Presentation Transcript

1. The Cell Membrane

   Dr. John M. Bartlett, D.C. Board Eligible Chiropractic Neurologist Certified Clinical Research Associate Board Certified North American Academy of Impairment Rating Physicians (past) Post-Graduate Faculty Member Texas Chiropractic College (past)
2. The cell is the structural and functional unit of all known livingorganisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life.
3. Cell Theory Cells are building blocks of all plants and animals Cells are produced by division of pre-existing cells Cells are smallest unit that perform all vital physiological functions Each cell maintains homeostasis on the cellular level Homeostasis in the organism at all levels reflects combined and coordinated efforts of many cells.
4. Cells in human body Trillions of them Our activities a result of coordinated responses of each cell Each cell also functions as an individual entity
5. Cytology – study of structure and function of cells Cell Biology – incorporates biology, chemistry, and physics Histology – study of structure and function of tissues
6. Microscopes In order to see small objects in biology – an individual uses a microscope There are two major types of microscopes- the Light Microscope and the Electron Microscope Two important parameters in microscopy are magnification and resolving power, or resolution.
7. Magnification versus Resolution Magnification is the ratio of an object’s image size to its real size X versus x Resolution is a measure of the clarity of an image; it is the minimum distance two points can be separated and still be distinguished as two points. For example, what appears to the unaided eye as one star in the sky may be resolved as twin stars with a telescope How close can you get those two dots and still say they are two dots instead of one dot?
8. Microscopes (Light) The light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest and simplest of the microscopes. In practice the best obtainable resolution is around 0.2 micrometers for a light microscope
9. Types of microscopes Light or compound microscope: The first compound microscope was assembled by Zacharias Janssen and father Hans J. Janssen, the Dutch spectacle makers, in 1590. It was simply a long tube with only two lenses. Various accessories were gradually added later by many different men. The compound microscope is the oldest and still the most commonly used for studying the structure of organisms and cells. Its essential parts are: Reflector, Condenser lens, Stage, Objective lens, Ocular lens, Adjustment screws.
10. Light or Compound Microscope
11. Bright Field Microscopy
12. Dark Field Microscopy A dark field microscope is a microscope designed to permit diversion of light rays and illumination, from the side, so that details appear light against a dark background; as opposed to light passing straight through the specimen.
13. Dark Field Microscopy
14. Dark Field Microscopy Can be used to examine live blood cells. Heat not a factor, as in bright field where heat kills the blood cells. Dark field not approved by FDA for blood analysis However, an increasing number of health professionals have found that the use of this technique allows inspection of cellular dynamics which normally escape analysis or diagnosis using orthodox medical tests.
15. Phase Contrast Microscopy Phase contrast is preferable to bright field microscopy when high magnifications (400x, 1000x) are needed and the specimen is colorless or the details so fine that color does not show up well. Cilia and flagella, for example, are nearly invisible in bright field but show up in sharp contrast in phase contrast. Amoebae look like vague outlines in bright field, but show a great deal of detail in phase. Most living microscopic organisms are much more obvious in phase contrast.
16. Phase Contrast Microscopy Phase contrast condensers and objective lenses add considerable cost to a microscope, and so phase contrast is often not used in teaching labs except perhaps in classes in the health professions and in some university undergraduate programs.
17. Phase Contrast
18. Fluorescence microscope It was invented Coons in 1945. Certain compounds are fluorescent that is absorbing light of sort wavelength and then reemit light of longer wavelength. Third phenomenon is called fluorescence and is used in microscopy. They fluorene microscope is essentially an ordinary microscope having two special filters.
19. Fluorescence microscope Using fluorescence microscopy, the precise location of intracellular components labeled with specific fluorophores can be monitored, as well as their associated diffusion coefficients, transport characteristics, and interactions with other biomolecules.
20. Fluorescence Microscopy
21. Polarizing microscope It was invented by Talbot in 1834. This microscope reveals the biological organisation at a level the limit of resolution for a light microscope. This is possible for the sub microscopic structures that are arranged in a very regular manner and have an optical property called birefringence i.e. refract light differentially in different planes.
22. Polarizing microscope Although similar to the common brightfield microscope, the polarized light microscope contains additional components that are unique to instruments of this class. These include a polarizer and analyzer, strain-free objectives and condenser, a circular graduated stage capable of 360-degree rotation, Bertrand lens, and an opening in the microscope body or intermediate tube for compensators, such as a full-wave retardation plate, quartz wedge, or quarter-wavelength plate.
