Biomembranes Flashcards
What are the basic components of bio membrane
Lipids Sterols and protiens
What does amphipathicity do
Phospholipis spontaneoutly form lipid bilayers in aqueous solution where the properties of the fatty acids confer properties on bilayers
What does saturated mean
No double bonds
What does unsaturated mean
One double bond
What does polyunsaturated mean
More than one double bond
What changes melting point
Increases with chain length decreases with increasing unsaturation
What is a fatty acid
Long hydrocarbon chain attached to a polar carboxyl head group
What are properties of biomemembranes
- Fluid
- Closed compartments
3, Semi permeable - Asymmetric
What makes a membrane more fluid
Increase in double bonds
Shorter fatty acids
What effects membrane fludity
Steriods
Protiens
Temperature if you are cold blooded
Double bonds
Fatty acid length
How can you measure flourence recovery
You bleache a cwertain area the flourcences from outside migrate in and the bleached will start to migrate out indirect measure on fluid things are
What makes fluidit slower
Diffusion is 10 x slower in plasma membranes that contain protiens than pure bilayers
What does cytosolic face mean for plasma membrane
Internal face
What does cytosolic face mean for vesicle membrane
External face
Where is the exoplasmic face
always facing the inside
What can pass through
Small uncharged or hydrophobic molecules pass freely
What cant pass through
Large hydrophillic or charged molecules
Where are carbohydrates found
Exclusively on the exoplasmic face
Where are protiens
Either embedded in the bilayer in a fixed orientation or are associated with only one side
What are the three types of membrane protiens
Intergral
Lipid linked
Peripheral
What are the three domains of integral membrane protiens
Cytoplasmic (hydrophilic)
(often amion acids such as Argo or lys)
transmembrane a or helix or b bareel
Exoplasmic domains are glycosylated
How many amino acids are alpha helix
20-25
What are lipid linked protiens
They have a GPI anchor
the exoplasmic requires sugar residues
What is acylation
Aclyation attaches through N-termial of GLy
What is prenylation
Attaches cys residuce at c terminus
What are some characterstics of lipid-linked protiens
Protien does not eneter bilayer
Has lateral mobility in membrane
What are peripheral protiens attached by
Attached through non-covalent interactions
Ionic interactions hydrogen bonds
Protien-protien interacations
Van der wall forces
How can intergral protiens link to cytoskelton
Usin peripheral membrane protiens
Where does translation occur
In the cytoplasma
Ribsomes will translate and continue to translate in the cytoplasam unless it has a reason not ot
What does translation start with
N terminal domain
N terminal single is cleaved and that is what tells the protien to go to the ER
What is STA
Stop transfer/membrane anchor sequence only be used to change protien from ER lumen to cytosol
What is SA
Single anchor internal uncleaved sequecence
What does a topogenic sequence do
Tell the ribsome what to do
What are tail anchored protiens require
Get3 recognition of hydrophobic C-terminal tail, membrane embedded Get 1 adn 2 and Atp hydrolosys
What are the steps of Tail anchored protiens
Hydrophobic c-terminal tail
Gets recgonized by Get3 and take it to the Er
Ger1 and Get 2 are also there
Using atp hydrolis it shoves the hydrophobic part into the membrane
no extracellular domain
Inserts hydrophobic tail and becomes an integral protien
What are the steps of the type 1 protiens
- Translate N terminal sequence into the Er recognize the topogenic sequence then it is recognized to take to ER lumen
- Protien peptidase puts into a translocon
- Sequence gets cleavedoff
- N terminal domain if not other sequence would just be a lumen
- Get to the STA this a TM domain gets transfered
- Rest of the peptide is translated in the cytosol
Steps of GPI- anchored protien
Starts like Type 1 portiens with N terminal in lumen and C terminal STA
Sequence near membrane is recognized by GP1 trasamidase which cleaves and transfers the luminal portion to the adjacent GPI
Later mobility
Since the STA is very close to the carboxyicl end it had no protien in the cytsol
Synthesis of type 2 and type 3 protiens
have a SA
Orientation is determined by the positvely charged amion acids
What end is in the cytsol in type 2
NH3
What end is in the cytsol for type 3
COO
How do you know which part will be in the cytsol
Have the charged particle right next to the NH3 that side will be in the cytsol
mean it is in the type 2
If the charge comes after the SA then the NH3 will be in the lumen and the COO in the cytsol
Syntheis of Type 4 protiens
Orientation of initial helix is determined by positively charged amino acids next to signle anchor sequence
Have alternating SA and STA
Even or odd transmembrane domains
What is type one
STA signal sequence gets cleaved and the NH3 ends up in the lumen
What is type 2
Has an SA which an internal single that tells you where to go this is where the chared is on the NH3 side and it ends up in the cytsolol
What is type 3
The charge is on the side of after the SA and the COO is ending up in the cytsol
What is type 4 A
The positve charge is before the SA which makes the amino side in the cytsol and the COO is in the lumen and then it switches at the next STA
What is type 4 B
You have 2 SA in a row
The spaces are the same
You have more Sa in the row
Start in the lumen
