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41 Cards in this Set

  • Front
  • Back
What are the roles of the Endoplasmic Reticulum?
-synthesis of lipids, glycolipids,
-secrete proteins
-Store Ca2+
Describe Gated transport
- Occurs in the nucleus
- selective of large molecules, but lets small and cytosolic proteins pass freely
- gate is complex and sorts well
Describe Transmembrane Transport
-Occurs in mitochondria, ER
- machinery is used to direct proteins across membrane
- ALWAYS need the right signature
What uses vesicular transport?

Describe what it is.
ER, Golgi, Secretory and endocytic pathways

Ferry stuff from one compart to another
- needs budding and fusion
- maintain topography of membrane so that cell will recognize it
How are gated and transmembrane transport similar?
Both need protein machinery to recognize, moniter, and assist transport
Where are all proteins initially synthsized?
cytoplasmic ribosomes, with sorting during or after translation
What do adaptor proteins do?
They bind to a sorting signal and bring the protein to the right compartment.
Do cells ever generate new organelles?
NO
What kind of cells use signal patches?
Golgi to Lysosome transport. Most most of everything else uses signal peptides in a straight line.
Would a myelin sheath have more lipid or more protein?

A mitochondria?

A plasma membrane?
More lipid

Mire protein

Even
What types of membrane proteins are there?
Transmembrane, peripheral, Lipid associated
What defines transmembrane proteins?

Examples?
amphipathic proteins across bilayer
intrinsic

-alpha helix with non-polar aas in center
-flanked by charged aa's
What defines peripheral Proteins?

Examples?
- Associate with an integral protein or a different comple, but not in it
-non-covalent
-no need to disrupt, just use a high ionic wash or NaOH to isolate the protein
What defines a lipid assocated protein?

Examples?
Protiens attached to bilayer by covalent attachment of a lipid anchor
Where is the N-terminus in a type 1 protein?
N terminus is either on the EC side or inside the lumen of an organelle.
How do multi-span proteins work?
-several transmembrane domains
- helices form bundles as they self-associate
How do you isolate an integral membrane protein?
You disrupt the bilayer with detergents
- like triton mild, SDS harsh, or sterols
What types of lipid-anchored proteins are there?
1-Covalent bonds to acyl chains on cytoplasm
2- covalently bound to polyisoprenoid anchors
3-Covalently bound to glycophosphatidylinositol (GPI) on EC face
What are the two fatty acid anchors?
- Myristate- amide w/ N-term Gly, stable

-Palmitate- thioester w/cysteine, dinamic, made in cytoplasm then enzymatically placed on lipid
What do polyisoprene anchors do? - 2nd type of lipid-anchored proteins
- Used for signal transduction or protein targetting

-either farnesyl w/ 3 isoprene units CAAX
-or geranylgeranyl- 4 iso units CC

link to cancer and RAS oncogene protein, stop farnesyl binding.
What are Glycophosphatidylinositols?
-On EC face
-Takes integral proteins and cleaves of transmembrane domain,and GPI anchor added

-then phosphoethanolamine links glycan-PI to C-terminus of target protein

- proteins include cell surface enzymes, adhesive proteins, nutrient receptors
What terminus does the GPI anchor associate with?
The C terminus
What are glycophorins?
- A family of large glycoproteins
-16 oligosaccharide chains with ltos of hexoses
- strong negative charge to membrane surface
- tail in cytoplasm interacts with cytoskeleton noncovalently
What do red bloodcells have to mediate bicorbanate and chloride exchange?
An anion exchanger with dimers as a transmembrane protein.

w/ankryin
What are spectrins
rod-like proteins that make a flexible 2D web

helps proteins to maintain network organization
What are porins made from?
- Beta-barrel structure
- hydrophilic channels that allow solute passage up to 600 daltons.
antiparallel arrangement in a channel. monomors form trimers
- in backteria, mitochondria, chloroplasts
What about protein mobility?
-no flip flop
-only lateral and rotational diffusion
-patching and capping of antigens
-depends on lipid content, other proteins
-needs ATP
What are basket-shaped structures through which all substances pass into the nucleus?
Nuclear pore complexes.
What allows for movement of proteins and RNAs in and out of nucleus?
Nucleo-cytoplasmic exchange

- proteins n like histones, polymerases
- stuff out like tRNA and mRNA
-some ribosomal proteins in then back out
What kind of molecules do the pores let in?
- small solutes really quickly in
-macromolecules require active transport with ATP and GTP
What make up Nuclear localization sequences? (NLS)?
-positively charged aa's - lysein, arginine, and proline
-no consensus
not clipped off after transport

- can be SV-40, bipartite, mat alpha 2
Is the outer or the inner nuclear membrane covered in ribosomes?
Outer - synthesized proteins transported into the nuclear space
What are nuclear pores made out of?
-luminal and column components,
-proteins of annular ring. spokes, filaments, fibrils of cages
FG repeats for import recepters
What anchors the nuclear pore complex to the nuclear membrane?
The transmembrane glycoprotein luminal component.
Which side of the nucleus is the fibrilla elements?
They are on both sides, but the cage/basket is on nuclear side
Are cages 1 way or 2 way?
1 way.
What is the adaptor for Nuclear pore import?
importin alpha

this binds to importin B later with the protein and associates with cytoplasmic fibrils
What is the roll of Ran GTPase in nuclear import?
- stimulates transport with GAP and GEF
-GAP makes GDP
-GEF makes GTP
- GTP is made in nucleus, then enters the cytosol
What are nuclear export factors?
- get rid of RNA's
-heterogeneous nuclear RNA-binding proteins
- bind to Nups.NPC receptors
-karyopherins are similar to NIR
What is an NES
-nuclear export signal
- leucine rich
-no consensus
What is NLS
-nuclear localization signal.
- necessary and sufficient
- basic complexes