23. Polarized Microscopy
24. Bone under Polarized Microscope
25. Left: Phase Contrast of cheek cells Right: DIC of cheek cells
26. DIC microscopy An excellent mechanism for rendering contrast in transparent specimens, differential interference contrast (DIC) microscopy is a beam-shearing interference system in which the reference beam is sheared by a minuscule amount, generally somewhat less than the diameter of an Airy disk. The technique produces a monochromatic shadow-cast image that effectively displays the gradient of optical paths for both high and low spatial frequencies present in the specimen
27. Cellular Anatomy Human body contains 2 classes of cells: Somatic – all cells in body except for sex cells Sex cells – also called germ cells or reproductive cells Sperm (male) Oocytes (female) We will discuss sex cells when we cover the reproductive systems
28. Typical somatic cell Kind of like saying the “average” person. There are, in reality, enormous variations, but the “typical” cell gives us a platform to start with
29. Extracellular fluid Watery medium surrounding cells Called interstitial fluid Cell membrane separates cell from interstitial fluid Cytoplasm can be divided into: Liquid portion – cytosol Intracellular structures - organelles
30. Cell membrane The cell membrane separates intracellular fluids from extracellular fluids Also called plasma membrane
31. Functions of Cell Membrane 1. Physical isolation: membrane is barrier to separate inside of cell from extracellular fluid. Conditions inside and outside of cell are very different and these differences have to be maintained to preserve homeostasis.
32. Functions of Cell Membrane 2. Regulation of exchange with the environment: membrane controls entry of ions and nutrients, elimination of wastes and release of cell secretions.
33. Functions of Cell Membrane 3. Sensitivity: membrane is first part of cell affected by changes in extracellular fluid such as composition, concentration, and pH. Contains variety of receptors so cell can recognize and respond to specific molecules. Single alteration in cell membrane may activate or deactivate an enzyme pathway.
34. Functions of Cell Membrane 4. Structural Support: Specialized connections between cell membranes or between membranes and extracellular materials give tissue a stable structure.
35. Structure of Cell Membrane Double bilayer of lipids with imbedded, dispersed proteins Bilayer consists of phospholipids, cholesterol, and glycolipids Glycolipids are lipids with bound carbohydrate Phospholipids have hydrophobic and hydrophilic bipoles
36. Fibers of extracellular matrix (ECM)

    Fig. 7-7

    Carbohydrate Glyco- protein Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE
37. Structure of Cell Membrane Contains lipids, proteins, and carbohydrates Phospholipids are largest component of cell membrane. Lipids form most of the membrane surface, but are only 42% of its weight. Proteins, which are dense are about 50%.
38. Why Phospholipids? They are amphiphatic – they like water at the polar side (phosphate group) and don’t like water the fatty acid component. Thus,water will approach the molecule at both sides – intracellular water and extracellular water. However, the fatty acid region (in the middle of the bilayer) will not let water or water soluble substances pass through easily – thus keeping excess water or water soluble substances from entering or leaving the cell.
39. Water and solutes cannot cross the lipid portion of the membrane bilayer.
40. Membrane Proteins Two types named in reference to location within the membrane. Integral Proteins (transmembrane and partial transmembrane) – transmembrane proteins span the entire thickness of the membrane & partial ones go partway through the membrane. Peripheral Proteins are not embedded in the lipid bilayer at all; they are appendages loosely bound to the surface of the membrane, often to exposed parts of the integral proteins. Greatly outnumber integral proteins.
41. Membrane Proteins Function as anchoring proteins, identifiers, enzymes, receptors, carriers, and channels.
42. Transmembrane Proteins

    Fig. 7-3

    Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein Peripheral Proteins
43. Anchoring Proteins Attach cell membrane to other structures to stabilize position of cell. Inside cell, membrane proteins attach to cytoskeleton, a network of supporting filaments in cytoplasm. Outside cell, membrane proteins may attach to extracellular proteins or other cells.
44. Recognition Proteins Cells of immune system recognize other cells as normal or abnormal on basis of presence or absence of recognition proteins. Most are glycoproteins.
45. Enzymes May be integral or peripheral. Catalyze reactions in extracellular fluid or within cytosol. Dipeptides are broken down into amino acids by enzymes on exposed membranes of cells lining the intestinal tract.
