B2.1 Membranes and membrane transport Flashcards
(45 cards)
lipid bilayers structure
phospholipids - 2 layers
hydrophobic tail
hydrophobic head
what are phospholipids known as
having both hydrophilic and hydrophobic parts - amphipathic
phosphate head of phospholipid
polar and therefore soluble in water (hydrophilic)
fatty acid tail of a phospholipid
nonpolar and therefore insoluble in water (hydrophobic)
phospholipid monolayer formation
phospholipids are placed in water
hydrophilic phosphate heads go towards the water
hydrophobic hydrocarbon tails go away from the water
monolayer
1 layer
bilayer
2 layers of phospholipids
lipid bilayer barriers - large molecules
Large molecules cannot pass through the barrier as the hydrophobic region is tightly packed and has low permeability to larger molecules
lipid bilayer barriers - polar molecules and ions
Polar molecules and ions cannot pass through the hydrophobic tails of the phospholipid structure
The hydrophilic nature of these molecules and ions means that they will not interact with the hydrophobic fatty acid tails of the phospholipids
lipid bilayer barriers - in general
The bilayer forms an effective barrier so that it is able to control which molecules pass through and out of the cell
Integral protiens
- partially hydrophobic
- embedded in the phospholipid bilayer
- can be embedded across both layers or just one layer
peripheral proteins
- attached to the surface of the bilayer
- hydrophilic
- inside or outside
increasing of diffusion rate
- increase in temp
- increase in surface area
- increase in distance
simple diffusion
- random continuous net movement of a molecule from a region of higher concentration to a region of lower concentration
Membrane protein function
transport, receptors, cell adhesion, cell-to-cell recognition and immobilized enzymes
transport protein
function
Transport proteins allow ions and polar molecules to travel across the membrane
Channel proteins
form holes, or pores, through which molecules can travel
Carrier proteins
change shape to transport a substance across the membrane, e.g. protein pumps and electron carriers
Receptors
- binding of peptide hormones, e.g. insulin
- The binding generates a signal that triggers a series of reactions inside the cell
Immobilised enzymes
integral proteins with the active site exposed on the surface of the membrane
Cell adhesion
Cell adhesion allows cells to attach to neighbouring cells within a tissue
Cell-to-cell recognition
cell’s ability to distinguish one type of neighboring cell from another.
occurs when complementary molecules on opposing cell surfaces meet.
Glycocalyz (protein + lipid) act as cell markers, or antigens, for cell-to-cell recognition
molecules that move by simple diffusion
oxygen
co2
Osmosis
net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane
