class 10

Question 1

To ensure that the highest number of translated polypeptides manage to successfully fold, ______ ______ often aid in the process

Answer 1

chaperone proteins

Question 2

The new polypeptide forms a ___ with chaperones that facilitate folding.

Answer 2

complex

Question 3

Some chaperones help simply by _______ to specific regions of the polypeptide to prevent them from ______ too early.

Answer 3

chaperones; folding

Question 4

How do proteins get to their correct cellular location?

Answer 4

Signal Sequences

Question 5

Where do almost all proteins begin translation?

Answer 5

cytoplasm

Question 6

What are signal sequences?

Answer 6

Short sequences of amino acids that direct proteins to their subcellular location.

Question 7

Gated transport

Answer 7

proteins move between the cytosol and the nucleus through nuclear pore complexes

Question 8

transmembrane transport

Answer 8

protein translocators directly transport specific proteins across a membrane from the cytosol to a space that is topologically distinct

Question 9

vesicular transport

Answer 9

membrane-enclosed transport vesicles ferry proteins from one compartment to another that is topologically equivalent

Question 10

Signal sequences corresponding with each organelle have unique features. How are signal sequences recognized?

Answer 10

complementary sorting receptors

Question 11

Proteins that function in the cytosol don’t contain sorting signals and thus…

Answer 11

remain there after they are synthesized

Question 12

Signal sequences are ___ and ____

Answer 12

necessary and sufficient

Question 13

Proteins are translocated either after or during ____

Answer 13

translation

Question 14

What is the point of entry into the entire endomembrane system for newly synthsized proteins?

Answer 14

the ER

Question 15

Once a protein enters the ER, does it return to the cytosol?

Answer 15

No

Question 16

How would proteins that need to leave the ER to travel to the next compartment in the endomembrane systen (Golgi) ?

Answer 16

They will get packaged into mebranous tubule extensions/vesicles (soluble proteins are in the lumen), which will bud from the ER and fuse with the Golgi membrane. This way the protein can travel between compartments without returning to the cytosol.

Question 17

How does a protein move through the stack of golgi sacs?

Answer 17

In sequences, from the cis face to trans face, and enter a vesicle

Question 18

What do motor protein kinesin do?

Answer 18

Walks vesicles along microtubules to the cell membrane

Question 19

How are soluble proteins different from membrane bound proteins?

Answer 19

Soluble proteins are released into the extracellular space, whereas membrane-bound proteins become incorporated into the plasma membrane

Question 20

Vesicles that are endocytosed from the plasma membrane use what to move the vesicle along microtubules to interior compartments (endosome, lysosome).

Answer 20

motor protein dynein

Question 21

What are endosomes?

Answer 21

Sorting organelles that receive and transport molecules from the plasma membrane and Golgi apparatus to other destinations, such as the vacuole or plasma membrane.

Question 22

Endosomes are involved in what process?

Answer 22

endocytosis

Question 23

What do transport vesicles do?

Answer 23

move materials, such as proteins, between different parts of the cell.

Question 24

How do transport vesicles form?

Answer 24

when a membrane bulges out and pinches off,
and they merge with another membrane to release their cargo

Question 25

Steps of co-translational translocation for a soluble protein:

Answer 25

- Translation continues and the polypeptide is translocated into the lumen of the ER - The signal sequence is later cleaved off by a protein called the signal peptidase. - Once that happens, the new protein is free and soluble in the ER lumen. - After the protein has been translocated and the signal sequence cleaved, the translocator plug moves back into position to close the channel.

Question 26

Constitutive vs. regulated secretion pathways from Golgi

Answer 26

-Constitutive secretion occurs continuously -regulated secretion, proteins are packaged into vesicle and stored; only secreted in response to a specific signal

Question 27

Why is constitutive secretion the default pathway?

Answer 27

it requires no special targeting sequence (beyond the ER insertion sequence required for cotranslational translocation) for cargo to get secreted via this pathway

Question 28

Targeting of lysosomal enzymes to the lysosome: where is the lysosomal enzyme first synthesized and what is added to it?

Answer 28

rough ER, a carboydrate (mannose)

Question 29

Start signal sequences

Answer 29

start moving the protein into the ER lumen

Question 30

Stop signal sequences

Answer 30

Stop moving the protein into the ER lumen (will now be cytosolic)

Question 31

N terminial initial signal sequence: N terminus will be in the___ and always ___

Answer 31

ER lumen, always cleaved

Question 32

Internal initial sequence: N terminus of protein will be on the ___

Answer 32

Cytosolic side

Question 33

The location of the C terminus depends on how many other ...

Answer 33

stop start sequences are in the protein

Question 34

A single internal START sequence produces a protein with...

Answer 34

one transmembrane domain and the N-terminus on the cytosolic side.

Question 35

An N-terminial START transfer sequence followed by a STOP transfer creates a

Answer 35

single-pass protein with an N-terminus in the lumen and a C-terminus in the cytosol.

Question 36

An internal START followed by a STOP creates a

Answer 36

double pass membrane protein with both an N-terminus and a C-terminus in the cytosol.

Question 37

Once a protein is inserted in the ER membrane, it must remain in an orientation that is

Answer 37

topologically equivalent

Question 38

A hydropathy plot can predict

Answer 38

transmembrane domains

Question 39

Hydropathy

Answer 39

the amount of free energy required to move a sequence of amino acids from a nonpolar solvent to water

Question 40

positive part of hydropathy part

Answer 40

hydrophobic

Question 41

negative part of hydropathy part

Answer 41

hydrophilic

Question 42

20-30 amino acids with a positive hydropathy index can indicate an

Answer 42

alpha helix that spans the lipid bilayer