Biomembranes

Question 1

What are the basic components of a biomembrane

Answer 1

Lipids Sterols and protiens

Question 2

What does a membrane do

Answer 2

Allow specialized functions to occur in a localized manner

Question 3

What is the reason that lipid bilayer spontanousley form in an aqueous solution

Answer 3

amphipathicity

Question 4

What properties interact with properties onto the bilayers

Answer 4

Fatty acids

Question 5

What is the formation of the fatty acid chain

Answer 5

Long hydrocarbon chain attached to the poral carboxyl head group

Question 6

What does Cx:y stand for

Answer 6

x= number of carbon molecules
y=number of double bonds

Question 7

What does the pressence of double bonds mean

Answer 7

No double bonds= saturated
One double bond= unsaturated
More than one double bond= polyunsaturated

Question 8

How does the chain length have an effect on melting point

Answer 8

The melting point increases with chain length

Question 9

How does saturation have an impact on melting point

Answer 9

Decreases with the ammount of unsaturation so the more double bonds the lower the melting point

Question 10

What componets of membrane lipids to fatty acids use

Answer 10

Phospholipids phosphoglycerides sphingolipids
Sterols

Question 11

What are the properties of biomembranes

Answer 11

1. Fluid
2. Closed compartments
3. Semi permeable
4. Asymmetric

Question 12

What are the two dimensional fluids

Answer 12

rapid lateral diffusion
slow (rare) transverse (flip-flop) movement between leaflets

Question 13

What are things that contribute to fludity

Answer 13

fatty acid lenfth and cis double bonds
steroids
protiens (lateral difusion link to cytoskelton)
temperature effects modify membrane of fluid if you are cold blooded

Question 14

What makes diffusion slower

Answer 14

Diffusion is slower in plasma membranes that contain protiens than pure bilayers
because the distance that is moved may be resitrected by protiens

Question 15

What is the cyosolic face in a plasma membrane

Answer 15

The internal face

Question 16

What is the cytosolic face in an vesicle membrane

Answer 16

external face

Question 17

What crosses the membrane freely

Answer 17

Small uncharged or hydrophobic molecules pass freely

Question 18

What doesnt cross the membrane freely

Answer 18

Large hydrophilic or charged molecules

Question 19

Do phospholipid composition differ between leaflets

Answer 19

Yes

Question 20

Where are carbohydrates found

Answer 20

On the exoplasmic face

Question 21

Where are protiens on the membrane

Answer 21

They are either embedded in the bilayer in a fixed orientation or are associated with only one side

Question 22

What are the three types of membrane protiens

Answer 22

1. Integral
2. Lipid-linked
3. Peripheral

Question 23

Are membrane protiens symmetric or asymmetric

Answer 23

Asymmetric

Question 24

What are the three domains of integral membrane protiens

Answer 24

Cytoplasmic (hydrophilic)
Transmembrane (hydrophobic)
Exoplasmic (hydrophilic)

Question 25

What is apart of the cytoplasmic domain

Answer 25

Amino acids such as arg and lys the charged amino acids are near the cytosolic side to interact with polar head groups

Question 26

What structure is the transmembrane domain

Answer 26

Hydrophobic secondary or tertiary structures that span the lipid bilayer. Generally an alpha helix or a b barrel

Question 27

What is part of the exoplasmic domain

Answer 27

They are mostly glycosylated

Question 28

What are some traits about the GPI anchor

Answer 28

exoplasmic and requires sugar residues

Question 29

What is acylation

Answer 29

It attaches through the N-terminal Gly residue

Question 30

What is prenylation

Answer 30

Prenylation attaches Cys resiude ar or near C terminus

Question 31

Does the polyepetide chain of lipid linked protiens enter the bilayer

Answer 31

NO

Question 32

What type of mobility does lipid link protiens have

Answer 32

Lateral

Question 33

How are peripheral protiens attached

Answer 33

Through non-covalent interacations such as ionic interacations, hydrogen bonds and protien-protien interacations and van der waals forces

Question 34

What filaments can associate with the bilayer through peripheral protiens

Answer 34

Cytoskelton filaments and ECM components

Question 35

What are components of Topogenic Sequences

Answer 35

N-terminal (cleaved) signal sequence Stop-transfer/membrane anchor sequence Signal anchor- Internal (uncleaved) sequence (SA) Hydrophobic C-terminus

Question 36

What is the steps of tail anchored protiens

Answer 36

You have a hydrophobic c terminal tail that is recognized by Get 3 it then takes its way to the ER where it attaches to Get 1 and Get 2 it then goes into atp hydrolosis which shoves the hydrophobic part into the membrane and there are no extracellular domain

Question 37

What are the steps of syntheis 1 type protien

Answer 37

the first thing that gets translated is the N terminal signal sequence which takes it to the ER this then gets cleaved by a peptidase it will then continue to translate the NH3 side until it is told not to by an STA once it comes across the STA it will become a transmebrane domain the rest of the product is now in the cytosol

Question 38

What is the difference between GPI-anchored protiens and Type 1

Answer 38

The GPI protiens o through the same process but then a sequence near membrane is recognized by GPI-transamidase whcih will cleave the and trasnfer the luminal portion to an adjacent GPI there is no carboxiclye end of the protien

Question 39

How is a type 2 protein inserted into the membrane

Answer 39

Type 2 has an SA sequence meaning that it is internal and is a charge it goes through teh same process as type one but in type two the SA the charge on the side of the amino end therefore the carboxyci=il end is in the lumen and Nh3 in the cytosol type three is vis versa

Question 40

How is the syntheis of Type 4 protiens

Answer 40

Orientation of inital helix is determined by positively charged amino acids next to signal-anchor (SA) sequence Have alternating singal-anchor (SA) sequence and STA Can have an even or odd number of transmembrane domains

Question 41

Whats is the difference between Type 4 A and Type 4 B

Answer 41

Type 4 B has an uneven number of domains it also has more and it has two SAs in a row and then continues to alternate after that Type A has an even number