Basic Principles of Biological Chemistry 1-35.pdf

BIOL 150 LECTURE 3 Structure and Properties of Water  Water is the Substance that makes Life possible as we know it here on Earth Importance of Water More than 70% of Earth is covered by water Water is major constituent to all life forms Most plants and animals...

BIOL 150 LECTURE 3 Structure and Properties of Water  Water is the Substance that makes Life possible as we know it here on Earth Importance of Water More than 70% of Earth is covered by water Water is major constituent to all life forms Most plants and animals contain more than 60% water by volume 50-75% of the human body is water. Uniqueness of Water Water is the only common substance to exist in the natural environment in all 3 physical states of matter… Solid Liquid Gas Importance of water Properties  Water: A Polar Molecule Polar molecules have an uneven distribution of charge (despite a net zero charge on whole molecule). Oxygen is more electronegative than hydrogen Oxygen has a greater pull on the shared electrons and is slightly negative (δ-). Hydrogen is slightly positive (δ+). This is called an electric dipole. http://tx.technion.ac.il/~schles/theory.html Chemical Polarity - In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end. Polar molecules must contain polar bonds due to a difference in electronegativity between the bonded atoms. A polar molecule with two or more polar bonds must have a geometry which is asymmetric in at least one direction, so that the bond dipoles do not cancel each other. ~ wikipedia  Polarity Allows for H-Bonds Oxygen (slightly negative charge) can bond to the hydrogen on another water molecule One water molecule can form up to 4 hydrogen bonds (no other H- bonding molecules can do this) H-bond is sufficiently strong and contributes to the many properties of water that make it so integral to life! http://bio1151.nicerweb.com/Locked/media/ch03/water_molecule.html States of Water  Fourth State of Water Water can be also found as a fourth state called supercritical fluid occurs when liquid and gas phases merge into a fluid that has both liquid and gas properties Requires extremely high temp/pressure Supercritical water coming from vents at bottom of Atlantic Ocean https://www.newscientist.com/article/dn14456-found-the-hottest-water-on-earth/  H-bonds and States of Water In liquid water, molecules are constantly breaking and reforming h-bonds between each other. However, temperature goes down, water molecules slow down movement and interact with one another less. So, the rate at which h-bond breaking and reforming occurs less often. Eventually, h-bonds will no longer be broken → molecules will be locked in place → ICE. https://www.tes.com/lessons/s6u1rMAkjQ0TLg/science-5-5b-boiling-melting-freezing Density Density of Water (1g/cm3)  Density of Water As temperature decreases, most liquids contract or get smaller. Water only contracts until it reaches 4˚C then it expands until it is solid. At freezing temperature, the volume of water is about 9% higher than liquid state. This is why ice floats on water and why pipes burst when they freeze! http://dev.physicslab.org/document.aspx?doctype=3&filename=thermalphysics_thermalexpansion.xml  Can you think of a major reason in nature of why ice floats… What would happen if it didn’t? Density of elements Least dense: 0.534 g/cm3 Most dense 22.59g/cm3 Uses Lithium – rechargeable batteries for mobile phones, laptops, digital cameras and electric vehicles Osmium – produce very hard alloys for fountain tip pens, needles and electrical contacts  Surface Tension Cohesion of water molecules at the surface of a body water is called surface tension. Water has the highest surface tension of the non-metallic liquids http://media.kids-myshot.nationalgeographic.com/2013/10/52631d5283d12IMG_1847_large_medium.JPG Surface Tension Surface tension Surface Tension Water is not attracted to wax paper No adhesion between the drop and the wax paper. Each molecule in the water drop is attracted to each other. The water pulls itself into a shape with the smallest amount of surface area, a sphere. All the water molecules on the surface of the bead are Try this at home: Drop water holding onto each other onto wax paper together or creating surface tension. Surface Tension Surface tension allows water striders to 'skate' across the top of a pond. Osmosis Osmosis and our cells Osmosis is when water moves from an area of LOW solute concentration (low osmolarity) to an area of HIGH solute concentration (high osmolarity) through a semipermeable membrane. Osmosis is one of the most important ways that plants and animals achieve homeostasis. Keeping the body's conditions stable makes it possible for living things to survive.  Cohesion and Adhesion Cohesion occurs when water is attracted to other water through hydrogen bonds. Due to its polar nature, water can also be attracted to other materials. This is called adhesion. http://ib.bioninja.com.au/standard-level/topic-2-molecular-biology/22-water/cohesive-and-adhesive-prope.html Adhesion Adhesion is responsible for water droplets clinging to spider web (another polar substance).  Capillary Action Capillary action is related to the adhesive properties of water. Capillary action is what you see when you place a straw into a glass of water and the water begins to climb up the straw. The water molecules are attracted to the straw molecules. When one water molecule moves closer to the straw molecules, the other water molecules (which are cohesively attracted to that water molecule) also move up into the straw. http://vision.eecs.ucf.edu/projects/pingkun/cac.html  Capillary Action Surface tension tends to straighten the surface, causing the surface to rise and more water to enter the straw. Capillary action is limited by gravity and the size of the straw. When the force of gravity is balanced by the adhesive force the process will stop. The thinner the straw, the higher up capillary action will pull the http://vision.eecs.ucf.edu/projects/pingkun/cac.html water.  Ex. of Cohesion/Adhesion in Biology Surface tension and capillary action are responsible for the movement of water up through the xylem in plants http://quizlet.com/12933881/bio-lecture-16-flash-cards/ Temperature Regulation Water has high specific heat capacity Specific heat capacity is the heat needed to raise the temperature of 1 kg of water by 1oC. High specific heat capacity means water can absorb a lot of heat before its temperature rises. Water also releases heat slowly when it cools. In the body, large temperature variations are therefore regulated by water. Temperature Regulation Compared to other molecules of its size, water has an extremely high boiling point….this is due to its H-bonds! Carbon dioxide (CO2) boils at -78oC. Water boils at 100oC. It takes a lot of energy to break the H-bonds in water. The amount of energy required for liquid water (lots of h-bonds) to boil and become steam (few h-bonds) is called the heat of vaporization. High Heat of Vaporization Allows water to regulate the Earth’s climate: Solar heat absorbed by ocean water is dissipated when surface water evaporates. As warm tropical air moves towards poles, water vapor releases heat as it condenses into rain. Stabilizes temperature in aquatic ecosystems. Helps keep organisms from overheating.