Chp 11 - Cell Communication
1. What is cell communication, and what types of molecules typically serve as signals?
Cells sending and receiving signals to coordinate activities. Signals are usually chemical messengers like
hormones or proteins.
2. Explain how Saccharomyces cerevisiae (yeast) and prokaryotes use cell-cell signaling.
Yeast: Release mating factors to find compatible partners.
Prokaryotes: Use quorum sensing to sense population size and coordinate behavior.
3. What are the differences between local and long-distance signaling?
Local: Nearby cells (short distance).
Long-distance: Across the body (through bloodstream).
4. How do animal and plant cells communicate through direct contact? What structures enable this?
Animal cells: Gap junctions
Plant cells: Plasmodesmata
These connect cells directly.
5. Which types of local cell signaling were discussed in class?
Paracrine signaling and Synaptic signaling
6. What type of chemical is used for long-distance cell signaling and how does that chemical travel
in the body?
Hormones — travel through the bloodstream.
7. What determines whether a cell can respond to a particular signal molecule?
It must have the correct receptor for that signal.
8. List and describe the three stages of cell signaling.
Reception – Signal binds to receptor
Transduction – Signal is passed inside the cell
Response – Cell reacts
9. What is a ligand? How does it interact with a receptor protein. What happens to a receptor
protein when it binds to a ligand?
A signal molecule that binds to a receptor. Binding changes the receptor’s shape and activates it.
10. What are the three main types of cell-surface transmembrane receptors?
GPCRs, Receptor tyrosine kinases (RTKs), and Ion channel receptors
11. What are G protein-coupled receptors (GPCRs), and how do they transmit signals inside the cell?
What role does GTP play in G protein activation?
Receptors that activate a G protein inside the cell. G protein uses GTP to turn “on.”
12. Describe how receptor tyrosine kinases (RTKs) work. What makes them unique in signal
transduction?
Two receptors join together and add phosphate groups to each other. Unique because they activate
multiple pathways at once.
13. Explain how ion channel receptors work. What causes them to open or close? List examples of
ions that rely on ion channel receptors to cross plasma membranes.
Open or close when a ligand binds. Let ions like Na⁺, K⁺, Ca²⁺, Cl⁻ cross the membrane.
, 14. Where within the cell are intracellular receptor proteins located, and what types of molecules
typically interact with these receptors? How do intracellular receptors trigger changes in gene
expression?
Located in cytoplasm or nucleus. Bind small nonpolar molecules (like steroid hormones). Turn genes
on/off.
15. What is a signal transduction pathway, and how is a signal transmitted across the cell membrane
and through multiple molecules?
A series of molecules passing along the signal inside the cell.
16. Define phosphorylation and dephosphorylation. What is a phosphorylation cascade, and what
enzymes are involved in this process (which enzymes phosphorylate molecules, and which
enzymes dephosphorylate molecules)?
Phosphorylation: Adding a phosphate group (by kinases)
Dephosphorylation: Removing a phosphate group (by phosphatases)
A phosphorylation cascade = chain reaction of activations.
17. What are second messengers? Give two common examples and explain how they function.
Small molecules that spread the signal. Examples: cAMP, Ca²⁺
18. What are some examples of cellular responses that occur at the end of a signaling pathway?
Turning genes on/off, Enzyme activation, Cell division, and Apoptosis
19. Explain the four ways that signaling pathways are regulated: amplification, specificity, efficiency,
and termination.
Amplification: One signal activates many molecules
Specificity: Only correct cells respond
Efficiency: Organized signaling
Termination: Signal is shut off
20. How does signal amplification occur? Why is it beneficial to the cell?
One molecule activates many others. Helpful because a small signal can cause a big response.
21. How can the same signal have different effects in different cell types?
Different cells have different receptors or proteins.
22. What are scaffolding proteins, and how do they increase signal transduction efficiency?
Hold signaling proteins together to make the process faster.
23. How is a signal terminated after the initial stimulus is gone?
Signal molecule breaks down or receptors turn off.
24. What is apoptosis, and why is it essential in multicellular organisms? Describe what happens to a
cell undergoing apoptosis. How does it prevent damage to neighboring cells?
Programmed cell death. Cell shrinks, DNA breaks down, membrane forms bubbles. Prevents damage by
containing the cell contents.
Chp 12 - The Cell Cycle
1. What is cell division, and what are its key functions in unicellular and multicellular organisms?
Making new cells. Unicellular: reproduction and Multicellular: growth and repair
2. Define the cell cycle and describe all phases within the cell cycle.
Interphase (G1, S, G2) and M phase (mitosis + cytokinesis)
1. What is cell communication, and what types of molecules typically serve as signals?
Cells sending and receiving signals to coordinate activities. Signals are usually chemical messengers like
hormones or proteins.
