* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Transport Across Cell Membrane
Survey
Document related concepts
Model lipid bilayer wikipedia , lookup
Lipid bilayer wikipedia , lookup
SNARE (protein) wikipedia , lookup
Magnesium transporter wikipedia , lookup
Membrane potential wikipedia , lookup
Cell culture wikipedia , lookup
Western blot wikipedia , lookup
Oxidative phosphorylation wikipedia , lookup
Signal transduction wikipedia , lookup
Cell-penetrating peptide wikipedia , lookup
Electrophysiology wikipedia , lookup
Cell membrane wikipedia , lookup
Transcript
Transport Across Cell Membrane Diffusion, Osmosis, Facilitated Diffusion and Active Transport Cell Membrane All cells are covered with a thin covering of a double layer of Phospholipids and associated Proteins present here and there. Each phospholipid has a polar (hydrophilic) head and non-polar (hydrophobic) tails. In the double layer the tails face each other forming a hydrophobic barrier which keeps water dissolved contents inside. Proteins may be Intrinsic – embedded in the lipid double layer and Extrinsic associated outside the lipid double layer. Proteins are gate keepers of cell and make the cell membrane selectively permeable. Cell Membrane and Transport In bacteria, plants, and fungi cell membrane is surrounded by a non-living cell wall. But cell membrane is the real boundary. Most cell walls are permeable others are impermeable. Semi-permeable: Cell membranes allow some materials to pass through them and prevent others from doing so. Regulators like hormones can change permeability of a cell membrane. Transport across membrane can be Passive or Active. Passive Transport Active Transport From high to low concentration Independent of conc. Gradient Energy (ATP) not required ATP required Passive Transport Passive Transport includes Diffusion, Osmosis and Facilitated Diffusion. Diffusion: All fluids (liquids + gases) move from area of higher concentration to area of lower concentration (concentration gradient). This movement of substances is called Diffusion. It can be through cell membranes. For example, spreading of fragrance, dissolving of ink drop in water, movement of O2 and CO2 between lungs and blood. Osmosis is always the net movement of water through cell membrane from its higher concentration (dilute solution) to its lower concentration (concentrated solution) when the 2 solutions are separated by semi-permeable membrane. For example absorption of water by roots of plants. Facilitated diffusion is faster than normal diffusion but needs a carrier protein though no ATP needed. For example, absorption of glucose and amino acids in intestine. Diffusion versus Osmosis Diffusion Osmosis Movement of solute Movement of water Membrane not needed Semi-permeable membrane needed High concentration low conc. of solution High conc. low concentration of water Active Transport Only active transport can operate against concentration gradient. It is the fastest mode of transport. It always consumes ATP directly or indirectly. It always needs one or more transport proteins. For example absorption of minerals by plant roots, absorption of nutrients when their conc. is already higher inside the cells. Vesicular Transport Large molecules like proteins cannot transport through membrane by passive or active transport discussed so far. These are packed into membrane bound vesicles and transported across cell membrane. Endocytosis is the bulk transport into the cell. If solid material including prey is brought in as Food Vacuole, the process is called Phagocytosis. For example, white blood cells eating bacteria. When cell brings in liquid bound in sac the process is called Pinocytosis. Exocytosis: When the cells releases solid or liquid in sacs the process is called exocytosis. For example Amoeba throws excess water outside to maintain required concentration (osmoregulation). Recap 1 Transport across Cell Membrane – Chapter 7 1. ---------synthesize proteins and ---------- synthesizes lipids. 2. ----------is movement of any substance from high to low concentration. 3. --------- consume O2 and generate -------- for energy. 4. -------is part of nucleus and assembles ribosomal subunits. 5. DNA in non-dividing cell is in form of -------- . 6. ----------- perform photosynthesis in plant cells. 7. Cytoskeleton of cell is formed of ---------- and --------------. 8. -------is bringing in a solid substance in a vesicle by a cell. 9. Diffusion of water across cell membrane is --------------. 10. -------- needs only carrier protein but -------- needs ATP besides carrier proteins.