Understanding Cellular Transport and Concentration in Biology
Explore the movement of materials into and out of cells, the relationship between cell volume and surface area, various cellular shapes observed in human cells, the functions of organelles, diffusion, cell fragility, units of concentration measurement, regulation of movement across plasma membranes, carrier-mediated transport, active transport forms, units of concentration in healthcare, IV percent solutions, and implications of cell size limits in clinical settings.
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How do we describe movement of materials into and out of cells? 8/30 How is cell volume related to surface area? What are some of the cellular shapes observed in human cells? What are organelles and what do they do for a cell? Diffusion and cell fragility
Try this video animation to review osmosis and crenation for lab the week after-Friday sign up next. Don t forget lab exam #1 (Bones) is next week. Friday: Lab Exam Sign-up sheets are posted http://www.youtube.com/watch?v=sdiJtDRJQEc http://www.youtube.com/watch?v=crpeX8nBgJE
Cells Units of Measurement and transport across plasma membranes What are the units of concentration measurement? How is movement across the plasma membrane regulated? How does carrier mediated transport work? Why does a Transport Maximum imply that a substance enters a cell through a carrier? What are the two different forms of active transport and how do they work?
What Units of Concentration are used in healthcare? The Math: 1 Mole = 600,000,000,000,000,000,000,000 things or 1 Mole of Calcium = 6 X 1023 atoms of Ca++ Molar concentration: moles molecule/liter Some molecules (i.e. NaCl) dissociate (dissolve) when in solution Osmolar: number particles/liter expressed in moles 1 Molar NaCl = 2 Osmolar The human body typically contains tiny amounts of each item, so we express this as millimolar or milliosmolar! 1000mosm/l=1osm/l Human Blood, intracellular fluids, and interstitial fluids between cells contain about 300 mosm solute/liter We seek to maintain homeostasis at this level in all compartments! An Isotonic NaCl Solution= 150 millimole/L = 300 mosm/L
Intravenous Injection: IV Percent Solutions : are expressed grams/100 milliliter Remember That: 1 gram=1ml water 1,000 milliliters=1 Liter Isotonic Saline: 0.9% NaCl= 1NaCl 1 Na+ and 1 Cl- in solution 0.9g/100mlX1000ml/L X 1mole/58 gX2 = about 0.3 Osm or 300 mOsm Isotonic Dextrose (glucose): 5% Dextrose Will this 10% Dextrose tend to promote crenation or lysis if you gave it as an IV Drip? Why do you give it?
Cells have size limits due to the strength of the plasma membrane and the demands of the metabolic reactions of the cell. Why is this clinically useful information if you have cancer?
Which cell will have the best ability to permit diffusion of oxygen into the cytoplasm? Which would be least able to do this? What limits does the flat cell have with respect to the strength of its plasma membrane? Large round Large flat Medium sphere Medium Cube
What shapes can a human cell have? Can you speculate on function and tissue stacking? We will see this again in CH 5!
Organelles allow for specialized function within a cell (intracellular). Some Sample Organelles Some Sample Organelles Microvilli: Cilia and flagella: Nucleus vs. Ribosome: Endoplasmic Reticulum (ER) Smooth ER- Rough ER- Golgi Apparatus and secretory vesicles- Lysosomes and digestion: Peroxisomes and digestion: V.I.P.-MITOCHONDRIA=ATP production The cytoskeleton organizes the organelles
Could you identify these organelles and their functions? This is pretty important for your study list this evening. Could you match functions, name and locations on these two figures for test?
What does the plasma membrane consist of? What is the function of each of its parts? What are the primary organelles and their functions? Make a labeled drawing with the key parts shown in pages 112-119 and indicate the function of each part. See Table 3.4 for a quick review? This should be review from High School Biology, if it is not, you will need to take time reviewing these important concepts. Drawing a cross-section of a plasma membrane and discussion the function of its parts makes a great test question.
Why is it so important to have a plasma membrane with a lipid bilayer rich in amphipathic phospholipids? Ans: To control diffusion of polar molecules!
Simple Diffusion is the net movement of particles from High to Low concentration. When does simple diffusion occur in your body? Bee sting in skin and Cortisone application to sting site- What things alter Diffusion Rate: What are health applications? Temperature: (Consider cooling or warming an injury)- Magnitude of Concentration Difference: (Consider how much drug or dose is present)- Size of Molecule/drug: (How does the brain prevent some drug entry)- Membrane Permeability: (Can all drugs enter the body? gut antibiotics)- Surface Area of Contact: (How does lung surface affect and oxygen uptake)-
Water content determines cell size/cell fragility! What determines cellular water content? Polarity of molecules inside/outside of cell: Ions/H-bonds? Does molecule have sphere of hydration? How big is sphere of hydration? Does molecule have water associated with it? Water wants to move by osmosis to the less watery side of a semipermeable membrane (Down the conc. Gradient for H2O). The Osmotic Pressure of polar molecules on one side of a membrane prevent water from leaving and potentially attract water to that side until equilibrium is reached. Effect of Cellular Protein Content on Cellular Water Content: What is the charge on amino acids? Do proteins carry water? What affect does protein content have on osmotic pressure?
How does environment effect cell volume? What are hypertonic, hypotonic and isotonic solutions? Assume the membranes below are impermeable to sucrose.
Regulation of Membrane Transport: How do you move things into/out of a cell given its phospholipid bilayer? Diffusion: non-polar molecules typically do not need special transport mechanisms! Examples: oxygen, carbon dioxide and even water to a degree Carrier Mediated Transport: Special transport mechanism required for substrate specific cellular entry/exit Polar things require special transport because the lipid membrane has a non- polar (hydrophobic) center! Non-Polar Repels Polar! Many kinds of Carrier Mediated. Tx. exist! Membrane proteins (enzymes) mediate this for cells very precisely!
Patterns of Carrier Mediated Transport: 1)What moves in what direction? 2)How many move in what direction? 3)What is energy source? Carrier implies a Transmembrane Protein 1) How many particles move through the port at a time? Uniport/Unitransport: one at a time! Symport/Co-Transport: move more than one at a time! 2) In what direction do things move across the symport ? Co-transport: same direction Antiport: opposite directions 3) What kind of energy is required to move objects? A)Diffusion: energy is chemical gradient itself and transport is facilitated though a special port : Facilitated Diffusion B) Move it directly with ATP as energy Source: Primary Active C) Piggy back with another Conc. Gradient: Secondary Active If you pump ions into/out of a cell why do you also pump water into/out of a cell V.I.P.? What if the pumps fail, can a cell die? Why? Remember transport specificity! If the key is not right it will not fit!
Transport using Carriers is ALWAYS rate limited! There is a maximum transport rate for a limited number of transporters, so there exists a maximum transport rate. Note hyperbolic curve for molecules that move across membrane via carrier mediated methods! After the conc. reaches Tm, increasing the concentration of the substrate does not increase tx membrane transport Transport Rate (mmole/time) Tm: Membrane Transport Enzymes Saturated Increasing concentration of carrier mediated molecule No Tmax exists for things that cross membrane by simple diffusion!
What Secondary Active Transport and Primary Active Transport mechanisms help Gatorade move sodium and glucose into your body? What pump (enzyme) creates a Na+ gradient inside the intestinal cell? What pump (enzyme) pumps 2 Na+ and 1 glucose into the cell from the gut? Why does water follow the sodium and glucose (V.I.P.)?
Why do healthy cells have more potassium inside the cytosol and less sodium outside? Why is ATP required? What happens to cell volume if ATP is unavailable (heart attack)?
