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3.1.1 State that the most frequently occurring chemical elements in living things are carbon,

hydrogen, oxygen and nitrogen.

http://en.wikipedia.org/wiki/File:CHONPS

Some fun with elements

Review ionic, covalent and h

ydrogen bonds
http://en.wikipedia.org/wiki/File:CHONPS.svghttp://www.youtube.com/watch?v=QnQe0xW_JY4http://en.wikipedia.org/wiki/File:CHONPS.svghttp://www.youtube.com/watch?v=W2Wwf1UVdFo


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3.1.2 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.svg

http://commons.wikimedia.org/wiki/File:Electron_shell_016_Sulfur.svg

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

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


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http://www.flickr.com/photos/csb13/1873194745/
http://www.flickr.com/photos/csb13/1873194745/http://www.flickr.com/photos/csb13/1873194745/


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3.1.3 State one role for each of the elements

Sulphuris an important element in some amino

acids. It allows disulphide bonds to form in proteins,influencing the proteins shape see HL 7.5 Proteins

What about iron?

http://commons.wikimedia.org/wiki/File:Granulated_sulphur02.jpg
http://commons.wikimedia.org/wiki/File:Granulated_sulphur02.jpghttp://commons.wikimedia.org/wiki/File:Granulated_sulphur02.jpg


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http://www.flickr.com/photos/csutka/3956855512/

Ironis in

haemoglobin, to

carry oxygen in

blood.

Calcium?
http://www.flickr.com/photos/csutka/3956855512/http://www.flickr.com/photos/csutka/3956855512/


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Calciumis

in Bones!

http://www.flickr.com/photos/mugley/3491817141/

Sodium?
http://www.flickr.com/photos/mugley/3491817141/http://www.flickr.com/photos/mugley/3491817141/


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Sodiumis

important

for nerveimpulses

See Core

6.5.5

http://commons.wikimedia.org/wiki/File:Nametal.JPG.jpg

Phosphorus?
http://commons.wikimedia.org/wiki/File:Nametal.JPG.jpghttp://commons.wikimedia.org/wiki/File:Nametal.JPG.jpg


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Phosphorus is in ATP


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And, of course, in

phospholipids incell membranes.

Here in Italian, just for a change.

See: Structure of the membrane 2.4.1

http://commons.wikimedia.org/wiki/File:Fosfolipide.svg
http://commons.wikimedia.org/wiki/File:Fosfolipide.svghttp://commons.wikimedia.org/wiki/File:Fosfolipide.svg


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and in DNA,

amongst

other things.

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

Also

CHON!
http://commons.wikimedia.org/wiki/File:DNA_Structure+Key+Labelled.pnghttp://commons.wikimedia.org/wiki/File:DNA_Structure+Key+Labelled.png


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3.1.4 Draw and label a diagram showing the structure of water molecules to show their polarity

and hydrogen bond formation.

Water is a weird andfreaky substance.

It is this way because

of its polar nature.

http://commons.wikimedia.org/wiki/File:Water_drop_animation_enhanced_small.gif
http://commons.wikimedia.org/wiki/File:Water_drop_animation_enhanced_small.gifhttp://commons.wikimedia.org/wiki/File:Water_drop_animation_enhanced_small.gif


13/33http://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpg

No,that kind
http://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpg


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Revisit the Crash Course

Biology video Carbon (on

slide 2) at the 8:08mark

O

H

H

-ve

+ve

+ve

The oxygen atom has 8

positive charges (protons)

at its nucleus.

Therefore it attracts theshared 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 apositively charged pole

(the hydrogens)
http://www.youtube.com/watch?feature=player_detailpage&v=QnQe0xW_JY4http://www.youtube.com/watch?feature=player_detailpage&v=QnQe0xW_JY4


15/33http://commons.wikimedia.org/wiki/File:Liquid_water_hydrogen_bond.png

Hydrogen bonds

form when the

negatively charged

oxygen on one

molecule is

electrostaticallyattracted to the

positive hydrogen on

another

3 1 O li h h l h i d l i f
http://commons.wikimedia.org/wiki/File:Liquid_water_hydrogen_bond.pnghttp://commons.wikimedia.org/wiki/File:Liquid_water_hydrogen_bond.png


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3.1.5 Outline the thermal, cohesive and solvent properties of water

Thermal: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/
http://www.flickr.com/photos/westy559/328563694/http://www.flickr.com/photos/westy559/328563694/


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Extra energy is required

to overcome the

hydrogen bonds

We say that water has a

very high specific heatcapacity

It absorbs a lot of

energy before changing

state

http://commons.wikimedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svg
http://commons.wikimedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svghttp://commons.wikimedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svg


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CohesiveThe polar nature of water makes it sticky

The molecules themselves stick together dueto hydrogen bonds (cohesion)

Water molecules stick to other substances,

e.g. glass (adhesion) for the same reason

If 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 tryingto pull the water into the smallest possible

volume, a sphere.