2. Explain how Saccharomyces cerevisiae (yeast) and prokaryotes use cell-cell signaling.
Yeast: Release mating factors to find compatible partners.
Prokaryotes: Use quorum sensing to sense population size and coordinate behavior.
3. What are the differences between local and long-distance signaling?
Local: Nearby cells (short distance).
Long-distance: Across the body (through bloodstream).
4. How do animal and plant cells communicate through direct contact? What structures enable this?
Animal cells: Gap junctions
Plant cells: Plasmodesmata
These connect cells directly.
5. Which types of local cell signaling were discussed in class?
Paracrine signaling and Synaptic signaling
6. What type of chemical is used for long-distance cell signaling and how does that chemical travel
in the body?
Hormones — travel through the bloodstream.
7. What determines whether a cell can respond to a particular signal molecule?
It must have the correct receptor for that signal.
8. List and describe the three stages of cell signaling.
Reception – Signal binds to receptor
Transduction – Signal is passed inside the cell
Response – Cell reacts
9. What is a ligand? How does it interact with a receptor protein. What happens to a receptor
protein when it binds to a ligand?
A signal molecule that binds to a receptor. Binding changes the receptor’s shape and activates it.
10. What are the three main types of cell-surface transmembrane receptors?
GPCRs, Receptor tyrosine kinases (RTKs), and Ion channel receptors
11. What are G protein-coupled receptors (GPCRs), and how do they transmit signals inside the cell?
What role does GTP play in G protein activation?
Receptors that activate a G protein inside the cell. G protein uses GTP to turn “on.”
12. Describe how receptor tyrosine kinases (RTKs) work. What makes them unique in signal
transduction?
Two receptors join together and add phosphate groups to each other. Unique because they activate
multiple pathways at once.
13. Explain how ion channel receptors work. What causes them to open or close? List examples of
ions that rely on ion channel receptors to cross plasma membranes.
Open or close when a ligand binds. Let ions like Na⁺, K⁺, Ca²⁺, Cl⁻ cross the membrane.
, 14. Where within the cell are intracellular receptor proteins located, and what types of molecules
typically interact with these receptors? How do intracellular receptors trigger changes in gene
expression?
Located in cytoplasm or nucleus. Bind small nonpolar molecules (like steroid hormones). Turn genes
on/off.
15. What is a signal transduction pathway, and how is a signal transmitted across the cell membrane
and through multiple molecules?
A series of molecules passing along the signal inside the cell.
16. Define phosphorylation and dephosphorylation. What is a phosphorylation cascade, and what
enzymes are involved in this process (which enzymes phosphorylate molecules, and which
enzymes dephosphorylate molecules)?
Phosphorylation: Adding a phosphate group (by kinases)
Dephosphorylation: Removing a phosphate group (by phosphatases)
A phosphorylation cascade = chain reaction of activations.
17. What are second messengers? Give two common examples and explain how they function.
Small molecules that spread the signal. Examples: cAMP, Ca²⁺
18. What are some examples of cellular responses that occur at the end of a signaling pathway?
Turning genes on/off, Enzyme activation, Cell division, and Apoptosis
19. Explain the four ways that signaling pathways are regulated: amplification, specificity, efficiency,
and termination.
Amplification: One signal activates many molecules
Specificity: Only correct cells respond
Efficiency: Organized signaling
Termination: Signal is shut off
20. How does signal amplification occur? Why is it beneficial to the cell?
One molecule activates many others. Helpful because a small signal can cause a big response.
21. How can the same signal have different effects in different cell types?
Different cells have different receptors or proteins.
22. What are scaffolding proteins, and how do they increase signal transduction efficiency?
Hold signaling proteins together to make the process faster.
23. How is a signal terminated after the initial stimulus is gone?
Signal molecule breaks down or receptors turn off.
24. What is apoptosis, and why is it essential in multicellular organisms? Describe what happens to a
cell undergoing apoptosis. How does it prevent damage to neighboring cells?
Programmed cell death. Cell shrinks, DNA breaks down, membrane forms bubbles. Prevents damage by
containing the cell contents.
Chp 12 - The Cell Cycle
1. What is cell division, and what are its key functions in unicellular and multicellular organisms?
Making new cells. Unicellular: reproduction and Multicellular: growth and repair
2. Define the cell cycle and describe all phases within the cell cycle.
Interphase (G1, S, G2) and M phase (mitosis + cytokinesis)
