This PDF is papered for book 1 topic 1 biology book (person) and the data is expanded with drawings and more information for a better understanding of the topic but the book must be studied before looking at the PDF also I papered a couple of questions with answer key which I upload later which hel...
A molecule of water contains one atom of oxygen chemically bonded to two atoms of hydrogen and the bonds
between the oxygen and hydrogen atoms are covalent bonds.
oxygen atom is slightly negative and hydrogen atoms are slightly positive
Due to these charges, water is a polar molecule.
Due to opposite charges, water molecules can attract each other and form hydrogen bonds.
,Hydrogen bonds are quite weak bonds but because of a large number of water molecules even in a small volume
of water therefor they contain large quantities of hydrogen bonds which affect the strength of the bond and
properties of water.
In liquid water molecules of water move randomly.
, properties of water
water has a very high specific heat capacity [100'C]. when water is heated heat energy starts to weaken
and break the water molecules rather than increase the kinetic energy of water molecules, therefore,
water acts as a buffer against rapid temperature changes. In other words, the temperature of water tends
not to change rapidly. Therefore water acts as a habitat for aquatic organisms.
If conditions are icy, water eventually freezes and turns to ice, and ice is less dense than liquid water. So
ice floats and makes a habitat for many organisms like polar bears. Ice also insulates the water below and
prevents it from freezing thus organisms can continue to live in the water under the ice.
Another important property of water is that it has a very high latent heat of vaporisation. this means it
takes a large amount of heat energy to evaporate water this allows organisms to cool themselves without
losing a great deal of water. e.g sweating
Another role of water is as a solvent. lots of substances can dissolve in water and both eukaryotic and
prokaryotic cells contain a large number of dissolved substances for example the chemicals e.g. glucose /
involved in metabolic reactions such as respiration. as well as enzymes needed to carry out these
reactions. water also dissolves oxygen making water habitable for fish and organisms living in the water
and they can carry out respiration. Because water is a good solvent, it can transport substances e.g. blood
plasma. water also transports substances like electro-light [Na, K, CL, Mg] ions in the plants (Xylem
vessels).
Also water molecules tend to stick together which is called cohesion because of hydrogen bonds between
water molecules. cohesion also makes surface tension where water meets air it is useful because it makes
the surface of water act as a habitat e.g. insects such as Pondskaters.
water plays a vital role in metabolic reactions for example water is a reactant in many different reactions
like Hydrolysis and Photosynthesis and also water is produced in certain metabolic reactions
including Condensation reaction and Aerobic respiration.
Monosaccharides
Carbohydrates: are a major part of the human diet because sugars like sucrose and starch are found
in them
glucose has a ring shape and has the formula of C6H12O6.
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