Membrane transport - under contruction Flashcards
The plasma membrane is selectively permeable, what does this mean?
Some molecules can move across it, while others cannot. Water moves across the membrane through the lipid layer, and also freely through aquaporins.
Describe the roles of the membrane for the cell
Six major functions of the cell membrane
Describe the structural elements of cell
membranes and their function
Lipid bilayer with phospholipids, these have a hydrophilip head and hydrophobic tail
List the properties of membrane proteins
Describe how membrane structure results in
selective permeability
Cell membranes are lipid bilayers, which are impermeable to most esential molecules and ions
The only thing gets across the membrane need to be non polar/uncharged and small that gets across by simple passive diffusion
A little bit of water gets across
Lipid bilayers are not permeable to:
ions such as K+, Na+, Ca2+
small hydrophillic molecules like glucose and fructose (because they are to polar, not becasue of their size)
macromolecules like proteins and RNA, the above mentioned would need to go through a protein pump or aquaporon to enter the cell
Rationalise the process of osmosis
Compare and contrast passive diffusion,
facilitated diffusion and active transport
Passive diffusion happens when neutral molecules can move across the cell membrane, these do not have a ion charge
- requires no work of the cell membrane
Facilitated diffusion happens via the praoteins in the cell membrane, faceilitated diffusion can go from high density to low
active transport - molecules move across the cell membrane from a low concentration to high concentration
Describe the processes for bulk transport across
the cell membrane
Exocytosis and endocytosis
is the plasma membrane semi-permeable?
Yes!
Osmotica
Ions, sugars, proteins, important as they are key nutrients!
