Membranes Key Words 1 Flashcards
Active transport
Energy-requiring movement of substances across a biological membrane against a concentration gradient
Carrier protein
Transmembrane proteins that permit facilitated diffusion. Able to change their shape to allow a molecule to diffuse across the cell membrane. Very selective. Provide the correct environment for molecules to pass the cell membrane, but do not actively push them through
Channel protein
Transmembrane proteins that make hydrophilic tunnels through membranes. Provides a favourable environment for molecules to pass through by diffusion. Highly selective of molecules they allow across, and will usually only aid in the transport of one molecule or a group of similar molecules. Some are always open, others only open in response to signals from within or outside the cell
Cholesterol
Role in membrane fluidity and also reduces the permeability of the cell membrane. Fits into spaces between phospholipids and prevent water-soluble molecules from diffusing across the membrane
Endocytosis
Active transport of bulk materials where molecules are engulfed by the plasma membrane forming a phagosome or food vacuole within the cell
Exocytosis
Process by which substances are transported in bulk from the inside of the cell to the outside. Occurs through vesicles which fuse to the cell membrane and allow the release of the particles
Pinocytosis
Process by which liquid droplets are ingested by living cells. Pinocytosis is a type of endocytosis
Partially Permeable Membrane
Membrane that is permeable to small non-polar molecules, small polar and some large non-polar molecules but does not allow the passage of large polar molecules and charged molecules.
Glycoprotein
Protein molecule that has had a carbohydrate attached to it
Glycolipid
Carbohydrate that is covalently linked to a lipid. Found in the phospholipid bilayer of the cell membrane with a carbohydrate component extending to the outside of the cell. Involved in cellular recognition
