Chapter 12: The Endomembrane System and Peroxisomes

Sites for protein synthesis, processing, and sorting; lipid synthesis, and drug detoxification

Endoplasmic Reticulum and Golgi Apparatus

Carry and sort material brought into the cell

Endosomes

Digest ingested material and unneeded cellular components

Lysosomes

Houses hydrogen peroxide degradation reactions. Perform diverse metabolic functions. Contains catalase specific for hydrogen peroxide

Peroxisomes

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

Endoplasmic Reticulum

The ER consists of membrane-bound tubular and flattened sacs called?

cisternae

The internal space of the ER is called?

lumen

Contains ER exit sites. Areas where the transport vesicles that contain lipids and proteins made in the ER, detach from the ER, and start moving to the Golgi Apparatus

Transitional ER

Formed using the ER material. Will contain the protein that was being built and synthesize in the rough ER. Bud off from the ER

Transport vesicle

Functions of ER

protein and lipid synthesis

A type of ER that form large flattened sheets

Rough ER

A type of ER that form tubular structures

Smooth ER

Flow of genetic information in a cell. Final output is protein

Central Dogma

Most of the genes associated with eye color are related to the production, transport, and storage of the pigment protein called?

melanin

amount and quality of melanin in the front layers of the iris

eye color

TRUE OR FALSE:

Brown eyes have less melanin and blue eyes have more melanin

False

Carries the genetic code for protein synthesis to the cytoplasm

mRNA

Serves as the site for protein synthesis

rRNA

Reads the code (mRNA) and carries the amino acid to be incorporated to the developing protein

tRNA

TRUE OR FALSE:

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

True

Newly synthesized proteins enter the endomembrane system how?

cotranslationally

Proteins are inserted through this in the ER membrane into the rough ER lumen as the polypeptide is synthesized by the ER bound ribosome

pore complex

The site for the initial steps of addition of carbohydrates to glycoproteins. Assembly of multimeric protein complexes. A membrane factory for the cell

Rough ER

Quality control proteins that are incorrectly folded modified or assembled are exported for degradation

ER associated degradation

What step is this statement in the protein synthesis?

As the protein elongates, the end of the polypeptide enters the ER. As the amino acid gets longer, it penetrates inside the lumen of the ER

Step 2

What step is this statement in the protein synthesis?

Addition of sugar units (glycoproteins)

Step 3

What step is this statement in the protein synthesis?

Semi completed length of the polypeptide, there would also be a budding of vesicle which will transport the molecule that buds of in the Golgi Apparatus where everything else happens before secretion [release] happens

Step 4

It started in the cytoplasm then entered in the RER and synthesized

Cotranslational protein synthesis

Has no role in protein synthesis. Involved in the synthesis of lipids and steroids such as cholesterol and its derivatives. Responsible for inactivating and detoxifying potentially harmful substances

Smooth ER

Critical functions in muscle contraction. Can store calcium in the SER

Sarcoplasmic reticulum

Drug detoxification often involves

hydroxylation

Adding hydroxyl groups to hydrophobic drugs increases their solubility

hydroxylation

TRUE OR FALSE:

When drug is less soluble, it can easily release (detoxify)

False

The elimination of barbiturate drugs is enhanced by what enzymes in the smooth ER

hydroxylation

Hydroxylation is catalyzed by a member of what family of proteins?

cytochrome P-450

Prominent in the liver for detoxification

Smooth ER

TRUE OR FALSE:

The more cytochrome P-450 a patient have, the faster detoxification is.

True

The study of the differences in the presence or activity of particular cytochrome P—450 genes in different patients

Pharmacogenetics

This stores glucose as glycogen in granules associated with smooth ER

liver

When glucose is needed by the body, glycogen is broken down to glucose-6-phosphate by an enzyme called? (This is unique to SER)

Glucose-6-Phosphatase

If a patient can’t breakdown glycogen, what part of the endomembrane system is responsible for that?

Smooth ER

TRUE OR FALSE:

The SER and Glycogen are near to each other in terms of proximity.

True

Smooth ER that specializes in calcium storage

sarcoplasmic reticulum

It is released when needed for muscle contraction

Calcium

The SER lumen contains high concentrations of

calcium-binding proteins

A membranous structure surrounding each myofibril (like ER). Responds to the action potential. Stores and release Ca2+ when an action potential is received

Sarcoplasmic Reticulum

Sarcoplasmic reticulum contains this chambers that is attached to T tubules

Terminal cisternae

If a patient found to have malfunctioning ineffective muscle contraction, who is the culprit and why?

