Membrane Structure 1.3 Flashcards
Phospholipids
Phospholipids, aref lipids whose molecule has a hydrophilic “head” containing a phosphate group and two hydrophobic “tails” from fatty acids,
Phospholipid bilayers
The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules
Polar vs Non Polar
Polar: A structure having an uneven distribution of electron density.
A structure in which electron density is more or less evenly distributed is called nonpolar.
Amphipathic
Has both Hydrophilic and Hydrophobic Parts
Hydrophilic
Water loving - attracted to water molecules and tends to be dissolved by water = Polar
Hydrophobic
Property of a substance that repels water. It means lacking affinity for water, and tending to repel or not to absorb water.
Hydrophobic molecules tend to be non-polar molecules and group together.
The Phospholipid Head
Phosphate group bonded to glycerol
Heads attract water molecules
The Phospholipid Tail
It is hydrophobic meaning that it does not attract water
Made of 2 fatty acids
Gorter and Grendel Model
Founders of the “Bi-layer” model
Extracted phospholipids from red blood cell
Very Simple
Davson-Danielli Model
Showed how there were no integral, peripheral and lipid (Diamond shape) proteins to the structure of the membrane
Falsified as the fluid mosaic model made more sense
Fluid Mosaic Model
Showed how there has a phospholipid bi - layer and integral, peripheral and lipid proteins. Also had glycogen chains, cholesterol and kinks in tail for space of cholesterol.
Integral proteins could be channel, carrier or a pump.
Simple Diffusion
simple diffusion is a form of diffusion that does not require the assistance of membrane proteins.
Facilitated Diffusion
Facilitated diffusion is the process of spontaneous passive transport of molecules or ions across a biological membrane via specific transmembrane integral
Needs integral protein as the transport vesicles are to big to simply go through the heads
Passive Transport
Passive transport is a type of membrane transport that does not require energy to move substances across cell membranes.
Instead of using cellular energy, like active transport, passive transport relies on the second law of thermodynamics to drive the movement of substances across cell membranes.
Active Transport
Occurs when molecules such as glucose or amino acids move from high concentration to low concentration facilitated by carrier proteins or pores in the membrane.
Active transport requires energy for the process by transporting molecules against a concentration or electrochemical gradient.
Concentration gradient
A concentration gradient occurs when the concentration of particles is higher in one area than another.
Like the unequal distribution of ions on one side of the membrane
Hydrocarbon Tail
The hydrocarbon chain that makes up fatty acids
Making the tail end of the molecule hydrophobic, or water resistant, while the glycerol head is hydrophilic, or “water-loving.” These properties are due the polarity of the molecules that make up each side
Saturated vs Unsaturated
The difference between saturated and unsaturated fat lies in the number of double bonds in the fatty acid chain. Saturated fatty acids lack double bonds between the individual carbon atoms, while in unsaturated fatty acids there is at least one double bond in the fatty acid chain.
Unsaturated would have a double bond when the chemical is kinked downwards (C is double bonded)
Functions of Membrane Proteins
Junctions – Serve to connect and join two cells together
Enzymes – Fixing to membranes localises metabolic pathways
Transport – Responsible for facilitated diffusion and active transport
Recognition – May function as markers for cellular identification
Anchorage – Attachment points for cytoskeleton and extracellular matrix
Transduction – Function as receptors for peptide hormones
JetRat***
Membrane Fluidity
The plasma membrane is a fluid combination of phospholipids, cholesterol, and proteins
Integral proteins
proteins embedded in the phospholipid bilayer.
Peripheral proteins
proteins on the surface of the plasma membrane.
Permeability
the rate of passive diffusion of molecules through the membrane, which depends on the electric charge, size, and polarity of the molecule.
