Lecture 20 Transmembrane proteins, Golgi, COP

Question 1

A protein targeted to the ER lumen, after it
is fully synthesized and properly folded,
has 1 of 2 options

Answer 1

Option 1. It is retained in the ER lumen, if
that is where it functions

Option 2. It is transported from the ER to the Golgi complex for further modification and delivered to distal parts of the biosynthetic/secretory pathway (e.g. Golgi, lysosomes, plasma membrane). In some cases, the final destination could be outside the cell

Question 2

The Golgi apparatus receives proteins and lipids from….

Answer 2

the ER and sorts them to other organelles, the plasma membrane or the cell exterior

Question 3

Material moves from ER to…

Answer 3

Golgi and then to other
compartments and the
plasma membrane in a
proximal to distal direction

Question 4

what does TGN and CGN stand

Answer 4

trans-Golgi
network, cis-Golgi
network

Question 5

what is the Structure of Golgi Complex?

Answer 5

• Smooth, flattened, disk-like cisterna (~0.5-1 micron in diameter).
• ~8 (or fewer) cisternae/stack—range
  from a few to several 1000 stacks per cell.
• Curved like a shallow bowl.
• Shows polarity: cis medial–trans cisternae.
• Cisternae are biochemically unique.
• Membrane supported by protein skeleton (actin, spectrin).
• Scaffold linked to motor proteins that direct movement of vesicles
  into and out of the Golgi.

Question 6

CGN acts as a what

Answer 6

sorting station (i.e.,
sorts whether proteins should continue
on to the next Golgi station or be shipped back to the ER)

Question 7

TGN sorts protein into different types of what

Answer 7

vesicles—vesicles go to plasma
membrane or other intracellular
destinations (e.g. lysosomes)

Question 8

Golgi is the ______ ______of the cell

Answer 8

processing plant

Question 9

In addition to sorting, the Golgi is also involved in synthesis of ________ and
specific ________ of proteins and lipids (glycosylation and proteolytic modification)

Answer 9

polysaccharides, modification

Question 10

Different cisternae of the Golgi contain

Answer 10

different enzymes that modify proteins

Question 11

Proteins are modified _____-_____ as they traverse the Golgi; fully processed _______
at the TGN

Answer 11

step-wise, proteins

Question 12

the differential staining of the Golgi cisternae reflects their…

Answer 12

biochemical differences

Question 13

Fully processed proteins are sorted to the…

Answer 13

trans-Golgi network (TGN), and then sorted and delivered to their final
destinations

Question 14

Exocytosis:
Mucin secretion is
an example of

Answer 14

constitutive
secretory pathway

Question 15

the release of
insulin and
neurotransmitters
is what pathway?

Answer 15

regulated secretory pathway

Question 16

Defective protein targeting and trafficking causes many diseases through what mechanisms? (2)

Answer 16

Protein truncations / Single-nucleotide polymorphisms (SNPs)

Question 17

Cystic fibrosis (CF) is caused by a mutation what gene

Answer 17

in the cystic fibrosis transmembrane conductance regulator
(CFTR) gene

Question 18

name and describe the most common mutation

Answer 18

ΔF508, is
a deletion of three nucleotides that results in a loss of the amino acid phenylalanine (F) at the 508th position of the protein. This mutation accounts for two-thirds (66–70%) of CF cases worldwide.

Question 19

where are Fully processed proteins sorted to

Answer 19

the trans-Golgi network (TGN) then to final destinations

Question 20

The transfer of vesicles from ER to
Golgi, and between the Golgi sub-compartments, is achieved by…

Answer 20

coat proteins

Question 21

Coat proteins have 2 functions:

Answer 21

1. Helps form the vesicle.
2. Helps select ‘cargo’ (i.e. material inside or on vesicle)

Question 22

Electron micrographs reveal what on vesicles

Answer 22

dense protein coat (COPI and COPII)

Question 23

what are COPI and COPII

Answer 23

protein complexes that assemble on the
cytosolic surface of donor compartment membranes at sites where
budding takes place

Question 24

what protein complex does this describe?

coated vesicles move in
retrograde direction

Answer 24

COPI

Question 25

what protein complex does this describe?

coated vesicles move in
anterograde direction

Answer 25

COPII

Question 26

Lysosomes: Key Features

Answer 26

• Digestive organelles
• Size: 25 nm to 1 μm
• Internal pH of 4.6 (proton
  pump or H+-ATPase)
• Contains hydrolytic enzymes: acid hydrolases
• Lysosomal membrane is
  composed of glycosylated
  proteins that act as a protective lining next to acidic lumen