Unit 2 Flashcards
Meselson & Stahl experiment
showed that DNA replication is semiconservative
Method: old strands will labeled with heavy
- new nucleotides were labeled as lighter (new)
Results: hybrid dna would be not be conservative because conservative is heavy and it would be semiconservative
- another replication is light and hybrid this would not be dispersive and would be semiconservative cuz we have light and medium
conservative, semiconservative and dispersive models
Conservative - has light and heavy second replication
Semiconservative - has light and medium second replication
Dispersive model - has medium second replication
Replication fork
where new DNA strands are extended
helicases
- enzyme
- split dna molecules
- unravels dna strand
single-strand binding proteins
- binds on the single strand
this proteins keeps helicase from closing the dna strand
topoisomerase
breaks down and keep DNA strands unraveled
RNA primer, primase, DNA polymerases I and III, ligase
Primase - adds RNA primer first
Nucleotides will add on the end of 3’ in RNA PRIMER
DNA polymerase - cannot start synthesis unless RNA Primer adds nucleotides at the end of 3’
DNA Poly I exchanges Rna with DNA nucleoties
DNA poly III adds to the 3’ end
DNA Ligase - dna which joins together
Leading strand
DNA Poly synthesizes a leading strand moving toward replication fork and its the strand that starts
lagging strand
DNA poly works away from replication fork
and has to do with segments called okazaki fragments
* RNA primer will be found more when there is lagging strand
Okazaki fragments
these fragments have to do with lagging strand and joined together by DNA ligase
mismatch repairs
repair enzymes correct errors in base pairing
telomeres
an enzyme that catalyzes the lengthening of telomeres
- shortening telomeres might protect the cell
What is chromatin? Where is it found?
a complex of DNA and protein found in the nucleus in eukaryotic cell
Extenal signaling
yeast cell a/alpha mating
two mating type
they both mate together and both contain genes from original cell
external signaling
bacteria biofilm
when bacteria cell atttaches to surface by molecules secreted by the cell
- biofilm protects the cell in it
Stage 1 of cell signaling: Reception
G Proteins (GCPR)
largest family receptors
- work with the help of a G protein
- if GDP is bound to the g protein then its inactive
- when GCPR recieves a message, GDP switches to GTP to activate the g protein
Stage 1 of cell signaling: Reception
Receptors Tyrosinse Kinases (RTKs)
receptor that attaches phosphate to tyrosinase
- it can trigger multiple signal pathways at once
- ligand attached to send signals
- asocciated with many cancers
Stage 1 of cell signaling: Reception
Ion Channel receptors
acts like a gate when recepter chnages shape
- when ligand binds to specific receptor it alows Na+ or Ca 2+ through
Stage 1 of cell signaling: Reception
Intracellular Reception
found in the cytosol or nucleous
- small or hydrophobic
- ex. steriod and thyroid hormones
- an active hormone receptor acts as a transcrip factors turning on genes
Stage 2 of cell signaling: Transduction
Signal Transduction pathaways
mostly protein
- its like dominos: receptors activates another protein and then so on
Stage 2 of cell signaling: Transduction
Protein Kinases
Protein Phosphatases
kinases - adds phosphate (turns on)
phospatases - removes the phospates (turns off)
Stage 2 of cell signaling: Transduction
secondary messanger: cAMP: Adenylyl cyclase
second messenger: small non proteins that participate in pathaways that GCPR and RTK start
- cAMP (& calcium ions) are common second messenger
Adenylyl cyclase - enzyme in plasma membrane, converts ATP to cAMP
Stage 3 of cell signaling: Response
Final outcome: nuclear and cytoplasmic
active enzyme, transcription, active ion channels
response occurs in cytoplasm or nucleus
- regulates enzyme
Stage 3 of cell signaling: Response
Fine - Turning of the Response
4 aspects
- amplyfying the signal
ligands - lots of glucose - specificity of the response
a and alpha a - factors - overall efficiency of response , enhanced by scaffolding proteins
keeps all same pathway protein together - termination of the signal
turn off/on signals
Apoptosis
Caspases
what triggers apoptosis
enzymes that cut up proteins and carry out apoptosis
- death signaling ligand
- dna damaged in nucleous
- protein misfolding
