Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Title: Plasma Membrane
Description: This note regarding the plasma membrane. its all point wise information make notes easy to remember.
Description: This note regarding the plasma membrane. its all point wise information make notes easy to remember.
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Page 1
Plasma Membrane
quick review
Page 2
1
...
2
...
According to
this, the plasma membrane is formed of a bimolecular layer of
phospholipids (35 Å thick) sandwitched between two layers of proteins
(each 20 Å thick)
...
e
...
The model was proposed even before the plasma membrane was seen
under the electron microscope
...
J
...
Robertson (1959) proposed a “unit membrane concept”
...
(a) These are about 75 Å thick
...
(b) These have a characteristics trilaminar appearance when
viewed with electron
microscope
...
(c) The three layers are a result of the same arrangement of
proteins and lipids as proposed by Danielli and Davson
...
Singer and Nicolson (1972) put forward the “fluid mosaic model” of
membrane structure
...
According to this model, the cell membrane consists of a highly viscous
fluid matrix of two layers of phospholipids molecules
...
Protein molecules on their complexes occur in the membrane,
but not in continuous layer; instead, these occur as separate particles
asymmetrically arranged in a mosaic pattern
...
Others (called integral or intrinsic proteins), penetrate deeply into the lipid
layer
...
These are called Trans membranes
or tunnel proteins
...
The plasma membrane contains lipids (32%), proteins (42%),
carbohydrates (6%) and water (20%) although variations are always
there
...
The carbohydrates occur only at the outer surface of the membrane
...
The carbohydrates so bound to
membrane components constitute the glycocalyx of cell surface
...
The sugar portions of glycolipids and glycoproteins are involved in recognition
mechanisms:
...
This enables cells to orient
themselves and to form tissues
...
(b) Through glycoproteins, bacteria recognise each other (female
bacteria are recognized by male bacteria; Paramoecia of different
mating types recognize each other)
...
(c) These provide the basic of immune response and various control
systems, where glycoproteins act as antigens
...
Lipids and integral proteins are amphipathic in nature (i
...
have both
hydrophobic and hydrophilic groups)
...
Thus, the membrane is held together primarily by hydrophobic attraction
...
These links
prevent close packing of molecules and make the membrane structure
more fluid
...
9
...
These may be purely structural (provide elasticity and mechanical
support) or have additional functions as :
...
...
10
...
11
...
Unchanged and fat soluble molecules pass through membranes much
more rapidly
...
Endocytosis occurs by an infolding or extension of plasma membrane to
form a vacuole or a vesicle (small vacuole)
...
(a) Phagocytosis (i
...
cell eating): Material is taken up in solid form
...
g
...
The vesicle/vacuole formed is called
phagocytic vacuole
...
(b) Pinocytosis (i
...
cell drinking): Material is taken up in liquid
(solution/colloid/ suspension) form
...
13
...
14
...
Nehar and
Sakmann got Noble prize for discovery of single ion channels
...
Pseudopodial Movement: Pseudopodia are blunt outgrowths which are
formed by three developments
...
g
...
17
...
Title: Plasma Membrane
Description: This note regarding the plasma membrane. its all point wise information make notes easy to remember.
Description: This note regarding the plasma membrane. its all point wise information make notes easy to remember.