46. Receptor Proteins Sensitive to presence of specific extracellular molecules called ligands.
47. Carrier Membrane Proteins Bind solutes and transport them across cell membrane. Carrier protein changes shape after binding and returns to original shape after release of solute. May or may not require ATP. Glucose = no ATP Ca and Na = need ATP
48. Channels Some proteins act as channels or pores through the membrane. Ions cannot dissolve in lipid bilayer, so require protein channel to cross membrane. Two major types of channels: Leak channels Gated channels
49. Leak channel Permit water and ion movement at all times.
50. Gated channel Can open or close to regulate ion passage.
51. Structure of the Cell Membrane“Fluid Mosaic Model” Double bilayer of lipids with imbedded, dispersed proteins Bilayer consists of phospholipids, cholesterol, and glycolipids Glycolipids are lipids with bound carbohydrate Phospholipids have hydrophobic and hydrophilic bipoles
52. Membrane structure Not rigid Embedded proteins drift across surface of membrane Inner and outer surfaces differ in protein and lipid composition Receptors only on outside Cytoplasmic enzymes on inside
53. Membrane Carbohydrates About 3% of weight of cell membrane Components of proteoglycans, glycoproteins, and glycolipids Carbohydrate portion of these molecules extend away from the outer surface of cell membrane forming a layer called the glycocalyx.
54. Glycocalyx function Lubricates and protects cell membrane Sticky glycoproteins help anchor cell. Participate in locomotion of specialized cells Function as receptors Recognition by cells of immune system as to whether cell is normal or abnormal Blood type Self or foreign cells
55. Membrane permeability The cell membrane is permeable to some substances and impermeable to others. Called a selectively permeable membrane. Permits passage of some things and restricts others. Selectivity can depend on size, charge, shape, lipid solubility or any combination of these.
56. Passage across membrane Passive or active Passive Moves a substance across membrane without cell expending energy. Active Cell has to expend energy, usually ATP
57. Categories of transport processes Diffusion Results from random motion of molecules Passive process Filtration Hydrostatic pressure forces fluid and solutes across the membrane Passive process Example is glomerulus of kidney
58. Categories of transport processes Carrier-mediated transport Cell uses a specialized integral membrane protein May be passive or active Vesicular transport Movement of materials within small membranous sacs or vessicles Active process
59. Diffusion
60. Carrier mediated Transport
61. Vesicular Transport
62. Diffusion A result of continuous random motion is that, over time, molecules in any given space tend to become randomly distributed. A net movement of material from areas of high concentration to areas of lower concentration. Difference between the concentration areas is called concentration gradient.
63. Diffusion Diffusion eliminates this concentration gradient. Net diffusion – we can quantify the movement from high to low concentration. When concentrations are equal, particles still diffuse, there is just no longer a net diffusion.
64. With the second-highest obesity rate in the country—behind only neighboring Mississippi—you’d expect to find some fattening culprits in the deep-fried-bacon-loving south. And Chef Kevin Layton of Greer’s Market, in Mobile, does not disappoint with his bacon-wrapped meatloaf recipe. “People ask for it on a weekly basis,” he told WKRG News in 2008. Ingredients: Meatloaf made with ground beef, onion, bell pepper, celery, eggs, breadcrumbs, and seasonings, then wrapped in bacon. Fat content: One 3-ounce serving of 80% lean meatloaf has roughly 14 grams of fat. Each slice of bacon will cost you an additional 3 grams of fat.
65. Alaska: Eskimo Ice Cream Also known as Eskimo Ice Cream, akutaq, (pronounced agoodik or agooduk) is a classic native dish that is still popular today. Traditionally, women made a batch of the frosty treat when the men returned with a freshly killed polar bear or seal. Today, modern versions are usually prepared with Crisco, but traditional recipes called for meat and fat from caribou, moose, bears, seals, and fish. Ingredients: Reindeer fat, seal oil, salmonberries, blackberries Fat content: It’s hard to estimate without a known serving size of this native treat. But consider this: An average serving of reindeer fat packs a whopping 91 grams of fat. A different version made with fish, berries, and seal oil contains 9 grams of fat.
