Biology 224- Chapter 9- Cell Communication
Call Kai
Learn
Practice Test
Spaced Repetition
Match
Flashcards
Knowt Play1/133
There's no tags or description
Looks like no tags are added yet.
134 Terms
What does cell signaling involve?
Both incoming and outgoing signals.
What is an agent that can influence the properties of cells?
Signal
What recognizes signals?
Receptors.
What recognize signals and cause a cellular response?
Receptors
What is a change in a cell's shape or activity due to signal binding?
Cellular response
What are the basic types of cell signaling?
Direct Intercellular Signaling
Contact-dependent Signaling
Autocrine Signaling
Paracrine Signaling
Endocrine Signaling
What type of signaling is whet signals pass directly between cells through cell junctions?
Direct intercellular signaling
What is an example of direct intercellular signaling?
Gap junctions
What type of signaling is when one cell has a membrane-bound signal recognized by a receptor on another cell?
contact-dependent signaling
Where is the signal located in contact-dependent signaling?
Attached to the membrane of one cell.
In contact-dependent signaling, what recognizes the membrane-bound signal?
A receptor on another cell.
What type of signaling is when a cell secretes a signal that binds to receptors on its own surface and stimulates itself?
autocrine signaling
Can autocrine signals affect neighboring cells?
Yes. They can stimulate neighboring cells of the same type.
What two types of cells can autocrine signaling stimulate?
The cell releasing the signal and neighboring cells of the same type.
What type of signaling occurs when a cell secretes a signal that affects nearby target cells?
Paracrine signaling
Does paracrine signaling affect the cell that releases the signal?
No. It affects nearby cells, not itself.
How do target cells respond to paracrine signals?
The signal binds to their receptors and influences them.
What type of signaling is when a cell secretes a hormone into the bloodstream to affect distant cells?
endocrine signaling
How do endocrine signals travel through the body?
Through the bloodstream.
How far can endocrine signaling affect cells?
Far from the original source of the signal.
What are the three steps of a cellular response to signals?
Receptor Activation
Signal Transduction
Cellular Response
What happens during receptor activation?
A signaling molecule binds to a receptor, activating it.
What happens to the receptor when a signaling molecule binds?
It undergoes a conformational change (change in shape).
What does the conformational change do?
It activates the receptor's function.
Why can't most signals enter cells through the membrane?
Most signals are hydrophilic (water-loving).
What happens because most signals cannot enter the cell?
The initial signal must be converted into a second signal inside the cell.
What does signal transduction mean?
Converting the initial signal into a second signal inside the cell.
Where does the second signal form?
Inside the cell.
What is one way cells respond to signals?
They activate enzymes inside the cell.
What do signals affect?
The function of structural proteins and transcription factors.
What are proteins that bind to and directly regulate the activity of genes?
Transcription factors
What are ligands?
Signals that bind to receptors.
How do ligands bind to receptors?
Non-covalently and temporarily.
Is ligand binding to a receptor permanent?
No. The binding is temporary.
What happens when a ligand binds to a receptor?
It changes the receptor and activates its ability to initiate a cellular response.
Is ligand binding permanent?
No. Binding is temporary and reversible.
What happens when a ligand is released from a receptor?
The receptor is no longer activated.
What does reversible binding mean?
The ligand can bind to and later detach from the receptor.
Why are cell surface receptors necessary?
Most signals are hydrophilic or large and cannot diffuse through the plasma membrane.
Why do many cells need membrane-bound receptors?
To bind signals that cannot pass through the plasma membrane.
What types of receptors do cells contain?
Large numbers of different types of receptors (A–E).
Do all cells have just one type of receptor?
No. Cells contain many different types of receptors.
What is a receptor where the signal, often a hormone, binds to the extracellular domain?
Enzyme-linked receptor
Where does the signal bind on an enzyme-linked receptor?
The extracellular domain.
What function does the intracellular domain have?
A catalytic function.
What happens when the extracellular domain binds a signal?
The intracellular domain becomes activated.
What happens when the extracellular domain binds a signal?
The intracellular domain becomes activated.
What function do most enzyme-linked receptors have in their intracellular domain?
Protein kinase function.
What happens when a signal binds to an enzyme-linked receptor?
The kinase function leads to phosphorylation of other proteins.
What is phosphorylation?
