Exam 3 - Lecture 6

Question 1

The endomembrane system is an_____and what are its 3 functions?

Answer 1

internal membrane system within the eukaryotic cell that
carries out a variety of functions such as:
 Synthesis of proteins and their transport
 Metabolism and movement of lipids
 Detoxification

“DMs”

Question 2

membrane communication

Answer 2

The membranes of the system are either directly in contact with each other or can communicate through the formation of vesicles

Question 3

What are the functions of The endoplasmic reticulum and the Golgi complex are sites for

Answer 3

protein synthesis, processing, and sorting

Question 4

what is the function of Endosomes

Answer 4

carry and sort material brought into
the cell

Question 5

what is the function of the Lysosomes

Answer 5

digest ingested material and unneeded cellular
components

Question 6

describe the ER compositon/ appearance

Answer 6

The endoplasmic
reticulum (ER) is a
continuous network of flattened sacs, tubules, and
vesicles through the
cytoplasm of a eukaryotic
cell

The membrane-bound sacs
are called ER cisternae,
and the space inside them is the lumen
is the ER lumen

Question 7

The endoplasmic
reticulum (ER) is a
continuous network of

Answer 7

flattened sacs, tubules, and
vesicles through the
cytoplasm of a eukaryotic
cell

Question 8

ER cisternae

Answer 8

membrane bound sacs

Question 9

ER lumen

Answer 9

space inside the cisternae

Question 10

Rough ER is characterized by

Answer 10

ribosomes on the cytosolic
side of the membrane
 form large flattened sheets

Question 11

Smooth ER lacks

Answer 11

ribosomes
and form tubular structures

Question 12

2 different ribosome locations

Answer 12

in the cytosol - responsible for protein

ER - membrane proteins come from ER

Question 13

The lumenal spaces of rough and smooth ER are

Answer 13

continuous

Question 14

Rough ER Functions

Answer 14

Biosynthesis of proteins: Ribosomes on the cytosolic side of the
rough ER membrane synthesize both membrane-bound and
soluble proteins for the endomembrane system

Question 15

Rough ER is the site for

Answer 15

 The initial steps of addition of carbohydrates to glycoproteins
 The folding of polypeptides
 Recognition and removal of misfolded proteins
 Assembly of multimeric proteins

C.R.A.P
- Carb addition to gylcoprotiens
- Recognition and removal of misfolded proteins
- Assembly of multimeric Protein
- Polpeptide folding

Question 16

Funtions of the ER

Answer 16

1. Synthesis of proteins for Incorporation into the
   plasma membrane,Organelles of the
   endomembrane system, and Export from the cell
2. Synthesis of lipids
3. Plays a Central Role in the
   Biosynthesis of Membranes

Question 17

Smooth ER Functions

Answer 17

1. Drug Detoxification:
   involves hydroxylation: adding hydroxyl groups to hydrophobic drugs increases
   their solubility, making them easier to excrete from the body
2. Carbohydrate Metabolism:
    involved in breakdown of stored glycogen using glucose-6-phosphatase
   enzyme (unique to smooth ER)
3. Calcium Storage
    Example: calcium ions stored in ER lumen of
   muscle cells and released when needed for muscle
   contraction.
4. Steroid Biosynthesis
    large amounts of smooth ER are found in cells that synthesize cholesterol and steroid hormones

Question 18

Both types of ER are present in _________ but________

Answer 18

most eukaryotic cells, but there is variation in the relative amounts

 Cells involved in synthesis of secretory proteins have prominent rough ER networks

 Cells producing steroid hormones tend to have extensive networks of smooth ER

Question 19

Be able to differentiate look, funciton, structure

Answer 19

see slides

Question 20

After the ER Glycoproteins and membrane lipids from the ER undergo

Answer 20

further processing and are sorted and packaged for transport IN the Golgi complex

Question 21

the golgi complex plays a central role

Answer 21

in membrane and protein trafficking in eukaryotic cells

Question 22

Golgi stack

Answer 22

a series of 3-8 of cisternae is called a Golgi stack

Question 23

what is the function of vesicles

Answer 23

carry lipids and proteins from the ER to the
Golgi complex and then to various destinations in the cell

