PowerPoint Presentation

13.1.1 State that the most frequentlyoccurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen.

http://en.wikipedia.org/wiki/File:CHONPS.svgSome fun with elements

Review ionic, covalent and hydrogen bondshttp://www.youtube.com/watch?v=QnQe0xW_JY423.1.2 State that a variety of other elements are needed by living organisms, including sulphur, calcium , phosphorus, iron and sodium

http://commons.wikimedia.org/wiki/File:Electron_shell_020_Calcium.svghttp://commons.wikimedia.org/wiki/File:Electron_shell_016_Sulfur.svghttp://commons.wikimedia.org/wiki/File:Electron_shell_015_Phosphorus.svghttp://commons.wikimedia.org/wiki/File:Electron_shell_026_Iron.svghttp://commons.wikimedia.org/wiki/File:Electron_shell_011_Sodium.svg

3http://www.flickr.com/photos/csb13/1873194745/CaFe NaPS!43.1.3 State one role for each of the elementsSulphur is an important element in some amino acids. It allows disulphide bonds to form in proteins, influencing the proteins shapesee HL 7.5 ProteinsWhat about iron?http://commons.wikimedia.org/wiki/File:Granulated_sulphur02.jpg5http://www.flickr.com/photos/csutka/3956855512/Iron is in haemoglobin; Iron is the oxygen binding component of blood. Also helpful in blood clottingCalcium?6

Calcium: used in structure of Bones and teethhttp://www.flickr.com/photos/mugley/3491817141/Sodium?7Sodium is important for nerve impulses

Also...found in some amino acids (NOT ALL)

See Core 6.5.5http://commons.wikimedia.org/wiki/File:Nametal.JPG.jpgPhosphorus?8

Phosphorus is in ATP

9

And, of course, in phospholipids in cell membranes.

Here in Italian, just for a change.

See: Structure of the membrane 2.4.1http://commons.wikimedia.org/wiki/File:Fosfolipide.svgand in DNA, amongst other things.

http://commons.wikimedia.org/wiki/File:DNA_Structure%2BKey%2BLabelled.pngAlsoCHON!

113.1.4 Draw and label a diagramshowing the structure of water molecules to show their polarity and hydrogen bond formation.Water is a weird and freaky substance.

It is this way because of its polar nature.

http://commons.wikimedia.org/wiki/File:Water_drop_animation_enhanced_small.gif12http://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpgNo,notthat kindof polar13Revisit the Crash Course Biology video Carbon (on slide 2) at the 8:08 mark OHH- + +The oxygen atom has 8 positive charges (protons) at its nucleus. Therefore it attracts the shared electrons more strongly and they spend more time orbiting the O than the H.

Thus water molecules are polar, i.e. they have a negatively charged pole (the oxygen) and a positively charged pole (the hydrogens)Polar covalent pond14http://commons.wikimedia.org/wiki/File:Liquid_water_hydrogen_bond.pngHydrogen bonds form when the negatively charged oxygen on one molecule is electrostatically attracted to the positive hydrogen on another15

3.1.5 Outline the thermal, cohesive and solvent properties of waterThermal:You know about the phases (states) of water: Solid, Liquid and Gas.Water changes from solid to liquid and gas progressively as more energy (heat) is added.The weird thing about water is that it takes more energy than it should to change from one state to the next. Why do you think that might be?http://www.flickr.com/photos/westy559/328563694/16

Extra energy is required to overcome the hydrogen bonds

We say that water has a very high specific heat capacity

It absorbs a lot ofenergy before changing statehttp://commons.wikimedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svg17CohesiveThe polar nature of water makes it stickyThe molecules themselves stick together due to hydrogen bonds (cohesion)Water molecules stick to other substances, e.g. glass (adhesion) for the same reasonIf water did not have this cohesive nature then it would not form into drops like in the background. Drops form because the cohesive forces are trying to pull the water into the smallest possible volume, a sphere.18SolventWater is sometimes called the universal solvent Again, this is to do with the polar nature of water

Consider the sodium chloride below. The sodium and chloride atoms are held together by ionic bonds.

DissolvingNaClNaCl

http://commons.wikimedia.org/wiki/File:Sodium-3D.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.png19SolventThe polar water molecules have a stronger affinity for both Na+ and Cl- than those ions do for each other.So the Na and Cl dump each other and drift off with the water molecules

NaClNaCl

ChlorineSodium

WaterDissolving20The polar water molecules have a stronger affinity for both Na+ and Cl- than those ions do for each other.

So the Na and Cl dump each other and drift off with the water molecules.

Note how on the right of the diagram the oxygen in each water molecule is close to the Na+ and the hydrogen in the water molecules is close to the Cl-

NaClNaCl

Dissolving21

Check out the animationAlso, the relatively small size of the water molecules means that they can gang up on the ions

(not to scale)

http://commons.wikimedia.org/wiki/File:Water_molecule.svgAll your ion are belong to us!!!223.1.6 Explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport mediumhttp://www.flickr.com/photos/bukutgirl/205304794/Waters thermal properties, its high specific heat, means that it can cool us.Evaporating sweat (water changing phase from liquid to gas) takes heat away from the body

Water is also the main component of blood plasma.It transfers heat from the internal organs to the skin.23Cohesion allows plants to pull water up their xylem via transpirationAdhesion aids cohesion in drawing water up due to capillary actionhttp://www.flickr.com/photos/jaxxon/37559138/xylem is derived from the Greek word meaning "wood"; the best-known xylem tissue is wood though it is found throughout the plant. Its basic function is to transport water24Waters solvent properties mean that waste and nutrients can be moved around by blood in the veins and arteries.

It enables trees to transport gases and solutes as wellhttp://www.flickr.com/photos/roughgroove/3554305017/25Waters nature as a solvent means substances dissolved in it can react with one another.

The main component of cytoplasm, where many reactions occur, is water.http://www.flickr.com/photos/cambridgeuniversity-engineering/5431155934/26http://www.flickr.com/photos/alexyo1968/4985953786/Extension: Water as habitatThese water striders rely on the cohesive nature of water resulting in surface tension27

http://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.pngLiquid waterIceWhat are the implications of ice being less dense (due to its highly organised crystalline structure) than liquid water?28http://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpgBack to the bearI have somewhere to stand and hunt.See 5.2.6 to see why you humans are worrying me!29Imagine if ice sank instead of floatedhttp://www.flickr.com/photos/toniblay/52925332/30Lakes at high latitudes would freeze from the bottom up. Solid. And remain so for most if not all of the year at high latitudes.The seas would be similarly affected. The water that is usually insulated by the ice, at above freezing temperatures, would not exist. There would be no habitat for the bottom dwellers.

In fact, the pressure of the overlying water would make the water at the bottom freeze. Even in the tropics.31Lucky for us water is the way it is!32Further information:

We didnt watch this in class but this is a good video

http://www.youtube.com/watch?v=HVT3Y3_gHGg33