1.4 membrane transport Flashcards
Active transport
The movement of substances against a concentration gradient across membranes using energy in the form of ATP. Protein pumps/carriers are used, but not channels.
Passive transport
No direct energy is needed for this type of transport.
ATP
Adenosine triphosphate - The energy molecule.
Concentration gradient
A gradient resulting from an unequal distribution of ions across the cell membrane.
Exocytosis
Vesicles fuse with the plasma membrane to secrete materials from the vesicle to outside the cell.
Endocytosis
The process in which the cell takes in materials from the outside by infolding of the membrane to form a vesicle.
Diffusion
The passive movement of particles from a region of higher concentration to a region of lower concentration.
Facilitated diffusion
The passive movement of particles from a region of higher concentration to a region of lower concentration through integral proteins [carrier or channel proteins].
Osmolarity
The concentration of a solution expressed as the total number of solute particles per litre.
Osmoregulation
The control of the water balance of a living organism.
Osmosis
The passive diffusion of water molecules from a region of lower solute concentration to a region of higher solute concentration across a partially permeable membrane either directly through the phospholipid bilayer or through aquaporins.
Hypertonic
When the external solution is more concentrated [ie higher osmolarity] than the cell solution [cytosol] and there is a net flow of water out of the cell by osmosis.
Hypotonic
When the external solution is less concentrated [ie lower osmolarity] than the cell solution [cytosol] and there is a net flow of water into the cell by osmosis.
Isotonic
When the external solution is the same concentration [same osmolarity] as the cell solution [cytosol], and there is no net entry or exit of water from the cell by osmosis.
Aquaporins
Protein water channels in the plasma membrane.
Secretion
When useful material is released from a cell.
Partially-permeable membrane
A membrane that allows some substances to diffuse through but not others.
Transport pumps
Proteins in the plasma membrane that use the energy from ATP to move substances across the membrane.
Sodium potassium pumps
A type of protein pump which actively transports sodium and potassium in opposite directions to maintain the concentration gradient of each.
Vesicles
Small, spherical, membrane-enclosed sacs that transport cellular products.
