Biology Molecule Essays - Intermolecular Forces, Properties Of Water

Biology Molecule Unit 1 -man is high 50's to 60% water -distribution in body divided into 3 compartments: 1) intracellular - 28 litres 2) intercellular/interstitial fluid - 11 litres - 80% 3) blood plasma - 3 litres - 20% -women contain less water than men -organisms can contain 60-80% water -bacteria have lots of water -fat cells have little -water's properties result from its structure and molecular interactions -water is polar -polar covalent bonds and asymmetrical shape give it opposite charges on opposite sides -electrons spend more time around O giving H a slight positive charge -hydrogen bonds form between the oxygen of one molecule and the hydrogen of another -cohesion: substance being held together by hydrogen bonds -hydrogen bonds are transient yet enough is always held together to give water more structure than almost any other liquid -beads and meniscus formed by cohesion (also helps upward transport of water in plants) -adhesion counteracts downward pull of gravity -water has greater surface tension than most liquids -surface molecules are hydrogen bonded to molecules below and around them -surface tension can hinder life (i.e. beading in the alveoli of lungs) -makes water "unwettable" -surfactants used to counteract this -water has a high specific heat which allows it to resist extreme temperature changes -has a high heat of vaporization that causes it to require alot of energy to change states -when sweating, heat energy is utilized to change states from liquid to gas, causing a drop in temperature -as a solid water is less dense than as a liquid and will float -charged regions of molecules have an electrical attraction to charged ions -water surrounds ions separating and shielding them from one another -polar compounds are generally soluble -charged regions of water are attracted to oppositely charged regions of other polar molecules -polar molecules are miscible in other polar liquids -most water molecules don't dissociate (~ 1/554 million do) -hydrogen atom in hydrogen bond between the two water molecules may shift from the oxygen atom it is covalently bonded to the unshared orbitals of the oxygen that it is hydrogen bonded to -hydrogen ion is transferred creating a hydronium ion and leaving a hydroxide ion -the solvent is water itself -at equilibrium water is not dissociated -at equilibrium in pure water at 25oC [H+] = [OH-] -pH of this solution is 7 (neutral) -high pH = low acidity -acids are substances that increase the relative [H+] and remove OH- because it tends to combine with H+ to form water - if [H+] * [OH-] , it is acidic and has a pH between 0 and 7 -bases are substances that reduce the relative [H+] in a solution -it may increase the [OH] -if [H+] * [OH-] , it is basic and has a pH greater than 7 -buffers are important in the body to keep the pH range between 6 and 8 -pH of blood is between 7.34 and 7.44 -mustn't shift below 7.2 or acidosis will occur -some body zones may have a pH as low as 0.5 or as high as 10 -buffers minimize sudden changes and are a combo of hydrogen donors and hydrogen acceptors -ions are accepted when in excess and donated when in short supply -in biological systems an example is the bicarbonate buffer -in response to a rise in pH, the carbonic acid dissociates to form a carbonate ion and a hydrogen proton -if there is a drop, it is reversed (pH up = to right, pH down = to left) -equilibrium is established but it is always moving to the left or the right -a balance is the optimum pH -other body buffers include protein molecules which donate and accept amino acids to stabilize pH -most of the rest of organisms is made up of carbon based compounds like carbs, lipids, proteins, nucleic acids -carbon compounds are known as organic -vitalism is the belief in a life force outside the control of chemical laws -this has been disproved as water, ammonia, hydrogen and methane have been combined in a lab to form organic substances -C+O+H = carbohydrates -C+H+N = amino acids, urea, proteins, lipids -carbon atoms are the most versatile building blocks -each has 4 valences where bonds can form -carbon chains form the skeleton of most organic molecules -may be straight or branched, long or short, or in closed rings -hydrocarbons contain only hydrogen and carbon -they form when organic matter decomposes and functional groups break off leaving a skeleton -hydrocarbon chains, branches, and rings can be modified by other elements which