A* A Level Biology Essay on 'Importance of Hydrogen Bonding in Organisms'
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Course
Bonding
Institution
AQA
A high grade fully completed A Level Biology essay on the topic of ' Importance of hydrogen bonding in organisms'. Completed to a high standard with teacher corrections applied as well. Four different topics described and evaluated to a great extent. Very detailed. Specialist vocab used in each par...
A hydrogen bond is a weak bond between two molecules resulting from an electrostatic attraction
between a proton in one molecule and an electronegative atom in the other.
One way that hydrogen bonds are used in living organisms is in the structural polymer of cellulose.
Celulose is made of beta glucose, where every other glucose molecule is inverted. This therefore
allows the development of hydrogen bonds between adjacent cellulose molecules. The many
hydrogen bonds provide great structural support and stability. This is important as cellulose is used
in plant cell walls, so must be rigid and help to prevent the plant cell from bursting. Allowing plants
to be turgid also helps them get maximum exposure to the sunlight in order to undergo
photosynthesis which is vital to all plants.
Hydrogen bonds are also vital to the structure of DNA due to their interactions between nucleotides.
DNA is an alpha helix structure with two strands of nucleotides, antiparallel. The nucleotides are
complementary to each other, which guanine and cytosine (having two hydrogen bonds between
them) and thymine and adenine (having three hydrogen bonds between one another). This is
important to DNA structure as the hydrogen bonds make this structure extremely stable as there are
MANY hydrogen bonds working together, preventing the very reactive nucleotides from being
exposed and preventing damage to the genetic information. Hydrogen bonding is also important in
DNA as it is involved in based pairing in the replication of DNA to become mRNA.
Furthermore, hydrogen bonds are involved assisting water movement through a plant. Water
cohesion involves hydrogen bonds causing water molecules to stick together. This causes the water
to form a column, unbroken. This means when water evaporates from the unbroken column the
water molecules below get pulled up the xylem keeping the flow of water constant throughout the
plant. This is important because this allows the plant a fresh constant supply of water to undergo
photosynthesis, and for the synthesis of ATP.z
Another way that hydrogen bonds are important to living organisms is their role in the structure of
enzymes within the organism. Enzymes require a specific structure for a complementary active site
which allows induced fit to occur between the enzyme and the substrate, forming enzyme-substrate
complexes which allows the reaction to be catalysed. Bonds between amino acids and polymer
chains allows this structure to be complementary as without these bonds the enzyme would be
dysfunctional. Hydrogen bonds are involved with the shape of polypeptide chains as a result of
hydrogen bonding, this shape is usually an alpha helix. The tertiary structure of enzyme’s is also held
together by many bonds, hydrogen, disulphide and ionic bonds included. This is important because
many proteins and enzymes in the body undergo very important actions in the body, such as
catalysing chemical reactions in the body; antibodies require a specific shape to work within the
immune system; collagen also has a structural function, so its fibrous proteins are very important to
its overall function.
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