Cell Biology Study Guide 8

List the three best studied coated vesicles as outlined in the text (p. 295) and briefly explain their roles in trafficking materials in the cell.

- COPII-coated vesicles move materials from the ER to the golgi complex -COPI-coated vesicles move materials in a retrograde direction from the ERGIC and Golgi to the ER -Clathrin-coated vesicles move materials from the trans golgi network to endosomes, lysosomes, and plant vacuoles. Also move materials from the plasma membrane to cytoplasmic compartments along the endocytic pathway

Provide a brief overview of the process and path of a protein through the Golgi complex.

- Cis golgi to cis/medial golgi to medial golgi to medial/trans golgi to trans golgi - removal of three glucose residues, various mannose residues are all removed while sugars are added by specific glycosltransferases.

Provide a short overview of the role of the rough endoplasmic reticulum in the processing of newly synthesized proteins.

- Major processing plant, contains molecular chaperon's to give proteins a chance to fold correctly.

What are the two primary functions of proteins coats as they relate to vesicles?

-Act as a mechanical device that causes the membrane to curve and form a budding vesicle -Provide a mechanism for selecting components include A. cargo consisting of secretory, lyosomal and membrane proteins to be transported and B. the machinery required to target and dock the vesicle to the correct acceptor membrane.

What is the cis Golgi network?

-Composed of an interconnected network of tubules. Primary function is to sort and distinguish between proteins to be shipped back to the ER or those who go to the golgi station.

Where does membrane biosynthesis begin?

-ER -From preexisting membranes. Grow as new proteins and lipids are inserted into existing membranes. Move from ER to every other compartment of the cell. *Membranes grow as newly synthesized proteins and lipids are inserted into existing membranes in the ER*.

The text's definition of secretory pathway (also referred to as a biosynthetic pathway) provides a perfect overview for this section. You should be able to write the complete definition of the secretory pathway (as provided in the glossary of the text) out on the exam in order to show that you have a general understanding of how the organelles of the endomembrane system function together.

-Route through the cytoplasm by which materials are synthesized in the endoplasmic reticulum or Golgi complex, modified during passage through the golgi complex, and transported within the cytoplasm to various destination such as the plasma membrane, a lysosome, or a large vacuole of a plant cell. Many of the materials syntheized in the endoplasmic reticulum or golgi complex are destined to be discharged outside the cell; hence the term secretory pathway has been used.

What is the trans Golgi network?

-Sorting station where proteins are segregated into different types of vesicles heading either to the plasma membrane or to various intracellular destinations.

What are the three listed roles of vacuoles in the text?

-Store toxic compounds -Contain active transport system that pump ions, water can leave and enter, provides mechanical support for soft tissues of a plant and also stretches cell wall during cell growth -Site for intracellular digestion

Briefly describe the roles of t-SNARES and v-SNARES in the docking and fusion of vesicles to a target compartment.

-V-SNARE: which become incorporated into membranes of transport vesicles during budding(synaptobrevin) -T-SNARE: located in the membranes of target compartments(syntaxin and SNAP-25)

What are the components of the endomembrane system?

1. Endoplasmic reticulum, 2. Golgi complex, 3. Endosomes, 4. Lysosomes, and 5. vacuoles

What are the three primary functions of smooth endoplasmic reticulum highlighted in the text?

1. Synthesis of steroid hormones in the endocrine cells of the gonad and adrenal cortex; 2. Detoxification of a wide variety of organic compounds; and 3. Sequestration of calcium ions.

translocon

A protein-lined channel embedded in the ER membrane; the nascent polypeptide is able to move through the _____n in its passage from the cystol to the ER lumen.

vacuole

A single membrane-bound, fluid filled structure that comprises as much as 90% of the volume of many plant cells.

What is the cargo of vesicles associated with the secretory pathway?

Cargo consisting of secretary lysosomal membrane proteins

quality control

Cells contain various mechanisms that ensure that the proteins and nucleic acids they synthesize have the appropriate structure. Example, misfolded proteins are translocated out of the ER and destroyed by proteasomes in the cytosol; mRNA's that contain premature termination codons are recognized and destroyed.

constitutive secretion

Discharge of materials synthesized in the cell into extracellular space in a continual manner

regulated secretion

Discharge of materials synthesized in the cell that have been stored in membrane-bound secretory granules in the peripheral regions of the cytoplasm, occurring in response to an appropriate stimulus.

What is the best studied Golgi activity?

Glycosylation

snare

Key proteins that mediate the process of membrane fusion. T-Snares are located in the membranes of target compartments. V-SNARES incorporate into the membranes of transport vesicles during budding

What is the primary mechanism for properly targeting lysosomal enzymes?

Low PH(maybe)

endocytosis

Mechanism for the uptake of fluid and solutes into a cell. Bilk-phase ______ which is non-specific and receptor-mediated ______ which requires the binding of solute molecule such as ldl or transferrin to a specific cell-surface structure

endosome

Organelles of the endocytic pathway. Materials taken up by endocytosis are transported to early ______ where they are sorted and then on to late ______ and ultimately into lysosomes

Briefly describe the primary functions and mechanisms of the lysosome.

Play a key role in autophagy, regulated destruction of the cell's own organelles and their replacement. Surrounds organelle with double membrane, fuses lysosome to organelle, degrades organelle. Selective process

phagocytosis

Proccess by which a particulate materials are taken into cells. Materials are enclosed within a fold of the plasma membrane, which buds into the cytoplasm to form a vesicle called a _____

endocytic pathway

Route for moving materials from outside of the cell to compartments, such as endosomes and lysosomes, located within the cell interior.

signal sequence

Special series of amino acids located at the N-terminal portion of newly forming proteins that triggers the attachment of the protein-forming ribosome to an ER membrane and the movement of the nascent polypeptide into the cisternal space of the ER.

autophagy

The destruction of organelles and their replacement during which an organelle is surrounded by a double membrane. The membrane surrounding the organelle then fuses with a lysosome.

turnover

The regulated destruction of cellular materials and their replacement

Transport vesicle

The shuttles, formed by budding from a membrane compartment, that carry materials between organelles.

coated vesicle

Vesicles that bud from a membrane compartment typically possess a milti-subunit protein coat that promotes the budding process and binds specific membrane proteins. COPI-, COPII-, and clathrin-coated vesicles are the best characterized ______

secretory granules

large, densely packed, membrane-bound structure containing highly concentrated secretory materials that are discharged into the extracellular space following a stimulatory signal

coated pits

specialized domains of the plasma membrane; _______ serve as the collection points for receptor that bind substances that enter a cell by means of endocytosis