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SolventWater 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.

DissolvingNaCl NaCl

http://commons.wikimedia.org/wiki/File:Sodium-3D.png

http://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.png
http://commons.wikimedia.org/wiki/File:Sodium-3D.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.pnghttp://commons.wikimedia.org/wiki/File:Sodium-3D.pnghttp://commons.wikimedia.org/wiki/File:Sodium-3D.pnghttp://commons.wikimedia.org/wiki/File:Sodium-3D.pnghttp://commons.wikimedia.org/wiki/File:Sodium-3D.png


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SolventThe 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

NaCl NaCl

Chlorine

Sodium

Water

Dissolving


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The 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-

NaCl NaClDissolving


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Check out the animationAlso, the relatively small size of

the water molecules means thatthey can gang up on the ions

(not to scale)

http://commons.wikimedia.org/wiki/File:Water_molecule.svg

All your

ion are

belong to

us!!!

3 1 6 Explain the relationship between the properties of water and its uses in living organisms as
http://commons.wikimedia.org/wiki/File:Water_molecule.svghttp://commons.wikimedia.org/wiki/File:Water_molecule.svghttp://www.sumanasinc.com/webcontent/animations/content/propertiesofwater/water.html


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3.1.6 Explain the relationship between the properties of water and its uses in living organisms as

a coolant, medium for metabolic reactions and transport medium

http://www.flickr.com/photos/bukutgirl/205304794/

Waters thermalproperties, its

high specific heat, means that itcan 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.
http://www.flickr.com/photos/bukutgirl/205304794/http://www.flickr.com/photos/bukutgirl/205304794/


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Cohesion allows plants to pull

water up their xylem via

transpiration

Adhesionaids

cohesion in

drawing water

up due to

capillary action

http://www.flickr.com/photos/jaxxon/37559138/

See HL Plant Science 9.2.6
http://www.flickr.com/photos/jaxxon/37559138/http://www.flickr.com/photos/jaxxon/37559138/


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Waters solventproperties

mean that waste and nutrients

can be moved around by bloodin the veins and arteries.

It enables trees totransport gases and

solutes as well

http://www.flickr.com/photos/roughgroove/3554305017/
http://www.flickr.com/photos/roughgroove/3554305017/http://www.flickr.com/photos/roughgroove/3554305017/


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Waters nature as a solvent

means substances dissolvedin 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/

E i W h bi
http://www.flickr.com/photos/cambridgeuniversity-engineering/5431155934/http://www.flickr.com/photos/cambridgeuniversity-engineering/5431155934/http://www.flickr.com/photos/cambridgeuniversity-engineering/5431155934/http://www.flickr.com/photos/cambridgeuniversity-engineering/5431155934/


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http://www.flickr.com/photos/alexyo1968/4985953786/

Extension: Water as habitat

These water striders

rely on the cohesive

nature of waterresulting in surface

tension
http://www.flickr.com/photos/alexyo1968/4985953786/http://www.flickr.com/photos/alexyo1968/4985953786/


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http://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.png

Liquid water Ice

What are the implications of ice being less dense

(due to its highly organised crystalline structure)than liquid water?
http://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.pnghttp://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.pnghttp://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.pnghttp://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.pnghttp://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.pnghttp://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.pnghttp://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.pnghttp://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.png


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http://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpg

Back to the bear

I have somewhere tostand and hunt.See 5.2.6 to see why you

hoomans are worrying me!
http://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpghttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpg


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Imagine if

ice sank

instead offloated

http://www.flickr.com/photos/toniblay/52925332/
http://www.flickr.com/photos/toniblay/52925332/http://www.flickr.com/photos/toniblay/52925332/


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Lakes 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 freezingtemperatures, would not exist.

There would be no habitat for the bottom dwellers.

In fact, the pressure of the overlying water would makethe water at the bottom freeze. Even in the tropics.


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Lucky for uswater is the

way it is!

Further information


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Further information:

Properties of water

Three of the best sites for

IB-specific Biologyinformation. The top link

takes you to the PPT by

Stephen Taylor
http://www.tokresource.org/tok_classes/biobiobio/biomenu/chemicals_water/index.htmhttp:/www.tokresource.org/tok_classes/biobiobio/biomenu/cell_division/index.htmhttp://i-biology.net/ibdpbio/01-cells-and-energy/chemical-elements-and-water/http://www.youtube.com/watch?feature=player_embedded&v=HVT3Y3_gHGghttp://click4biology.info/c4b/3/Chem3.1.htmhttp://www.visionlearning.com/library/module_viewer.php?mid=57http://www.northland.cc.mn.us/biology/biology1111/animations/dissolve.html

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