7A- Membrane structure and proteins

Cell Bio

Lipids are typically about what percentage of the 30% of chemicals in bacterial cells?

2%

There are numerous types of membranes in cells

true

What different types of membranes are in cells?

nucleus

Golgi apparatus

mitochondria

Endoplasmic reticulum

peroxisome

endosome

lysosomes

thylakoids

chloroplasts

Cell membranes are ( ), generally speaking, the lipids and integral membrane proteins can ( ) throughout the membrane 

fluid mosaics 

readily diffuse 

mosaic meaning?

combination of many small pieces that create a whole object

mosaic nature of membranes means they have ( )- due to the ( )

various structures along their surfaces

various lipids and membrane proteins

what are the the main components lipids?

1)head

2)connector

3)tails

Structure of ( ), the connector/backbone group of ( )lipids which are by far the most ( )

glycerol

glycero

general structure of phospholipids:

lipids are ( )

amphiphilic/amphipathic

what is amphiphilic?

polar plus hydrocarbon non-polar components

what is amphipathic

polar and nonpolar parts

lipids comprise ( )% of mass of most animal cell membranes - other ( )% is ( )

50

50

protein 

3 main components of lipids:

1) Head group: may or may not contain a phosphate, if it does, then it is a ( ). May or may not contain one or more sugars if it does, then it is a ( )

2) connector- if glycerol, then it is a ( )

3) tails-hydrocarbon so ( )

phospholipid

glycolipid

glycerolipid 

hydrophobic 

look at slide 13/14 and 16

okat

most abundant lipids- ( )

phospholipids

biological membranes are lipid bilayers that contain ( ) 

proteins 

different cells have different ( ) compositions

lipid

lipids can form ( )layers or ( )layers

mono

bi

( ) surround cells and (usually) organelles within cells 

lipid bilayers 

phospholipids form a sphere because it is the most ( ) form in aqueous solution like ( )

energetically favorable

cytosol

( ) are the most energetically favorable configuration for lipids- in an ( ) environment

sealed bilayers

aqueous

a lipid bilayers is more like a “( )” hence a “( )”

two-dimensional liquid (semi-solid)

fluid mosaic 

in which way do lipids move?

flexion

rotation

flip-flip (rarely occurs)

lateral diffusion

Biological membranes are lipid bilayers that have what main general characteristics?

1)they have hydrophilic surface layers (one on outside and one on inside)

2)they have a hydrophobic inner layer

3) they have proteins imbedded in them

-often these proteins have sugars chains attached (i.e. are glycosylated)

saturated fatty acids:

-tend to ( ) more ( ) and ( )

-( ) at relatively higher temperatures-compared to unsaturated lipids 

pack

closely

tightly

solidify

Unsaturated fatty acids:

-tend to pack less ( )- so membranes composed of them are “looser”

-takes lower ( ) (vs.saturated) to start to solidity

closely

temperatures

The more kinked (not kinky!… tightly curled) unsaturated fatty acids are, the ( ) the membrane formed

looser

pure lipid bilayers serve are barriers for large and/or charged or polar molecules, this allows movement across membranes to be ( )

regulated

look at slide 27

okayyy

proteins can associate with a lipid bilayer in several ways:
1)( )

2( )

3( )

4( )

integral membrane proteins

peripheral membrane proteins

anchored membrane proteins

indirectly

( ) membrane proteins- tightly associated with membrane (i.e. cannot easily be removed)

-many (but not all) are ( ) 

-the ones that are not transmembrane penetrate into membrane and are ( ) 

integral

transmembrane proteins

tightly associated

( ) membrane proteins- more loosely associated (i.e. can be removed but relatively easy extraction methods)

• can be just on ( ) or ( ) into the membrane

peripheral

surface

penetrate

( ) membrane proteins- attached by lipid-tail-like structures

anchored

( )- by interactions with membrane proteins

indirectly 

look at slide 30

OKAY

some membrane proteins, are