1.3. Membrane Structure
1.
____________ _______
A.
_________ of Phospholipids
i.
A _____ head (___________)

ii.
composed of a ________ and a _________ molecule
___ _________ tails (___________)

compose of _____ ____ (hydrocarbon) chains
Phospholipids are ___________ (contain both ___________ and __________ regions)
B.
___________ in membranes
i.
_____________ arrange into a _______
ii.
The ___________ tail regions → face _______/are ________ from the surrounding _____
______
iii.
The ___________ head regions → associate with the _________ and _____________
______
C.
__________ of the Phospholipid Bilayer
i.
The _______ held together by weak ___________ ____________ between the _____
ii.
Hydrophilic / hydrophobic layers restrict the _______ of many __________
iii.
__________ _____________ can move within the bilayer, allowing for ________ ________
and ___________
iv.
This fluidity allows for the ___________ ________ and _________ of membranes
(___________/__________)
2.
Membrane Proteins
Phospholipid bilayers are embedded with ________, which may be either ___________
___________ attached to the membrane


A.
________ proteins

___________ attached to the membrane

Typically, _____________ (span across the bilayer)
__________ proteins

___________ attached by ____________ interactions

Associate with ___ surface of the membrane
_________ of membrane proteins
i.
_____ _____ of a membrane protein

Localized according to ________

_________ (___________) amino acids


ii.
_____ (___________) amino acids

Are located __________

Face _______ solution
_____________ proteins (________ proteins)

B.
Associate ________ with the _____ _______
Typically adopt ___ of two ________ __________

______ _______ / _______ _______

____ _______ (common in _______ proteins)
Membrane Protein Structures
i.
________ Proteins

_______

___________

___________


_______ ______

_______

____________

_________
_________

ii.
__________ Proteins

C.
_______, _________, ____________ (carriers)
_________ of Membrane proteins
i.
_________

ii.
iii.
May function as _______ for cellular ______________
_________

vi.
Responsible for ___________ _________ and ______ _________
___________

v.
Fixing to membranes _________ _________ pathways
_________

iv.
Serve to _______ and ____ two cells together
_______

__________ points for ____________ and _____________ matrix
____________

3.
____________ (channel proteins)
Function as _________ for _______ hormones
Cholesterol
A _________ of animal cell __________

Functions to maintain _________ and __________ _________

______ in _____ cells

The plasma membranes are surrounded and supported by a rigid ____ ____
made of cellulose
Cholesterol is an ___________ molecule → has both ___________ and ___________ regions


Cholesterol’s ________ group

___________

Aligns towards the _________ _____ of phospholipids
The _________ of the molecule (steroid ring and hydrocarbon tail)

___________

Associates with the ____________ _____
Phospholipids bilayers are _____

A.
Phospholipids are in ________ movement relative to one another
___________ of Cholesterol with _____ ____ _____
Cholesterol interacts with the _____ ____ _____ of phospholipids to ________ the properties
of the membrane

__________ the outer surface of the membrane → reducing ________

Makes the membrane ____ _________ to very small water-soluble molecules that
would otherwise freely cross

________ phospholipid _____
→ prevent _______________ of the membrane

Helps ______ __________ proteins by forming ____ _______ _____ _____ capable of
_________ the protein
4.
Fluid-Mosaic Model
Cell membranes are represented according to a ____________ model

______
The phospholipid bilayer is _______ and __________ phospholipids can move position

______
The phospholipid bilayer is _____ with proteins, resulting in a ______ of components
A.
Structure of the Plasma Membrane (Fluid-Mosaic)
B.
__________ of the Plasma Membrane

_____________

Form a _______ with _________ _____ facing outwards and fatty acid tails facing
inwards


5.
___________

Found in ______ cell membranes

Improve _________ and reduce ________
________

May be either ________ (transmembrane) or __________

Serve a _______ of roles
Membrane models
i.
________ ___ ______ model (1935)

The _____ model that attempted to describe the position of ________ within the
bilayer

Proposed a model whereby ___ ______ of protein _______ a _______ phospholipid
bilayer

Described as a ____________ ________

The lipid layer was __________ between two _______ layers

The ____ ________ seen under microscope were identified as representing
the _______ layers (_______)

Problems with the ____________ ________ model

It assumed all membranes were of a _______ _________ and would have
________ _____________ _____

It assumed all membranes would have ___________ ________ and ________
surfaces

It did not account for the ____________ of certain substances (did not
recognize the need for ___________ pores)

The ___________ at which membranes solidified did not _________ with those
expected under the proposed model
ii.
Falsification Evidence

Membrane proteins were discovered to be _________ in water (indicating
___________ surface) and varied in ____

Such proteins would not be able to form a _______ and __________ layer
around the outer surface of a membrane

Fluorescent antibody tagging of membrane proteins showed they were ______
and ___ _____ in place

Membrane proteins from two different cells were tagged with red and
green, fluorescent markers respectively

When the two cells were _____, the markers became _____ throughout the
membrane of the fused cell

This demonstrated that the membrane proteins _____ ____ and did not
form a ______ layer (as per Davson-Danielli)

Freeze fracturing was used to split open the membrane and revealed _________
_____ surfaces within the membrane

These rough surfaces were interpreted as being _____________ proteins,
demonstrating that proteins were not ______ _________ to the outside of
the membrane structure
iii.
New model

_______________ model

Proposed by Seymour Singer and Garth Nicolson in 1972

Proteins were ________ within the _____ _______ rather than existing as
separate layer

Known as the ____________ model