66. Arizona: Quadruple Bypass Burger The Grand Canyon State takes celebrating fatty foods to a whole new level at the Heart Attack Grill. Patrons weighing over 350 pounds eat for free. The Quadruple Bypass Burger—estimated by some to be worth 8,000 calories—is at least refreshingly honest about its potential impact on your health. Ingredients: Four beef patties, eight slices of cheese, tomato, onions, sauce, on a bun Fat content: Four patties alone clock in at around 60 grams of fat, which is just about the upper limit of 65 grams that the USDA recommends for the average woman eating 2,000 calories a day.
67. Arkansas: Catfish The south is notorious for frying just about anything. For a traditional southern fish fry, Arkansas catfish is an old standby. When you consider that this dish is often served with hush puppies, another southern fried favorite, you can bet you’re reeling in quite a bit of fat along with your fish. Ingredients: Catfish, cornmeal, flour, eggs, seasonings Fat content: This dish is faux fried in the oven and still packs a whopping 25 grams of fat per serving.
68. California: In-N-Out Burger Double Double Golden State residents are known for their fit bodies, gym-sculpted abs, and love for In-N-Out Burger. This West Coast drive-thru chain uses fresh ingredients, but its Double Double should also be known for its fat content, nearly double the fat in a McDonald’s Double Cheeseburger. Ingredients: Two beef patties, lettuce, tomato, two slices of American cheese, and spread Fat content: 41 grams. A McDonald’s Double Cheeseburger contains a comparably reasonable 23 grams of fat.
69. Colorado: Jack-N-Grill’s 7-pound breakfast burritos While this mountainous state is well known for its healthy reputation—it is the state with the lowest obesity rate in the country—it is home to one of the most giant burritos of all time. Finishing one of Jack-N-Grill’s 7-pound breakfast burritos is such a feat it was featured on an episode of the Travel Channel’s Man v. Food. Ingredients: 7 potatoes, 12 eggs, a pound of ham, a whole onion, cheese, and chili. Fat content: A pound of ham and 12 eggs alone have nearly 100 grams of fat, almost twice a woman's upper daily limit for fat, and that’s not counting the fat in the cheese and chili.
70. Connecticut: 2-foot-long hot dog Man v. Food also made an appearance at Doogie’s, a hot dog joint outside Hartford. Being a local favorite in Connecticut, the hot dog is available in over 24 places in Hartford alone. Doogie’s has taken the diet-buster to a new level with its 2-foot-long hot dog smothered in half a pound of additional toppings. Ingredients: 2-foot-long pork and beef hot dog, three rolls, onions, peppers, chili, cheddar cheese sauce, and bacon Fat content: The average foot-long hot dog will set you back about 24 grams of fat, 10 grams of it saturated. But this is double that, plus it has bacon, chili, and cheddar cheese.
71. Delaware: Deep-fried pastry The First State is known for a deep-fried pastry appetizer stuffed with crabmeat and cheese, similar to the Chinese appetizer crab Rangoon. Ingredients: Recipes vary, but most include cooked crab or imitation crabmeat, cheddar cheese, mayonnaise, seasonings, and oil for frying. Fat content: Crab is relatively low-fat fare, but many recipes are heavy on butter and mayonnaise. One small puff can have anywhere from 3 grams of fat to 8 grams of fat, and richer recipes can pack as many as 20 grams of fat per serving.
72. Diffusion example Carbon dioxide Concentrated inside cell due to metabolic processes Less concentrated in extracellular fluid Even less concentrated in blood So, cell membranes are freely permeable to carbon dioxide and it diffuses “down” the concentration gradient from cell to blood and then to lungs.
73. Factors that influence diffusion rates Distance Gradients eliminated quickly over short distance. Longer distance means more time needed. Size of the gradient The larger the concentration gradient, the faster diffusion proceeds
74. Factors that influence diffusion rates Molecule Size Small particles diffuse faster than large particles Temperature Higher temperature = faster diffusion rate due to molecules moving faster Electrical Forces Interior of cell is negatively charged relative to outside of cell because of proteins (remember Pr-?)
75. Electrical forces, con’t. Negative charge inside cell pulls positively charged ions from extracellular fluid into the cell. Na+ and Cl- ions are in high concentration in interstitial fluid. Both the concentration gradient and electrical gradient favor diffusion of sodium. Concentration gradient favors chloride but electrical repels it. The net result of the chemical and electrical forces acting on diffusion of ions and particles is called the electrochemical gradient.