Sarcoplasmic Reticulum can’t store or release calcium

Smooth ER in some cells is the site of

steroid biosynthesis

If a patient has high cholesterol, it can be due to unhealthy diet or?

hyperactive SER

TRUE OR FALSE:

Smooth ER has also been found associated with plastids in some plants, and may be involved in plant hormone synthesis

True

Part of protein synthesis wherein it is partially finishing the structure of the protein. Adding sugars/carbohydrates to polypeptides

Glycosylation

Start of protein synthesis is in the

cytosol

As the polypeptide elongates, it penetrates the

lumen

Using the membrane of the ER, it will bud off forming this, a vehicle that transports the partially finish polypeptide to the Golgi Apparatus for packaging and release

vesicle

TRUE OR FALSE:

Polypeptide synthesis beings in the cytosol but takes one of three alternative routes when the polypeptide is approx. 30 amino acids long

False

the primary source of membrane lipids with a few exceptions

ER

Mitochondria synthesize

phosphatidylethanolamine

Peroxisomes synthesize

cholesterol

Chloroplasts contain enzymes for

chloroplast-specific lipids

Type of diffusion that is flip-flop and changes postion

transverse diffusion

The rotation of the ER

own axis

Type of diffusion that is neighboring

lateral diffusion

It plays an important role in processing and packaging secretory proteins, and in complex polysaccharide synthesis. Here, glycoproteins and membrane lipids from the ER undergo further processing and are sorted and packaged for transport thru transport vesicles

Golgi Complex

The Golgi complex consists of flattened membranous sacs called

cisternae

A series of cisterna, usually 3-8, is called

Golgi stack

the cis face is oriented towards the ER, the Golgi compartment on this side is called the (receiving end)

cis-Golgi network (CGN)

The opposite side is called the trans face and the compartment on this side is called the (shipping side)

trans-Golgi network (TGN)

Has plasma membrane because they are only bud off of the ER. Received by the CGN

Vesicles

Movement of material towards the plasma membrane (left to right)

anterograde transport

The flow of vesicles from Golgi cisternae back to the ER (right to left)

retrograde transport

What is the composition of a vesicle?

Phospholipid bilayer

TRUE OR FALSE:

Through the antegrade transport, the lipids that compose the vesicle are disappearing. Through the retrograde transport, it ensures that there’s a supply of materials to form new vesicle

True

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. This flow of lipid toward the plasma membrane must be balanced

Anterograde

This allows the cell to balance the flow of lipids toward the plasma membrane. It also ensures a supply of materials for forming new vesicles

Retrograde

Are carbohydrate chains containing 3-10 sugar units

Oligosaccharides

FILL IN THE BLANKS:

Enzyme-catalyzed reactions involving the resulting ______ then modify the oligosaccharide side chain

glycoproteins

The initial steps of N-glycosylation take place on the

cytosol

What is the core oligosaccharide complex ratio of a carbohydrate?

2N:9M:3G

used in the formation of sugar units start in the cytosol where they are attached to the (carrier of oligosaccharides unit for glycosylation)

Dolichol phosphate

Needs to be transported and will be transported by the (translocator)

Flippase

A protein is expected to have sugar units is not functional as it doesn’t have sugar units. The culprit is?

Flippase

Proteins in a vesicle are released to the exterior of the cell as the vesicle fuses with the plasma membrane

exocytosis

Secrete hormones, mucus, milk proteins, and digestive enzymes through exocytosis

animal cells

Secrete enzyme and structural proteins for the cell wall

Plants and fungal cells

ARRANGE THE PROCESS OF EXOCYTOSIS

A. Fusion with the plasma membrane discharges the contents of the vesicle

B. Vesicles containing products for secretion move to the cell surface

C. The membrane of the vesicle becomes part of the cell membrane

D. The membrane of the vesicle fuses with the plasma membrane

B, D, A, C

The cell will receive molecules inside the cell

Endocytosis

ARRANGE THE PROCESS OF ENDOCYTOSIS:

A. A small segment of the plasma membrane folds inward

B. It pinches off to form an endocytic vesicle containing ingested substances or particles

A, B

The ingestion of large particles up to and including whole cells or microorganisms

phagocytosis

For more complex organisms, phagocytosis is usually restricted to specialized cells called

phagocytes

In humans, WBC cells use phagocytosis as a means of

defense

Detoxify hydrogen peroxide which can be reactive oxygen species which we don’t like to accumulate in our body

Peroxisomes