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AP Biology Campbell Active Reading Guide Chapter 11 - Cell Communication
Terms in this set (31)
1. What is a signal transduction pathway?
A signal transduction pathway is a series of steps of cellular response, after receiving a signal.
2. How does yeast mating serve as an example of a signal transduction pathway?
Mating signals received by yeast cells induce a signal transduction pathway which prepares a cell for fusion.
3. What is quorum sensing? How is it related to biofilms?
Quorum sensing allows bacteria to monitor local cell density via signalling molecules. This allows bacteria to aggregate to surfaces, as seen in biofilms.
4. Paracrine signaling - (Description and Specific Example)
Synaptic signaling - (Description and Specific Example)
1. Description - a secreting cell discharging local regulator into EC fluid, which acts on larger cell.
Specific Example - growth factors (EGF)
2. Description - Nerve cells release neurotransmitter molecules into synapse, stimulating target cell.
Specific Example - neurotransmitters in nervous system
5. How does a hormone qualify as a long-distance signaling example?
Hormones reach targets by traveling through vessels over long distances.
6. Explain each step of a signal transduction pathway.
Reception - the target cell's detection of a signal molecule coming from outside the cell
Transduction - conversion of the signal to a form that can bring about a specific cellular response.
Response - the specific cellular response to the signal molecule
7. Explain the term ligand.
A ligand is a molecule that bind to another molecule to serve a biological purpose.
8. Describe the role of the three components in a G protein-coupled receptor pathway.
G protein coupled receptor -
G protein -
G protein coupled receptor - membrane receptor that works with the help of a G protein
G protein - a protein that binds to the energy-rich molecule GTP
GDP - low energy molecule that inactivates a protein
9. Describe what happens in step 2.
When signaling molecules bind to the EC side of receptors, the receptor is activated and changes shape. Its cytoplasmic side binds to inactive proteins, causing GTP to displace GDP, activating protein.
10. Describe what happens in step 3.
G protein binds to specific enzyme and activates it. The activated enzyme can trigger the next step in pathway, leading to cellular response.
11. Describe how signal is halted.
Enzyme changes are temporary because G proteins can function as GTPase, which which hydrolyses its bound GTP, returning to its inactive form.
12. What activates a G protein?
A G protein is activated when GTP replaces its GDP.
13. A G protein is also called a GTPase enzyme. Why is this important?
This allows the protein to shut itself off when needed.
14. The second type of receptor is called a receptor tyrosine kinase. Explain what a kinase enzyme does.
Kinase enzymes catalyze the transfer of phosphate groups to receptor tyrosine kinases, activating them.
15. How does tyrosine kinase function in the membrane receptor?
It is an enzyme that catalyzes transfer of a phosphate group from ATP to tyrosine on a substrate protein.
16. What is a key difference between receptor tyrosine kinases and G protein-coupled receptors?
Receptor tyrosine kinases have the ability of a single ligand binding event to trigger multiple pathways.
17. Explain what happens in step one of a receptor tyrosine kinase pathway.
Each receptor tyrosine kinase has an EC binding site, α helix in the membrane, and intracellular tail that contains multiple tyrosines.
18. Explain what happens in step two of a receptor tyrosine kinase pathway.
Binding of signalling molecule causes two receptor molecules to form dimer complexes.
19. Explain how receptors are affected in step 3.
Dimerization activates the tyrosine kinase region of each monomer; each tyrosine kinase adds a phosphate group from ATP to a tyrosine on the tail of the other monomer.
20. Explain how the activated receptor can stimulate multiple cellular response pathways.
Activated receptor proteins initiate a unique cellular response for each phosphorylated tyrosine.
21. Each activated protein in the previous figure triggers a signal _______ pathway, leading to a _______ response.
22. Explain the role of the labeled molecules in ion channel receptors.
ligand-gated ion channel receptor -
ligand - signaling molecule
ligand-gated ion channel receptor - gate remains closed until a ligand binds to the receptor
ions - particles that flow through the channel inside the cell
23. Explain what occurs with the binding of the ligand to the receptor.
When the ligand binds to the receptor, gates open and ions can flow through the channel.
24. The ligand attachment to the receptor is brief. Explain what happens as the ligand dissociates.
When the ligand dissociates, the ion gate closes and ions can no longer enter the cell.
25. In what body systems are ligand-gated ion channels and voltage-gated ion channels of particular importance?
The nervous system
26. Intracellular receptors are found either in the ______ or ______ of target cells. In order to be able to pass through the plasma membrane, the chemical messengers are either ________ or very small, like nitric oxide.
cytoplasm, nucleus, hydrophobic
27. Explain what is happening in the cell at each step of an intracellular receptor pathway.
1. The steroid hormone testosterone passes through the plasma membrane.
2. Testosterone binds to receptor proteins in the cytoplasm, activating it.
3. The hormone receptor complex enters nucleus and binds to specific genes.
4. The bound protein acts as a transcription factor, stimulating transcription of genes into mRNA.
5. The mRNA is translated into specific protein
28. Explain the function of transcription factors in the cell.
They are special proteins that control which genes are transcribed into mRNA.
29. What are two benefits of multistep pathways?
1. Greatly amplify signal
2. Provide more opportunities for coordination and regulation than simpler systems do.
30. Explain the role in transduction of these two categorues of enzymes.
1. Protein Kinase
2. Protein Phosphates
protein kinase - relay molecules in signal transduction pathways.
protein phosphatases - dephosphorylate proteins, turning off protein kinases, and thereby, turning off signal transduction pathways, when initial signal is not longer present.
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