What is a protein kinase?
Protein kinase transfers phosphates from ATP to proteins in phosphorylation.
What role does protein kinase play in a signal transaction pathway?
it regulates the activity of a large proportion of the thousands of proteins in a cell.
What is the significance of having many steps in the pathway?
It amplifies the signal and increases control in the pathway than in a simpler system.
Protein phosphorylation is involved with
1. activation of receptor tyrosine kinases
2. activation of protein kinase molecules
3. regulation of transcription by signaling molecules
What is the difference between a protein kinase and a second messenger molecule?
A second messenger is not a protein and activates protein kinase.
What is the actual signal being transduced in any signal transduction pathway?
The signal that is being transduced is the information that a signaling molecule is bound to the cell-surface receptor.
T or F: During apoptosis, the plasma membrane is disrupted and the cell's content flies out.
False: during necrosis, the plasma membrane is disrupted and the cell's content flies out.
T or F: During necrosis, the cell swells.
True
T or F: During apoptosis, little "blebs" form in the cell and the cell shrinks.
True
T or F: Different cells have different responses to the same signal because cells all have different DNA.
True
T or F: Scaffolding proteins make cell communication less efficient and slower.
False: scaffolding proteins make cell communications more efficient.
If protein Ced-9 on the mitochondria is inactivated, then....
Apoptosis begins. The inactivated Ced-9 allows Ced-4 and Ced-3 to become active and trigger the release of caspases.
The scaffolding protein is important because...
They allow protein kinases to travel more efficiently around the cell.
When the amount of active receptors is below a certain threshold, then...
The signal is terminated: GTP? GDP, cAMP? AMP, etc.
What can trigger apoptosis?
1. DNA damage inside the nucleus
2. Excessive protein misfolding in the endoplasmic reticulum
3. The binding of a death-signaling ligand
4. A baby's normal morphogenesis of hands and feet
The protein that holds together multiple proteins in a transduction pathway is called:
Scaffolding protein
Signal amplification is most often achieved by
a phosphorylation cascade involving multiple relay proteins
If we studied the effects of epinephrine on liver cells, we might conclude that
there is a "second messenger" that transmits the signal of epinephrine binding on the plasma membrane to the enzymes involved in glycogen breakdown inside the cell
How do cells identify their mates?
By chemical signaling
What are the two sexes of the cells?
a and alpha a
What are the two things a cell does before it mates?
Grow and change shape
What are secreting factors?
Way cells locate each other, specific to their kind of cell
What is quorum sensing?
Bacterial ability to sense concentration of signaling molecules in local area Ex. biofilm
Direct contact is what type of signaling?
Local Signaling
What type of signaling uses the Growth Factor?
Paracrine Signaling
Do plants use the same mechanisms as animals for local signaling?
No
Where does Synaptic Signaling occur?
Animal's nervous system
How do plant Growth Regulators most likely travel to the target cell?
moving through cells or diffusing through the air as a gas
What kind of signaling do both animals and plants use for long-distance signaling?
Hormonal Signaling
What are the three stages of Cell Signaling?
Reception, Transduction, Response
What is the name of the molecules in stage two of cell signaling?
Relay Molecules
What do the relay molecules make up?
Signal Transduction Pathway
Name any response a signal can trigger.
1. Catalysis
2. Activation of Specific Genes
3. Rearrangement of cytoskeleton
What happens when a signaling molecule binds to a receptor protein?
it causes it to change shape
Where do most water-soluble signal molecules bind to specific sites on receptor proteins in the cell?
plasma membrane
What are the three main types of membrane receptors?
-G protein-coupled receptors
-Receptor tyrosine kinases
-Ion channel receptors
What does the ligand-gated ion receptor act as?
a gate
What happens if a ligand is not present?
Then the ligand-gated ion receptor will not change shape, the ions will not flood into the cell, and a cellular response will not occur.
Can any ion pass through a ion-channel receptor? Why or why not?
No, only specific ions can pass through a given ion-channel receptor
What is the most important difference between the receptor tyrosine kinase and the other receptor?
A receptor tyrosine kinase can trigger multiple signal transduction pathways at once while the other receptor can be a cause of cancer
Why can abnormally functioning RTKS cause cancer?
RTKs that continue to function without the ligand molecules are often related to cancer because they cause cell growth and reproduction to continue, even without triggers, leading to the creation of tumors.
Where are the G-protein linked receptors located?
Plasma membrane
What happens when the G-protein is activated?
GTP replaces GDP on the protein. The G-protein then binds to and alters an enzymes activity.
Where are Intracellular receptor proteins found?
In the cytosol or nucleus of target cells
What type of chemical messengers can readily cross the membrane and activate receptors?
small or hydrophobic chemical messengers
What is an example of a small chemical messenger?
Hydrophobic messengers: steroids and thyroid hormones of animals
Small messenger: Nitric oxide gas
What is a transcription factor?
An activated hormone-receptor complex that turns on specific genes