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Molecular Biology
Molecular
| Term | Definition |
|---|---|
| Cell Membrane | The cell membrane, also known as the plasma membrane, is a thin, semi-permeable barrier that surrounds the cell, separating its internal contents from the external environment. |
| Composition | The cell membrane is primarily composed of a lipid bilayer, which consists of phospholipids, cholesterol, and glycolipids. Proteins are also embedded within the lipid bilayer. |
| Phospholipids | Phospholipids are the main components of the cell membrane. They have a hydrophilic (water-loving) phosphate head and two hydrophobic (water-repelling) fatty acid tails. |
| Cholesterol | Cholesterol is a lipid molecule present in the cell membrane. It helps maintain the fluidity and stability of the membrane. |
| Glycolipids | Glycolipids are lipids with attached carbohydrate chains. They play a role in cell recognition and cell signaling processes. |
| Proteins | Proteins in the cell membrane have various functions, including transport of molecules, cell adhesion, signal reception, and enzymatic activities. |
| Selective Permeability | The cell membrane exhibits selective permeability, allowing certain substances to pass through while restricting others. This property helps maintain the internal environment of the cell. |
| Transport Proteins | Transport proteins facilitate the movement of molecules and ions across the cell membrane. They can be classified as channels, carriers, or pumps. |
| Cell Recognition Proteins | Cell recognition proteins are involved in cell-cell recognition and adhesion. They play a role in immune responses and tissue formation. |
| Lipids | Lipids are a diverse group of biomolecules that include phospholipids, cholesterol, and glycolipids, which are essential components of the cell membrane. |
| Hydrophilic Head | The hydrophilic head of a phospholipid is attracted to water and is located on the outer and inner surfaces of the cell membrane. |
| Saturated Fatty Acids | Saturated fatty acids have no double bonds between the carbon atoms in their hydrocarbon chain. They tend to make the lipid bilayer less fluid and more rigid. |
| Fluidity and Unsaturated Fatty Acids | An increase in the proportion of unsaturated fatty acids in the lipid bilayer enhances its fluidity, allowing greater movement and flexibility of the membrane. |
| Adaptation to Temperature | Membranes can adjust their fatty acid composition in response to changes in temperature. More unsaturated fatty acids are produced in colder conditions to maintain appropriate fluidity. |
| Melting point | The temperature at which it transitions from a solid to a liquid state. The melting point varies depending on the fatty acid's chemical structure, particularly its degree of saturation |
| Lateral Diffusion | the movement of lipids within the same leaflet of the lipid bilayer. Lipids can move freely laterally, allowing for membrane fluidity. |
| Rotational Motion | Lipids can undergo rotational motion around their axis within the lipid bilayer, contributing to the overall fluidity and flexibility of the cell membrane. |
| Transbilayer (Flip-Flop) Diffusion | involves the movement of lipids from one leaflet of the lipid bilayer to the opposite leaflet. It occurs less frequently and is facilitated by specific enzymes. |
| Flippases | enzymes that catalyze the transbilayer movement of lipids in the cell membrane (outside to inside). |
| Role of Lipid Movement | Lipid movement in the cell membrane is essential for maintaining membrane integrity, supporting membrane protein function, and facilitating membrane remodeling processes. |
| Protein-Membrane Association | various mechanisms, including transmembrane domains, lipid anchors, and peripheral interactions. |
| Transmembrane Proteins | span the lipid bilayer, with portions of the protein exposed on both sides. They can have alpha-helical or beta-barrel structures. |
| Lipid-Anchored Proteins | are attached to the membrane through covalently linked lipid molecules, such as fatty acids or prenyl groups. |
| Peripheral Proteins | Peripheral proteins are associated with the membrane through electrostatic interactions or binding to other membrane-associated proteins. |
| Passive Transport | Passive transport is the movement of molecules or ions across the cell membrane without the input of energy. It occurs along the concentration gradient and includes diffusion and osmosis. |
| Diffusion | the passive movement of molecules from an area of higher concentration to an area of lower concentration. It is driven by the random motion of molecules. |
| Osmosis | the diffusion of water molecules across a selectively permeable membrane in response to concentration differences of solutes. |
| Active Transport | the movement of molecules or ions across the cell membrane against their concentration gradient, requiring the expenditure of energy, usually in the form of ATP. |
| Carrier Proteins | are involved in facilitated diffusion and active transport. They bind to specific molecules or ions and undergo conformational changes to transport them across the membrane. |
| Channel Proteins | form aqueous pores in the cell membrane, allowing the passive movement of specific ions or molecules down their electrochemical gradient. |
| Aquaporins | are specialized channel proteins that enable the rapid and selective diffusion of water molecules across the cell membrane. |
| Ion Channels | are channel proteins that specifically facilitate the movement of ions across the cell membrane, regulating electrical signaling and ion balance. |
| Tonicity | refers to the relative concentration of solutes inside and outside a cell. It determines the direction and intensity of water movement across the cell membrane. |
| Cotransport | is the simultaneous transport of two different substances across the cell membrane. (symport and antiport) |
| Function of Membrane Proteins | transport of molecules, enzymatic activity, cell adhesion, cell signaling, receptor function, and structural support of the cell membrane. |
| Intercellular joining | Function of membrane that is important for tissue formation. |
| Sttachment to extracelullar matrix or cytoeskeleton | Give the shape of cell. |
| CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) | is an ion channel protein responsible for regulating the flow of chloride ions across cell membranes. Mutations in the CFTR gene lead to dysfunctional CFTR protein in cystic fibrosis. |
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Andabi0
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