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Gene Regulation, Cell Motility, and Cell Signaling
How can gene expression be regulated
During transcription, translation, and after translation
What do bacterial cells use as their food supply
glucose
When is the enzyme ß-gal present in the cell
when it is required
What operon gene is a good example of the regulation of gene expression
the lac operon
What does a promoter do
it promotes thr transcription of a gene by rna polymerase
When lactose is absent, the operon is what
turned off
Why is the operon turned off when lactose is absent
There is a repressor blocking rna polymerase from binding to the promoter
When lactose is present, what happens
mRNA is transcribed and translated
What happens to the repressor when lactose is present
It binds to the repressor, which causes it to change shape
What two things can eukaryotes influence gene expression through
chromatin remodeling and RNA processing
What does chromatin remodeling do to the promoter
it exposes it by loosening the DNA wrapped around it
How do cells move through their environment
By swimming or crawling
How do bacteria swim
Using flagella
What is the bacterial flagella made of
flagelllin
How do bacterial flagella move
they rotate or spin
What protein is eukaryotic flagella made of
dynein
How do eukaryotic flagella move
they bend
What is ameboid movement
cell crawling
What two fibers are involved in ameboid movement
actin and myosin
What is myosin
the motor protein for movement along actin filaments
True or false: The ability of the myosin motor protein to function depends on its ability to remain unchanged
False, The ability of the myosin motor protein to function depends on its ability to change shape using energy from ATP.
What is crossbrisge cycling
How myosin generates the force required to cause muscle contraction
What kind of muscle is skeletal muscle
striated muscle
What is a sarcomere
a functional unit of striated muscle
What happens to the sarcomere when myosin heads walk down actin filaments
they contract
What is the only thing can myosin bind to
myosin binding sites on the surface of actin
What controlls access to myosin binding sites
calcium ions
What is the sarcoplasmic reticulum
the smooth er
What is the neuromuscular junction
the location where a nerve cell and a muscle cell communicate via ACh neurotransmitters
What is paracrine signaling
signaling over a short distance
What is endocrine signaling
signaling over a long distance
What is juxtacrine signaling
signaling between touching cells
What is autocrine signaling
signal targets the cell that produced it
What is signal transduction
when a cell receives a signal
Step 1 of signal transduction
The message has to be received. This involves the signal interacting with a protein called a receptor
Step 2 of signal transduction
The signal must be transduced or carried into the cell. This can involve multiple proteins
Step 3 of signal transduction
The signal is often amplified meaning that multiple proteins get involved in the transduction step
Step 4 of signal transduction
The final step is the response of the cell to the signal. As we will see this step can take several forms
Steps of the signaling process
reception
transduction
response
True or false: There are different types of signaling depending on the source of the signaling molecule
true
What 3 ways can a cell respond to information from receptors
Alter the activity of a cytoplasmic protein, Alter the activity of an integral membrane protein, Alter gene expression
What are the three major signaling pathways involving receptor proteins
STEROID HORMONE RECEPTORS, G-PROTEIN COUPLED RECEPTORS, RECEPTOR-TYROSINE KINASE
What 4 things do steroid hormone receptors do
Steroid hormones bind to receptors in the cytoplasm
Move into nucleus to bind DNA
Act as a transcription factor (alters gene expression)
Alter protein synthesis
Are steroids hydrophilic or phobic
hydrophobic because they are lipids
What 4 things do GPCR’s do
Are integral membrane proteins
Can bind a signal molecule
Interacts with G proteins on the cytoplasmic side of the membrane
Are associated with the activity of second messengers
What are g proteins
small peripheral membrane proteins
When do g proteins become active
when they bind a molecule of GTP
When GTP converts to GDP what happes to the GCPR
they become inactive
What does adenylyl cyclase make
cyclic AMP (cAMP)- is a second messenger
Can second messengers influence the activity of enzymes
yes
What do RTK’s trigger
Phosphorylation cascades
RTK step 1
signal arrives and binds to receptor
RTK step 2
signal receptor complex changes conformation and is phosphorylated
RTK step 3
Proteins form a bridge to RAS, which exchanges its GDP for a GTP
RTK step 4
Ras catalyzes the phosphorylation of an intracellular protein, activating it
RTK step 5
A phosphorylation cascades results
What is cross talk
the various pathways can overlap or interact in a process
What does cross talk allow cells to fo
allows a cell to modify its response according to the all information it is receiving
Note 
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