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week 1 notes

by: Grace Gerhards

week 1 notes vs 331

Grace Gerhards
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This is some of the power points i answered in class
dr joan
Class Notes
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This 4 page Class Notes was uploaded by Grace Gerhards on Monday July 18, 2016. The Class Notes belongs to vs 331 at Colorado State University taught by dr joan in Summer 2016. Since its upload, it has received 17 views. For similar materials see histology in Biology at Colorado State University.


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Date Created: 07/18/16
Grace Gerhards transmembrane pre activity Transmembrane transport  Lipid bilayer o The lipid bilayer is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all living organisms and many viruses are made of a lipid bilayer, as are the membranes surrounding the cell nucleus and other sub-cellular structures. The lipid bilayer is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be. Lipid bilayers are ideally suited to this role because, even though they are only a few nanometers in width,[1] they are impermeable to most water-soluble (hydrophilic) molecules. Bilayers are particularly impermeable to ions, which allows cells to regulate salt concentrations and pH by transporting ions across their membranes using proteins called ion pumps.  Solute o The rate of flow of a solute across the bilayer is directly proportional to the difference in its concentration on the two sides of the membrane. Multiplying this concentration difference (in mol/cm3) by the permeability coefficient (in cm/sec) gives the flow of solute in moles per second per square centimeter of membrane.  Transmembrane protein o A transmembrane protein (TP) is a type of integral membrane protein that spans the entirety of the biological membrane to which it is permanently attached. Many transmembrane proteins function as gateways to permit the transport of specific substances across the biological membrane. They frequently undergo significant conformational changes to move a substance through the membrane. o Transmembrane proteins are polytopic proteins that aggregate and precipitate in water. They require detergents or nonpolar solvents for extraction, although some of them (beta-barrels) can be also extracted using denaturing agents.  Membrane permeability o The cell membrane (also known as the plasma membrane or cytoplasmic membrane) is a biological membrane that separates the interior of all cells from the outside environment.[1][2] The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells.[3] The basic function of the cell membrane is to protect the cell from its surroundings. It consists of the phospholipid bilayer with embedded proteins. Cell membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity and cell signalling and serve as the attachment surface for several extracellular structures, including Grace Gerhards transmembrane pre activity the cell wall, glycocalyx, and intracellular cytoskeleton. Cell membranes can be artificially reassembled  ΔG‡ of solute passage o If the exchange of substances occurs in the direction of the gradient, that is, in the direction of decreasing potential, there is no requirement for an input of energy from outside the system; if, however, the transport is against the gradient, it will require the input of energy, metabolic energy in this case.[3] For example, a classic chemical mechanism for separation that does not require the addition of external energy is dialysis. In this system a semipermeable membrane separates two solutions of different concentration of the same solute. If the membrane allows the passage of water but not the solute the water will move into the compartment with the greatest solute concentration in order to establish an equilibrium in which the energy of the system is at a minimum. This takes place because the water moves from a high solvent concentration to a low one (in terms of the solute, the opposite occurs) and because the water is moving along a gradient there is no need for an external input of energy.  Electrochemical gradient o An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and the electrical gradient, or difference in charge across a membrane. When there are unequal concentrations of an ion across a permeable membrane, the ion will move across the membrane from the area of higher concentration to the area of lower concentration through simple diffusion. Ions also carry an electric charge that forms an electric potential across a membrane. If there is an unequal distribution of charges across the membrane, then the difference in electric potential generates a force that drives ion diffusion until the charges are balanced on both sides of the membrane ΔG of solute o At any constant temperature and pressure, two factors determine the ΔG of a reaction and thus whether the reaction will tend to occur: the change in bond energy between reactants and products and the change in the randomness of the system. Where H is the bond energy, or enthalpy, of the system; T is its temperature in degrees Kelvin (K); and S is a measure of randomness, called entropy. If temperature remains constant, a reaction proceeds spontaneously only if the freeenergy change ΔG in the following equation is negative:  Channel protein o A channel protein is a protein that allows the transport of specific substances across a cell membrane. Remember that a protein is a biological macromolecule made up from a menu of 20 different amino Grace Gerhards transmembrane pre activity acids and that the sequence of those chains determines the specific shape and function of the protein  Transporter proteins o Carrier proteins are proteins involved in the movement of ions, small molecules, or macromolecules, such as another protein, across a biological membrane. Carrier proteins are integral membrane proteins; that is, they exist within and span the membrane across which they transport substances.  Passive diffusion o Passive transport is a movement of biochemicals and other atomic or molecular substances across cell membranes without need of energy input. Unlike active transport, it does not require an input of cellular energy because it is instead driven by the tendency of the system to grow in entropy.  Active transport o Active transport is the movement of molecules across a cell membrane from a region of their lower concentration to a region of their higher concentration in the direction against some gradient or other obstructing factor (often a concentration gradient)  Primary active transport o n primary active transport, the energy is derived directly from the breakdown of ATP. In the secondary active transport, the energy is derived secondarily from energy that has been stored in the form of ionic concentration differences between the two sides of a membrane.  Secondary active transport o Secondary active transport is a form of active transport across a biological membrane in which a transporter protein couples the movement of an ion (typically Na+ or H+) down its electrochemical gradient to the uphill movement of another molecule or ion against a concentration/electrochemical gradient.  Na+/K+ ATPase or Na+ pump o Na+/K+ -ATPase (sodium-potassium adenosine triphosphatase, also known as the Na+/K+ o pump or sodium-potassium pump) is an enzyme (EC (an electrogenic transmembrane ATPase) found in the plasma membrane of all animal cells. The Na+/K+ o -ATPase enzyme is a solute pump that pumps sodium out of cells while pumping potassium into cells, both against their concentration gradients. This pumping is active (i.e. it uses energy from ATP) and is important for cell physiology. An example application is nerve conduction. o It has antiporter-like activity but is not actually an antiporter since both molecules are moving against their concentration gradient.  homeostasis/steady state o Steady State o A system that is in a steady state remains constant over time, but that constant state requires continual work. This condition is also referred Grace Gerhards transmembrane pre activity to as a system in dynamic equilibrium. Were the process maintaining the system to cease, the conditions would not remain. A system in a steady state has a higher level of energy than its surroundings. Steady state processes can be complex biochemical reactions or as simple as a constant addition of a chemical to a system to maintain concentrations of a substance being lost from the system. o o Equilibrium o A system at chemical equilibrium, or just equilibrium, is stable over time, but no energy or work is required to maintain that condition. No free energy will be entering or leaving a system in equilibrium. The system is maintained in a low free energy state that is no different from that of its surroundings. Some biological systems are in true equilibrium such as the pH of blood in mammals, but many times they are actually in a dynamic equilibrium or a steady state. Systems in equilibrium are often inorganic, such as the chemicals in a beaker after a reaction has proceeded to completion.


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