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Information about CHEM 121 02 STRUCTURE OF THE CELL

Published on November 13, 2008

Author: cpesison


Slide 1: The special chemical properties of water make it ideal as the main physiologic solvent for polar substances in the body. Slide 2: Within the water molecule, the oxygen nucleus draws electrons away from the hydrogen atoms, producing an internal charge separation that makes each molecule magnetic or polar. Slide 3: Substances that dissolve well in water are referred to as polar or hydrophilic. Slide 4: Molecules that dissolve sparingly in water are nonpolar or hydrophobic Slide 5: Water molecules bind with each other through important noncovalent interactions called hydrogen bonds. Hydrogen bonds result from attraction between the partially positively charged hydrogen atoms of one molecule and the electronegative atom, usually fluorine, oxygen or nitrogen, of another molecule. Slide 6: Water has a high surface tension where it comes in contact with air. Surface tension is the force acting to push together the liquid molecules at an air-liquid interface. This property causes the liquid to form droplets and to resist passage of substances across the interface. Slide 7: The surface tension of fluid at the alveolar air-water interface of the lungs contributes to elastic recoil that causes the alveoli to return to the original volume after inflation during breathing. Slide 8: Water has a high heat of vaporization Large amount of heat needed to convert from liquid to gas phase. Slide 9: This property allows water to carry away heat efficiently as it evaporates, which accounts for the cooling effects of perspiration. Slide 10: Water has a high dielectric constant, which is a measure of its ability to carry electrical current, as it does in nerve cells. Slide 11: Electrolytes are compounds that separate or dissociate in water into a positively charged cation and a negatively charged anion. Because of their polar nature, electrolytes are soluble in water. Slide 12: Important cationic electrolytes in human physiology include Na+, K+, Ca2+, and Mg2+, whereas Cl− and HCO3− are critical anionic electrolytes. Slide 13: The Henderson-Hasselbalch equation is derived from the rearrangement of the equilibrium equation for dissociation of a weak acid. Slide 14: The effectiveness of a buffering system is maximal when it is operating at a pH near its pKa. Slide 15: The carbonic acid-bicarbonate system is the most important buffer of the blood. The carbonic acid-bicarbonate buffer system has a pKa of 6.1, yet is still a very effective buffer at pH 7.4 because it is an open buffer system, in which one component, CO2, can equilibrate between blood and air. Slide 16: Substances that have both a hydrophilic group and a hydrophobic region, often a hydrocarbon tail, are referred to as amphipathic. Amphipathic molecules do not dissolve fully in water but instead cluster together to form specialized structures with their polar groups oriented toward the water and nonpolar regions pointed away from the water. Slide 17: Micelles are spherical structures that have the polar groups on the outside surface where they form hydrogen bonds with water, and the nonpolar tails are clustered in the core of the structure Slide 18: An important structure formed by amphipathic molecules is the lipid bilayer, in which the hydrocarbon tails line up in a parallel array with the hydrophilic head groups facing the polar fluids on either side. Slide 19: Lung surfactant is a mixture of proteins and amphipathic lipids that acts like a detergent or soap to greatly decrease the surface tension forces at the alveolar fluid-air interface. Slide 20: Plasma Membrane is a phospholipid bilayer Capable of lateral (sideway) movement hence is said to be fluid in nature Embedded proteins throughout the bilayer gives a textured (mosaic) form. Slide 21: Integral Membrane Proteins (IMP) serves as channel, carriers, and pumps for the passage of polar materials into and out of the cell. (a) Glycoproteins serves as for recognition purposes. Receptors for various ligands that affect cellular activity through signal transduction. Forms the glycocalyx or “sugar coating” of animal and human cells. (2) Peripheral Membrane Proteins (PMP) supports the plasma membrane and serve as anchor for the cytoskeleton Slide 22: Some of the transport process happens "passively" without the cell needing to expend any energy to make them happen. These processes are called "passive transport processes". Other transport processes require energy from the cell's reserves to "power" them. These processes are called "active transport processes". Slide 23: Diffusion is the movement of ions or molecules from regions of higher concentration to regions of lower concentration. (Down a concentration gradient) Slide 24: Molecules that pass through the phospholipid bilayer easily And those that don’t pass through easily. Characteristics of a molecule that determine the permeability of the membrane to that species are: Polarity - (Nonpolar > Polar) Charge - (Uncharged > Charged) Size - (Small > Large) Slide 25: Facilitated Diffusion is a form of passive transport facilitated by transport proteins. Slower than diffusion. Uptake of simple sugars and amino acids by cells. Slide 26: Osmosis is diffusion of particles through a semi-permeable membrane Slide 27: Effect of different solutions on animal and plant cells. Slide 28: Active Transport uses ATP to go against the concentration gradient (opposite diffusion) Slide 29: Active Transport uses ATP to go against the concentration gradient (opposite diffusion)

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