1) Which of the following statements about transport into the mitochondria is FA
ID: 92894 • Letter: 1
Question
1) Which of the following statements about transport into the mitochondria is FALSE?
a) The signal sequence on proteins destined for the mitochondria is recognized by a receptor protein in the outer membrane of the mitochondria.
b) Proteins that are transported into the mitochondria are unfolded as they are being transported.
c) Transport of proteins into the mitochondria requires SRP and the SRP receptor.
d) After a protein is made in the cytosol it must move through two protein translocators to reach the inner mitochondrial matrix.
2.Which coat protein is involved in vesicle formation during endocytosis – vesicle forms from plasma membrane and fuses with endosomes?
a) COPI
b) COPII
c) v-SNARES d) Clathrin
3. Which of the following statements about vesicular membrane fusion is TRUE?
a) Membrane fusion does not always immediately follow vesicle docking.
b) The interactions of the v-SNAREs and t-SNAREs pull the vesicle membrane and the target organelle together so that their lipids can intermix.
c) NSF and SNAP disassemble the SNARE complex so the SNAREs can be recycled.
d) All of the above are true.
Explanation / Answer
Answer=
1) the following statements about transport into the mitochondria is FALSE?
c) Transport of proteins into the mitochondria requires SRP and the SRP receptor.
Explaination=mitochondrial protein are first synthesized as precursor proteins in the cytosol.& then translocated into mitochondria by a posttranslational mechanism.
Most of proteins have a signal sequence at their N -terminus that is rapidly removed after import by a protease in the mitochondrial matrix
proteins that are transported into endoplasmic reticulum requires SRP receptors not mitochondrial proteins
INCORRECT OPTIONS =
a) The signal sequence on proteins destined for the mitochondria is recognized by a receptor protein in the outer membrane of the mitochondria.=in the first step of translocation process ,the mitochondrial proteins from aggregating or folding up spontaneously before they engage with the TOM complex in the outer mitochondrial membrane .TOM complex,recognize the mitochondrial signal sequences.& acts as a receptor protein
b) Proteins that are transported into the mitochondria are unfolded as they are being transported.= mitochondrial precursor proteins do not fold into their native structures after they are synthesized.
They remain unfolded through interactions with other proteins in the cytosol.
all these interacting proteins helps to prevent the precursor proteins from aggregating or folding up spontaneously .
.
d) After a protein is made in the cytosol it must move through two protein translocators to reach the inner mitochondrial matrix.= protein translocation across mitochondrial membrane is mediated by multi- subunit protein complexes that function as protein translocators .
there are 2 protein translocators . TOM complexes & TIM complexes
TOM -require for import of all nucleus -encoded mitochondrial protein
TIM - hepls to insert intermembrane proteins into inner membrane
2.Which coat protein is involved in vesicle formation during endocytosis – vesicle forms from plasma membrane and fuses with endosomes?
Answer =
d] Clathrin
explaination = clathrin is the coat protein that forms vesicles
clathrin may interact directly or indirectly with molecular corgo being internalized
clathrin coated pits are basket -like
clathrin forms multiple complexes based on its association with different adaptor protein (APs )
Clathrin that is associated with AP2 forms vesicles from the plasma membrane during endocytosis that transport to the early endosome
INCORRECT OPTIONS ARE =
a) COPI = IT forms vesicles for both intra-golgi transport & retrograde transport from the golgi to ER
b) COPII = it forms vesicles for anterograde transport from ER to Golgi
c) v-SNARES - are integral membrane proteins present on vesicles
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