BIOL Chapter 9 Review

Examples of endocrine signalling Complete the sentences with the correct terms.

- In direct intracellular signaling, signals pass through a cell junction from one cell to adjacent cells. - Membrane-bound signals bind to receptors on adjacent cells in the process of contact-dependent signaling. - An example of autocrine signaling is when cells release signals that affect themselves and nearby target cells. - In paracrine signaling, cells release signals that affect nearby target cells. - Cells release signals that travel long distances to affect target cells during endocrine signaling.

Signal transduction composition Complete the sentences with the correct terms.

- Intracellular receptors are activated by signaling molecules that pass through the plasma membrane. -vIn extracellular signaling, ligands bind to cell surface receptors. -vMost types of enzyme-linked receptors function as protein kinases. - In mammals, receptors for steroid hormones are intracellular.

Arrange the following in the proper order in which they occur during signal amplification. 1. Activation of protein kinase 2. Activation of G protein 3. Activation of adenylyl cyclase

2, 3, 1

Epinephrine inhibits salivary gland activity and muscle cell contraction in the airways, yet stimulates glycogen release in muscle cells and heart muscle cell contraction. How could one hormone have opposing effects on different organs?

Cells in the different tissues would have epinephrine receptors coupled to different signaling pathways.

The sodium channel is formed by a channel protein. Which of the following statements about channel proteins is TRUE?

Channel proteins can be opened or closed by cell signaling molecules.

Epinephrine has to cross the cell membrane to bind to its receptor in the cytoplasm.

False

The second messenger cAMP is made from ADP.

False

The binding of epinephrine to its receptor activates a(n)

G protein.

Nicotine is a molecule that is chemically similar to acetylcholine and binds to the same receptors. What affect will nicotine have on the cell shown in the animation?

It will open sodium channels.

Which of the steps in a signal cascade is NOT involved in signal amplification?

Several extracellular signal molecules bind to several cell surface receptors

Why is it possible for Na+ to enter the cell when the channel is open?

The Na⁺/K⁺ pump previously built a high concentration of Na⁺ on the outside of the cell, so Na⁺ is diffusing.

If a ligand were stuck in the G-protein-linked receptor, what would be the effect to the cell?

The pathway would be over active.

Cell surface receptors may be enzyme-linked or G protein-linked.

True

Most signaling molecules are found in low concentrations inside the cytoplasm.

True

Sodium channels have receptor sites for acetylcholine

True

The alpha subunit can repeatedly dissociate from and associate with the remainder of the G-protein as long as the ligand is bound to the receptor.

True

The second messenger cAMP is synthesized by the enzyme

adenylyl cyclase.

The ligand that activates the G-protein linked receptor is ______.

an extracellular signaling molecule

An example of a second messenger is

cAMP.

The enzyme alpha-kinase adds ________ to proteins.

phosphates

As a result of the ligand binding to its site on the G-protein-linked receptor,

the G-protein changes conformation and GTP replaces the GDP on the alpha subunit.