Cell Membrane

endocytosis 1. what proteins target and stimulate membrane proteins for endocytosis 2. invagination of plasma membrane at what sites allow for this process to take place. explain

1. escrt 1-4 2. invagination of the PM at lipid raft sites allow for the plasma membrane to take in small hydrophillic molecules.

Palmitoylation 1. happens with what kinds of proteins 2. this modification happens primarily where in the cell? 3. how is this and myristoylation attached

1. fatty acylated proteins 2. cytoplasmic side of the plasma membrane because of how it functions in transmembrane signaling 3. covalently

myristolation 1. takes place with what kind of proteins 2. this functions in what processes? 3. this is key towards what process that we are studying in class? how?

1. fatty acylated proteins 2. signal transduction cascade, protein protein interactions and mechanisms that help regulate protein targeting and functioning 3. apoptosis! when the BH3 interacting domain death agonist aka BID is subjected to this process, it causes the release of cytochrome c which causes cell death

Cell membrane maintains a barier between what and what

extracellular space and the contents within the cell

constitutive secretion -function -found where

packages and modifies proteins produced constantly golgi

regulative secretion -function -found where

packages and modifies proteins produced in response to a specific stimulus golgi

what are the key phospholipids present within the lipid bilayer

phosphatidylcholine phosatidylethonalimine phosphatidylserine sphingomyelin

endocytosis regulates the concentration of what things how

protein and phospholopid concentration at the plasma membrane takes them into the cytosol through the MVBs(AKA LATE ENDOSOMES)

V snare once fused. what happens

trans-SNARE complex will become the cis-SNARE complex because the two membranes have become one. the SNARE complex is then unfolded and released back into the cytosol to be recycled

Alpha Helical 1. belongs to what kind of protein 2. this is located where

transmembrane proteins inner membrane of the plasma membrane

ESCRT 1-4 proteins 1. works with what (stimulates and targets what proteins in particular?)? in order to do what?

ubiquitin stimulates and targets membrane proteins for endocytosis. helps degrade receptors and recycle

phosphatidylserine's role in apoptosis

usually its held by the enzyme flippase but when a cell undergoes apoptosis, its no longer restricted to the cytosolic side by flippase. Instead scramblase catalyzes the rapid exchange of phosphatidylserine between the two sides. When the phosphatidylserines flip to the extracellular (outer) surface of the cell, they act as a signal for macrophages to engulf the cells.

V snare during fusion. what happens

v and t snare combine to form a trans-SNARE complex

Epsin main function an example of what

Family of highly conserved (abundant) membrane proteins that are important in creating membrane curvature. adaptor protein

Glycolipids -they are __ with a ___ attached by a _____ -role is to do what

Glycolipids are lipids with a carbohydrate attached by a glycosidic bond. markers for cellular recognition and also to provide energy.

Vesicles travel across microtubule and actin filaments to target membrane. what proteins are key for this

Kinesin : anterograde aka forward dynein: retrograde aka backwards

lipid rafts how are they ordered and packed

Lipid rafts are more ordered and tightly packed than the surrounding bilayer, but float freely in the membrane bilayer.

glycolipids where are the carbs found and what do they do

The carbohydrates are found on the outer surface of all eukaryotic cell membranes. They extend from the phospholipid bilayer into the aqueous environment outside the cell where it acts as a recognition site for specific chemicals maintain the stability of the membrane attaching cells to one another to form tissues

the molecules that are packed into MVBs and bud off the trans-cisternae and are transported throughout the cell. where do these vesicles travel to?

Vesicles travel across microtubule and actin filaments to target membrane

clathrin free vesicle has shed what coat

adaptin and clathrin via hsp70

phospholipid bilayer is ___ and _____

amphipathic and mobile

lipid rafts -3 functions

assemble signaling molecules influencing membrane fluidity and membrane protein trafficking, regulating neurotransmission and receptor trafficking.

