Chapter 6: Cell Signals and Responses Flashcards
Signal transduction pathway
a sequence of molecular events and chemical reactions that lead to a response to the signal
Juxtacrine signals
diffuse between cells through gap junctions and plasmodesmata or a membrane-bound signal binds to a membrane receptor
In plants, _______ can allow long-distance transport
plasmodesmata
Chemical signals travel to target by _____
diffusion
Paracrine signals
bind to receptors on nearby cells
Autocrine signals
bind to receptors on the same cell that secreates them
How do cells signal from a distance?
Endocrine signals (hormones) are transported by the circulatory system and bind to receptors on distant cells
Ligand binding causes receptor protein to ______
change shape (shape change activates receptor)
Steps to a signal transduction pathway
- 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
Short-term signal changes
enzyme activation, cell movement
Long-term signal changes
altered DNA transcription
signal transduction often involves enzymes that exhibit ______
allosteric regulation
T/F Binding is noncovalent and reversible
T; ligands are not changed by binding
Intracellular/cytoplasmic receptors
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
Membrane receptor
A signal that is polar and/or large cannot diffuse through the cell membrane, so its receptor is embedded in the membrane
Three examples of Membrane receptors
Ion channel, protein kinase receptors, G protein-linked receptors
Signals for ion channel receptors
chemical ligands, electric charge differences, sensory stimuli
steps in a ligand-gated ion channel
- 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
Protein Kinase Receptors
Transmembrane proteins that also have a cytoplasmic kinase domain that catalyzes phosphorylation of themselves and/or other proteins