76. Two ways that an ion or molecule can diffuse through cell membrane 1. through a membrane channel 2. move across lipid portion of membrane If there is an electrochemical gradient for a particular ion or molecule, whether it will diffuse or not depends on two factors: Lipid solubility Size relative to sizes of membrane channels
77. Lipid solubility factor Alcohol, fatty acids, and steroids diffuse easily. Oxygen, carbon dioxide and lipid soluble drugs diffuse easily.
78. Size factor If molecule is not lipid soluble, has to use channel. Channels are 0.8 nm in diameter Water, sodium, potassium, calcium, hydrogen, and chloride diffuse through these. Glucose is too big.
79. Osmosis Special case of diffusion. The net diffusion of water across a membrane is so important, it is given it’s own name…Osmosis. Osmosis refers to water movement only whereas diffusion refers to any other solute.
80. Osmosis Total concentration of dissolved ions and molecules on either side of the cell membrane remains fairly constant. The reason this equilibrium exists is that the membrane is freely permeable to water.
81. Osmosis If a concentration gradient of a solute exists, then there is also a concentration gradient for water. Higher solute concentration = lower water concentration. SO: water diffuses across the membrane toward the solution that is more concentrated with the solute.
82. Three characteristics of Osmosis Osmosis is diffusion of water molecules across a cell membrane Osmosis occurs across a selectively permeable membrane that is freely permeable to water but not freely permeable to solutes. In osmosis, water will flow across a membrane toward the solution that has the higher concentration of solutes, because that is where the water concentration is lowest.
83. Florida: Empanadas The South American influence on Floridian cuisine is impossible to miss. Empanadas are folded meat pies served across the country, but they are particularly popular in the southern part of the Sunshine State. Ingredients: The dough is made with lard. The filling is up to the chef, but can range from cheese to veggies to assorted meats. Fat content: Various recipes for empanadas place them at around 10 to 22 grams of fat each. Depending on what you choose to put inside, an empanada can slide around on the nutritional value scale. Still, as the dough is usually made with lard, it’s never a low-fat choice.
84. Georgia: Luther Burger The story behind the Luther Burger is murky. But the general consensus is that this monstrosity was invented at a suburban bar in Decatur, Ga., and named after R&B legend (and diabetic) Luther Vandross. In 2008 Paula Deen of the Food Network took it one step further by topping it off with a fried egg. Ingredients: Ground-beef patty, topped with cheese and bacon between two donuts instead of a bun Fat content: The two KrispyKreme glazed donuts are worth 24 grams of fat and the patty is another 16.
85. Hawaii: Loco Moco Legend says the islands’ comfort food dates back to 1949, when a group of hungry teens wanted the owner of Hilo’s Lincoln Grill to whip up something cheap but filling. He reportedly threw together some white rice, a beef patty, and gravy, which came to be known as the Loco Moco. Ingredients: Today, variations abound. The Large at Island Cuisine Maui, a Maui restaurant, has two hamburger patties, two eggs, three scoops of jasmine rice, plus onions, fish, and mushroom gravy. Fat content: Two hamburger patties clock in at 32 grams fat, two eggs have 10 more grams of fat, and a serving of mushroom gravy has about a gram of fat, all of which edge this dish close to the daily recommended limit.
86. The movement of water across a semi permeable membrane. Osmosis is the movement of water (red dots) through a semipermeable membrane to a higher concentration of solutes (blue dots).
87. Osmosis and Osmotic pressure Measurement of the force of the water movement into that solution as a result of its solute concentration.
88. The magnitude of the pressure required to completely impede the flow of solvent is defined as the "osmotic pressure". If the applied hydrostatic pressure exceeds the osmotic pressure (see figure below), flow of solvent will be reversed, that is, solvent will flow from the concentrated to the dilute solution. This phenomenon is referred to as Reverse Osmosis. The figure illustrates the concepts of osmosis, osmotic pressure and reverse osmosis schematically.
89. Why does osmosis work so fast? Water is attached to other water molecules so water moves in groups of molecules. This is called bulk flow
90. Osmolarity Necessary to understand basics of this for patient care or research of any kind. Total solute concentration in an aqueous solution. If solution is same concentration as cytoplasm, it as called isotonic.
