E3 Flashcards
How are biological membranes formed
By phospholipid bilayers
Membranes are amphipathic
Having a hydrophobic and hydrophilic regions
Characteristics of phospholipid bilayer membrane
They spontaneously seal to form closed structures that separate 2 aqueous compartments
Structures of membrane phospholipid
Gylecerol backbone
2 fatty acids can be saturated or unsaturated ( double bonds cause kinks )
Phosphate head
Alcohol
Some may contain cholesterol which can make it rigid and influence membrane fluidity
Molecules associated with membranes
Integral membrane protein inserted into membranes via hydrophobic transmembrane domain
Proteins on the external or internal part are peripheral proteins
Movement of molecules across a membrane can be
Active or passive
Passive transport
Does not need metabolic energy
Driven by concentration gradient
Involves diffusion and sometimes require integral membrane channel proteins (porins)
By facilitated diffusion involving specific integral membrane protein that are specific for a particular molecule and may involve changes in confirmation
Passive transport
Does not need metabolic energy
Driven by concentration gradient
Involves diffusion and sometimes require integral membrane channel proteins (porins)
By facilitated diffusion involving specific integral membrane protein that are specific for a particular molecule and may involve changes in confirmation
Transport of a molecule against its concentration gradient
Needs metabolic energy ATP
Secondary active transport
Movement of molecules down a concentration gradient ( usually ions)
Includes
Symporters Co transport of 2 molecules in the same direction
Antiporters co transport of 2 molecules in opposite direction
How do receptors transfer information
They bind extra cellular compounds without transporting them across a membrane and allow cells to respond to extra cellular signals
