Class lectures mod 5 (exam 3) Flashcards
amino acids
monomer building blocks for polypeptides
polypeptides
polymers of amino acids
mRNA
specifies the order in which amino acids are added to the polypeptide chain
tRNA
the “translator” that decodes the information in the mRNA nucleotides to the polypeptide (amino acdis)
ribosome
the structure in the cytoplasm where translation takes place
Codons in translation with mRNA and tRNA
mRNA: has a codon of which amino acids goes where
tRNA: has an anticodon on one end and the amino acid on another end
aa-tRNA
a tRNA molecule bound to an amino acid called an amino-acyl TRNA
some special codons: AUG
-specifies met (methionine) and starts translation, so every protein that has a Met as the first amino acid
special codons: UAA, UAG, UGA
-they are stop codons and they specify where translation should end
-there is no tRNA with the corresponding anti-codons
what are the stages of translation
-initiation
-elongation
-termination
internal membrane system
separates the cell into compartments
address labels for the proteins reside in the
amino acid sequence
while in the process of translation, proteins targeted to the endomembrane system
have a “tag” that tells the ribosome where this mRNA should be translated while sitting on the ER
signal sequence
-“tag”
-stretch of amino acids that is recognized by receptors on the cytosolic surface of the ER
secretory proteins initate
translation on ribosomes in the cytosol
sequence for address labels for proteins
1) signal recognition particles (SRP) binds to the signal peptide
2) the SRP brings the ribosome to the ER by binding to the receptor on the ER and the receptor and other proteins form a pore through ER
3) ribosome translates the polypeptide as it moves through the ER pore
4) signal peptidase snips off signal peptide and translation goes until it is done
5) polypeptide released and may have further processing
subcellular fractionation
-how we know protein goes into cell
-cell compartments are separated from one another by density and he speed that is needed to force them to the bottom of the centrifuge tube
larger, dense compartments, will pellet
LOWER speeds than less dense compartments
soluble proteins in the cytosol don’t form a pellet at
high speeds so we can separate the different compartments in the cell
western blotting
-proteins w/in a compartment are separated from one another by gel electrophoresis that separates proteins based on size and charge
once we have different compartments, we can transfer proteins onto
a membrane and then stain with an antibody that recognizes the protein of interest
-we will only see staining in the lane containing proteins from the compartment in which the protein is located
some proteins are targeted to organelles
AFTER they have been translated
proteins bound for secretion are targeted to the secretory pathway
WHILE in translation
every time a cell divides it must
accurately replicate the genetic information in the DNA so it can be passed onto the 2 daughter cells
DNA must be
consistently replicated and the genetic information has to be readily transferable for the next generations
Matthew Meselson and Franklin Stahl conducted a
pulse-chase experiment to determine the correct model of the DNA
what are the steps from Meselson and Stahl’s experiment
-extract DNA to form heave and light cultures
- mix DNA together and spin it (centrifuge)
if DNA replication is semiconservative
it makes 2 new DNA double helices containing one old strand and one new strand
if DNA replication is conservative
-theoretical model
-the original parental DNA strands remains completely intact
-result is one completely new strand and one old strand
if DNA replication is dispersive
-hypothetical model
-parental DNA breaks into fragments and serves as a template for new DNA segments
-both daughter DNA molecules containing mixture of old and new strands, making a “hybrid”
mitosis
nuclear division associated with somatic cells, producing 2 genetically identical daughter cells
meiosis
nuclear division that produces cells that develop into gametes
daughter cells have two times more DNA than mother, so
therefore cells need to replicate DNA before division
spindle checkpoint
mechanism that ensures chromosome is equally separated during cell division
how do we know what stage of the cell cycle the cell is?
calculate the mitotic index: the proportion of cells undergoing mitosis in a population of cells
DNA = 2N (2C)
the DNA content of cell prior to replication
DNA = 2N (4C)
has twice the DNA content of the cells prior to replication
mitosis 6 stages
1) interphase
2) prophase
3) prometaphase
4) metaphase
5) anaphase
6) telophase and cytokinesis