91. Osmolarity If solution has higher solute concentration than the cytosol(plasm) it is called hyperosmotic. (cytosol - intracellular fluid (or cytoplasmic matrix) is the liquid found inside cells. ) If solution has lower concentration than cytosol, called hyposmotic. When describing the effects of osmotic solutions on cells, we more commonly use the term tonicity instead of osmolarity.
92. Why is tonicity important? Mainly for IV infusions. IV has to be same osmolarity (isotonic) as cytoplasm or cells will shrink or burst…especially RBCs. If RBC put into hypotonic solution, water flows into cell and it swells and bursts (hemolysis) If RBC put in hypertonic solution, water flows out of cell and it shrinks/dehydrates (crenation).
93. Broadly, IV fluids are ordered for the following purposes: To maintain fluid balance (replace insensible water losses + sweat + urine output when patients are NPO or otherwise unable to drink as much as they need to for replacement) To replace volume losses (i.e., surgical blood volume loss, losses from the GI tract from vomiting or diarrhea) To repair imbalances (electrolyte imbalances, acidosis/alkalosis).
94. An IV solution’s effect on body fluid movement depends in part on its tonicity, or concentration. A solution is isotonic if its tonicity falls within (or near) the normal range for blood serum – from 275 to 295 mOsm/kg. A hypotonic solution has lower osmolarity (<250), and a hypertonic solution has higher osmolarity (>350). IV solutions with very high (>500mEq/L) tonicities should only be given via central lines to prevent tissue death within the peripheral veins.
95. Isotonic Solutions Remember, in the usual situation the intravascular and extravascular fluids have more or less settled into a stable balance (whether or not it’s a healthy one). When an isotonic solution is given, there is little or no change in the concentration of solute and water in the bloodstream, so osmosis neither moves water into the circulation nor pulls it out. That’s why isotonic solutions like normal saline (0.9% sodium chloride), Ringer’s lactate, Ringer’s acetate, and D5W (5% dextrose in sterile water) are given to replace fluid losses.
96. Hypotonic Solutions Commonly infused hypotonic fluids include 0.45% saline or 0.25% saline (with or without dextrose). Potassium chloride is sometimes added in low concentrations. When hypotonic solutions are administered, more water (relative to solute) is being infused than is already present in the vessel and inside the cells. Therefore, water moves into the cells, including the cells of the tunica intima of the vein at the catheter insertion site. This extra water causes the cells to swell and burst, exposing the basement membrane of the vein and starting the process of inflammation that can potentially become phlebitis and lead to infiltration (due to swelling of the venous pathway).
97. Hypertonic Solutions Hypertonic solutions are those with tonicities exceeding 350 mEq/L. Most admixed medications infused intravenously fall into this category, since they are generally mixed into a solution that was isotonic to begin with and the drug formulations tend to be quite hypertonic. When hypertonic fluids are infused, osmosis pulls water out of the cells. This causes the cells to shrink. When they shrink at the site of IV infusion, the basement membrane of the lining of the vein is exposed, subjecting it to the same complications seen with hypotonic infusions. Hypertonic solutions are used in repairing electrolyte and acid/base imbalances, and also include total and partial parenteral nutrition solutions.
98. Hypotonic saline fluids Hypotonic saline fluids such as 0.45% sodium chloride solution, which expand the intracellular compartment, are indicated for hypertonic dehydration, gastric fluid loss, and cellular dehydration from excessive diuresis. Hypertonic Dehydration- Second most common type of fluid volume deficit. 􀂊 When water loss from the ECF is greater than electrolyte loss. Common causes of hypertonic dehydration are: excessive sweating, hyperventilation, ketoacidosis, prolonged fevers, diarrhea, endstage renal failure, and diabetes insipidus
99. Isotonic saline fluids Isotonic saline fluids such as 0.9% sodium chloride solution can temporarily expand the extracellular compartment during times of circulatory insufficiency, replenish sodium and chloride losses, treat diabetic ketoacidosis, and replenish fluids in the early treatment of burns and adrenal insufficiency. Because their osmolality is similar to that of blood, they're also the standard flush solutions used with blood transfusions.
100. Hypertonic saline fluids Hypertonic saline fluids such as 5% dextrose in 0.9% sodium chloride solution are used cautiously to treat severe hyponatremia. Hyponatremia is a metabolic condition in which there is not enough sodium (salt) in the body fluids outside the cells.
101. Carrier Mediated Transport Integral proteins bind specific ions or organic substances and help them move across the cell membrane.
