Water Discussion (Biology PDF)

2.2 Water Essential idea: Water is the medium of life. The cohesive nature of nature gives it surface tension. The surface tension in turn allows organisms such as pond skaters (above) to move across the surface. For pond skaters the surface of water is their habit...

2.2 Water Essential idea: Water is the medium of life. The cohesive nature of nature gives it surface tension. The surface tension in turn allows organisms such as pond skaters (above) to move across the surface. For pond skaters the surface of water is their habitat. The surface tension transmits vibrations from fallen invertebrates - this allows pond skaters to detect and locate their prey. Understandings, Applications and Skills Statement Guidance 2.2.U1 Water molecules are polar and hydrogen bonds form between them. 2.2.U2 Hydrogen bonding and dipolarity explain the Students should know at least one example of cohesive, adhesive, thermal and solvent properties a benefit to living organisms of each property of water. of water. Transparency of water and maximum density at 4°C do not need to be included. 2.2.U3 Substances can be hydrophilic or hydrophobic. 2.2.A1 Comparison of the thermal properties of water with Comparison of the thermal properties of water those of methane. and methane assists in the understanding of the significance of hydrogen bonding in water. 2.2.A2 Use of water as a coolant in sweat. 2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water. 2.2.U1 Water molecules are polar and hydrogen bonds form between them. Water molecules and their bonds Water (H2O) is made up of two hydrogen atoms covalently bound to an oxygen atom While this bonding involves the sharing of electrons, they are not shared equally The number of protons in each atom is different; oxygen atoms have 8 whilst hydrogen atoms have just 1 having more protons, the oxygen atoms attract the electrons more strongly Thus the oxygen end of the molecule becomes slightly negative and the hydrogen end becomes slightly positive Covalently bonded molecules http://www.colorado.edu/physics/200 that have a slight potential charge are said to be polar 0/applets/h2ob.html The slightly charged regions of the water molecule can attract Screen Shot 2014-05-03 at 20.52.18.png other polar or charged Animated tutorial compounds on hydrogen Water molecules can associate bonding via weak hydrogen bonds Hydrogen bonds are transitory in nature – they constantly http://programs.northlandcollege.edu/biology/biology1111/animations/hydrogenbonds.html http://programs.northlandcollege.edu/biology/biol form, break and re-form ogy1111/animations/hydrogenbonds.html 2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water. Properties of water molecules Nature of science: Use theories to explain natural phenomena - the theory that hydrogen bonds form between water molecules Cohesion: explains the properties of water. (2.2) This property occurs as a result of the The observable properties of water are explained by cohesion, adhesion, solvent and thermal properties, which are in turn polarity of a water molecule and its explained by hydrogen bonding. ability to form hydrogen bonds Although hydrogen bonds are weak the large number of bonds present (each water molecule bonds to four others in a tetrahedral arrangement) gives cohesive forces great strength Water molecules are strongly cohesive (they tend to stick to one another) Water droplets form because the cohesive forces are Surface tension is caused by the trying to pull cohesive hydrogen bonding the water resisting an object trying to into the penetrate the surface. smallest possible n.b. capillary action involves volume, a cohesion and adhesion and so http://ib.bioninja.com.au/standard- level/topic-3-chemicals-of-life/31- sphere. dealt with under adhesion. chemical-elements-and.html 2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water. Properties of water molecules Nature of science: Use theories to explain natural phenomena - the theory that hydrogen bonds form between water molecules Adhesion: explains the properties of water. (2.2) This property occurs as a result of the polarity of a water Water molecule and its ability to form hydrogen bonds droplets stick Water molecules tend to stick to other molecules that are to surface and seem to charged or polar for similar reasons that they stick to each defy