Week 2 - Cell Biology Flashcards
What are the 4 major phospholipids?
Phosphatidylethanolamine (ER)
Phosphatidylcholine (ER)
Phosphatidylserine (ER)
Sphingomyelin (golgi)
What does cholesterol do in plasma membrane?
Stiffens
Reduces permeability
Inhibits phase changes
What is a glycolipid?
A sugar attached to a fatty acid
What is the orientation of glycolipids?
Present only on non-cytostolic surface… so on outside of plasma membran or the lumen of organelles
Functions of glycolipids?
Protection (glycocalix)
Cell adhesion
Cell identification
Surface properties of membranes
What is NANA
A negatively charged glycolipid
What are phosphainositols?
Lipid with inositol sugar that can be phosphorylated at different positions.
Can activate and signal enzymes on cell surface
Flippase
Enzyme that can flip phospholipids from one side of membrane to the other
Scrambleases
Enzyme that can scrample phospholipids.. random.. promotes apoptosis
Where are phospholipds the most asymetrically distributed?
On plasma membrane.. most mixed up in ER and gets more asymetrical as they move from ER to Gogi to cytoplasm to cell membrane
Choline and sphigo
Serine (- charge) and ethanolamine (cytosol)
What is a lipid raft?
Specialzed patch of lipids and proteins..
Signals tranduction events and endocytosis
What are different types of membrane proteins?
Transmembrane - alpha helix and beta barrel
Cytosolic surface - GPI anchor lipid chain anchor
Peripheral membrane - binded to imbeded proteins
What is the glycocalix?
Protein covalently binded to multiple sugar groups
Protect, identify, adhesion
Non cytosolic surface of membrane
Found in intestinal cells.. harsh environments
What ways are proteins organized in membranes?
Integral proteins -
Self assembly into aggregates
Tethered to extra cellular molecules
Tethered to intracellular molecules
Bind to proteins on adjacent cells
Syntaxin
SNARE proteine used in synaptic vesicle plasma membrane fusion
Integrin
Integral membrane protein that binds to extracellular molecules such as collagen and fibronectin, or cytoskeleton
What to metastatic cancers to do survive?
interfeare with apoptoic pathway so they are not killed.. linnked to integrin
Glycophorin and Band 3
integral membrane proteins that interact with molecules made of actin and spectrin. Critical for RBC funciton and elasticiy of RBC membrane
Cadherin
Large integral membrane protein that self associate in presence of Ca - it links cells together!
Sec 61 translocator
bidirectionally gated pore that lets polypepdies in or out of membrane
Chaperone proteins
Proteins that make sure other proteins fold correctly in ER
ER signal sequence
sequence of amino acids signaling for protein to bind to ER
What are SRPs
On ER, recognize signal sequence on polypeptide.
Bind the mRNA - ribosome - SRP and transfer to Sec 61 to be brought into ER
RER functions
Protein Synthesis
Membrane (integral membrane proteins)
Luminal (ER lumin)
Protein for secretion by cell
SER Functions
Lipid synthesis
Ca regulation
Detoxification
Ribosomes
Synthesize protiens
Polysomes
Multiple ribosomes on an mRNA can be free floating or attached to ER
Glycosylation
Covalent linkage of oligosachcharide chaine to certain amino acids
Cytosolic Proteins
Not made in ER.. made by special cytosolic ribosomes*
Glycosilation functions
Protein folding
Sorting and transport
Protection
Cell signaling
Types of glycosilation
O-linked
N-linked
N-linked glycosylation
Attatched to asparagine
Glycosylated in ER
14 sugar oligosaccharide attached on a membrane lipid called a dolichol, then transfered to growing polypeptide chain
This is why glycosylation is always on LUMINAL side…
O-linked Glycosylation
Occurs in golgi
attached to serine of threonine
What are proteoglycans?
Heavily glycosylated proteins (O-linked)
GAG sugar chains usually negatively charged
This charge attracts water to make hydrated gels..
Proteasome
Ubiquinate and destroy misfolded proteins in CYTOPLASM
Dysfunction causes disease like Alzheimers, Parkinsons, Cystic Fibrosis, Gauchers..
Heat Shock Response
Response to an acuumulation of misfolded proteins in cytoplasm
Increases chaperones
Unfolded protein response
Response to an accumulation of misfolded proteins in ER
Increases ER chaperones
Ca distribution in cells
Cytoplasm - low Ca
ER - Active transport of Ca from cytoplasm into ER lumen
Detoxification of cells in SER
Carried out by cytochrome P450 enzymes
Render foreign compounds more hydrophilic so they are released into bloodstream and eliminated by the kidneys
What are the three sensors to ditect unfolded proteins?
