Topic 4.1: Cell Communication
What are the three general ways cells can communicate through?
1. Direct contact
2. Local signaling
3. Long distance
What are the three stages of cell-to-cell messaging during a signal transduction pathway?
1. Reception
2. Transduction
3. Response
True or false: Signal transduction pathways influence how the cell responds to its environment?
True
The internal and external cell environments never change.
True or false?
false
Which phase of the cell cycle does a cell spend the majority of its time in?
Interphase
What are the channels between neighboring plant cells called, and what types of molecules travel through these?
plasmodesmata; small, water soluble molecules
What causes a protein receptor to activate?
ligand binds, inducing a conformational change
If there is a loss of function mutation in a transmembrane protein receptor, how will that affect transduction and response in cell signaling?
phosphorylation cascade will not be activated, and there will be no cellular response
What is the definition of homeostasis?
the maintenance of a stable internal environment.
How many phases are in mitosis, and what are they?
There are 5 stages in mitosis, they are known as:
Prophase
Prometaphase
Metaphase
Anaphase
Telophase and cytokinesis
How does the location of the protein receptor differ for a protein-based ligand vs. a lipid-based ligand?
protein based: transmembrane receptor protein (extracellular)
lipid based: intracellular protein receptor, typically to activate gene expression in nucleus
What is the name of the two enzymes that are involved with signal transduction pathways, and what do they do?
Kinases: phosphorylate/ activate
Phosphatases: dephosphorylate/ deactivate
What would happen if Ras, the second messenger in the signaling pathway for cell proliferation, remained active even in the absence of a growth factor?
uncontrolled mitosis--> cancer
When you are exercising hard, CO2 builds up and oxygen levels fall. As a result, you start breathing quicker to bring oxygen levels back up to normal. Is this a negative feedback loop or a positive feedback loop?
Negative feedback- counteracting stimulus to restore homeostasis
Describe the effect of a mutation in a tumor suppressor gene
No p53--> cell cycle proceeds, unregulated
What do neurons secrete during synaptic signaling to communicate with each other?
neurotransmitters
What is the primary role of cyclic AMP, commonly known as cAMP?
second messenger in the cell--> relays the message intracellularly and activates the first kinase to begin the phosphorylation cascade
If damage is detected properly during the cell cycle, the cell should trigger a response for programmed cell death. What is this called, and what is the name of the protein that will typically trigger this response?
Apoptosis, triggered by P53 protein
What type of feedback loop does our body use to regulate its body temperature? EXPLAIN how you know.
Cyclin proteins and P53 proteins have opposite jobs when it comes to regulation. What are the jobs of these proteins?
Cyclins- activate CDKs to promote cell cycle if everything is OK
P53- halt cell cycle and/or activate apoptosis pathway for cell destruction if damaged
Explain how signaling by the endocrine system works.
Specialized cells release hormones into the circulatory system where they reach target cells.
Give an example of cellular response that might occur as a result of the endocrine system releasing EITHER insulin or epinephrine.
insulin: reduce blood glucose levels
epinephrine: increase blood glucose levels by breaking down glycogen (fight or flight)
Acetylcholine is a signaling molecule that causes muscle contractions. Acetylcholinesterase is an enzyme that breaks down acetylcholine.
What would be the effect of inhibiting acetylcholinesterase?
inhibited acetylcholinesterase= more acetylcholine= more muscle contractions
Give an example of a positive feedback loop
Childbirth
Lactation
Ovulation
Blood clotting
fruit ripening
Why do individuals undergoing chemotherapy treatment often lose their hair?
Chemotherapy is designed to attack cancer cells, which are rapidly dividing cells, but other rapidly dividing cells are often collateral damage, such as hair cells.