gravity other because of Again similarly individual hydrogen bonds are weak, but form because the adhesive large number of bonds gives adhesive forces great strength forces that bond them to the surface of the grass Capillary action is caused by blade. the combination of adhesive forces causing water to bond to a surface, e.g. the sides of a xylem vessel and the cohesive forces bonding water molecules together. Capillary action is helpful in the movement of water http://click4biology.info/c4b/9/plant9.2.htm during transpiration and also when you drink using a http://commons.wikimedia.org/w straw. iki/File:GemeineFichte.jpg 2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water. Properties of water molecules Nature of science: Use theories to explain natural phenomena - the theory that hydrogen bonds form between water molecules Solvent: explains the properties of water. (2.2) Water can dissolve many organic and inorganic substances that have charged or polar regions. The polar attraction of large quantities of water molecules can interrupt intra-molecular forces (such as Metabolic reactions happen most readily in ionic bonds) and resulting in the dissociation of the solutions of water – water in cells dissolves the atoms reactants /substrates Positive atoms, e.g. Na+ end up being surrounded by the negative oxygen regions of water molecules and Cells are mostly water therefore diffusion into and out of them happens most easily if the Cl- being surrounded by the positive hydrogen the substance concerned is in solution, e.g. region of water molecules before oxygen diffuses from the alveoli to Because of this water is often (wrongly) referred to as the blood it dissolves into the moist layer being the ‘universal solvent’, it is however a very good lining the alveoli. solvent for many substances. Screen Shot 2014-05-04 at 09.52.51.png Screen Shot 2014-05-03 at 20.59.13.png http://upload.wikimedia.org/wikipedia/commons/8/8b/Alveoli.svg Soluble substances such as sucrose can be easily transported around the plant in http://www.sumanasinc.com/webcontent/animations/content/propertiesofwater/water.html http://www.northland.cc.mn.us/biology/Biology1111/animations/dissolve.swf http://www.sumanasinc.com/webcontent the phloem. Once dissolved in the water http://www.northland.cc.mn.us/biology/ /animations/content/propertiesofwater/w Biology1111/animations/dissolve.swf ater.html of the phloem the sucrose can be moved to where it is needed by mass flow. 2.2.U3 Substances can be hydrophilic or hydrophobic. hydrophilic This term is used to describe substances that are chemically attracted to water. ( water loving ) All substances that dissolve in water are hydrophilic, including polar molecules such as glucose, and particles with positive or negative charges such as sodium and chloride ions. Substances that water adheres to, cellulose for example, are also hydrophilic. A space filling molecular diagram of glucose showing the positive and negative charges http://www.middleschoolchemistry.com/img/content/multimedia/chapter_5/lesson_7/glucose.jpg 2.2.U3 Substances can be hydrophilic or hydrophobic. hydrophobic This term is used to describe substances that are insoluble in water ( water fearing ) Molecules are hydrophobic if they do not have negative or positive charges and are nonpolar All lipids are hydrophobic, including fats and oils Hydrophobic molecules dissolve in other solvents such as propanone (acetone) http://upload.wikimedia.org/wikipedia/commons/thumb/f/f1/Water_and_oil.jpg/450px-Water_and_oil.jpg 2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water. Transport of molecules in the blood Blood plasma consists mainly of water (95%) plus dissolved substances which it transports. Glucose polar molecule hence freely soluble carried by the blood plasma http://4.bp.blogspot.com/-71TuXJIWv8o/UChT59p73fI/AAAAAAAAAFY/B1zkMgT- dlA/s1600/Glucose.png 2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water. Transport of molecules in the blood Amino acids Positive and negative charges (due to the amine and acid groups) therefore soluble in water R group varies, can be polar, non-polar or charged R group determines the degree of solubility carried by the blood plasma There is an internal transfer of a hydrogen ion from the -COOH group to the -NH2 group to leave an ion with both a negative charge and a positive