chapter 9 - bio

What condition or event triggers quorum sensing to begin?

a. a sufficient number of bacteria are present

Cancer cells that continue to divide when defective often show changes in what cellular function?

a. apoptosis

Which type of molecule acts as a signaling molecule in yeasts?

b. mating factor

Apoptosis can occur in a cell under what conditions?

d. all of the above

Where do DAG and IP3 originate?

d. they are the cleavage products of the inositol phospholipid, PIP2

Review the activity involved in a signaling molecule binding to an internal receptor, as depicted in the illustration. Identify the best description of the differences between internal receptors and cell-surface receptors.

a. Internal receptors bind to ligands that are hydrophobic and the ligand-receptor complex directly enters the nucleus, initiating transcription and translation. Cell- surface receptors bind to hydrophilic ligands and initiate a signaling cascade that indirectly influences the making of a functional protein.

Epinephrine mediates the fight-or-flight response of the body. One of the effects is to increase the amount of glucose available to muscles. What does the signaling pathway triggered by epinephrine cause to occur in liver cells?

a. activation of metabolism

Why are endocrine signals transmitted more slowly than paracrine signals?

a. ions are too large to diffuse through the membrane.

Which of the following properties prevents the ligands of cell-surface receptors from entering the cell?

b. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane.

What is the function of a phosphatase?

b. a phosphatase removes the phosphate group from phosphorylated amino acid residues in a protein.

Dopamine is a neurotransmitter in the brain that causes long-term responses in neurons and binds to a G-protein-linked receptor. Which of the following chemicals would you expect to increase in concentration immediately after dopamine binds its receptor?

b. cAMP

Why are ion channels necessary to transport ions into or out of a cell?

b. ions are charges particles and cannot diffuse through the membrane, thus they require ion channels.

Cells grown in the laboratory are mixed with a dye molecule that is unable to pass through the plasma membrane. If a ligand is added to the cells, the dye is then observed entering the cells. Interpreting this result, what type of receptor did the ligand bind to on the cell surface?

b. ligand-gated ion channel

The secretion of hormones by the pituitary gland is an example of which type of signaling?

c. endocrine signaling

What is the difference between intracellular signaling and intercellular signaling?

c. intracellular signaling occurs within a cell. Intercellular signaling occurs between cells

Yeast releasing mating factor can be classified as which type of signal?

c. paracrine

The hormone insulin binds to a receptor tyrosine kinase on the surface of target cells. Which of the following steps takes place before phosphorylation of tyrosine residues?

c. the receptor forms a dimer.

What property enables the residues of the amino acids serine, threonine, and tyrosine to be phosphorylated?

c. they contain a hydroxyl group

The same second messengers are used in many different cells, but the response to those second messengers differs in each cell. How is this possible? Compare explanations below and select the one that supports this claim of varying responses.

d. Cells produce different receptors that bind to the same ligand, or the same receptor that binds to the same ligand with different signaling components, activating different responses in each cell.

Aldosterone is a steroid hormone that regulates reabsorption of sodium ions in the kidney tubular cells. What is the probable mechanism of action of aldosterone?

d. it binds to an intracellular receptor and activates gene transcription.

The gas nitric oxide has been identified as a signaling molecule. Which of the following mechanisms of action would you expect from a gaseous molecule?

d. it binds to an intracellular receptor.

How does NF-κB induce gene expression?

d. phosphorylation of the inhibitor IκB dissociates the complex between it and NF-κB, allowing NF-κB to enter the nucleus and stimulate transcription.