor; intracellular receptor agonist receptor; antagonist receptor autocrine receptor; paracrine receptor

	The strength of binding between a ligand and a receptor is usually expressed as the   Km. endocrine constant. affinity constant (Ka). paracrine constant.

	A transcription factor is a receptor with three domains: a ligand-binding domain, a DNA-binding domain, and a transactivation domain. What kind of receptor is a transcription factor?   intracellular receptor receptor enzyme ligand-gated ion channel G-protein-coupled receptor

	How does a ligand-gated ion channel work?   When a ligand binds to an ion channel, an enzyme facilitates the passage of ions across the membrane. When a ligand binds to an ion channel, the channel interacts with a G-protein that subsequently opens another ion channel nearby, allowing ions to cross the membrane. A ligand-gated ion channel is generally open and allows ions to cross the membrane. However, in the presence of a ligand, an ion channel will close. When a ligand binds to an ion channel, the channel changes conformation and the ion channel opens, allowing ions to cross the membrane.

	Which of the following statements about receptor-enzymes is false?   A receptor-enzyme has an extracellular ligand-binding domain, a transmembrane domain, and an intracellular catalytic (enzyme) domain. Three types of receptor-enzymes found in animals are 1) receptor guanylate cyclases 2) receptor tyrosine kinases, and 3) receptor serine/threonine kinases. The signal transduction pathways of receptor-enzymes involve phosphorylation cascades. Receptor-enzymes interact with an intracellular protein called a "G-protein".

	_____________ rely on ___________, such as Ca2+, cyclic GMP, phosphatidylinositol, and cyclic AMP, to activate (or inactivate) a variety of pathways within the cell.   Intracellular receptors; ligands G-protein-coupled receptors; second messengers Receptor-enzymes; G-proteins G-protein-coupled receptors; G-proteins

	Which of the following statements about G-protein signaling pathways is false?   The first second messenger to be identified was cAMP. Most Ca2+ -mediated signal transduction cascades act through the protein calmodulin, a Ca2+ -binding protein that is present in every eukaryotic cell. Receptor serine/threonine kinases directly activate G-proteins, which in turn activate second messengers. Inositol triphosphate (IP3) and diacylglyerol (DAG) act as second messenger in two branches of the phosphatidylinositol signaling pathway.

	The autocrine/paracrine signaling system has a ____________signaling distance and ___________duration of response.   short; long long; long long; short short; short

	Communication among neurons and between neurons and other target cells occurs across short distances at a structure called the __________, a region where the signaling cell and the target cell are very close together.   synapse neurotransmitter catecholamine neural receptor

	Which of the following is not a chemical class of hormones?   amines peptides MAP kinases steroids

	Because steroids generally act by _______________, their effects are typically _______________ than the effects of peptide hormones.   regulating transcription; slower activating second messengers; slower opening ion channels; faster regulating transcription; faster

	Norepinephrine, acetylcholine, and serotonin are what kind of hormones?   peptide hormones steroids prohormones amines

	Animals use _____________ cell-to-cell communication to send signals between individuals.   gap junction autocrine exocrine paracrine

	_____________ are chemicals released by one animal that cause reactions in another animal of the same species.   Pheromones Tropic hormones Mineralocorticoids Exocrine glands

	In a ______________, a sense organ senses the stimulus and sends a signal to the integrating center (e.g., the brain), which sends out a signal via a neuron to an endocrine gland. The endocrine gland releases a hormone into the circulatory system, which carries the hormone to the target organs (e.g., heart, lungs, and muscles).   third-order feedback loop second-order feedback loop first-order feedback loop direct feedback loop

	Scientists hypothesize that cell signaling in animals evolved from   ancestral ion channel receptors in bacteria. mitochondrial signaling pathways. ancestral mechanisms that unicellular organisms use to sense their environment. phosphate signaling pathways in plants.

	Which of the following statements related to the evolution of cell signaling is false?   Similar to animals, bacteria possess transmembrane receptor proteins that have an extracellular ligand-binding domain, a membrane-spanning domain, and an intracellular signaling domain. Scientists believe that pheromones evolved only recently, as there is no evidence that they exist in unicellular organisms. Cell signaling pathways in plants and animals share many common features, but they are also distinctly different from each other. Many unicellular eukaryotes including yeast and slime molds have complex cell signaling systems that use chemical messengers.

	What is ecdysone?   A G-protein-coupled receptor found only in invertebrates. A neurotransmitter found only in invertebrates. A steroid hormone found only in vertebrates. A steroid hormone found only in invertebrates.

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