IRE1
PERK
ATF6
What is membrane trafficking?
The supply of lipds and proteins to other membrane bound organells.. Supplied by ER
Membrane Flow
It is the formation and transport of membrane-bound vesicles by the ER, golgi, lysosomes, and plasma membrane
What cell pathway is defective in familial hypercholesterolemia
The endocytic pathway
Golgi
Post office of cell.
Recieves lipids or proteins from ER
Returns escaped proteins to ER
Modifies glycoproteins
What are two faces of golgi?
Trans face - Where material leaves the golgi
Cis face - recieves product from ER in memrane bound vesicles
What are primary routes of travel from the golgi?
Lysosomes
Secretory vesicles
Plasma membrane
Vesicular transport
Movement of material betweein ER, Golgi, lysosomes, and plasma membrane
ER - Golgi trasport involves what?
Both tubules and vesicles
What is budding and fusion?
Budding is when a vesicles forms out of donor compartmetn membrane in vesicular transport
Fusion is when that vesicle fuses into the target compartment
Coat proteins
Specific coat proteins are needed to facilitate vasicle formation between ER and Golgi
COP I and COP II
Coat proteins
COP I -> Golgi to ER and Intra to Golgi
COP II -> ER to Golgi
How are coat protein coated vesicles formed?
GEF catalyzes receptor Arf or Sar1 (phosphorilizes GDP to GTP on protein) which extends hydrophobic tail into bilayer
Arf or Sar1 recruit proteins to concentrate cargo and curve membrane
Sec13/31 is recruited to form cage like structure and pinch of formed vesicle with cargo inside
Sar 1 and Arf
Membrane bound protein for formation of coat proteins
Arf - for formation of COP I
Sar 1 - for formation of COP II
GED
Guanine nucleotide exchange factor
Catalyzes membrand proteins Sar1 and Arf in coat protein vesicle formation
Sec 13/31
Forms cage like strucure around vesicle in coat protein vesicle formation (COP I&II)
Sanflippo Syndrome organell defect
Defect in lysosomes
KDEL
KDEL is a protien receptor on Golgi that detects proteins and lipds that should remain in ER but escape..
Escaped material is packaged and returned to ER by COP II
What proteins/lipds are involved to grab fusion vesicles and insure correct delivery?
Rabs
Rab effectors
SNAREs
Lipid content of membrane
Rabs and Rab effectors
Proteins involved with delivery of fusion vesicles on receiving membrane
Rabs - identify proper location (Rab GTP)
Rab effector - Effector proteins are bound to Rab GTP to bind the vesicle to correct target site
SNARE
Involved with accurate fusion of vesicles to recieving membrane
Binding of v-snare with its corresponding t snare (on fusion vesicle) bind and pull vesicle in close enough to facility fusion
Phosphatydleinositol in fusion of vesicles
Plays important role in identifying corrct membranes for fusion vesicles to fuse into
What are the paths of golgi proteins?
Can remain in golgi
Returned to ER
Take path out of golgi to cytoplasm
What are three paths out of golgi to cytoplasm?
Sortred to lysosomes (requires specific signal)
Sorted to secretory granules (Specific signal)
Packaged into vesicles for direct exocytosis (defult if no signal)
Lysosome
Compartments filled with hydrolytic enzymes that carry out digestion of cellular materials
What enzymes to lysosomes contain?
Proteases
nucleases
glycosoidases
lipases
phosphatases
sulfatases
What is the safety mechanism in lysosomes?
All enzymes in lysosomes are acid hydrolases.. so they must have a low pH to function (4.5 - 5)
So… if they escape into cell they will become inactive
They contain a proton pump to produce acidic lumen and are highly glycosylated
What are the three paths into the lysosomes?
Autophagy
Phagocytosis
Endocytosis
Phagocytosis
Engulfment of large particles by cell, then moved to lysosome
What are two classes of phagocytes
Macrophages and neutrophils
Endocytosis
Formation of lysosomes from golgi and ensdosomes
Coated vesicle is formed containing material to be digested.
Coat is removed, the vesicle fuses to endosome (early)
Transport vesicles are removed and returned to membrane through budding
The early endosome receives hydrolitic enzymes from Golgi
Eventually it turnes into late endosome where most digestion takes place then finally turnes into the classic lysosome
Clathrin
Coat protein for Golgi to Plasma membrane or visa versa
Binds to adaptor proteins during formation of encocytotic vesicle, creates coat
Clathrin then deforms membrane and invaginates material forming the vesicle
Dynamin pinches vesicle off
The clathrin coat then falls off and is recycled to make early endosome
Mast Cell
Big cell used in exocytosis.. common signal for realease is Ca spike
Mitochondria
Powerhouse of cell
ATP production
Where do mitochondria localize?
