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transports across the membrane

Membrane proteins Proteins that interact with or are part of biological membranes. Two categories: integral and peripheral membrane proteins
Passive transport Movement of ions and other substances across cell membranes that doesn’t need any energy input. Passive transport includes diffusion, osmosis and facilitated diffusion
concentration gradient unequal distribution of a substance across the cell membrane. The concentrations on the two side of the membrane are different.
active transport is the movement of molecules across a membrane against their concentration gradient: from a region of low concentration to a region of high concentration. This transport requires energy.
vesicle transport Large molecules cannot cross the membrane so they are loaded into vesicles to be delivered to their destination within or outside the cells.
Diffusion the net movement of molecules from an area of high concentration to an area of low concentration
Osmosis Net movement of water across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration, in other word in the direction that tend to equalize solute concentrations.
Ion an atom or molecule with a net electric charge due to the loss or gain of one or more electrons
Hydrophilic molecule A molecule that is soluble in water.
Hydrophobic molecule A molecule that repels water and cannot be dissolved in it.
Facilitated diffusion Molecules diffuse across the plasma membrane, down their concentration gradient, only with the assistance of specific membrane proteins
Equilibrium a molecule is at equilibrium when its concentration on the two side of the membrane is equal.
Concentration the amount of a solute divided by the total volume of the solution
Osmotic pressure The minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane
Colligative property Properties of solutions that depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the nature of the chemical species present
Tonicity The ability of an extracellular solution to make water move into or out of a cell by osmosis
Hypotonic solution the extracellular fluid has a lower osmotic pressure than the fluid inside the cell. In other words, has a lower concentration of solutes relative to the cytosol. Water will tend to enter into the cell.
Isotonic solution The extracellular fluid and the cell’s cytoplasm have the same osmotic pressure: the same solute concentration. There is no net movement of water.
Hypertonic solution the extracellular fluid has a higher osmotic pressure than the fluid inside the cell. In other words, has a higher concentration of solutes relative to the cytosol. Water will tend to exit from the cell.
Carrier proteins protein that can move a specific molecule (hydrophilic molecules) from one side of the membrane to the other
Ligand-gated channel Pore in the membrane that opens (or closes) in response to chemical signal
Voltage-gated channel Pore in the membrane that opens in response to changes of the membrane’s electrical potential
Mechanically-gated channel Pore in the membrane that opens in response to mechanical stress, pressure or distortions
ATP Adenosine triphosphate: the source of energy for cells to perform their tasks.
Primary active transport Utilizes energy in form of ATP to transport molecules across a membrane against their concentration gradient
Secondary active transport is a form of active transport across a membrane in which a transporter protein couples the movement of an ion down its concentration gradient to the movement of another molecule (or ion) against its concentration gradient
bulk transport mechanisms transport mechanisms in which large particles (or large quantities of smaller particles) are moved across the cell membrane. They include endocytosis and exocytosis.
Protein pump a protein that is capable of pumping a compound (usually an ion) against its concentration gradient by hydrolyzing ATP.
sodium-potassium pump a membrane-bound pump that transports potassium ions into the cytoplasm from the extracellular fluid while simultaneously transporting sodium ions out of the cytoplasm to the extracellular fluid
Phosphorylation A biochemical process that involves the addition of phosphate to an organic compound.
De-phosphorylation A biochemical process in living cells in which a phosphate group is removed from an organic compound through hydrolysis
Phosphate group A functional group comprised of phosphorus attached to four oxygen, and with a 3 net negative charges (PO43-)
Conformational change alteration in the shape usually the tertiary structure of a protein as a result of alteration in the environment (pH, temperature, ionic strength) or the binding of a ligand (to a receptor) or binding of substrate (to an enzyme)
Co-transporters subcategory of membrane transport proteins that couple the favorable movement of one molecule with its concentration gradient and unfavorable movement of another molecule against its concentration gradient.
Symporters co-transporter that move two molecules in the same direction
Antiporter co-transporter that move two molecules in opposite directions
Sodium-calcium exchanger Also called NCX, it is an antiporter membrane protein that removes calcium from cells. It uses the energy that is stored in the electrochemical gradient of sodium in exchange for the counter-transport of calcium ions outside the cell.
Endocytosis it is a form of active transport in which a cell transports molecules INTO the cell by engulfing them with its plasma membrane.
Exocytosis it is a form of active transport in which a cell transports molecules OUT OF the cell. These molecules are firstly packed into a vesicle, and they are released in the extracellular fluid through fusion of the vesicle with the cell membrane.
Phagocytosis the process by which a cell, such as a white blood cell, ingests microorganisms, other cells, and foreign particles.
Phagosome a membrane-bound vesicle in the cytoplasm of a cell, containing a phagocytosed particle.
Pinocytosis the uptake of fluid and dissolved substances by a cell by invagination and pinching off of the cell membrane.
Receptor-mediated endocytosis A process of capturing specific target molecules by using receptor proteins which are clustered in regions of the plasma-membrane known as coated pits. Once the molecules bind the receptors, these complexes are engulfed by the plasma membrane.
Coated pits regions of the cell membrane specialized in receptor-mediated endocytosis. Their cytoplasmic surface is coated with a specialized protein: clathrin.
Secretory vesicles membrane-bound vesicle derived from the Golgi apparatus and containing material that is to be released from the cell.
Constitutive exocytosis it involves the regular secretion of molecules that is performed by all cells. This pathway serves to deliver membrane proteins and lipids to the cell's surface or to expel components of the extracellular matrix
Calcium triggered exocytosis Is used to secrete molecules in a timely, regulated manner, such as the release of neuro-transmitters or hormones
Created by: SaraLUNEX
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