Chapter 6: Cell Signals and Responses

Question 1

Signal transduction pathway

Answer 1

a sequence of molecular events and chemical reactions that lead to a response to the signal

Question 2

Juxtacrine signals

Answer 2

diffuse between cells through gap junctions and plasmodesmata or a membrane-bound signal binds to a membrane receptor

Question 3

In plants, _______ can allow long-distance transport

Answer 3

plasmodesmata

Question 4

Chemical signals travel to target by _____

Answer 4

diffusion

Question 5

Paracrine signals

Answer 5

bind to receptors on nearby cells

Question 6

Autocrine signals

Answer 6

bind to receptors on the same cell that secreates them

Question 7

How do cells signal from a distance?

Answer 7

Endocrine signals (hormones) are transported by the circulatory system and bind to receptors on distant cells

Question 8

Ligand binding causes receptor protein to ______

Answer 8

change shape (shape change activates receptor)

Question 9

Steps to a signal transduction pathway

Answer 9

• signal arrives at target cell, binds to a receptor protein, which changes 3D conformation of the receptor
• the activated receptor activates a signal transduction pathway
• signal transduction pathway activates the cell’s response

Question 10

Short-term signal changes

Answer 10

enzyme activation, cell movement

Question 11

Long-term signal changes

Answer 11

altered DNA transcription

Question 12

signal transduction often involves enzymes that exhibit ______

Answer 12

allosteric regulation

Question 13

T/F Binding is noncovalent and reversible

Answer 13

T; ligands are not changed by binding

Question 14

Intracellular/cytoplasmic receptors

Answer 14

A nonpolar signal can diffuse directly across the lipid bilayer of the cell membrane to encounter it’s receptor in the cytosol or nucleus; it can enter the nucleus and affect gene expression

Question 15

Membrane receptor

Answer 15

A signal that is polar and/or large cannot diffuse through the cell membrane, so its receptor is embedded in the membrane

Question 16

Three examples of Membrane receptors

Answer 16

Ion channel, protein kinase receptors, G protein-linked receptors

Question 17

Signals for ion channel receptors

Answer 17

chemical ligands, electric charge differences, sensory stimuli

Question 18

steps in a ligand-gated ion channel

Answer 18

• something binds to the subunits causing the channel to change shape and open
• the channel is lined with negatively charged AAs allowing Na+ to flow through
• Na+ building initiates events that lead to muscle contraction

Question 19

Protein Kinase Receptors

Answer 19

Transmembrane proteins that also have a cytoplasmic kinase domain that catalyzes phosphorylation of themselves and/or other proteins