Study guide chapter 11
Chapter 11: cell communication
11.1
a. yes
b. in plants, hormones (often called growth regulators) may reach their target cels
by traveling through vessels, through cells via plasmodesmata, or even through
the air as a gas.
11.2
The G protein is also a GTPase enzyme that hydrolyzes is bound GTP to GDP
and inactivates itself. It then dissociates from the enzyme it had activated, and that
enzyme returns to its original state.
11.3
a. signal molecules
b. alpha helix in the membrane
c. phosphates
d. ATP -> ADP
e. tyrosines
f. activated relay proteins
g. cellular responses
11.4
a. A target cell has a protein receptor that is specific for that signal.
b. Signals that bind to the surface receptors are large, polar and/or ionic. These
hydrophilic molecules cannot pass through the membrane. Intracelluluar signals
are small or hydrophobic and can move through the lipid membrane.
11.5
a. A protein kinase transfers a phosphate group from ATP to a protein; adding a
charged phosphate group causes a conformation change that usually activates the
protein.
b. A protein phosphatsae removes phosphate group from a protein, usually
inactivating the protein.
c. A phosporylation cascade is a series of protein kinase relay molecules that are
sequentially phosphorylated.
11.6
a. signal molecule (first messenger)
b. G-protein linked receptor
c. activated G protein (GTP bound)
d. adenylyl cyclase
e. ATP
f. cAMP (second messenger)
g. protein kinase A
h. phosphorylation cascade to cellular response
11.7
a, signal molecule
b. G protein
c. membrane phosolipid.
d. IP3
e. Ca2+
f. endoplasmic reticulum
11.8
a. Signal molecules reversibly bind o reception and when they leave a receptor,
the receptor reverts to its inactive form. The concentration of signal molecules
influences how many are bound at any time.
b. Activated G protein are inactivated when the GTPase portion converts GTP to
GDP.
c. Phosphodieserase converts cAMP to AMP, thus damping out this second
messenger.
d. Protein phosphates remove phosphate groups from activated proteins. The
balance of active protein kinases and active phosphatases regulates the activity of
many proteins.
Suggested answers to structure your knowledge
1. Cell signaling is essential for communication between ells. Unicellular organisms
use signals to relay environmental or reproductive information. Communication in
multicellular organisms allows for the development and coordination of
specialized cells. Extracellular signals control the crucial activities of cells, such
as cell division, differentiation, metabolism and gene expression.
2. Cell signaling occurs through signal transduction pathways that include reception,
transduction and response. First a signal molecule binds to a specific receptor.
The message is transduced as the activated receptor activates a protein that may
relay the message through a sequence of activations, finally leading to the
activation of proteins that produce the specific cellular response.
3. The sequence described in the previous answer results in the activation of cellular
proteins. When the signal is transduced to activate a transcription factor, however
the cellular response is a change in gene expression and the production of new
proteins.
4. In an enzyme cacade, ch step in the pathway activates multiple substrates of the
next step, hus amplifying the original message to produce potentially millions of
activated proteins and thus a large cellular response to few signals.
Answer to test your knowledge:
1. c p. 130
2. d p. 202
3. a p. 326
4. b p. 206
5. e p. 207
6. d p. 65
7. c p. 202
8. e p. 212
9. c p. 295
10. a p. 202
11. c p. 203
12. e p. 206
13. b p. 206
14. d p. 212