Cell Transport Notes PDF

Control of the Cell's Internal Environment  Internal Environment in order for the cell to survive, it needs to control what goes in and out of it. the cell membrane is set up to do this. The hydrophilic heads will repel non-polar (uncharged) molecules, while the...

Control of the Cell's Internal Environment  Internal Environment in order for the cell to survive, it needs to control what goes in and out of it. the cell membrane is set up to do this. The hydrophilic heads will repel non-polar (uncharged) molecules, while the hydrophobic tails will repel polar (charged) molecules. particles that are very small (ex: water molecules) will pass through freely. the cell needs to allow certain things inside (food, water, hormones, ions, etc.) and certain things to leave (wastes, poisons, etc.). the transport of these items can be done actively (using energy) or passively (no energy is involved). Cell Membrane The proportions of proteins, lipids, and carbohydrates in the plasma membrane vary with cell type. For example, myelin contains 18% protein and 76% lipid. The mitochondrial inner membrane contains 76% protein and 24% lipid.  Fluid Mosaic https://www.youtube.com/watch? v=RT61MUjogRo  Homeostasis All organisms undergo change each day, hour minute. The ability of an organism to regulate the changes and stay in a relative state of balance is homeostasis. Ex. Body temperature, blood sugar  The Cell Membrane and Homeostasis Homeostasis depends on the movement of certain molecules into and out of the cell. All of these materials must pass through the cell membrane. Several factors affect the movement of substances. 1. Size of particles – most large particles can not move through the membrane 2. Particles dissolving in Water- if a substance does not dissolve in water than it usually does not pass 3. Conditions inside and outside the cell- affect absorption 4. Structure of membrane itself – there are spaces for the particles to pass in the membrane but sometimes they are too small  Passive Transport this takes place because some molecules are able to pass through tiny gaps in the cell membrane. all particles will naturally move from an area of a high concentration to an area of a low concentration. this movement is known as "diffusion". the diffusion of water through a selectively permeable membrane is known as "osmosis".  Homeostasis –all organisms want to get to a state of balance or equilibrium. All the following mechanisms will get them to that state of balance.  Diffusion Diffusion - The movement of molecules passively using the concentration gradient or following their natural kinetic energy. Concentration, temperature and pressure influence rate of diffusion.  Osmosis Osmosis – the diffusion of water through a selectively permeable membrane from an area of higher concentration to an area of lower concentration.  Terms with Osmosis 1. Tonicity - the extracellular solution’s ability to make water move inside or outside the cell by the process of osmosis 2. Osmoregulation - the process of regulating a constant osmotic pressure of the cellular fluid by controlling the water flow and solute concentrations relative to the surrounding 3. Hypotonic – water outside the cell has higher concentration than inside the cell. Means water will move into the cell. Ex. Blood cell placed in distilled water 4. Hypertonic- water outside the cell has lower concentration than inside the cell. Means water will move out of the cell. Ex. Celery in salt water. 5. Plasmolysis- the cell’s water content shrinks when placed in hypertonic solution. 4. Turgor pressure – a pressure that forces the cytoplasm against the cell wall. 5. Isotonic – concentration is same inside and outside Passive Transport https://youtu.be/-ZwXUrZolD0 Plasmolysis  Animal Cells Animal cells do not have cell walls so pressure can not build up to the point where osmosis stops. The net flow in, continues until the cell bursts. Many singled celled organisms have contractile vacuoles which pump out water out of the cell. In multicellular animals excess water is carried to the lungs, kidneys and skin.  Let’s Check! https://biomanbio.com/ HTML5GamesandLabs/Cellgames/ osmosis-interactivepage.html https://biomanbio.com/ HTML5GamesandLabs/Cellgames/ osmosis-interactivepage.html  Active Transport this takes place when the cell wants to move something that will not normally pass through the membrane. This means against the concentration gradient. it may do this to transport food in, wastes out, or to move water to control the internal concentration of the cell. there are two mechanisms for active transport: This process takes energy.  Carrier molecules these are proteins that are buried in the phospholipid bilayer. Using energy from ATP, they latch on to a molecule and pull it through the membrane.  Inpocketing in this process, liquids and solids are taken in or expelled from the cell by a bending and fusion with the cell membrane. there are two types of inpocketing:  Types of Inpocketing Endocytosis - when materials are brought into the cell. i) phagocytosis - when food is brought in. ii) pinocytosis - when liquid with dissolved materials is brought in. Exocytosis - when materials are pushed out of the cell. http://www.stanford.edu/group/Urchin/GIFS/exocyt.gif Active Transport https://www.youtube.com/watch? v=5asMngTQqxQ