Signal Transduction Pathways

In a signal transduction pathway, the signal activates a(n)

• receptor

• hormone

• effector molecule

Signals that travel to distant cells through the circulatory system are known as

• neurotransmitters

• white blood cells

• hormones

Vitamin A is a relatively small, lipid-soluble molecule that can behave as a hormone. Most likely its receptor

• is an ion channel receptor.

• is a protein kinase receptor.

• involves a G protein.

• is not connected to the cell membrane.

A molecule that binds to the particular three-dimensional structure of another molecule’s receptor site is known as a(n)

• responder.

• receptor.

• ligand

Which statement is false?

• Cells are bombarded with numerous signals, but they respond to only a few.

• A cell’s receptors determine whether or not the cell will respond to a signal.

• Receptor proteins are very specific.

• Protein kinase receptors are a type of cytoplasmic receptor.

A benefit of the many steps involved in a protein kinase cascade is that they allow for

• activation or inhibition of many enzymes.

• amplification of the signal.

• distribution of the signal throughout the inside of the cell. d

• variation in the response.

• all the answer choices are correct

How does a protein kinase cascade amplify an intercellular signal?

• The activated G protein binds and activates a second protein, amplifying the signal.

• Sequential activation of protein kinases can lead to the activation of thousands of effector proteins.

• Second messengers create shortcuts that create multiple cascades.

Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?

• Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP

• Epinephrine binds to a cell-surface receptor; the activated receptor catalyzes the conversion of glycogen to glucose

• Epinephrine diffuses through the plasma membrane; the hormone dimerizes in the cytosol

• Epinephrine is taken into the cell by endocytosis; glycogen is converted to glucose in the endocytotic vesicle

Which of the following is correct about signal transduction pathways?

• Signal transduction pathways are found only in the cells of the most complex animals

• Signal transduction pathways have evolved recently along the development of enlarged brain size in mammals

• In the signal transduction pathways, a single molecule can stimulate the release of thoundsands of molecules of product within a cell

• Signal transduction pathways are unique in that receptors that stimulate the pathway are located only on the surface of a plasma membrane

The three stages of cell signalling are

• paracrine, local, and synaptic
• reception, transduction, and response
• transcription, translation, and folding
• alpha, beta, and gamma