Question 24

what are the two faces of the Golgi Complex called

Answer 24

The cis face is oriented toward the ER, and the Golgi compartment on this side is called the
cis-Golgi network (CGN)
 The opposite side is called the trans face, and the compartment on this side is called the trans-Golgi network (TGN)

Question 25

The cis face is oriented toward

Answer 25

the ER, and the Golgi compartment on this side is called the
cis-Golgi network (CGN)

Question 26

Proteins and lipids leave the Golgi in

Answer 26

transport vesicles that continuously bud from the tips of the TGN

Question 27

medial cisternae location and function

Answer 27

Between the TGN and CGN
where much of the processing of proteins occurs

Question 28

2 models have been proposed
Flow of Lipids and Proteins Through the Golgi Complex

Answer 28

The stationary cisternae model
The cisternal maturation model

Question 29

Explain The stationary cisternae
model:

Answer 29

each cisterna in the Golgi stack is a stable structure

 Transport from one cisterna to another is mediated by shuttle vesicles

 These bud off from one cisterna and fuse with the next cisterna in a cis-to- trans sequence

Question 30

The cisternal maturation model

Answer 30

the Golgi cisternae are transient compartments

 They gradually change from CGN through medial cisternae to TGN

 Enzymes not needed in later compartments are returned to earlier compartments in vesicles

Question 31

Anterograde transport:

Answer 31

movement of material toward the plasma membrane

As a secretory granule fuses with the plasma membrane and discharges its contents (exocytosis), a bit of membrane from the ER becomes part of the plasma membrane

Question 32

Retrograde transport

Answer 32

the flow of vesicles from Golgi cisternae back to the ER

allows the cell to balance the flow of lipids toward the plasma membrane
 ensures a supply of materials for forming new vesicles

Question 33

Two methods (unique to eukaryotes) for transporting materials across the plasma membrane are

Answer 33

exocytosis and endocytosis

Question 34

how can proteins be tracked

Answer 34

Proteins were radioactively labeled briefly and tracked through time using electron microscopy and autoradiography

Question 35

Exocytosis

Answer 35

the process by which secretory vesicles release their contents outside the cell

 Adds lipids and proteins to the plasma membrane

 Animal cells secrete hormones, mucus, milk proteins, and digestive enzymes
this way
 Plant and fungal cells secrete enzyme and structural proteins for the cell wall

Question 36

Endocytosis

Answer 36

the process by which cells internalize external materials
 Removes lipids and proteins from the plasma membrane

Question 37

The Process of Exocytosis

Answer 37

1. Vesicles containing products for secretion move to the cell surface
2. The membrane of the vesicle fuses with the plasma membrane
3. Fusion with the plasma membrane discharges the contents of the vesicle
4. The membrane of the vesicle becomes part of the cell membrane

Question 38

Endocytic vesicles develop into early

Answer 38

endosomes, which fuse with vesicles from the TGN
They acquire digestive enzymes and form new lysosomes

Question 39

In phagocytosis

Answer 39

solid particles are ingested

Question 40

In pinocytosis

Answer 40

liquids are taken up

Question 41

The lysosome is an organelle of the endomembrane system that contains

Answer 41

digestive enzymes

Question 42

lysosome function

Answer 42

It is capable of degrading all the major classes of biological macromolecules
 Isolate digestive enzymes from the rest of the cell

Question 43

lysosome size

Answer 43

Vary in size and shape but are usually ~0.5 μm in diameter, bounded by a single membrane

Question 44

how is the lysosome protected form its digestive enzymes

Answer 44

The lumenal side of the membrane is coated with glycoproteins to protect the membrane from degradation

Question 45

Lysosomes Properties

Answer 45

Lysosomes maintain an acidic environment (pH 4.0–5.0) inside

 due to ATP-dependent proton pumps in the membrane  There are numerous enzymes inside lysosomes; all are
acid hydrolases

Question 46

Heterophagic lysosomes

Answer 46

contain substances that originated outside the cell

Question 47

Autophagic lysosomes:

Answer 47

Those with materials that originated inside the cell