transport across cell membranes Flashcards
What is the Fluid-mosaic model of membrane structure?
Proteins and Phospholipids in the membrane can move around within it
Give 6 components of the Cell Membrane
Phospholipid bilayer
Embedded proteins (intrinsic or extrinsic)
Channel and carrier proteins (intrinsic)
Glycolipids (lipids and attached polysaccharide chain)
Glycoproteins (proteins with polysaccharide chain attached)
Cholesterol (binds to phospholipid hydrophobic fatty acid tails)
Phospholipid Bilayer
Phosphate Heads
- hydrophilic > attracted to water
- orientate to the aqueous environment either side of the membrane
Fatty Acid Tails
- hydrophobic > repelled by water
- orientate to the inside/interior of the membrane
Give 3 ways molecules can enter/leave the cell
- Phospholipid Bilayer
- Channel Proteins
- Carrier Proteins
How does the phospholipid bilayer control movement of substances in and out of the cell? [4]
- Allows movement of small non-polar molecules
- (e.g. oxygen / water / CO2)
- Down a concentration gradient
- via passive process of simple diffusion
How do channel proteins control movement of substances in and out of the cell? [5]
- Allows movement of large, water-soluble, polar molecules / ions
- Through its pore
- Down a concentration gradient
- via passive process of facilitated diffusion
- Different proteins facilitate the diffusion of different specific molecules
How do carrier proteins control movement of substances in and out of the cell? [6]
- Allows the movement of molecules / ions
- Against a concentration gradient
- By protein changing shape when molecule attaches
- Using ATP via active transport
- Different proteins facilitate the diffusion of different specific
molecules
Give 3 ways the plasma membrane is adapted for its other functions
Phospholipid bilayer > maintains a different environment on each side of the cell
Phospholipid bilayer is fluid > can bend to take up different shapes for phagocytosis
Surface proteins > cell recognition / act as antigens / receptors
What is the role of Cholesterol? [2]
- Makes the membrane more rigid, stable and less flexible
- By restricting lateral movement of molecules in membrane
Simple Diffusion [5]
- Net movement of small, non-polar molecules
- (e.g. oxygen / water / CO2)
- across a selectively permeable membrane
- down a concentration gradient
- Passive process (no ATP / energy required)
What factors affect the rate of simple diffusion? [3]
- surface area
- concentration gradient
- diffusion distance
Facilitated Diffusion [6]
- Net movement of larger, water-soluble, polar molecules / ions
- (e.g. glucose)
- Across a selectively permeable membrane
- Down a concentration gradient
- Through a channel/carrier protein
- Passive process (no ATP/energy required)
What factors affect the rate of Facilitated Diffusion? [3]
- surface area
- concentration gradients
- number of channel/carrier proteins
Active Transport [5]
- Net movement of molecules/ions
- Against a concentration gradient
- Using carrier proteins
- Using energy from the hydrolysis of ATP
- To change the shape of the tertiary structure and push the substances though
What factors affect the rate of Active Transport? [4]
- pH (affecting tertiary structure of carrier protein)
- temp (affecting tertiary structure of carrier protein)
- rate of respiration (ATP production)
- speed/number of carrier proteins
