A signal molecule that binds to a plasma-membrane protein is a

• ligand
• second messenger
• protein kinase
• receptor protein

What determines whether a cell is a target cell for a particular signal molecule?

• phosphorylation cascade
• cAMP
• signal receptors
• phosphatase

What determines whether a signal molecule binds on the surface or enters the cell?

• size
• polarity
• ability to cross the membrane
• all of these are correct

One very common receptor protein in eukaryotes is the __.

• G protein-coupled receptor

• cAMP receptor

• phosphorylation receptor

• ATP receptor

The binding of a ligand to a ligand-gated ion channel can cause the channel to ___.

• open

• close

• both answers can be correct

A cell converting a chemical signal into a cellular response is known as __.

• energetics

• transduction

• ligand response

• transformation

After a ligand binds, the intracellular domain of a receptor protein changes _____, initiating transduction of the signal.

• color

• size

• shape

One cellular response to a signal is apoptosis, otherwise known as programmed cell ____.

• division

• death

• growth

• reproduction

Which of the following is a chemical message that usually travels through the bloodstream to target cells?

• hormone

• local regulator

• endocrine cell

• plasmodesmata

Signal amplification is most often achieved by

• an phosphorylation cascade

• binding of multiple signals

• branching pathways

• action of adenylyl cyclase