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1

The cytosol of a mammalian cell is divided by ___ into specialized compartments.

Membranes

2

Describe the basic composition of a mammalian cell vis a vis cytosol and organelles.

50% cytosol, 50% organelles

3

The majority of a cell's membrane is found ___.

Internally

4

What are the organelles typically found in a cell?

Nucleus, endoplasmic reticulum, mitochondrion, Golgi apparatus, peroxisome, lysosome, endosome, free polyribosomes

5

Approximately how many mitochondrion are found in the cell?

~200

6

The nucleus is ~___ of cell volume and its membrane is continuous with the ___.

10%; ER

7

What organelles are involved in the sorting and exocytic networks?

ER, Golgi, secretory vesicles

8

What organelles are involved in the endocytic network?

Plasma membrane, endosomes, lysosomes

9

___ are derived from the ER.

Peroxisomes

10

Internal luminal compartments are ___ to the outside of the cell.

Topologically equivalent

11

Translation occurs in the ___.

Cytosol

12

Gated transport takes place ___ between the cytosol and the ___.

Bidirectionally; nucleus

13

Transmembrane transport takes place ___ between the cytosol and what 4 organelles?

unidirectionally; mitochondria, endoplasmic reticulum, plastids, peroxisomes.

14

Vesicular transport involves what 6 organelles?

Golgi, early endosome, late endosome, lysosome, secretory vesicles, cell exterior

15

Vesicular transport occurs bidirectionally from the Golgi to the ___, ___, and ___.

Late endosome, early endosome, secretory vesicles

16

Vesicular transport occurs unidirectionally from the Golgi to the ___, from the early endosome to the ____, from the late endosome to the ___, and from the secretory vesicles to the ___.

Cell exterior; late endosome; lysosome; cell exterior.

17

What are the three types of transport occurring in the cell?

1. Gated transport
2. Transmembrane transport
3. Vesicular transport

18

What do sorting signals do?

Direct proteins to specific compartments

19

Sorting signals are specified by ___.

the amino acid sequence of the protein

20

What are the two general types of sorting signals?

1. Linear sequences, often at the ends of proteins
2. Several separated regions that form a signal patch when folded

21

What are the general signal peptides for the following actions?
1. Import into the ER
2. Import into the mito
3. Import into the nucleus
4. Import into the peroxisome
5. Export from the nucleus

1. Hydrophobic center
2. Amphipathic alpha helices
3. Basic
4. SKL-COOH
5. Nonpolar

22

The nucleus is bounded by a ___ that is perforated by ~4,000 ___ per cell.

Double membrane; nuclear pores

23

What is the nuclear envelope?

The inner and outer nuclear membranes

24

True or false - nuclear pores are only open sometimes.

False - nuclear pores are always open.

25

The nuclear pore is a complex structure with properties of a molecular ___.

Sieve

26

Nuclear pores contain 8-fiber "___."

Baskets

27

Fibrils of the nuclear pore extend into the ___ and the ___ and adhere to trafficking ___.

Nucleus; cytosol; cargo.

28

The nuclear pore is permeable to molecules ___. Larger cargo requires ___ and ___, and active energy-dependent gated transport.

Less than 60kDa; NES; NLS

29

For larger molecules, transport through the nuclear pore requires participation of what two things?

1. Cargo receptors
2. Ran, a small monomeric GTP binding protein

30

Describe the RAN GTPase cycle.

Ran-GDP moves down its concentration gradient into the cell where RanGEF (guanine nucleotide exchange factor) exchanges GDP for GTP, creating Ran-GTP. Ran-GTP moves down its concentration gradient to the cytoplasm, where RanGAP (GTPase activating protein) dephosphorylates Ran-GTP to Ran-GDP. The cycle can begin again.