Unit 5 Flashcards
(42 cards)
Using radiolabeled amino acids, Palade and colleagues were able to define the pathway taken by secreted proteins. Which of the following represents that pathway?
Rough ER -> Golgi -> secretory vesicles -> cell exterior
A signal sequence in the polypeptide chain targets all but ………proteins to the rough ER surface
mitochondrial
Ribosomes that are free in the cytosol and those that are bound to the ER membrane have…
the same types of large and small subunits
When compared to polypeptides synthesised in vitro on free ribosomes, the polypeptides synthesized from the same mRNA on mocrosome-bound ribosomes are…
smaller
As they emerge from the ribosome, signal sequences are recognised and bound by a(n)…
signal recognition particle
Which of the following provides evidence for the signal hypothesis for the targeting of a secretory protein to the rough ER?
a. The protein is larger when synthesized in vitro on free polysomes.
b. The secretory protein ends up on the cytosol when a short sequence is deleted by genetic engineering
c. A normally cytosolic protein is secreted when a specific sequence is added to it by genetic engineering
If the secretory protein is isolated from the secretory vesicles and injected into the cytosol, it will…
remain in the cytosol until it is degraded
Protein folding in the ER is assisted by a chaperone called…
BiP
Most higher eukaryotic plasma membrane proteins are synthesised on…
rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the Golgi apparatus
The signal sequence that targets a nascent polypeptide and its mRNA to the rough ER is rich in ………….. amino acids
hydrophobic
Disulfide bonds within or between proteins form easily in which of the following?
The ER but not the cytolsol
GPI-anchored proteins are synthesised…
as transmembrane proteins, cleaved and attached to the GPI group on the lumenal surface of the ER
Proteins attached to the outer half of the plasma membrane bilayer are usually attached by a…
Glycosylphosphatidylinositol (GPI) anchor
The unfolding response involves…
a. general inhibition of protein synthesis
b. increased synthesis of chaperones
c. increased activity of proteosomes
Most cellular lipids are synthesised in…
the endoplasmic reticulum
Newly synthesised membrane lipids are found in both halves of a membrane bilayer because they are…
synthesised on one surface and flipped to the other surface by proteins called flippases
The sequence Lys-Asp-Gu-Leu-(KDEL) serves as an ER retention signal for proteins by binding to KDEL receptors that…
transport the proteins from the Golgi apparatus back to the ER
Vesicles enter the Golgi apparatus by fusing with ………. and they exit………….
the cis (convex) face, the trans (concave) face
Which proteins do not pass through the Golgi apparatus?
Ribosomal proteins
Which of the following types of vesicles does not bud directly from the trans Golgi network?
Lysosomes
N-linked oligosaccharides are added in the …………and modified in the …………….
ER; Golgi
Lysosomal proteins are marked by the addition of a phosphate to a … group.
mannose
The enzyme that modifies the mannose group on lysosomal proteins recognizes and binds to a(n)…
signal patch
Which of the class of lipids is synthesised in the Golgi apparatus?
Glycolipids