charge. http://chemwiki.ucdavis.edu/Under_Construction/Chemguide_(Jim_Clark)/Properties_of_Organic_ Compounds/XIII._Amino_Acids_and_Other_Biochemistry/A._Amino_Acids/2._Acid- Base_Reactions_of_Amino_Acids 2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water. Transport of molecules in the blood Oxygen Non-polar molecule O=O Due to the small size of an oxygen molecule it is soluble in water, but water becomes saturated with oxygen at relatively low concentrations As temperature increases the solubility of oxygen decreases At body temperature (37 °C) very little oxygen can be carried by the plasma, too little to support aerobic respiration hemoglobin in red blood cells carry the majority of oxygen Hemoglobin has (4) binding sites for oxygen Hemoglobin https://upload.wikimedia.org/wikipedia/commons/thumb/3/3d/1GZX_Haemoglobin.png/480px-1GZX_Haemoglobin.png 2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water. Transport of molecules in the blood Fats Large, non-polar molecules insoluble in water They are carried in blood inside lipoprotein complexes (in the plasma) Lipoprotein complex Outer layer consists of single layer of phospholipid molecules hydrophilic phosphate heads of the phospholipids face outwards and are in contact with water Cholesterol The hydrophobic hydrocarbon tails face molecules are hydrophobic, apart inwards and are in contact with the fats from a small hydrophilic region at one end cholesterol molecules are positioned in the This is not enough to make cholesterol phospholipid monolayer - hydrophilic region dissolve in water facing outwards They are carried in blood in lipoprotein Proteins are also embedded in the complexes (in the plasma) phospholipid layer (hence the name) http://chienlab.wikispaces.com/file/view/lipoprotein.jpg/45882185/lipoprotein.jpg 2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water. Transport of molecules in the blood Sodium Chloride ionic compound freely soluble in water dissolving to form sodium ions (Na+) and chloride ions (Cl-) carried in the blood plasma http://www.northland.cc.mn.us/biology/Biology1111/animations/dissolve.swf 2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water. Properties of water molecules Nature of science: Use theories to explain natural phenomena - the theory that hydrogen bonds form between water molecules explains the properties of water. (2.2) Thermal: Screen Shot 2014-05-03 at 20.59.13.png Water has a high specific heat capacity (4.2 Joules is required to raise the temperature of 1 g of water by 1°C) Water has a high heat of vaporization (amount of energy needed to change from a liquid to a gas or vapor) Water has a high heat of fusion (amount of energy needed to http://www.sumanasinc.com/webcontent/animations/content/propertiesofwater/water.html be lost to change liquid water to ice) http://www.sumanasinc.com/webcontent/a nimations/content/propertiesofwater/water.html These properties are due to many hydrogen bonds that need to be formed or broken to change the temperature or state of water Therefore the temperature of water remains relatively stable Water is used by Leaves as a coolant. The heat lost from leaves for evaporation prevents them over-heating. If the leaves get too hot enzymes in their cells will start to denature. http://www.flickr.com/photos/jaxxon/37559138/ 2.2.A2 Use of water as a coolant in sweat. 2.2.A1 Comparison of the thermal properties of water with those of methane. Comparing and contrasting the properties of water and methane Methane Water Methane waste product of anaerobic respiration in certain prokaryotes living in anaerobic conditions Methane can be used as a fuel If present in the Formula CH4 H2 O atmosphere it contributes to the greenhouse effect. Molecular mass 16 18 Bonding Single covalent Key chemical property that causes Polarity nonpolar polar the major differences seen in the physical properties. Density (g cm-3) 0.46 1 Specific Heat Capacity Methanogenic prokaryotes 2.2 4.2 (J g-1 oc-1) can be found in swamps, wetlands, the guts of Latent heat of 760 2257 animals (including cattle vapourisation (J g-1) and sheep) Melting point (oC) -182 0 can also be found in waste Boiling point (oC) -160 100 dumps https://commons.wikimedia.org/wiki/Water_molecule#mediaviewer/File:Water_molecule.svg https://upload.wikimedia.org/wikipedia/commons/5/55/3D_methane.PNG React on the following: Bibliography / Acknowledgments