Along microtubules
Near sites that require lots of ATP
(near myofibers in muscles)
(wrapped around sperm tail)
Mannos 6 Phosphate
Is a tag on acid hydrolysis containing vesicles going from trans face golgi to endosomes
Pinocytosis
Cell ‘drinking’
Transcytosis
Mediated of transport of material from one side of cell to the other
Ex. transportation of antigens form one side of gut epithelial cells to the other…
How are nuclear-encoded cytosolic mitochondrial proteins recognized and imported into mitochondria?
Requires signal sequence on polypeptide
AND
Receptor on outside of mitochondria (TOM)
then TIM (2) inside mitochondrial membrane transport into mitochondria
TOM and TIM and OXA
TOM trasporter on outer mitochondral membrane for INcoming proteins
TIM (2 of them) transporter on inner mitochondral membrane for INcoming proteins
OXA transports proteins OUT of mitochondria
Cardiolipin
Phospholipid found in abundent quantities on inner mitochondral membrane
Perioxisome
Spherical structures bound by single membrane to produce and remove hydrogen perioxide
Nucleus
Reposatory of genetic information (non mitochondral)
Site of DNA synthesis and gene expression (transcription) occur
Nucleolus
Site of transcription in nucleus
Made of nuclear organizing regions of chromosomes
Site of ribosome production
Lamins
Filamentous scaffolding structure to provide sites of attatchment for chromosomes
MARs/SARs
Areas of SOME chromosomes that bind to muclear matrix
Areas of TOPO I and II (topoisomerase) activity - to reduce torsional stress*
Large looped domain of chromosomes
Area between MARS on chromosome used for transcription
Prouces Ribosomes
Nuclear envelope
Nucleus is bounded by nuclear envelope
Contains:
Outermembrane
Innermembrane
Nuclear pores
Nuclear lamina
Nuclear pores
Semi-permiable
Permiable for particles up to 5kDa
Proteins between 5kDa and 60kDa can be transported but is slower and requires specific receptor proteins
Nuclear Localization Signal (NLS)
Amino acid sequence in proteins that move nuclear bound proteins into the nucleaus (because, like all proteins are synthesized IN CYTOPLASM)
Not the signal that matters but actual folding (lysine rich)
What is Ran
It is a small G-protein
It binds to GDP in cytoplasm to transport proteins into nucleus, then dissociates in presence of GTP to release protein in nucleus
Exact opposite to export proteins.. Ran binds to GTP in nucleus, transports protein out of nucleus, then dissociates in GDP
Cytoplasm: GDP rich
Nucleus: GTP rich
Microfilaments
Muscle of cell
Suport/organize plasma membrane
Cell Shape
Cell division
Cell motility
Actin filaments*
Microvillus*
Microtubules
Railroad tracks
Organize cytoplasm
Intracellular transport
Cell Division
Cilia/glagellae motility (sperm)
Centrosome (microtubules anchored in it)
Intermediate filaments
Strenghthen Cytoplasm/tissues
Support nucleus
Epidermal appendages (nails, hair)
Cell to Cell junctions
Actin
Double helix of dimers of globular proteins
Actin + ATP leads to addition of + end
Actin + ADP.. will fall off..
Tubulin
Medium sized globular proteins make tall stacks then form cylinder
Tubulin + GTP adds to + end and grows
GDP makes it fall off, GTP much more stable
Makes microtubules
Intermediate filament proteins
Vary in size
Over 50 gene products in 4 subfamilies
Polymerization appears to be regulated by phosphorylation
Make a coiled coil
NO polarity
Polymerization/Depolymerization of tubulin and actin..
Tubulin and actin polymerize in presense of GTP/ATP and grow from + end
GDP/ADP will depolymerize and make them dissasemble and shrink from + end..
What causes polymerization of actin?
Nucleotide hydrolysis
What is the Rho family of actin
Rho - stress fibers (parallel bundles with myocin)
Rac - lamellipodia (meshworks stabilized with filamin)
Cdc42 - Filopodia (parallel bundles stabilized with cross linking)
What are the actin associated motor proteins?
Myocin Type I and Type II
Type II polimerize for muscles…
What helps cell movement?
The polymerization of actin proteins
