Cell Bio Exam #2

FRAP

Using lasers in fluorescence microscopy to bleach the fluorescence of a GFP protein attached to a membrane protein. The reapperance if fluroecene in that spot later can suggest protein movement in the membrane.

lipid domains

distinct regions in the cell where specific proteins and lipids cluster together to perform special functions.

Uniport

carrier protein that transports a single solute across the cell membrane. Ex: glucose transporter

Symport

Two solutes are transported together. One solute going towards its gradient enables the other to go against it. Ex: Na/K pump)

Antiport

Two solutes are transported in opposite directions. One going towards its gradient enables the other to go against it. Ex: Cl and HCO3 anion exchange protein

cotranslational ER entry

Proteins destined for the ER are inserted through a translocon on the rough ER as it is being translated. The SRP protein binds to the ER signal sequence on the polypeptide chain and the SRP protein binds the ribosome to the translocon

Method of quality control in the Rough ER

Misfolded or defective proteins are sent to proteasomes to be degraded

How are proteins targeted for certain destinations?

Tags on proteins direct them to a vesicle that carries them to the right location. Tags can be sugar chains, certain amino acid side chains, or hydrophobic domains.

Where do proteins destined for the cell vs. outside the cell and the membrane of the cell synthesized?

Cytoplasm vs ER

anterograde transport

ER-Golgi-Cell Membrane

retrograde transport

Cell membrane-Golgi-ER

stationary cisternae model

cisternae are stationary and shuttle vesicles carry materials from one cisternae to the next in a cis-trans direction

cisternal maturation model

Cisternae are transient and gradually change from cis to trans. Enzymes not needed in later compartments are returned to the cis side via transport vesicles.

GLUT1 Mutation

GLUT1: Mutation leads to low levels of glucose transporters. This leads to the brain having less of its main source of energy leading to neurological effects

phosphoglycerolipid

Glycerol-based phospholipid in membranes. Maintains structure and fluidity.

sphingolipid

Sphingosine-based phospholipids in membranes. Helps in cell signaling and recognition insulation of the myelin sheath.

Transition temperature

Temperature at which the cell membrane transitions from a tightly packed phase to a fluid phase. Influenced by the amount of unsaturated and saturated fatty acids.

homeoviscous adaptation

ability to adjust the lipid composition in the cell membrane so that cells can maintain proper fluidity through environmental temperature changes.

Flippase

Proteins that catalyze the flip-flop of membrane lipids.

Transmembrane segment

Hydrophobic segment of an integral membrane protein that anchors it to the membrane.

Glycolipid

Lipid with an attached sugar group that plays a role in cell-to-cell recognition (ABO blood groups).

Glycoproteins

Proteins with an attached sugar to an amino acid side chain. They play a role in cell to cell recognition.

glycocalyx

Coat formed by glycoproteins and lipids. They play a role in cell-to-cell communication and adhesion.

Adhesive Junctions

Hold cells together (cadherins)

Tight Junctions

Forms a water tight seal between cells

Gap Junctions

Allows for communication between adjacent cells.

Plasmolysis

Plasma membrane pulling away from a fungal or plant cell wall due to a hypertonic environment.

Liposomes

Small spherical vesicles of lipids forming a bilayer lacking proteins.

ATPase Pumps

transport proteins driven by the hydrolysis of ATP (direct active transport)

ABC transporter

Can pump antibiotics or drugs out of cells. MDR proteins cause high resistance to drugs.

ER cisternae

membrane bound sacs of the ER

ER lumen

Space inside of the cisternae of the ER

Transition elements/ER

Play a role in the formation of vesicles that transport lipids and proteins to the Golgi for processing

signal sequence

Sequence on the polypeptide that directs the polypeptide ribosome complex to the surface of the rough ER

Secretory Proteins

Proteins destined to leave the cell are made mainly in the rough ER

cytochrome P450

Enzymes that oxidize compounds like drugs and sterols. A deficiency can cause Congenital Adrenal hyperplasia and Antley-Bixler Skeletal syndrome.

Detoxification

Involves hydroxylation, adding hydroxyl groups to hydrophobic groups to increase their solubility (smooth ER).

Smooth-ER calcium storage

Sarcoplasmic reticulum: releases calcium ions that come into the lumen during muscle contraction.

glucose-6-phosphatase

involved in the breakdown of stored glycogen to form glucose (smooth ER of the liver).

four membrane functions

Protects the cell (phospholipids), cell signaling (glycolipids/proteins), selective permeability (phospholipids, channel/carrier proteins), cell adhesion (glycoprotein), cell recognition (glycoprotein)

3 processes that occur to a protein in the Rough ER

Protein folding

glycosylation

vesicle packaging

What kind of processing occurs in the rough ER for quality control?

Chaperones assist in folding, glycosylation targets the protein, and tracks folding status; the protein is checked for any misfolding or mistakes.