Bio 1113 Week 5 Notes
Bio 1113 Week 5 Notes Biology 1113
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This 4 page Class Notes was uploaded by Jessy Notetaker on Friday September 23, 2016. The Class Notes belongs to Biology 1113 at Ohio State University taught by Dr. Ball and Dr. Weinstein in Summer 2015. Since its upload, it has received 18 views. For similar materials see Biology 1113 in Biology at Ohio State University.
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Date Created: 09/23/16
Cell communication con’t. Membrane transport Membrane is selectively permeable All molecules can't just pass through whenever Nonpolar molecules can cross easily Ions and polar molecules need a doorway Types of transport Simple diffusion Passive transport Moves a molecule from high concentration areas to low concentration areas Moves down its own concentration gradient Spontaneous Not really fast Means it doesn't require energy Each molecules moves on its own gradient Osmosis Molecules moving across a barrier Reaches equilibrium Solutes are independent of one another Facilitated diffusion Passive transport Membrane does not allow ions and polar molecules Transport proteins help them diffuse passively across the membrane High concentration to low concentration Channel proteins Provide a doorway, but with no door Transports 3 billion water molecules per second Carrier proteins Changes shape Doorway with a swinging door High concentration to low concentration Active transport Requires ATP Movement of molecules against their concentration gradient Does not happen on its own Sodiumpotassium exchange pump Works in neurons Builds up concentration gradients Once they are built up enough, they move down their gradient, with another molecule that is building theirs Bulk transport Allows large amounts of molecules and particles to enter the cell Requires energy Endocytosis Cell encompasses the molecules/particles Brings things into a cell Tonicity Refers to the environment around a cell (gain/looe water) Isotonic Same amount of solute inside the cell as outside the cell No net loss or gain of water Cell is stable Hypertonic More solutes outside of the cell More solutes = less water Water moves out of the cell Cells shrivel up Hypotonic More water in the environment Water moves into the cell Animal cells may burst Tophat questions Which of the following would move through the lipid bilayer most rapidly? Not a polar molecule Not a large molecule Not an ion CO 2 What statement about osmosis is correct? The presence of aquaporins would speed the process up Cell signaling Local signaling Cell junctions allow signaling molecules to pass freely between adjacent cells Direct physical contact Cell to cell recognitio via cellsurface molecules Can tell a neighboring cell what they are Paracrine signaling Molecule is released in a vesicle will enter other cells with the other cells that have the right receptors Can respond to itself Cell division Longdistance signaling Use hormones Hormones travel through the bloodstream to reach target cells Ability of cell to respond depends on whether or not it has receptors that can bind to the signaling molecules Adrenaline Prepares you to respond in some way Fight or flight 3 stages of cell signaling Reception Signal is detected by the cell A receptor protein on the surface of the cell (or inside the cell) binds to a signaling molecule (ligand) and transmits the signal Binding is very specific Usually causes the receptor to change its shape 3 types of membrane receptors G proteincoupled receptors Plasma membrane receptors that are associated with G proteins G protein acts as an on/off switch When GDP is attached it is off No phosphate attached When signaling molecule enters the receptor, it kicks GDP off and makes GTP that turns it on Phosphate is attached Makes GTPase If the G protein lacks the ability to change to GTPase, what will happen? The G protein will continuously function Receptor tyrosine kinases (RTKs) Each is a monomer, come together to make a dimer Membrane receptors with enzymatic activity which attach phosphates to tyrosine residues Signal molecules bind outside of the cells and cause the monomers to come together and make a dimer One RTK may activate 10 or more different pathways Ion channel receptors Binding of a ligand causes conformational change Opens the channel Allows specific ions through How nerves work Intracellular receptors Inside the cell Found either in the cytoplasm or nucleus Signaling molecule must be able to move through the membrane Small molecules Steroid hormones Thyroid hormones Nitric oxide Nothing polar Must be hydrophobic Transduction The relay of signals from receptors to target molecules in the cell Often involves multiple steps More steps amplify the signal Allows for more regulation Message is often passed along through a change in shape of the protein Phosphorylation = add phosphate Protein kinase Makes a phosphorylation cascade Dephosphorylation = remove phosphate Phosphatases Second messengers Small, nonprotein, watersoluble molecules Can easily spread a throughout message cAMP Cyclic adenosine monophosphate ATP> cAMP
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