POGIL “Cellular Communication” KEY
The receptor is specific for a particular ligand (signaling molecule).
D because the signal has to travel long distance.
A – autocrine
B – juxtacrine
C – paracrine
D – endocrine
**Know these prefixes!
7. No! Each ligand has to have a specific shape to bind with a specific receptor. If all ligands had the same
chemical structure, how would a certain cell know that it is the one that needs to have a cellular response?
a. paracrine
b. juxtacrine
c. paracrine
d. endocrine
a. paracrine
b. autocrine
c. paracrine
d. endocrine
10. The researcher could develop a medicine that blocks the receptor on the cell that normally receives the
signal. Another possible solution could be to develop a medicine that prevents the release of the signal.
11. Develop a medicine that mimics the signal (ligand) or a medicine that makes the cell release more of the
signal than it normally would.
Extension Questions
11. Scientists can compare the signals and receptors across different species. They could also compare the
signal transduction pathways across different species.
12. Since estrogen and testosterone are lipids and nonpolar, they can pass directly through the nonpolar fatty
acids of the cell membrane. Therefore, they do not need a cell surface receptor. Instead, they probably will
bind to an intracellular receptor (a receptor in the cytoplasm of the cell).
13. Fight or flight response – release of epinephrine. Light could cause cell communication within a plant.
Food (sugar), a growth factor, drugs, illness.
POGIL “Signal Transduction Pathways” KEY
1. Inside
2. They are a “perfect match.” The ligand is round, and the receptor also has a round shape.
4. “Transduction” – based on Model 1, a possible definition is when an activated protein, in turn, activates
other proteins. (Actual definition – the conversion of a signal from outside of the cell to a form that
brings about a cellular response. Usually involves many steps, with conformational changes in
a. “Amplification” – to make louder
b. 1 protein activates 3 proteins – resulting in 3 responses
6. Turn gene on/off, proteins are made, enzymes are activated/inactivated, cell divides, apoptosis, secretion
of chemical signals (like in the immune response, a Helper T cell sending out cytokines)
7. The proteins in the transduction pathway need to be inactivated or shut off.
8. An active relay protein activates protein kinase 1
a. 4, 5
b. It comes from ATP. ATP becomes ADP because it loses one of its phosphate groups to the
10. Kinases
12. A transcription factor is activated (that means it is a protein that will turn on transcription of a specific
gene. Transcription of DNA into mRNA, and then it is assumed that mRNA will be translated into
13. In a signal transduction pathway, amplification means that a single protein can activate many other
proteins. In this case, in step 3, that would mean that the active relay protein can activate many protein
kinase 1. In step 4, a sincle protein kinase 1 can activate many protein kinases 2, etc…
14. One signal can lead to a large cellular response.
15. There would be continual phosphorylation, and a continued cellular response, whatever it may be.
16. The initial relay protein needs to be deactivated, the phosphate needs to be removed form the kinases
17. See Fig. 11.8 in textbook
18. Similar process of phosphorylation/dephosphorylation
19. An active relay protein opens up a transport protein in the cell membrane. The opening of this channel
allows the entrance of a secondary messenger into the cell, which activates another relay protein that
leads to a cellular response.
a. facilitated diffusion (needs a channel, but is going from high concentration outside the cell to
lower concentration inside the cell)
b. an active relay protein binds to the channel, which causes a conformational change and opens the
21. Cells have certain receptors depending on their function. An immune cell will have different receptors
than a muscle cell. Therefore a ligand that is meant for an immune cell would not affect a muscle cell
because the muscle cell would not have a receptor for that particular ligand.

POGIL “Cellular Communication” KEY