What are the key proteins present within the cell membrane CC D EE ILPRST

integral transmembrane lipid anchored Peripheral SNARE ESCRT 1-4 Proteins Rab Dynamin Epsin Clathrin Caveolae

multivesicular bodies split into

clathrin mediated secretory vesicles clathrin independent secretory vesicles

what does cholesterol do

contributes to the fluidity of the membrane during different temperatures

glycocalyx function

covers the cell membrane and serves to protect it from chemical injury

Ubiquitin tags proteins for what? how? what kind of environment do endosomes provide?

degradation Once endocytic vesicles have uncoated, they fuse with early endosomes. Early endosomes then mature into late endosomes before fusing with lysosomes. Endosomes provide an environment for material to be sorted before it reaches the degradative lysosome

Is cell membrane appearance uniform or different among cell types? how thick is it usually

different; 5nm

V snare has two stages. what are they

during fusion and once fused

polarized cells of plasma membrane provide an example where do their differences lie

epithelial cells of small intestines and respiratory tract, hepatocytes they have distinct apical, basal and lateral surfaces

where do leukocytes attach?

to endothelial cells of blood vessels because they mediate the inflammatory response

Lipid Anchored Proteins 1. what are they exactly 2. what are the 3 types

1. covalently attached embedded lipids of the plasma membrane 2. prenylated fatty acylated GPI

Clathrin 1. what does it coat on the membrane and assemble into what which drive ? 2. binding of clathrin is mediated by what 3. clathrin mediated pathway of ____ demonstrates what 4. made up of what helices? one leg of clathrin contains how many _ 5. name for it 6. more clathrin induces what

1. Protein that coats the cytoplasmic surface of cell membranes and assembles into basket-like lattices that drive vesicle budding. 2. - Binding of clathrin is mediated by adaptor proteins 3. - Clathrin-mediated pathway of endocytosis demonstrates a limit size for internalization of about 200 nm 4. alpha helices; 10 helix repeats 5. transkelion 6. more curvature of the clathrin coated vesicle https://www.youtube.com/watch?v=X8Z0jW7XKHs

phosphatidylethanolamine -aka -key fact -found where

- "Cephalin" - 2nd most abundant phospholipid - Found in the cytosolic leaflet

caveolin 1. what does its amino acid sequence predict it to be 2.plays a role in what 3. whats the observation in humans

- Amino acid sequence predicts caveolin to be integral protein - Role in cellular transport of cholesterol via caveolae - observation that in normal human fibroblasts cholesterol moves directly to surface caveolae within minutes after being synthesized in the ER

caveolae mediated internalization was found to be the predominant pathway of entry for what particles

- Caveolae-mediated internalization was found to be predominant pathway of entry for particles of 500 nm in size

phosphatidylserine -found where -held in place by -important for

- Found in the cytosolic leaflet - Held in place by the enzyme flippase - Important signaling role in apoptosis

sphingomyelin -most abundant where -forms what -found where

- Most abundant in the myelin sheath and neural tissues - Forms lipid rafts with cholesterol - Found in the outer leaflet

Epsin -contribute to what? like in what? -blocks what? -how does it induce bilayer curvature -by itself it can facilitate what

- contribute to membrane "deformations"- like endocytosis - blocks vesicle formation during mitosis. - An amphipathic -helix in epsin is coupled to protein complex binding that may induce curvature of a bilayer - Epsin alone can facilitate the formation of clathrin-coated invaginations on monolayer

Golgi and Golgi Network -main function -what kinds of secretions are present

-Intracellular transport and modification of phospholipids -constitutive and regulative

Rab proteins 1. members of what family 2. what do Rab GTPases do

1. Ras superfamily of monomeric G proteins 2. regulate many steps of membrane traffic including vesicle formation vesicle movement along actin and tubulin networks membrane fusion

Prenylated Proteins 1. define prenylation 2. what kind of process is prenylation? reversible or non-reversible? 3. what is this responsible for

