3.2.3 Transport across cell membranes Flashcards
what is the phospholipid bilayer structure
- hydrophilic heads and outside bilayer
- hydrophobic fatty acid tails inside bilayer
- form selective permeable barrier
- phospholipids move - fluid
what is the cell membrane structure (fluid-mosaic model)
- phospholipid bilayer
- proteins - extrinsic and intrinsic
- glycoproteins
- glycolipid
- cholesterol
why are heads on outside of phospholipid bilayer hydrophilic
form intermolecular forces with water
why are fatty acid tails on inside of the bilayer hydrophobic
from intermolecular forces with each other
why is the phospholipid bilayer selectively permeable
only non-polar molecules can diffuse through fatty acid core
what are channel proteins
allow for movement of substances across membranes
what are the functions of intrinsic, extrinsic proteins
reception, signalling molecules, membrane stability
what is a glycoprotein
- protein with short carbohydrate chain
- used for cell recognition and signalling, cell attachment
what is a glycolipid
- phospholipid with a short carbohydrate chain
- used for cell recognition and attachment
what is a cholesterol
- reduces membrane fluidity by restricting the movement of other molecules
what are the types of movement across membranes
- simple diffusion
- facilitated diffusion
- osmosis
- active transport
- co-transport
what is simple diffusion
- passive movement from higher concentration to lower concentration
- across phospholipid bilayer
- nonpolar molecules only
what is facilitated diffusion
- passive movement from higher to lower concentration
- requires channel or carrier proteins - specific to substance
- polar molecules and ions
what is osmosis
- diffusion of water molecules from higher to lower water potential
- limited across phospholipid bilayer - rapid movement requires channel proteins
- water potential = ability of water molecules to move freely
- pure water = 0kPa. All solutions have neagtive water potentials
what is active transport
- movement from lower concentration to higher concentration
- requires specific carrier proteins in membrane
- requires hydrolysis of ATP - phosphorylates carrier protein, causing change shape
what is co-transport
- movement for two substances simultaneously through a carrier protein
- one substances moves against concentration gradient (active transport)
- one substance moves down concentration gradient (facilitated diffusion)
what are adaptations to increase the rate of transport across membranes
- increased number of channel and carrier proteins
- increased surface area of membrane
- mechanisms to increase concentration gradients
- increased number of mitochondria to supply more ATP for active transport
what is rate of diffusion proportional to (Fick’s Law)
surface area x difference conc./
length of diffusion path
