Topic 4, Lecture 1

Question 1

List the types of protein transport.

Answer 1

Gated transport, transmembrane transport, vesicular transport, and engulfment

Question 2

Which organelles use gated transport?

Answer 2

Nucleus

Question 3

Which organelles use transmembrane transport?

Answer 3

Plastids, mitochondria, peroxisomes, endoplasmic reticulum

Question 4

Describe gated transport.

Answer 4

Gated transport only occurs in the nucleus. Gated transport requires the use of a large pore to accommodate folded proteins.

Question 5

Describe transmembrane transport.

Answer 5

Transmembrane transport is transport from cytosol across a membrane into an organelle.

Question 6

Describe vesicular transport.

Answer 6

Protein resides in an organelle and moves to another organelle.

Question 7

We can describe signaling sequences as _______ and _________.

Answer 7

Necessary and Sufficient

Question 8

When analyzing signaling sequences it is important to pay attention to…

Answer 8

Length, Nature, Distance, Location

Question 9

What does it mean for a signaling sequence to be closer to the amino or carboxy termini?

Answer 9

If a signaling sequence is closer to either end of the polypeptide, it makes it easier to cleave after transport.

Question 10

What does it mean for a signaling sequence to be in the middle of a polypeptide?

Answer 10

The signaling sequence contributes to the permanent three-dimensional structure of the polypeptide and cannot be cleaved after transport.

Question 11

What is the relation between the nucleus and the endoplasmic reticulum?

Answer 11

The nuclear membrane is continuous with the endoplasmic reticulum.

Question 12

Which organelles have a double membrane?

Answer 12

Nucleus and Mitochondria

Question 13

How many phospholipid layers correspond to double membranes?

Answer 13

Four phospholipid layers are equivalent to a double membrane

Question 14

What are the unique characteristics of the nuclear membrane?

Answer 14

It is punctuated with pores and lined with a cytoskeletal lamina.

Question 15

What is the difference between the nuclear pore and the nuclear pore complex?

Answer 15

The nuclear pore is just the opening but the nuclear pore complex is the opening and all\ of its associated proteins.

Question 16

What do we refer to the cytoskeletal lamina as when it is on the nuclear membrane?

Answer 16

Nuclear lamina

Question 17

What does the nuclear lamina look like?

Answer 17

Gauze glued to the inside

Question 18

Give a basic description of the nuclear pore complex.

Answer 18

The nuclear pore complex is a bunch of proteins that act like a gate at the nuclear pore.

Question 19

Describe the morphology of the nuclear pore complex.

Answer 19

The nuclear pore complex has an octagonal structure that extends down into the nucleus that is tied together to create a basket on the inside. Long filaments extend into the nucleoplasm in a terminal ring called the nuclear basket.

Question 20

How many Daltons is the nuclear pore complex?

Answer 20

66 million daltons

Question 21

What are proteins referred to as when they belong to the nuclear pore complex?

Answer 21

Porins

Question 22

How long are the filaments that extend into the nucleoplasm?

Answer 22

8-100 nanometers

Question 23

What is the most important aspect in the selective nature of the NPC?

Answer 23

The nuclear pore complex has FG nuceloporins.

Question 24

Describe FG nucleoporins.

Answer 24

FG nucleoporins are hydrophobic repeats made of phenylalanine and glycine that stick together and to other nonpolar molecules and serve as binding sites to the beta subunits for the importin receptor.

Question 25

Give the analogy for the FG nucleoporins.

Answer 25

Sieve

Question 26

Describe the functionality of the FG nucleoporins.

Answer 26

They’re flexible so the molecules adjust to allow whichever molecules try to come in that have the appropriate sequence can come in.

Question 27

NLS

Answer 27

Nuclear localization signal

Question 28

Describe the usage of importin.

Answer 28

The importin (import receptor) has an alpha and beta subunit. The alpha subunit recognizes and binds to the protein because of high affinity and the beta subunit binds to the FG nucleoporins

Question 29

Describe the nuclear localization sequence.

Answer 29

Short, middle, basic/polar

Question 30

Karyopherins

Answer 30

Importin alpha and beta–form a heterodimeric nuclear-import receptor

Question 31

What happens if we change one of our lysine’s in our NLS to a threonine when visualizing our cells?

Answer 31

With the original sequence, we can see little circles (nucleus), however, when we use the replaced sequence, we see the cytoplasm of our cells but blanks in place of the nucleus.

Question 32

GEF

Answer 32

Guanine Exchange Factor, replaces GDP with a GTP

Question 33

GAP

Answer 33

GTPase Activation (accelerating) Protein, GTP back to GDP, accelerates the rate at which GTP hydrolysis occurs, inactivates protein by speeding up hydrolysis

Question 34

How is unidirectional transport achieved?

Answer 34

Moving down the concentration gradient

Question 35

Draw and explain nuclear import with RAN.

Answer 35

Ight