1. adding hydrophobic molecules to a protein 3. a reversible post translational modification 3. interactions with the membrane that are important in signaling functions

phosphatidylcholine -aka -found where -key fact -obtained from

-lecithen -outer leaflet -most abundant phospholipid in our body -diet, soybeans and egg yolks

caveolae -special type of what -size? -these are what part of the plasma membrane -not coated with what -this is a plasma membrane subdomain enriched in what -participates in what -found in what -utilizes what key protein -rich in molecules that function in -what kind of pathway is it associated with

-lipid raft -small, 50-100 nm -invaginations of the plasma membrane -cholesterol and sphingolipids -clathrin -endocytosis -endothelial cells and adipocytes -caveolin -signal transduction -caveolae mediated internalization

Integral Proteins 1. where are they attached 2. can they freely move within the bilayer 3. how can they be removed 4. allow the movement of _ through _ 5. how do they correlate to transmembrane proteins 6. The stretch of the integral protein within the hydrophobic interior of the bilayer is ____, made up of _____. Like the lipid bilayer, the exposed ends of the integral protein are _______. 7.When a protein crosses the lipid bilayer it adopts an _ configuration

1. permanently attached to the membrane 2. yes 3. detergents which disrupt them 4. polar molecules; non-polar interior 5. all integral membrane proteins are transmembrane but not all transmembrane are integral membrane proteins 6. The stretch of the integral protein within the hydrophobic interior of the bilayer is also hydrophobic, made up of non-polar amino acids. Like the lipid bilayer, the exposed ends of the integral protein are hydrophilic. 7.When a protein crosses the lipid bilayer it adopts an alpha-helical configuration

Fatty Acylated Proteins 1. what kinds of proteins are these? what do they include? 2. what kind of processes occur with these proteins? simply list them

1. proteins that are post translationally modified to include the attachments of fatty acids specifically myristic and palmitic acid 2. myrisolation and palmitoylation

plasma membrane can take place in 1. _ permeability 2. _ transport 3. _ transport

1. selective permeability 2. active transport 3. bulk transport which includes endo and exocytosis

Carriers 1. are they specific or nonspecific? why? 2. what are the five main types

1. specific because of the binding sites present on the carriers 2. channels electrochemical transporters primary active transporters group translocators electron carriers

exocytosis 1. secretes molecules in response to what 2. what does it add to the PM

1. stimulus or homeostasis of the cytosolic concentrations 2.proteins and phosplipids are added

Peripheral proteins 1. these have what kind of adherence? why? 2. function? 3. provide an example of its function

1. temporary adherence because of binding to integral proteins or penetrating peripheral regions of the bilayer 2. transportation and cellular communication 3. cytochome c: transport electrons to generate energy and initiate apoptosis

Transmembrane Proteins 1. how much of the membrane do the span 2. function 3. what are the two structural types 4. what are the topological types 5. when does the topological type matter

1. they span the entire membrane 2. they are gateways for specific substances 3. alpha helical and beta barrels 4. I, II, III, IVA AND IVB 5.During the translocation and ER-bound translation, when the protein has to be passed through the ER membrane in a direction dependent on the type.

Receptors 1. many are ___ 2. what are the main classes 3. what are two kinds

1. transmembrane 2. ion channel linked, enzyme linked, g protein coupled 3. glycoproteins and lipoproteins

Beta Barrels 1. belongs to what kind of protein 2. this is located where

1. transmembrane proteins outer membrane of mitochondria via porins

SNARE proteins 1. mediate what process? provide an example 2. most are what kinds of proteins? explain how they are structured and positioned 3. can vary in what things 4. share what things 5. two kinds?

