Selective permeability Flashcards
Easy passage across the membrane
Small nonpolar, hydrophobic molecules
1. Hydrocarbons
Difficult or protein assisted passage across the membrane
Hydrophillic, polar molecules, large molecules, ions
1. Sugars, water
Passive transport
Transport of a molecule that does NOT require energy from the cell because the solute is moving with its concentration or electrochemical gradient.
Diffusion
Passive transport, spontaneous process resulting from the constant motion of molecules, substances move from a high to low concentration
Osmosis
The diffusion of water down its concentration gradient across a selectively permeable membrane
Facilitated diffusion
Diffusion of molecules through the membrane via transport proteins, increases rate of diffusion for small ions, water, and carbs
Channel proteins
Provide a channel for molecules and ions to pass, channel is hydrophilic
Aquaporins
Specific channel protein for water
Carrier proteins
Undergo conformational changes for substances to pass
Active transport
Transport of a molecule that requires energy because it moves a solute against its concentration gradient.
ATP and active transport
ATP can transfer the terminal phosphate group to the transport protein, which changes the shape of the transport protein to better move a substance
Pumps
Maintain membrane potential
Membrane potential
Unequal concentrations of ions across the membrane results in an electrical charge
Electrogenic pumps
Proteins that generate voltage across membranes, which can be used later as an energy source for cellular processes
Sodium potassium pump
3 Na get pumped out of the cell and 2 K get pumped into the cell resulting in a positive net charge
Proton pump
Integral membrane protein that builds up a proton gradient across the membrane, pumps H+ out of the cell
Cotransport
The coupling of a favorable movement of one substance with an unfavorable movement of another substance, favorable movement-downhill diffusion, unfavorable movement-uphill transport
Transport of large molecules is done through….
Exocytosis and endocytosis
Phagocytosis
When a cell engulfs particles to be later digested by lysosomes
Pinocytosis
Nonspecific uptake of extracellular fluid containing dissolved molecules
Receptor-mediated endocytosis
Specific uptake of molecules via solute binding to receptors on the plasma membrane
Exocytosis
Secretion of molecules via vesicles that fuse to the plasma membrane
Endocytosis
Uptake of molecules from vesicles fused from the plasma membrane
