cell and molecular biology exam 4

definition of signal transduction

one type of signal is converted into another one

categories of signal transduction

paracine

endocrine

neuronal

autocrine

paracine

goes a short distance and effects multiple cells in vicinity

• ex. pacemaker cell

endocrine

travels over larger distances, travels in bloodstream to target cell

• ex. hormones

neuronal

hybrid type

stimulates neuron that causes release of neurotransmitter over a short space called the synapse

autocrine

cell “self-targets” signal, will go back to cell it was released from

extracellular cells act rapidly when

altering an existing protein

ex. contracting muscles

extracellular signals act slowly when

you have to make a new protein (proteins synthesis)

• size and type of protein can dictate how long it takes

ex. building muscle

cell surface receptors use

cell surface receptor proteins that sends message to intracellular signaling molecule

cell surface receptor signals can’t

cross the membrane

intracellular receptors receive

small hydrophobic signal molecules that are able to cross the membrane to the intracellular receptor (ex. hormones)

major types of cell surface receptors

ion channel-coupled receptors

G-protein coupled receptors (GPCR)

enzyme-coupled receptors

ion channel-coupled receptors

signal molecule attaches to channel to open channel and let selected ions through

once ions pass into cytosol, they can become 2nd messengers

G-protein coupled receptors (GPCR)

once receptor receives signal, it recruits and activates G protein

G protein recruits and activates the enzyme (which can be a 2nd messenger)

enzyme-coupled receptors

signal molecules bind to 2 receptors at the same time that have enzyme activity (enzyme built in)

2nd messengers help

amplify and spread the intracellular signal

common 2nd messengers

cyclic AMP (most common)

cyclic GMP

inositol triphosphate

Diacylglycerol (DAG)

calcium

two common 2nd messenger systems

phosphorylation & G-protein

protein phosphorylation

kinase cascade

scaffold helps bring kinases closer together so they can phosphorylate

protein kinase means

on

protein phosphatase means

off (removes phosphate)

with G-protein, GTP binding means

on

with G-protein, GDP hydrolysis means

off (breakdown of GTP to GDP)

stages of cell cycle

1. G1 phase

2. S phase

3. G2 phase

4. M phase

G1 and G2 phase

growth

S phase

synthesis/duplicate DNA

M phase

mitosis/cell divides

interphase is considered

G1, S, and G2 phase

CDKs

cyclin dependent kinases

CDK only work when

kinases are bonded to cyclin protein

in order to get through a CDK

you must have the right amount of cyclin to turn on kinase

degrading cyclin

turns off

S-CDK (S cyclin)

between G1 and S

M CDK (M cyclin)

between G2 and M

G1/S checkpoint

checks to make sure no DNA is damaged

G2/M checkpoint

checks to make sure complete replication of DNA has occurred and no new mutations

cancer has occurred in

man and other animals throughout recorded history

“karkinos” (Hippocrates) means

crabs

cancer can arise because of

genomic instability (damage to DNA)

examples of genomic instability

radiation

chemicals

loss of repair mechanisms

some viruses

to create a cancer cell you need

a series of mutations

alterations in multiple pathways are needed to

transform a normal cell to cancer cell

what alterations are needed to transform a normal cell to cancer cell

cell proliferation

DNA damage response

cell growth

cancer cells have mutations that turn on BLANK and BLANK signaling pathways all of the time

survival and growth

cancer cells disable BLANK, which causes the cell to grow out of control

death signaling pathways (apoptosis)

proto-oncogene is the

normal form of the gene

oncogene is the

mutation form, which is a dominant mutation that causes excessive cell survival, proliferation, or both

Ras gene (proto-oncogene)

mutation in this gene causes the Ras protein to always be active, promoting cell proliferation

tumor repressor gene is the

normal gene

for mutations in tumor suppressor genes

both copies must be mutated (recessive)

Retinoblastoma (Rb) controls the activity of

E2F transcription factors

E2F factors are needed for

S-phase genes

active G1 CDKs phosphorylate Rb which will

inactive it while it attaches to the E2F protein, causing it to release the E2F protein, allowing S-phase to progress

BLANK or BLANK can inactive Rb

mutations or viral proteins (ex. human papillomavirus)

Rb mutation can lead to

eye tumors in young children

inactivation of both copies of p53 allows

cancer cells to continue to survive and divide, even in the presence of damaged DNA

apoptosis =

programmed cell death

cell have apoptosis to

make sure cells with abnormal DNA, cell cycle division, or other messed up critical pathways are killed to protect the organism

genome alteration in proto-oncogene

mutation in coding sequence

gene amplification

chromosome rearrangement

mutation in coding sequence of proto-ocnogene normal result

hyperactive protein made in normal amounts

gene amplification in proto-ocnogene normal result

normal protein overproduced

Chromosome rearrangement in proto-oncogene normal result

nearby regulatory DNA sequence causes normal protein to be overproduced

Chromosome rearrangement in proto-oncogene abnormal result

fusion to actively transcribe gene produces hyperactive fusion protein

tyrosine kinase receptor is a type of

hyperactive receptor fusion that can lead to cancer

BLANK, BLANK, BLANK can lead to cancer hyperactive receptor that is ON ALL THE TIME

point mutation

fusion of receptor intracellular domain with 2nd messenger

overproduction of receptor

PDGF acts through

receptor tyrosine kinase (IDK)

TEL-PDGFR-beta is an example of

oncogene-fusion

the helix-lopp-helix domain of TEL transcription factor fused to BLANK causing dimerized receptor

PDGF receptor beta

the TEL-PDGFR-beta causes

chronic Myelomonocytic Leukemia (CMML) (white blood cell cancer)

first parentheses in translocation gives

chromosomes involved

second parentheses gives

precise location

q =

long arm

p =

short arm