Unit 4 - Signal Transduction, Cell Communication & Cell Cycle Flashcards
Lipid Characteristics
- nonpolar
- cross the membrane
- receptors in nucleus
steroid hormones
Protein Characteristics
- polar
- CANNOT cross the membrane
- membrane protein receptors
Direct
- Plasmodesmata
- Gap Junctions
Short Distance w/ signals
- nerve cells
- skin (white blood cells, same cell, local regulators—immune system)
Long Distance w/ signals
- hormones in endocrine (travel through blood)
- different cells
Endocrine
secrets ligand that travels through blood
Paracrine
sends ligand and binds to nearby cell
Autocrine
sends ligand which binds to its own membrane
Synaptic signaling
Neurotransmitters are the ligand which go to the ion channel receptor which is a gate
Endocrine example
Gland will release ligand (can be lipid or protein)
Lipid will go through blood stream and enter nucleus directly
Protein will have to bind to another receptor which will then go to a target cell
Quorum Sensing
Restriction of activity until there is a high density
Then bacteria will sense that it is time to start and turn on gene expression
Receptor mutation
chemicals can activate/inhibit the release of signals
G-Protein signal transduction
Ligand attaches to the protein which starts a signaling pathway
The G-protein is inactive until the ligand binds and the GDP will turn to GTP and move the alpha sub unit to the Adenylyl Cyclase
This will convert a bunch of ATP into cAMP (secondary messenger) which will attach to kinase that will phosphorylate proteins as the response
Signaling Cascade
Amplifies a signal
Kinase
phosphorylate other molecules to enable them to do work
Negative Feedback Loop
Body temp, maintaining homeostasis
Insulin and glucose in pancreas
Positive Feedback Loop
Amplify response
fruit ripening, child birth contractions, blood clots
G1
normal functions for life
- cellular content (minus the chromosomes) are doubled—cell grows
G1 checkpoint
checks if there is any DNA damage, cell size/growth, nutrients
go = irreversibly commited
S
copy the DNA
parent will split into 2 identical daughter cells
mutations can occure
G2
finals checks of the doubled DNA
G2 checkpoint
checks for the completion of replication and DNA damage
go = mitosis
stop = try to fix/apoptosis
M checkpoint
check the microtubule attachment on chromosomes at metaphase
go = anaphase
stop = allow spindles to attach
Chromatin
uncondensed DNA
Kinetochore
where spindle fibers attach
Prophase
- duplicated chromosomes condense
- nuclear encelope breaks down
- centrosomes (each sister chromatid) move to opposite sides
Metaphase
- line chromosomes up int he middle
- centrosomes send out spindle fibers to attach to kinetochore
Anaphase
- sister chromatids are pulled to opposite sides
- once they are separated they are considered individual chromosomes
Telophase
- new nuclear envelope
- DNA uncondenses
Cytokinesis
Animals: cleavage burrow
Plants: new cell plate
back in G1
Cyclin/CDK
There is always a constant amount of CDK in the body
Depending on checkpoints and whether to go or not, cyclin will activate CDK to start a response and then stop/break down to stop a response
P53
Tumor suppressor cell
creates a CDK inhibitor – if it is not functioning, there is no inhibitor which will allow mutated DNA to pass through the checkpoint and uncontrolled cell growth
RAS (Proto-oncogene)
active even without a ligand
leads to overexpression and overdividing
Anchorage Dependence
rely on the attachment of other cells/the extracellular matrix to divide
Chi < critical
Chi > critical
fail to reject the null
reject the null
