Plasma Membrane unit Vocabulary
Diffusion - the movement of molecules in a fluid from regions of high concentration to regions of low concentration, (driven by a concentration gradient.) Example: If you put a drop of food coloring in pure water, with out siring or shaking the dye will eventually become distributed even throughout the water.
Concentration gradient – the difference in concentration of a substance between two parts of a fluid or across a membrane
Active transport – the movement of materials across a membrane through the use of cellular energy. Usually across a concentration gradient.
Osmosis- the diffusion of water across a semi permeable membrane. Water will move to the side of the membrane that has a lower concentration of water or a higher concentration of solutes (stuff dissolved in the water.)
Hypotonic –refers to a solution having a lower concentration of dissolved particles than the cytoplasm of a cell. (Usually causes the free water to move into the cell.)
Isotonic –refers to a solution that has the same concentration as the cytoplasm of a cell.
Hypertonic –refers to a solution having a higher concentration of dissolved particles than the cytoplasm of a cell. (Usually causes water to move out of a cell into the solution)
Permeable – a substance that allows liquids and gasses to pass through.
Semipermeable membrane -a membrane which will allow certain molecules or ions to pass through it by diffusion.
phospholipid –a lipid consisting of a glycerol with to which two fatty acids and one phosphate are bonded. Molecules that make up cell membranes. The phosphate “head” is hydrophilic and the lipid “tail” is hydrophobic.
phospholipid bilayer – a double layer of phospholipids that make up all cellular membranes. The hyrophillic phosphate heads face the outside, contacting the extra-cellular fluid and the cytoplasm. The hydrophobic lipid tails face each other on the inside of the membrane.
Hydrophilic –literally meaning “water-loving”. Refers to a substance that dissolves readily in water, or to parts of a large molecule which forms weak hydrogen bonds with water.
Hydrophobic –literally means “water-fearing”. Refers to a substance that does not dissolve in water, such as oil and other lipids.
Glycoprotien – a protein to which a sugar or carbohydrate is attached.
Glycolipid – a lipid to which a sugar is attached.
Transport proteins – a protein that regulates the movement of water-soluble molecules through the cell membrane.
Channel proteins –a protein that forms a channel or pore completely through the membrane. And that is usually permeable to one or more water-soluble molecules such as ions.
Carrier proteins – a membrane protein that facilitates (helps) diffusion of specific substances across the membrane. The molecule to be transported binds to the outer surface of the carrier protein, the protein then changes shape allowing the molecule to move across the membrane through the protein.
Receptor proteins –protein in the cell membrane that recognizes and binds to specific molecules. Often trigger some response by the cell such as endocytosis or cell division.
recognition proteins – a protein or glycoprotein that identifies the cell as belonging to a specific species or organ. Helps immune system tell invading cells from cells belonging to the organism.
Passive transport –Movement of materials across a membrane without the use of energy. Usually moves from an area of high concentration to an area of lower concentration.
Endocytosis – the movement of material into the cell in which the plasma membrane engulfs extracellular material (material from outside of the cell), forming a membrane bound sac that enters the cytoplasm.
Exocytosis –The movement of material out of a cell in which the material within the cell is enclosed in a membrane-bound sac that moves to the plasma membrane and unites with it. Releasing the material outside of the cell.