Chapter 6

Which of the following statements is not true? During signal transduction (a) the cell converts an extracellular signal into an intracellular signal (b) nitric oxide is typically produced (c) the signal is amplified (d) relay of the signal is regulated (e) the signal is terminated

Which of the following statements is not true? Local regulators (a) are signaling molecules (b) typically carry on paracrine regulation (c) include growth factors (d) transmit electrical signals (e) signal target cells

In animals, hormones (a) are secreted by endocrine glands (b) are electrical signals (c) include neurotransmitters (d) terminate signals during signal transduction (e) are primarily produced by glands with ducts

When a ligand binds with a receptor, (a) G proteins are inactivated (b) a third messenger is activated (c) cell signaling is stopped (d) the signaling cell is activated (e) the receptor is activated

A G protein-linked receptor (a) inactivates G proteins (b) activates first messengers (c) consists of 18 transmembrane alpha helices (d) is a member of a family of about 10 different receptors (e) has a tail that extends into the cytosol and has a binding site for a G protein

An enzyme-linked receptor (a) is an integral membrane protein (b) would not be found on plant cell surfaces (c) aggregates with another enzyme-linked receptor when a ligand binds to it (d) is typically an adenylyl cyclase molecule (e) typically activates ion channels

G proteins (a) relay a message from the activated receptor to an enzyme that activates a second messenger (b) are GTP molecules (c) terminate cell signaling (d) directly activate protein kinases (e) function as first messengers

When activated, a G protein (a) consists of four subunits (b) releases GDP and binds with GTP (c) detaches from adenylyl cyclase (d) acts as a second messenger (e) typically terminates a signaling cascade

Which is the correct sequence? 1\. phospholipase activated \(2 .\) G protein activated \(3 .\) PIP \(_{2}\) split 4\. proteins phosphorylated 5. DAG produced (a) 1,2,5,3,4 (b) 4,2,3,1,5 (c) 2,1,3,5,4 (d) 5,2,3,1,4 (e) 2,3,5,4,1

Ras proteins (a) act as second messengers (b) are growth factors (c) are transcription factors (d) are a group of small R proteins (e) trigger a cascade of reactions that can activate genes

Nitric oxide (a) binds directly with GTP (b) stimulates the blood vessel dilation necessary for penile erection (c) is released by many target cells (d) acts as a second messenger (e) is a signaling molecule that combines with enzyme-linked receptors

Scaffolding proteins (a) release kinases and phosphatases into the extracellular fluid (b) increase the probability that an enzyme can be used by several different pathways (c) increase accuracy but slow signaling cascades (d) organize groups of intracellular signaling molecules into signaling complexes (e) are found mainly in plant cells

Each adenylyl cyclase molecule produces many cAMP molecules. This is an example of (a) receptor up-regulation (b) receptor down regulation (c) signal amplification (d) scaffolding (e) paracrine regulation