Biological Molecules Revision Notes

so i made these notes just on biological molecule :) hopefully youll find them usedful! :D

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Biological Molecules
(a) Describe how hydrogen bonding occurs between water molecules, and relate this, and other
properties of water, to the roles of water in living organisms
The negative charge of the oxygen molecule attracts to the
positive charge of the hydrogen molecule forming a weak
hydrogen bond.
Example
Property Importance/explanation
Solvent Water molecules are attracted to the Respiratory and photosynthetic gases dissolve
charged part of solute molecules. before entering cells; digestion produces soluble
products; metabolism takes place in solution.
Liquid Hydrogen bonding between the water Transport in plants and animals require liquid water
State molecules mean it is liquid at biologically
important temperatures (0-100oC).
Cohesio Water molecules stick together and are Surface tension on water; transport of water in
n and
attracted to surfaces. xylem relies upon cohesion (and adhesion).
Adhesio
n
Freezing Density changes as water freezes ­ less Water bodies freeze from the top down. Lakes
dense, so ice floats (layer of ice also seldom freeze completely; organisms survive in the
insulates). cold, deeper water.
Thermal High specific heat capacity; high latent heat Water temperature quite stable; evaporation has a
of vaporisation. cooling effect.
Metabol Metabolism takes place in aqueous solution; Hydrolysis; condensation; H2O used in
ism
reactant/produced in some. photosynthesis.
(b) Describe, with the aid of diagrams, the structure of an amino acid
Amino acids are the building blocks from which all
proteins are made. Amino acids have a carbon atom
to which is bonded an amine group (-NH2), a
carboxylic acid group (-COOH), a hydrogen and a
variable R-group

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Describe, with the aid of diagrams, the formation and breaking of peptide bonds in the
synthesis and hydrolysis of dipeptides and polypeptides
As two amino acids come
close together a peptide
bond is formed by two
hydrogen atoms from one
amino acid join with an
oxygen atom from the other
to form a water molecule.
This is condensation.
With the polypeptide
combines with a water
molecule the peptide bond is
broken between two amino
acids. This is hydrolysis.…read more

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The proteins secondary structure is formed when the primary structure coils or folds to form an
helix or a pleated sheet. Hydrogen bonds hold all these coils in place.…read more

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Fe+2)
(h) Describe with the aid of diagrams the structure of a collagen molecule
Collagen is a fibrous protein made up of a triple helix of
polypeptide chains, hydrogen bonds are present between the
chains. Each collagen molecule forms covalent cross-links with
other collagen molecules, these are called collagen fibrils.
Many fibrils form a collagen fibre.…read more

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State the structural differences between glucose and glucose
On an glucose molecule the -OH on 1st Carbon atom is below the C where as on a glucose it is
above.…read more

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Describe, with the ad of diagrams, the structure of glycogen
(o) Explain how the structures of glucose, starch (amylose), glycogen and cellulose molecules
relate to their functions in living organisms
Glucose- simplest sugar used in respiration
Starch- insoluble in water so doesn't affect water potential of cell, the storage polysaccharide in
plants
Glycogen- so highly branched can be broken down in to glucose very quickly, the storage
polysaccharide in animals
Cellulose - hundreds of polypeptide chains lay side by side forming hydrogen bonds with each…read more

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Triglyceride- Glycerol molecule and 3 fatty acid groups
Phospholipid-Glycerol molecule, 2 fatty acids, and a phosphate group
(q) Explain how the structures of triglycerides, phospholipid and cholesterol molecules relate to
their functions in living organisms
Triglycerides- compact and water potential not affected as it is insoluble, stored as fat.…read more

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