Transport Mechanism
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The plasma membrane functions as a barrier and for signal transmission. It is composed of phospholipids, cholesterol, integral proteins, and peripheral proteins. Passive transport mechanisms like diffusion, facilitated diffusion, and osmosis move substances down their concentration gradients without energy use. Active transport mechanisms like primary and secondary active transport move substances against their gradients by utilizing energy. Bulk transport mechanisms of endocytosis and exocytosis transport larger particles and molecules into and out of the cell.
Transport Mechanism
- 2. Plasma Membrane • semi-permeable Functions: • Barrier of the cell from the external environment • Transmit signals by means of complex integral proteins. Component Function Phospholipid Main fabric of the membrane Cholesterol Dampens effect of temperature Integral Proteins Transport substance through membrane Peripheral Proteins Cell recognition Carbohydrate Cell recognition Effective interaction with the aqueous environment
- 4. i. Phospholipids -consist of a three-carbon glycerol backbone with two fatty acid molecule attached to carbons 1 and 2; and a phosphate- containing group attached to the 3rd carbon Hydrophilic head (water-loving) Hydrophobic tail (water-hating) Phosphate Glycerol Saturated fatty acid Unsaturated fatty acid
- 5. ii. Proteins -second major component of plasma membrane • Integral Proteins – proteins that act as tunnels or channels for the passage of water and other substance (uniporter, symporter and antiporter) • Peripheral Proteins- proteins that act as receptors for hormones, recognition center and antigens iii. Carbohydrates - third major component of plasma membranes ; - are found at the external surface of the membrane and are bound to either proteins (forming glycoproteins) or to lipids (forming glycolipids)
- 6. Passive Transport • naturally occurring phenomenon and does not require cell energy to accomplish the movement • substances move from an area of higher concentration to an area of lower concentration Concentration gradient- a physical space in which there is a range of concentrations of a single substance Diffusion Facilitated diffusion Osmosis
- 7. i. Diffusion Substances tend to move from an area of high concentration to an area of low concentration until the concentration is equal across the space ( dynamic equilibrium is reached )
- 8. Factors that Affects Diffusion Extent of the concentration gradient Mass of the molecules diffusing Temperature Solvent density Solubility Surface area and thickness of the plasma membrane Distance travelled
- 9. ii. Facilitated Diffusion Materials diffuse across the plasma membrane with the help of membrane proteins.Transport Proteins- integral proteins involved in the facilitated diffusion and functions as either channels or carriers Channel Proteins specific for a substance that is being transported. Carrier Proteins binds a substance and triggers a change in its own shape, moving the bound molecule from the outside of the cell to its interior
- 11. iii. Osmosis is the movement of water through a semipermeable membrane according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes Tonicity- describes how extracellular solution can change the volume of the cell by affecting osmosis Osmolarity- total solute concentration of the solution. Low Osmolarity- solvent > solute High Osmolarity- solvent < solute
- 12. OSMOLARITY OF THE CELL Hypertonic Solution- extracellular fluid has less water concentration than intracellular fluid. Hypotonic Solution- extracellular fluid has more water concentration than intracellular fluid Isotonic Solution- extracellular fluid has same water concentration than intracellular fluid
- 14. Active Transport • requires cell energy to accomplish the movement • substances move into the cell against its concentration gradient Electrochemical Gradient- a physical space in which there is difference of charge across the membrane Primary Active Transport Secondary Active Transport
- 15. Primary Active Transport moves ions across the membrane and creates a difference in charge across that membrane which is actually dependent in ATP Secondary Active Transport describes the movement of material that is due to the electrochemical gradient established by the PAT and does not primarily require ATP
- 17. Bulk Transport The process by which cell engulfs and removes larger molecules and particles Endocytosis Phagocytosis Pinocytosis Receptor-mediated Endocytosis Exocytosis
- 18. Endocytosis – is a type of active transport that move particles, such as large molecule, parts of the cells, and even the whole cell, into a cell Phagocytosis- a condition of cell-eating Pinocytosis- cell- drinking process Receptor-mediated Endocytosis- a molecule can bind into a surface (clathrin) of the membrane and stimulates the internal surface of the membrane to fold and do the phagocytosis
- 20. Exocytosis – the reverse process of endocytosis; its purpose is to expel material from the cell into the extracellular fluid Extracellular fluid