From molecules to cells © 2007 Paul Billiet ODWSODWS.
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Transcript of From molecules to cells © 2007 Paul Billiet ODWSODWS.
From molecules to cells
© 2007 Paul Billiet ODWS
THE CELL
Organelles CHLOROPLASTS, MITOCHONDRIA, NUCLEUS etc
Supramolecular assemeblies
ENZYME COMPLEXES, RIBOSOMES, CHROMOSOMES
Macromolecules NUCLEIC ACID
PROTEIN POLYSACCHARIDE LIPID
Building blocks NUCLEOTIDE AMINO ACID
SIMPLE SUGAR FATTY ACID &
GLYCEROL
Precursors from the environment CO2, H2O, MINERALS
The levels of organisation in cells
© 2007 Paul Billiet ODWS
Elements in living & non-living material
EARTH’S CRUST HUMAN TISSUES
RANK ELEMENT % ELEMENT %
1st O 62,5000 H 60,300
2nd Si 21,2000 O 25,500
3rd Al 6,4700 C 10,500
4th Na 2,6400 N 2,450
5th Ca 1,9400 Na 0,730
6th Fe 1,9200 Ca 0,266
7th Mg 1,8400 P 0,134
8th P 1,4200 S 0,132
9th C 0,0800 K 0,036
10th N 0,0001 Cl 0,032
© 2007 Paul Billiet ODWS
Elements in living & non-living material
EARTH’S CRUST HUMAN TISSUES
RANK ELEMENT % ELEMENT %
1st Oxygen 62,5000 Hydrogen 60,300
2nd Silicon 21,2000 Oxygen 25,500
3rd Aluminium 6,4700 Carbon 10,500
4th Sodium 2,6400 Nitrogen 2,450
5th Calcium 1,9400 Sodium 0,730
6th Iron 1,9200 Calcium 0,266
7th Magnesium 1,8400 Phosphorus 0,134
8th Phosporus 1,4200 Sulphur 0,132
9th Carbon 0,0800 Potassium 0,036
10th Nitrogen 0,0001 Chlorine 0,032
Water
Formula H2O Structure
Slightly () negative at the oxygen end and slightly positive at the hydrogen end -
+ +
O
H H
© 2007 Paul Billiet ODWS
The association between the polar water molecules
Weak hydrogen
bonds
© 2007 Paul Billiet ODWS
Comparing molecules
-61-8634H2SHydrogen sulphide
+19-9220HFHydrogen fluoride
+100018H2OWater
-33-7817NH3Ammonia
-161-18416CH4Methane
Boiling point / °C
Melting point/ °C
Molecular mass
FormulaMolecule
Compared to molecules of similar size and properties water has a very high melting point and boiling point
© 2007 Paul Billiet ODWS
Thermal properties
The molecules of water can absorb a lot of heat energy
Water has a very high thermal capacity (4.2 J°C-1 g-1)
The hydrogen bonding forms a lattice which does not easily fall apart as the temperature rises
© 2007 Paul Billiet ODWS
Thermal properties and life
Water is a very, thermally stable medium Water helps living organisms resist
changes in their environment To make water change from a liquid to a
vapour requires a lot of energy Evaporation of water on a the surface of a
body cools it down significantly
© 2007 Paul Billiet ODWS
African elephants (Loxodonta africana) bathing © Shirley Burchill 2007 © 2007 Paul Billiet ODWS
Solvent properties
The polar properties of water make it a good solvent for:
Polar molecules (e.g. sugars and alcohols) These form hydrogen bonds with the water
molecules Ionic compounds (e.g. salts, acids and bases) These dissociate into their component ions
© 2007 Paul Billiet ODWS
Solvent properties and life
Water is a very important transport medium for living organisms
because of its solvent properties and because it remains a liquid over a large
range of temperatures Water is also an important medium for
biochemical reactions
© 2007 Paul Billiet ODWS
Webvision
Cohesion
The cohesion (stickiness) between water molecules
Water molecules are also attracted to wettable surfaces
Very tall thin columns of water can be supported before they break
The tallest are at the physical limits of water trees (sequoia and eucalyptus are 100m tall)
© 2007 Paul Billiet ODWS
Giant red wood Sequoiadendron giganteum
California USA
Public Domain image
Eucalyptus
grandis
NSW Australia
Public Domain image
Surface tension Water molecules hold together forming a skin at the
surface This is strong enough for some organisms to be
supported
Water Skater © Shirley Burchill 2007
Water skater
Gerris gibbifer
© 2007 Paul Billiet ODWS
Density Water is densest at 4°C whilst it is still a liquid So ice floats on the surface of water Organisms which
live in water do not risk freezing solid so easily
Freezing is usually fatal
Water forms a good habitat for living organisms
Iceberg, Antarctica © Shirley Burchill 2007
© 2007 Paul Billiet ODWS
Transparency
Water is a transparent liquid, light passes though it Blue light, with the most energy, penetrates furthest, red
light is the weakest and penetrates least Plants can photosynthesise under water Animals can use their visual systems
Kelp forests (Macrocystis pyrifera) California
© Mike Graham, Phycology Lab @ Moss Landing Marine Laboratories
© Text 2007 Paul Billiet ODWS