The addition of phosphate groups to other proteins.
What do protein kinases do?
Remove a phosphate from ATP and attach it to a protein.
What happens when a protein is phosphorylated?
It is usually activated to cause a cellular response.
What is the purpose of protein phosphorylation?
To activate proteins that help cause a cellular response.
Why are G proteins called G proteins?
Because they can bind GTP as a substrate.
How many transmembrane segments do G protein receptors typically have?
Seven transmembrane segments.
Where are the transmembrane segments located?
Embedded in the plasma membrane.
What are the two subunits ( or main parts) of G proteins?
An α (alpha) subunit and a β/γ (beta-gamma) subunit.
What happens when a signal binds to a G protein-coupled receptor?
The receptor's intracellular domain contacts the G protein and causes it to release GDP and bind GTP.
What happens to GDP when the G protein is activated?
GDP is released and replaced by GTP.
What happens to the α subunit when it binds GTP?
The α subunit separates (dissociates) from the β/γ subunit.
What activates the G protein?
The exchange of GDP for GTP.
What happens to the α subunit after separating from the β/γ subunit?
It becomes activated and can initiate a cellular response.
What is the role of the activated α subunit?
To initiate a cellular response.
What happens when the original signal leaves the receptor?
The process is reversed.
What does the α subunit do to GTP?
Splits GTP into GDP.
What happens when GTP is converted to GDP?
The α subunit can rejoin the β/γ subunit.
What happens when the α subunit re-binds to the β/γ subunit?
The G protein becomes inactive.
What happens when the G protein becomes inactive?
The cellular response ends.
What causes the G protein to become inactive?
The α subunit converts GTP into GDP and rejoins β/γ.
What happens when a ligand binds to a ligand-gated ion channel?
The receptor changes shape (conformation), causing the channel to open so ions can flow through.
What causes a ligand-gated ion channel to open?
The binding of a signal (ligand) to the receptor.
Why can steroid hormones bind to intracellular receptors?
Steroid hormones can pass through the plasma membrane.
Where are intracellular receptors located?
Inside the cell.
What happens when a steroid hormone binds to an intracellular receptor?
The receptor changes shape (conformation), which activates it.
Where is the active signal-receptor complex found?
In the nucleus.
What does the active signal-receptor complex bind to in the nucleus?
Specific genes.
How does the active signal-receptor complex affect gene activity?
It acts as a transcription factor to activate specific genes.
What signal activates a Receptor Tyrosine Kinase?
Epidermal Growth Factor (EGF).
What does Epidermal Growth Factor (EGF) stimulate?
Cell division throughout the body.
How does EGF travel throughout the body?
It is secreted by endocrine cells into the bloodstream, which carries it throughout the body.
What happens when two EGF molecules bind to Receptor Tyrosine Kinases?
The receptors phosphorylate each other on tyrosine amino acids.
What are amino acids that are phosphorylated by the activated receptors?
Tyrosines
What does the activated Receptor Tyrosine Kinase activate?
Grb
What does Grb do after activation?
Grb binds to and activates Sos.
What happens when Sos is activated?
Sos causes Ras to release GDP and bind GTP.
What activates Ras?
Releasing GDP and binding GTP activates Ras.
What is the first kinase in the enzyme/protein kinase cascade?
Ras
What does Ras phosphorylate?
Raf
What does Raf phosphorylate?
Mek
What does Mek phosphorylate?
Erk
What is the order of the kinase cascade?
Ras → Raf → Mek → Erk.
Where does Erk go after being activated?
Into the nucleus.
What does Erk phosphorylate in the nucleus?
Transcription factors such as Myc and Fos.
What do Myc and Fos do after being phosphorylated?
They bind to approximately 100 genes.
What happens when Myc and Fos bind to genes?
The genes produce proteins that stimulate cell division.
What is the final cellular response in this pathway?
Production of proteins that stimulate cell division.
Why do most signals depend on a second messenger?
Most signals cannot enter the cell, so a second messenger carries the signal inside the cell to produce a cellular response.
What type of cellular responses do second messengers typically produce?
Quick and short-lasting cellular responses.
What happens when G protein receptors activate G proteins?
The α subunits are freed and activate other proteins.
What is one common enzyme activated by G protein α subunits?
Adenylyl Cyclase.