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Membrane Transport

Diffusion dissolved particles move from an area of higher concentration to an area of lower concentration. They are flowing down their concentration gradient and thus this passive process requires no energy.
Example of diffusion? cigarette smoke or perfume through the air; in cells it is the diffusion of oxygen and nutrients from capillary blood vessels (high concentration) to tissue cells (low concentration).
Brownian movement random moving of particles suspended in a fluid (liquid or gas) resulting from their bombardment by the fast-moving atoms or molecules in the gas or liquid
where can diffusion happen? through air (i.e. perfume or cigarette smoke), water or membranes
four factors which influence particle movement? 1) concentration gradient: (higher concentration = faster diffusion) 2)particle size: (smaller particles = faster diffusion) 3)temperature of solution (warmer temperature=faster diffusion 4)electrical charge of particles (opposite charges=faster diffus
Facilitated Diffusion a carrier molecule (intrinsic protein) picks up the diffusing substance on one side of the membrane and deposits it on the other side. The solute is still moving down its concentration gradient without need for energy expenditure, it just has a helper
LIPID SOLUBILITY: explain passive diffusion through the bilayer of solutes that don't need a carrier protein i.e. 'lipid solubility' fat-soluble particles (steroids, O2, CO2 & fat soluble vitamins) simply dissolve in lipid bilayer portion and diffuse to the other side.
PROTEIN CHANNEL: explain passive transport of small hydrophilic solutes (like Na+) through the membrane important solutes (ions, glucose and amino acids) are more polar/hydrophilic and can't simply dissolve through the lipids. They move through special pathways provided by proteins that span the membrane. Smaller solutes like Na+ pass through using channels
FACILITATED DIFFUSION: explain passive yet facilitated transport of large solutes (like glucose) through the membrane. larger solutes like glucose move through using carrier proteins that "rock back and forth". the solute attaches to a binding site and the carrier changes conformation and releases solute to the other side
Example of facilitated diffusion: what allows glucose to keep coming into cell? When glucose diffuses into the membrane, kinase enzyme changes it into "glucose-6-phosphate" This keeps the conc. of glucose relatively low inside the cell, so it can continue to to be transported via facilitated diffusion without wasting energy.
what accelerates facilitated diffusion of glucose in blood cells? insulin lowers blood glucose, which accelerates this process of allowing more glucose to passively enter a blood cell down its concentration gradient
Osmosis Net diffusion of water molecules across a semi-permeable membrane. Water diffuses from a less concentrated solute solution into a more concentrated solute solution; water dilutes solutes. It is a passive process that does not require energy.
Why is osmosis important in the body? EX albumin is a plasma protein floating in blood capillaries. It's tendency is to bring in excess water from tissues to maintain homeostatic fluid balance. Therefore it is responsible for "setting the gradient" needed to move water out of the tissues.
isotonic Having the same osmotic pressure as human cells, i.e. an RBC. The net diffusion of water goes into and out of the RBC equally because there are approx the same amount of particles in solution as RBC. The RBC is "happy".
Hypertonic Having a higher osmotic pressure than human cells; there is still net diffusion but more water moves out of the RBC since there are more particles in the solution than in the cell. this causes the cell to crenate (shrivel)
Hypotonic Having a lower osmotic pressure than human cells; there is still net diffusion but more water moves into the RBC which causes swelling and lysis (bursting) of the cell.
Draw an isotonic solution draw beaker with RBC. make sure same amount of particles inside in cell and water and make sure arrows are same length
Draw a hypertonic solution Make sure there are more dots outside the cell than inside, and the arrow leaving the cell is longer.
Draw a hypotonic solution Make sure there are more dots in the RBC than in the water and the arrow going into the cell is longer.
Active Transport a substance moving across a cell membrane against its concentration gradient, using a carrier protein and requiring ATP.
Example of active transport in thyroid Thyroid concentrates iodine from the blood to inside thyroid cells. It does this because it can't make thyroid hormones without iodine, therefore it still needs to bring in more iodine against its concentration gradient, so it requires energy
example of active transport: sodium potassium pump moving Na+ one way and K+ another way across the membrane, used in nerve transmission. Na+ and K+ change places, which sends one nerve signal. SPP will flip them back before another signal can be sent (3 NA out, 2 K in).
Draw an electrochemical gradient label extracellular & intracellular, draw the bilayer. overall neutral charge in far extracellular and far intracellular environment. Overall positive charge just outside of membrane(mostly Na with K leakage) and overall negative charge inside (mostly K)
what is the main cation and main anion on extracellular side of electrochemical gradient Main cation: Na+ Main anion: Cl -
What is the main cation and main anion on intracellular side of electrochemical gradient (inside the cytoplasm?) Main cation: K+ main anion : organic phosphates Negatively charged proteins
Membrane Potential polarization (an electrical charge difference) across the plasma membranes of all cells. also known as voltage.
what is the membrane potential of a nerve cell? -70mV in a neuron
What other function does sodium Potassium Pump have besides nerve transmission? You have slight ion leakage of Na + and K+ ions through the membrane, (K leaks out and Na leaks in) so every now and then the Sodium Potassium pump uses active transport to flip them back where they belong
Created by: kalmetina



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