ch 15 Flashcards
what does this show
nuclear membranes and the ER may have evolved through invagination of the plasma membrane and that is why the inner and outer nuclear membrane is continuous with the ER lumen
what does this show
mitochondria are thought to have originated when an aerobic bacterium was engulfed by a larger anaerobic eukaryotic cell
what are the three ways membrane-enclosed organelles import proteins
- transport through nuclear pores
- transports across membranes
- transport by vesicles
label the three ways membrane enclosed organelles import proteins
red: transport through nuclear pores
blue: transport across membranes
green: transport by vesicles
Describe the amino acid signals that are required for proteins to be IMPORTED INTO ER AND ENDOMEMBRANE SYSTEM
long hydrophobic stretch at N-terminus, 30 AA long (hydrophobic = green)
Describe the amino acid signals that are required for proteins to be RETAINED IN THE ER
K-D-E-L must be at C-terminus (lysine, aspartate, glutamate, leucine)
Describe the amino acid signals that are required for proteins to be IMPORTED INTO MITOCHONDRIA AND CHLOROPLAST
50 AA long at N-terminus, hydrophilic, few negative charges
Describe the amino acid signals that are required for proteins to be IMPORTED INTO NUCLEUS
series of positively charged AAs anywhere
(+AA = LYS lysine, ARG arginine, HIS histidine)
(positively charges = red)
what indicates the N-terminus of a protein
+H3N
what indicates the C-terminus of a protein
COO-
what do signal sequences do
- tell the protein where to go
- proteins can be moved by replacing its signal sequence
if a protein has no signal sequence it is a
cytosolic protein
the outer nuclear membrane is continuous with the ____________ ___________
endoplasmic reticulum
what makes up the nuclear envelope
- outer nuclear membrane
- inner nuclear membrane
what is this? label
this is a nuclear pore
red: nuclear basket
orange: nuclear pore complex proteins
blue: nuclear lamina
green: cytosolic fibers
the ________ ___________ is the most extensive membrane network in eukaryotic cells
endoplasmic reticulum
describe the role of clathrin in receptor mediated endocytosis
a protein that forms basketlike cages that shape membranes into vesicles, attaches to adaptin
describe the role of dynamin in receptor mediated endocytosis
assembles as a ring around the neck of each deeply invaginated clathrin-pinching coated pit and pinches off the vesicle from its parent membrane
describe the role of snares in receptor mediated endocytosis
helps anchor transport vesicles to their target proteins and catalyzes the final fusion of two membranes
Describe the process of protein glycosylation
- glycosylation is the addition of 14 sugars to the Asn when the sequence Asn-Xxx-Ser/Thr is present
-this occurs 1/200 amino acids
-the surface of the ER is home to many glycosylated proteins
Explain how a single peptide directs a protein to the lumen of the ER. Describe what happens at each stage from recognition of the signal to the protein floating freely in the lumen.
the signal sequence on a precursor protein is detected by a import receptor protein that send the protein through the protein translocator in the outer membrane and the protein translocator in the inner membrane to the lumen of the ER where its signal sequence will be cleaved off
describe how a single pass transmembrane protein is kept in the lipid bilayer
the stop transfer sequence stops it (series of hydrophobic AA)
describe how a double pass transmembrane protein is kept in the lipid bilayer
it has an internal ER signal sequence and a stop transfer sequence
