| Term | Definition |
|---|
| Phospholipids | A lipid consisting of a glycerol bound to two fatty acids and a phosphate group. |
| Globular Proteins | are one of the two main protein classes, comprising "globe"-like proteins that are more or less soluble in aqueous solutions |
| Fluid Mosaic model | A model conceived by S.J. Singer and Garth Nicolson in 1972 to describe the structural features of biological membranes. |
| Phospholipid Bilayer | A two-layered arrangement of phosphate and lipid molecules that form a cell membrane, the hydrophobic lipid ends facing inward and the hydrophilic phosphate ends facing outward |
| Transmembrane Proteins | is a protein that spans the entire biological membrane |
| Integral membrane proteins | are permanently attached to the membrane |
| Peripheral membrane proteins | are temporarily attached either to the lipid bilayer or to integral proteins by a combination of hydrophobic, electrostatic, and other non-covalent interactions |
| Glycoproteins | conjugated proteins containing one or more covalently linked carbohydrate residues. |
| lipid raft | is a cholesterol and sphingolipid-enriched microdomain or platform found in cell membranes |
| Transporters | is a protein involved in the movement of ions, small molecules, or macromolecules, such as another protein across a biological membrane. |
| Enzymes | are proteins that catalyze (i.e., increase the rates of) chemical reactions.[1][2] Nearly all known enzymes are proteins. |
| Cell-surface receptor | receptor is a protein molecule, embedded in either the plasma membrane or cytoplasm of a cell, to which a mobile signaling (or "signal") molecule may attach. |
| cell surface marker | marker is a protein molecule attached to a glycoprotein chain, embedded in either of the plasma membrane, it is used to identify cell types (e.g. live cells from brain cells). |
| cell adhesion | a protein molecule embedded in the plasma membrane with a certain configuration that allowa it to attache to adhesive protein on another cell, it resembles a key-hole relationship. |
| Attachments to the cytoskeleton | an integral protein structure that is attached to the micrutubules and microfilaments in the cytosol of the cell |
| Transmembrane domain | usually denotes a single transmembrane alpha helix of a transmembrane protein. It is called a "domain" because an alpha-helix in a membrane can be folded independently from the rest of the protein, similar to domains of water-soluble proteins. |
| Passive Transport | means moving biochemicals and atomic or molecular substances along a concentration gradient, which means movement from an area of higher concentration to an area of lower concentration. Unlike active transport, this process does not involve chemical energy. The four main kinds of passive transport are diffusion, facilitated diffusion, filtration and osmosis. |
| Concentration Gradient | In biology, a gradient results from an unequal distribution of ions across the cell membrane. When this happens, solutes move along a concentration gradient. This kind of movement is called diffusion. |
| Diffusion | is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion. |
| Carrier proteins | are proteins that transport a specific substance or group of substances through intracellular compartments or in extracellular fluids (e.g. in the blood) or else across the cell membrane. |
| Selectively permeable | is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion." |
| Ion Channels | pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of all living cells,they also regulate the flow of ions across the membrane in all cells |
| Gated Channels | channel through a membrane that can be opened or closed by chemical or electrical events. |
| Membrane Potential | is the voltage difference (or electrical potential difference) between the interior and exterior of a cell. |
| Facilitated Diffusion | Transport of substances across a biological membrane from an area of higher concentration to an area of lower concentration by means of a carrier molecule. |
| Saturation | The act, process, or result of saturating a substance, or of combining it to its fullest extent. |
| Osmosis | is the diffusion of water through a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. |
| Turgor Pressure | or turgidity is the main pressure of the cell contents against the cell wall in plant cells and bacteria cells, determined by the water content of the vacuole, resulting from osmotic pressure, |
| Hypotonic | contains a smaller concentration of impermeable solutes than the solution on the other side of the membrane |
| Hypertonic | contains a greater concentration of impermeable solutes than the solution on the other side of the membrane.[ |
| Aquaporin | proteins embedded in the cell membrane that regulate the flow of water. They are "the plumbing system for cells." |
| Hydrostatic Pressure | The pressure exerted or transmitted by the fluid (e.g. water) at rest. |
| Osmotic Pressure | A hydrostatic pressure caused by a difference in the amounts of solutes between solutions that are separated by a semi-permeable membran |
| Extrusion | a process where a cell exports large particles or organelles (transports them through its cell membrane to the outside). Requires energy. |
| Active Transport | A kind of transport wherein ions or molecules move against a concentration gradient, which means movement in the direction opposite that of diffusion – or – movement from an area of lower concentration to an area of higher concentration. Hence, this process will require expenditure of energy, and the assistance of a type of protein called a carrier protein. |
| Uniporters | an integral membrane protein that is involved in movement a single molecule or ions across a phospholipid membrane such as the plasma membrane |
| Symporters | an integral membrane protein that is involved in movement of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in the same direction, and is therefore a type of cotransporter. |
| Antiporters | an integral membrane protein which is involved in secondary active transport of two or more different molecules or ions (i.e. solutes) across a phospholipid membrane such as the plasma membrane in opposite directions. |
| Sodium-potassium pump | is an enzyme located in the plasma membrane which moves these two ions in opposite directions across the plasma membrane. |
| Coupled Transport | refers to the simultaneous or sequential passive transfer of molecules or ions across biological membranes in a fixed ratio |
| Counter Transport | one substance is transported in one direction at the same time as another substance is being cotransported in the other direction. |
| Endocytosis | A process in which cell takes in materials from the outside by engulfing and fusing them with its plasma membrane. |
| Phagocytosis | The process of engulfing and ingestion of particles by the cell or a phagocyte (e.g. macrophage) to form a phagosome (or food vacuole), which in turn fuse with lysosome and become phagolysosome where the engulfed material is eventually digested or degraded and either released extracellularly via exocytosis, or released intracellularly to undergo further processing. |
| Pinocytosis | A process of taking in fluid together with its contents into the cell by forming narrow channels through its membrane that pinch off into vesicles, and fuse with lysosomes that hydrolyze or break down contents. |
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