structure of cell membrane - matteus de silva Flashcards
Nuclear envelope
membrane enclosing the nucleus . the protein lined pores allow material to move in and out
chromatin
DNA plus associated protein
nucleolus
condensed region where ribosomes are formed
peroxisome
metabolises waste
rough endoplasmic reticulum
associated with ribosomes ; makes secretory and membrane proteins
smooth endoplasmic reticulum
makes lipids
microtubules
form the mitotic spindle and maintain the cell shape
centrosome
microtubule organising centre
intermediate filaments
fibrous protein that hold organelles in place
microfilaments
fibrous proteins that form the cellular Cortex
lysosome
digests food and waste material
Golgi apparatus
modifies proteins
mitochondria
produces energy
functions of the cell membrane
protective barrier
contains cytoplasm (fluid in cell)
regulated transport in and out of cell (selectively permeable)
interlocking surfaces bind cells together
allow cell recognition
provide binding site for enzymes
provide anchoring sites for filaments of cytoskeleton
receives signals from outside the cell for internal cellular activities
imports and exports molecules
movement of the cell
general structure of the cell membrane
a lipid bilayer that contains 2 sheets of lipids inter dispensed with proteins
Lipid structure
hydrophilic head- H2O loving due to polar group in the head
hydrophobic tail - H20 hating due to the long hydrocarbon tail
Amphiphatic molecules
contain both hydrophobic and hydrophilic parts
Lipids
most abundant lipid is the phospholipid
phospholipids have a PO4 group in the third OH- group of the glycerol instead of hydrocarbon
this can attach a hydrophilic group
- choline - phosphylicitycholine
-polar amino acids like serine - phosphatidylserine
properties of the lipid bilayer
due to the amphiphatic property of the membrane can reseal after an ‘injury’
bilayer is fluid - the orientation of the lipids and the outer aqueous surroundings keep the lipids in the bilayer
- the lipid can move around the layer
not the same as flexible - entire membrane being bended
importance of hydrocarbon on properties of layer
hydrocarbon tail will determine the fluidity of the membrane just as it does in fats and oils
two components are important
^the length of the hydrocarbon chain
- 14 to 24c but usually 18-20 present
^level of unsaturation (number of double c bonds)
- 1 tail has 1 or more double c bonds
- other tail is saturated
membrane fluidity
enables the membrane proteins to diffuse rapidly . simple means of distributing lipids and proteins allows membranes to fuse with one another . evenly distributed during daughter cell formation
cholesterol in the membrane
cholesterol is added to areas that have lots of unsaturated lipids to help fill in the gaps between the tails
helps to stiffen and stabilise the bilayer
> less fluid and less permeable
vesicles
the size of the membrane is increased and decreased with the interaction of vesicles . vesicles bringing material to the membrane to be secreted . increase the surface area of the plasma membrane and through the process of endocytosis , the surface area of the cell membrane decreases
endocytosis
process in which a substance gains entry into a cell without passing through the cell membrane .
results in the formation of an intracellular vesicle by virtue of the invagination of the plasma membrane
example : antibodies