Cell membranes and transport Flashcards
What is the fluid mosaic model?
A model that describes the structure of the plasma membrane as a mosaic of components.
What is meant by “fluid mosaic model”?
Fluid describes how particles move freely and mosaic describes the shape of the model when you look from above.
What does the fluid mosaic model contain?
Phospholipids, cholesterol, proteins and carbohydrates.
Roles of phospholipids
Provide barriers in cellular membranes to protect the cell, and they make barriers for the organelles within those cells.
Roles of cholesterol
Reduces permeability of lipid membranes.
Roles of glycolipids
To maintain the stability of thecell membraneand to facilitatecellular recognition.
Roles of proteins
Help the cell interact with its environment.
Roles of glycoproteins
They act incell-to-cellrecognition and binding of other molecules.
Roles of cell membranes
Prodiving protection to cell, providing a fixed environment inside the cell, regulating the transport of substances in and out of the cell, receiving chemical messengers from other cell and absorbing substances.
Process of cell signalling
First, reception, whereby thesignalmolecule binds the receptor. Then,signaltransduction, which is where the chemicalsignalresults in a series of enzyme activations. Finally, the response, which is the resultingcellularresponses.
Process of diffusion
Diffusionis the movement of a substance from an area of high concentration to an area of low concentration.Diffusionhappens in liquids and gases because their particles move randomly from place to place.Diffusionis an importantprocessfor living things; it is how substances move in and out of cells.
Facilitated diffusion
The process of spontaneous passive transport of molecules or ions across a biological membrane via specific transmembrane integral proteins.
Osmosis
The movement of a solvent across a semipermeable membrane from low to high concentration.
Active transport
The movement of ions or molecules across a cell membrane into a region of higher concentration
Endocytosis
Cellular process in which substances are brought into the cell.
Exocytosis
A form of active transport and bulk transport in which a cell transports molecules out of the cell.
Effect of changing surface area to volume ratio on diffusion
When the cell increases in size, thevolumeincreases faster than thesurface area, becausevolumeis cubed wheresurface areais squared. When there is morevolumeand lesssurface area,diffusiontakes longer and is less effective.
Effects of immersing plant tissues in solutions of different water potentials
When you immerse plant tissues in a solution oflower water potentialthan the cell contains, water leaves by osmosis to its surroundings. The cytoplasm pulls away from the cell wall and cell becomes flaccid (plasmolysis).
When a cell is in a solution ofhigher water potential,water enters by osmosis. Cytoplasm pushes hard against the cell wall and cell becomes turgid (turgor pressure).