1. vesicle fusion with the target membrane. example: lysosomes 2. integral membrane proteins with a single transmembrane helix at their c terminal ends 3. size and structure 4. SNARE motif in their cytosolic domain consisting of 60-70 amino acids 5. T and V snare

rab proteins 1. what do they regulate? how? 2. how can they communicate from one to another

1. vesicular traffic by recruiting effector proteins 2. RAB gtpases via effector proteins

GPI proteins 1. GPI stands for 2. found where in the cell 3. anchored by what 4. list 5 functions 5. many are associated with what kinds of proteins

1.Glycosulphosphatidyinositol linked proteins 2. extrerior surface of the plasma membrane 3. chains of phosphatidylinositol 4. acts as a hydrolytic enzyme adhesion molecule complementary regulatory proteins receptor protease inhibitor 5. membrane sphingolipids which form lipid rafts

caveolae may be involved in apoptosis. explain

: the pathway of the large molecules can bypass being digested in the lysosome by being exported from the endosome as opposed to being marked for destruction.

Communication between Rab GTPases through effector proteins allow for what? basically, what happens

Communication between Rab GTPases through effector proteins allow for membrane recognition and fusion specificity. Basically, Vesicles are transported to a specific membrane that is recognized by the effector proteins allowing for fusion to occur

microdomains are composed of what

Microdomains - composed of sterols and sphingolipids

once the invagination of the plasma membrane at lipid raft sites has taken place, what can happen to the small hydrophilic molecules what will happen to the receptor

Often to Lysosome or back to PM or other parts of the cell through Early Endosome mediation. it can be recycled or degraded

endo and exocytosis work simultaneously and together to main what

PM size, constitution, and function

adaptor proteins are involved with clathrin what are these proteins responsible for ? where?

Responsible for assembly of clathrin-coated vesicles (aka clathrin-coated pits) at plasma membrane & trans Golgi network. also involved in selection of the specific molecules to be incorporated into the vesicles

Dynamin large or small ____ responsible for what? what is its main function? works in both _ and _ where does it function

large gtpase: gtp hydrolysis responsible for endocytosis in the eukaryotic cell. budding and scission of newly formed vesicles both at the cell surface (particularly caveolae internalization) as well as at the Golgi apparatus. As a vesicle invaginates, dynamin forms a spiral around the neck of the vesicle. Once the spiral is in place, it extends lengthwise and constricts through GTP hydrolysis. This lengthening and tightening of the coil around the vesicle neck causes it to break and results in the pinching off of the vesicle from the parent membrane

oligosaccharides

markers for cell to cell interactions

what are the three domains of the plasma membrane

microdomain caveolae lipid rafts

Transmembrane Proteins IV

multipass proteins with two types of orientation

endosomes can be split into what two categories

multivesciular intraluminal

Transmembrane Proteins IVB

n terminal is towards the cytosol

Transmembrane Proteins IVA

n terminal is towards the extracellular environment

plasma membranes have receptors and carriers. in a carrier, once binding occurs what happens simply describe the main function of each

receptor: monitor changes in internal and external environment of cell by searching for a ligand carriers: transport large molecules that cant diffuse through the membrane by using energy. moves particles from low to high concentration. The molecule or ion to be transported (the substrate) must first bind at a binding site at the carrier molecule, with a certain binding affinity. Following binding, and while the binding site is facing the same way, the carrier will capture or occlude (take in and retain) the substrate within its molecular structure and cause an internal translocation so that the opening in the protein now faces the other side of the plasma membrane.[9] The carrier protein substrate is released at that site, according to its binding affinity there.

MVBS AKA LATE ENDOSOMES INHIBIT WHAT

receptors interacting with the cytosolic ligands

Transmembrane Proteins II

single pass proteins that anchored by a signal anchor and the C terminal is towards the cytosol

Transmembrane Proteins III

single pass proteins that are anchored by a signal anchor and oriented so that the N terminus is towards the cytosol

Transmembrane Protein I

single pass proteins that are anchored by a stop transfer. the N terminal is towards the cytosol

T snare 1. where is it located

snare protein on target membrane

V snare 1. where is it located

snare protein on the vesicular membrane

what effector proteins do rab proteins use

■ Sorting adaptors ■ Tethering factors ■ Motor proteins

golgi packages molecules into what? then what happens?

○ Package molecules into MVBs that bud off the trans-cisternae and are transported throughout the cell