Unit 1-2

Question 1

Membranes divide

Answer 1

the cytoplasm of eukaryotic cells into distinct compartments.

Question 2

The endomembrane system includes organelles such as (5):

Answer 2

(1) endoplasmic reticulum
(2) golgi complex
(3) endosomes
(4) lysosomes
(5) vacuoles

Question 3

Organelles of the endomembrane system are part of

Answer 3

an integrated network in which materials are shuttled back and forth.

Question 4

Materials are shuttled between organelles in

Answer 4

transport vesicles.

Question 5

Upon reaching their destination, transport vesicles:

Answer 5

fuse with the membrane of the acceptor compartment.

Question 6

The endoplasmic reticulum (ER) is

Answer 6

a network of interconnected internal membranes that extends from the nuclear membrane throughout the cytoplasm

Question 7

The ER membrane forms a continuous sheet enclosing a single internal space: the __

Answer 7

ER lumen

Question 8

The ER is the

Answer 8

largest organelle of most eukaryotic cells:

Question 9

the ER membrane is __ of all cell membranes and the ER lumen is __ of the total cell volume

Answer 9

The ER is the largest organelle of most eukaryotic cells: the ER membrane is ~50% of all cell membranes and the ER lumen ~10% of the total cell volume

Question 10

Three distinct types of ER perform different functions within the cell:

Answer 10

(1) The rough ER
(2) The smooth ER
(3) Transitional ER

Question 11

Ribosomes bound to the rough ER synthesize :

Answer 11

virtually all proteins to be secreted from the cell and proteins for most of the cell’s organelles including:

Question 12

Ribosomes bound to the rough ER synthesize virtually all proteins to be secreted from the cell and proteins for most of the cell’s organelles including (5):

Answer 12

a) the ER itself
b) the Golgi apparatus
c) lysosomes
d) secretory vesicles
e) the plasma membrane

Question 13

Many proteins are glycosylated within the ER by:

Answer 13

covalent attachment of sugars (glucose and mannose to their polypeptide chains)

Question 14

Proteins synthesized on free ribosomes in the cytosol either remain in the cytosol or are transported to:

Answer 14

a) the nucleus b) mitochondria c) chloroplasts d) peroxisomes

Question 15

The synthesis of lipids, including fatty acids, cholesterol and phospholipids, occurs in

Answer 15

the smooth ER

Question 16

The smooth ER makes a major contribution to

Answer 16

the lipid composition of membranes of all organelles by producing most of their lipids

Question 17

After their synthesis in the smooth ER, lipids are

Answer 17

transported from the ER to their ultimate destinations either in vesicles or by carrier proteins

Question 18

SER has developed specialized functions in specific cells: In endocrine cells:

Answer 18

synthesis of steroid hormones

Question 19

SER has developed specialized functions in specific cells: In liver cells:

Answer 19

detoxification of various organic compounds (home of the P450 enzymes)

Question 20

SER has developed specialized functions in specific cells: in muscle cells:

Answer 20

sequestration of calcium ion from cytoplasm of muscle cells

Question 21

Modifying the lipid composition of membranes: Three distinct mechanisms:

Answer 21

1. Enzymatic modification
   (head group)
2. Modification during
   vesicle formation
3. Modification by
   phospholipid transfer proteins

Question 22

The rough ER forms

Answer 22

oriented stacks of flattened cisternae

Question 23

The smooth ER forms a

Answer 23

fine network of tubules connected to the RER

Question 24

Transitional ER
A region of the ER where

Answer 24

secretory vesicles exit the ER en route to the Golgi apparatus

Question 25

Both proteins and lipids are exported from the ER in

Answer 25

transport vesicles

Question 26

Both proteins and lipids are exported from the ER in transport vesicles These vesicles bud from:

Answer 26

the transitional ER

Question 27

Both proteins and lipids are exported from the ER in transport vesicles These vesicles bud from the transitional ER After budding, these vesicles carry their cargo first to __ and then to __

Answer 27

(1)ER-golgi intermediate compartment (2) golgi appartus

Question 28

One of the main functions of the ER once a protein has entered this organelle is called

Answer 28

quality control, a system that monitors proper folding of a protein

Question 29

quality control

Answer 29

1. After initial glycosylation in the ER, glucose residues are removed leaving a single terminal glucose 2. The protein then associates with chaperones including calnexin 3. The terminal glucose is removed and if the protein is not folded correctly.... 4. ....the enzyme UGGT adds the glucose back.... 5. ....and refolding is attempted again. 6. If the protein then folds it can be transported to the next compartment. 7. If it remains unfolded after several attempts, more sugars (mannose) are removed.... 8. ....and the protein is dislocated from the ER to the cytoplasm to be degraded by the proteasome (ER- associated degradation (ERAD)).

Question 30

If too many unfolded proteins accumulate in the ER, then

Answer 30

the unfolded protein response (UPR) is activated:

Question 31

If too many unfolded proteins accumulate in the ER, then the unfolded protein response (UPR) is activated (3):

Answer 31

* Stops translation * Degrades misfolded proteins * Produces more chaperones

Question 32

Prolonged UPR leads to

Answer 32

apoptosis

Question 33

Morphologically the Golgi is composed of

Answer 33

flattened membrane- enclosed sacs (cisternae) and associated vesicles

Question 34

The Golgi apparatus is usually located

Answer 34

near the cell nucleus

Question 35

Functions of the Golgi (3):

Answer 35

1. A factory in which proteins received from the ER: a. are further glycosylated b. are sorted for transport to their eventual destinations 2. Some lipids, including glycolipids and sphingomyelin, are synthesized within the Golgi complex 3. In plant cells, the Golgi serves as the site at which the complex polysaccharides of the cell wall, including hemicelluloses and pectins, are synthesized

Question 36

Functions of the Golgi 1. A factory in which proteins received from the ER: a. are further glycosylated b. are sorted for transport to their eventual destinations (3):

Answer 36

- lysosomes - the plasma membrane - extracellular medium

Question 37

__are synthesized within the Golgi complex

Answer 37

Some lipids, including glycolipids and sphingomyelin

Question 38

. In plant cells, the Golgi serves as the site at which the

Answer 38

complex polysaccharides of the cell wall, including hemicelluloses and pectins, are synthesized

Question 39

The Golgi consists of an ordered series

Answer 39

of compartments

Question 40

Each Golgi stack has two distinct faces:

Answer 40

1. en entry, or cis, face 2. anexit,ortrans, face

Question 41

The cis face of the Golgi is adjacent to

Answer 41

the ER

Question 42

the trans face of the golgi points toward:

Answer 42

the plasma membrane

Question 43

Five functionally distinct compartments of the golgi:

Answer 43

1. the cis Golgi network 2. the cis compartment of the Golgi stack 3. the medial compartment of the Golgi stack 4. the trans compartment of the Golgi stack 5. the trans Golgi network

Question 44

The movement of proteins within the Golgi

Answer 44

1. Proteins and lipids enter the cis Golgi network in transport vesicles from the ER 2. The proteins and lipids then progress to the cis, medial and trans compartments (cisterna) of the Golgi stack 3. The proteins and lipids then move to the trans Golgi network, which acts as a sorting and distribution center, directing molecular traffic of transport vesicles to lysosomes, the plasma membrane and cell exterior

Question 45

The movement of proteins within the Golgi Vesicular transport:

Answer 45

cargo is shuttled from the CGN to the TGN in vesicles

Question 46

The movement of proteins within the Golgi:Cisternal maturation:

Answer 46

each cisterna matures as it moves from the cis face to the trans face, mediated by vesicles traveling from trans face to cis face