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[CAS BI 203] - Midterm Exam Guide - Everything you need to know! (66 pages long)


Department
Biology
Course Code
CAS BI 203
Professor
Kenneth Adams
Study Guide
Midterm

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BU
CAS BI 203
MIDTERM EXAM
STUDY GUIDE

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Lecture 1 10/15/14 6:09:00 PM
Two forms of enzyme/substrate binding
!1. Lock and key
!2. Induced fit
how do you regulate proteins
!1. allosteric regulation
!2. phosphorylation and dephosphorylation
!3. protein interactions
figure 8.43 = regulation of camp protein kinase
!this is one type of the pathway, composed of regulatory and catalytic subunit
!active site is the catalytic unit of the kinase
!when reg unit bound to active site the kinase is inactive
!cAMP – binds to kinase, when to reg unit, causes conformation change so then the
catalytic subunit is out.
!Shows how you can control something by having it bound
Discussion 1
Signal hypothesis
General answer: how a polypeptide chain is transferred across a membrane, how do specific
proteins get across the membrane
Hypothesis: secreted proteins have specific sequence that is recognized and brought to the
membrane that then allows for their entrance into the ER
!Ribosome/cytosolic proteins: in cytosol so don’t need to be brought into a membrane
because what they synthesize are in the cytosol, larger
!Ribosomes bound to the ER: proteins they synthesize are secreted proteins which then
go into ER then to golgi which then go to secretory vesicles when can then be
exported to the exterior of the cell, (p375 – different pathways that proteins can go),
shorter
Three proposals of what was going on: in context section
!1. Unique set of codons near 3’ initiation site for translation meaning that the codons
are slightly downway from the initiation site which is usually near the 5’ end.
!2. Once it is translated, it codes for specific amino acid sequence that will be at the
amino terminus (they go N C)
!3. Signal sequence will trigger the ribosome to the protein which triggers synthesis of
that protein as it goes into the ER
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!diagram on 377, this is exemplified
what cells can they look at for their experiment?
!Cancer cells usually called myeloma because
What experiments can they do?
!Density gradients and centrifugation because separates out the microsomes with
ribosomes attached, so you have two solutions one with microsomes with ribosomes
and other without ribosomes
!Then looking at these different solutions and how the proteins are being processed
!In vitro (cells instead of whole organism) talking about in vitro translation, the
synthesis of proteins as mrna goes to make a protein
o!Preribosomes = doing the translation of the protein, looking at light chain
mRNA and one with microsomes and one without, solution with 3 ribosomes
then they make a larger protein, so membrane bound ribosomes to ER
(microsomes) yield in shorter protein because the membrane is cleaved at
some point
!This tells us that sequence that needs to be removed
!Proteases – cut up peptide bonds, if microsomes so proteins inside microsomes, if just
preribosomes making protein then the protein would be degraded
!They found three main things
How do they visualize the proteins and determine the length?
!Gel electrophoresis, wanted to separate the proteins out based on their size, SDS
(detergent that breaks down and allows for the separation of the sizes) PAGE
o!Negative charge and positive charge, proteins are negatively charged by SDS,
so negative field causes them to move down the gel, gel is dense, smaller
proteins run down the gel lower and heavier ones will be higher, the smaller
proteins get to move through the dense gel quicker, because they want to run
to the positive field on the bottom and away from the negative field on the top
o!Western blotting =
o!S lane = secreted protein, normally
o!Free ribosomes translated into protein (longer, so heavier so slower) = lane 1
o!Lane 2 =membrane bound, because lower, so shorter and lighter proteins,
same size as the S
!membrane bound ribosomes
o!3 – expose membrane bound ribosomes to protease it is protected because it’s
the same size as if you don’t expose it and it is the same size of the normal
secreted protein
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