102. 3 characteristics of carrier-mediated transport Specificity: each carrier protein is selective in what substances it will bind and carry. The carrier that transports glucose does not transport other sugars. 2. Saturation: rate of transport of anything is limited by how many carrier proteins are present or can be limited by amount of substrate. Same principle as enzymes.
103. Third characteristic 3. Regulation: Carrier proteins activity can be modified by binding of other molecules such as hormones. Similar to enzymes having cofactors/coenzymes.
104. Additional transport mechanisms Cotransport – carrier transports more than one substrate at a time in the same direction. Countertransport – also called antiport. One substance moves in while another is moved out.
105. Facilitated Diffusion Glucose, sodium ions and choride ions are just a few examples of molecules and ions that must efficiently get across the plasma membrane but to which the lipid bilayer of the membrane is virtually impermeable. Their transport must therefore be "facilitated" by proteins that span the membrane and provide an alternative route or bypass. Facilitated diffusion is the name given this process. It is similar to simple diffusion in the sense that it does not require expenditure of metabolic energy and transport is again down an electrochemical gradient.
106. Active Transport ATP (or another high-energy compound like UDP or GTP) provides needed energy to move substances across the membrane. It has an energy cost but provides an IMPORTANT advantage: It is not dependent on the concentration gradient. It can import or export from areas of low concentration to areas of high concentration.
107. Ion pumps All living cells have specialized carrier proteins for ions such as Na, Cl, K, Mg, Ca, I, Fe. Most move a specific ion in only one direction. If a carrier moves one ion out while moving a different ion in (or vice versa) it is called an exchange pump.
108. Sodium-Potassium Exchange Pump Sodium concentration is high in extracellular fluid and low in cytoplasm. Potassium is just the opposite; low extracellular and high in cytoplasm. As a result of this concentration gradient, sodium slowly “leaks” into cell and potassium “leaks” out of cell through leak channels. To maintain homeostasis, sodium has to be ejected and potassium has to be recaptured.
109. Sodium-Potassium Exchange Pump The sodium-potassium exchange pump does this via a protein called sodium-potassium ATPase. For each ATP molecule used, three sodium ions are ejected and two potassium ions are reclaimed by a cell. Sodium-potassium ATPase consumes up to 40% of ATP produced by a resting cell.
110. Vesicular Transport Endocytosis: packaging of extracellular materials in a vesicle at cell surface for import into cell. This requires an import tax. (I crack myself up sometimes)
111. Types of Endocytosis Receptor-mediated endocytosis: materials in the extracellular fluid bind to receptors on the membrane surface. Receptors are glycoproteins and each binds to a specific target, or ligand. Once an area of the membrane is covered with ligands, it forms grooves, or pockets that pinch off to form vesicles. Cholesterol and Fe enter the cell this way.
112. Pinocytosis Cell drinking. Formation of small vessicles with extracellular fluid. Not selective.
113. Phagocytosis Cell eating Cell produces vessicles containing solid objects that may be as large as the cell itself. Pseudopodia surround the object and forms a vessicle called a phagosome. Macrophages ingest bacteria this way. Specialized
114. Exocytosis reverse of endocytosis. Membrane-bound vesicles move to the cell surface where they fuse with the plasma membrane. This accomplishes three things:
115. Exocytosis accomplishment 1 restores the normal amount of plasma membrane.
116. Exocytosis accomplishment 2 Any molecules dissolved in the fluid contents of these vesicles are discharged into the extracellular fluid - this is called secretion.
117. Exocytosis accomplishment 3 Any integral membrane proteins exposed to the interior surface of the vesicles will now be displayed at the cell surface because the vesicles turn inside out as they fuse with the plasma membrane. Thus exocytosis does not simply replace plasma membrane but ensures that the plasma membrane will display its characteristic cell-surface proteins
118. Examplesofexocytosis: Exocrine cells in the pancreas synthesize and secrete pancreatic digestive enzymes via exocytosis. The cells lining our intestine synthesize tiny droplets of fat and discharge them into the lacteals by exocytosis.
119. Modified Plasma membrane Small intestine has microvilli. Increase absorptive area. Rods and cones of eye have specialized photoreceptors. Upper portion of rod has two-layered, disc-shaped membranes called sacs that contain pigments involved in vision. Sterocilia: Found in ductusepididymus in males. Type of microvilli. Myelin sheath around nerve cells.