2025 MICRO 401 EXAM 2 (PASSED) QUESTIONS
WITH 100% ACTUAL SOLUTIONS!!
What are the types of proteins in the bacterial cell wall? Answer - lipoproteins,
integral membrane proteins, porins, peripheral membrane proteins, cell wall
attached proteins, periplasmic proteins, secreted proteins
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What are periplasmic associated proteins? Answer - GLOUBULAR proteins
retained within the periplasmic space in gram - cells and gram + equivalent
What are porins? Answer - INTEGRAL OUTER MEMBRANE proteins specific to
gram - cells (LPS)
What are secreted proteins? Answer - proteins secreted into the environment
from the cell
What are peripheral membrane proteins? Answer - associated with membrane
through GLOUBULAR domains that interact closely with lipids
What are lipoproteins? Answer - proteins with lipid modifications at the N
termini to embed in the membrane
What are integral membrane proteins? Answer - proteins that contain 1+ alpha
helical transmembrane domains
,What are cell wall associated proteins? Answer - proteins that are covalently
bonded to peptidoglycan, usually at the stem or bridge peptide
major mechanisms/general features/purpose of protein translocation across
the cytoplasmic membrane Answer - All proteins that function outside of the
cytosol need to translocate to reach their final destinations of secretion outside
the cell or exportation to the cell membrane and this process requires passage
through phospholipid bilayer which is an energetically unfavorable tprocess so
the SEC and TAT systems are used
Purpose of the SEC system Answer - to transport EXPORTED proteins such as
cell wall associated proteins, integral membrane proteins, periplasmic proteins,
-transports the proteins unfolded states and thread them across the membrane
within a protein channel
Purpose of the TAT system Answer - to transport SECRETED proteins outside
the cell and this system is only used for proteins that require cofactors [such as
vitamin K., metal ions, etc.]
-the proteins are transported in completely folded or partially folded states
What are the components of the Sec Translocation machinery? Answer - -are
targeted for export by a characteristic N-terminus of amino acids
-exported proteins have a signal/leader peptide called SP1 that recognizes the
overall topology of the N, H and C regions
-Sec proteins are synthesized at ribosomes in a normal fashion
Describe the TM domain of integral membrane proteins exported by the Sec
system Answer - The hydrophobic transmembrane domain (central H region)
of INTEGRAL membrane proteins serves as both a Sec substrate signal an as a
permanent structural element
, -TM proteins DO NOT have a recognition sequence for SPase
-have an alpha helical domain that is like the H region
Describe the sequence topology for Sec exported substrates Answer - The
exported proteins have a leader/signal peptide called SP1
-have an N REGION that has + charges AAs to interact with membrane
phospholipids
-a central H REGION that is hydrophobic AAs
-a POLAR C REGION that contains the recognition site has a A-X-A motif signal
peptidase that is cleaved by the SPase 1 after transport
Feature of Sec mediated transport of GLOBULAR proteins via SECB Answer - -
most globular preproteins are transported via a molecular chaperone to
prevent premature protein aggregation SecB
SecB importance and signal peptide importance Answer - -SecB is important to
Sec mediated transport of globular proteins because it is the molecular
chaperone
-The signal peptide helps to prevent premature folding and give SecB time to
step in and further prevent folding in the cytosol
How are globular cytoplasmic membrane proteins targeted to the Sec system?
Answer - they are targeted to the Sec system as ribosome bound nascent
chains (RNCs) by the Signal Recognition Particle (SRP) or by the molecular
chaperone SecB
How is pathway a or b chosen in Sec mediated transport? Answer - this choice
is driven by the hydrophobicity of the emerging peptide
-SRP likes hydrophobic peptides so it like the hydrophobic integral membrane
proteins
WITH 100% ACTUAL SOLUTIONS!!
What are the types of proteins in the bacterial cell wall? Answer - lipoproteins,
integral membrane proteins, porins, peripheral membrane proteins, cell wall
attached proteins, periplasmic proteins, secreted proteins
"Perfect Pretty Sexy People Love Iced Coffee"
What are periplasmic associated proteins? Answer - GLOUBULAR proteins
retained within the periplasmic space in gram - cells and gram + equivalent
What are porins? Answer - INTEGRAL OUTER MEMBRANE proteins specific to
gram - cells (LPS)
What are secreted proteins? Answer - proteins secreted into the environment
from the cell
What are peripheral membrane proteins? Answer - associated with membrane
through GLOUBULAR domains that interact closely with lipids
What are lipoproteins? Answer - proteins with lipid modifications at the N
termini to embed in the membrane
What are integral membrane proteins? Answer - proteins that contain 1+ alpha
helical transmembrane domains
,What are cell wall associated proteins? Answer - proteins that are covalently
bonded to peptidoglycan, usually at the stem or bridge peptide
major mechanisms/general features/purpose of protein translocation across
the cytoplasmic membrane Answer - All proteins that function outside of the
cytosol need to translocate to reach their final destinations of secretion outside
the cell or exportation to the cell membrane and this process requires passage
through phospholipid bilayer which is an energetically unfavorable tprocess so
the SEC and TAT systems are used
Purpose of the SEC system Answer - to transport EXPORTED proteins such as
cell wall associated proteins, integral membrane proteins, periplasmic proteins,
-transports the proteins unfolded states and thread them across the membrane
within a protein channel
Purpose of the TAT system Answer - to transport SECRETED proteins outside
the cell and this system is only used for proteins that require cofactors [such as
vitamin K., metal ions, etc.]
-the proteins are transported in completely folded or partially folded states
What are the components of the Sec Translocation machinery? Answer - -are
targeted for export by a characteristic N-terminus of amino acids
-exported proteins have a signal/leader peptide called SP1 that recognizes the
overall topology of the N, H and C regions
-Sec proteins are synthesized at ribosomes in a normal fashion
Describe the TM domain of integral membrane proteins exported by the Sec
system Answer - The hydrophobic transmembrane domain (central H region)
of INTEGRAL membrane proteins serves as both a Sec substrate signal an as a
permanent structural element
, -TM proteins DO NOT have a recognition sequence for SPase
-have an alpha helical domain that is like the H region
Describe the sequence topology for Sec exported substrates Answer - The
exported proteins have a leader/signal peptide called SP1
-have an N REGION that has + charges AAs to interact with membrane
phospholipids
-a central H REGION that is hydrophobic AAs
-a POLAR C REGION that contains the recognition site has a A-X-A motif signal
peptidase that is cleaved by the SPase 1 after transport
Feature of Sec mediated transport of GLOBULAR proteins via SECB Answer - -
most globular preproteins are transported via a molecular chaperone to
prevent premature protein aggregation SecB
SecB importance and signal peptide importance Answer - -SecB is important to
Sec mediated transport of globular proteins because it is the molecular
chaperone
-The signal peptide helps to prevent premature folding and give SecB time to
step in and further prevent folding in the cytosol
How are globular cytoplasmic membrane proteins targeted to the Sec system?
Answer - they are targeted to the Sec system as ribosome bound nascent
chains (RNCs) by the Signal Recognition Particle (SRP) or by the molecular
chaperone SecB
How is pathway a or b chosen in Sec mediated transport? Answer - this choice
is driven by the hydrophobicity of the emerging peptide
-SRP likes hydrophobic peptides so it like the hydrophobic integral membrane
proteins
