Unit 4: Cell Communication and Cell Cycle Flashcards
Types of signaling
Autocrine: Signaling within the cell (one single cell)
Paracrine: Signaling between nearby cells
Endocrine: Signaling through the bloodstream (farther distances) - endocrine system
Ligand + Receptor
Ligand: signaling molecule that moves from cell to receptor
Receptor: protein in membrane that detects extracellular signal
Ligand has specific shape to fit into receptor and shapes must match to relay the signal
Signal Transduction
the process of which an external signal leads to intracellular change (controls gene expression)
Gene expression
types/ amounts of genes turned on/off within the cell
Genes
specific sequences of DNA that codes for a specific protein and specific function
Transcription Factor
a protein that enters the nucleus and controls gene expression
-certain conditions lead to transcription factor binding to a gene and increasing or decreasing expression
Signal Cascade
intracellular sequence of events initiated by a receptor (relay protein + second messenger + transcription factor (how signal gets to nucleus)
Relay protein
proteins that help transmit a signal in signaling cascade (usually large on diagram)
- protein kinases are common relay proteins, and they break apart ATP to power other proteins
Second Messenger
small signaling molecule that is released as part of signaling cascade (very small on diagrams, CAMP is common second messenger)
- one thing can release a lot of second messenger that each go on to activate separate pathways
Amplification
usually activates/operates relay proteins (one activated protein can activate many others (normally enzymes))
- second messengers can also amplify (amplification for messengers is the step after they are produced not when they are produced)
Hormones vs Steroid Hormones
Hormone: Small signaling molecule that moves through body (endocrine system + signaling) - follows normal signaling cascade
Steroid Hormone: small nonpolar signaling molecule (moves through membrane and directly binds to receptor to make a complex which = transcription factor and then goes straight to nucleus to change gene expression)
Positive Feedback Mechanism
the stimulus = more stimulus (amplify themselves to push system away from homeostasis)
- uncommon (ex. birth & blood clotting)
Negative Feedback Mechanism
the stimulus = less stimulus 9aims to inhibit further stimulus in order to MAINTAIN HOMEOSTASIS)
- common regulatory system for hormone systems
Cell Cycle
Necessary for growth, replenishment, and asexual reproduction (for capable organisms) G1 = growth one: growth, normal function, make organelles
S= synthesis: DNA replication of 2 full sets
G 2 = growth 2: more growth
Mitosis: cell division
G1 + S + G2 = interphase
cells can exit the cycle (G0 phase when there’s no need for new cells so cells just live life)
Mitosis
Prophase: DNA condense, nucleus breaks down, spindle fibers form
Metaphase: spindle fibers attach to chromosomes & organize in middle/metaphase plate
Anaphase: chromatids separate to opposite poles using spindle fibers
Telophase: nucleus reforms, chromosomes decondense, cells begin to divide, spindle fibers degrade
Cytokinesis: proteins around equator contract & split ell into 2, nucleus reforms around new cell
Chromosomes + Chromatids
A chromosome can be one strand but once DNA replicates the on strand = a chromatid and 2 strand on a centromere = chromosome
(once they separate they become chromosomes again)
Cell Cycle Checkpoints
G1 checkpoint: checks for nutrients, DNA damage, growth factors (options = proceed with cycle or go to G0 to fix problems, kills itself if not fixed)
G2 checkpoint: checks for DNA damage, perfect replication of DNA, and cell size (size or DNA rep bad = stays to finish, DNA damage = death)
Metaphase/Spindle checkpoint: check formation and attachment to spindle fibers, correct alignment in middle (fails = apoptosis)
* if this check fails then the daughter will have the wrong DNA
Cancer
Cancer = disease of cell cycle (unregulated/checked mitosis) the risk increases with age b/c there’s more time for mistakes within the cells
Proto-oncogenes: genes that promote division (too active = too much cell growth)
Tumor Suppressor genes: genes that inhibit cell division (inhibited by carcogen/other = can’t suppress growth)
Tumors
results from messed up cell cycle (these takes up nutrients and space without providing any function for the body)
Metastasis = cancer spreads to other parts of the body (a little part breaks off and travels through blood to land in other areas)
Carcinogens = cancer causing chemicals/ agents
Cell Cycle Control Proteins
ANYTHING ABOUT THESE = CONTROLING CELL CYCLE
Cyclin Dependent Kinase = family of proteins that requires cyclins to be activated
Cyclins = family of protein that activate CDK’s (produced at increasing levels during cell cycle)
Maturing Promoting Factors: cyclin - CDK complex that stimulates mitosis, regulates G2 checkpoint (inhibited MPF = inhibiting mitosis)
Statistical Significance
Determines if result is due to random chance or a factor of interest (more data = more reliable, longer test period = more time to see trends)
- use error bars of chi squared test to understand
Error bars: visual rep of variability (small error bar = not variable, large error bar = more variable)
*if error bars overlap = not statistically significant and the points are the same data point
