A distinction assignment from BTEC Applied Science Unit 10- Biological molecules and metabolic pathways. it looks at the structure and function of water, carbohydrates, lipids, proteins and nucleic acids. Includes disruption of biochemical processes in living organisms.
Water is made up of 2 small, positively charged hydrogen
atoms and 1 large negatively charged oxygen atom which
are attracted to each other causing a covalent bond. The
formula for hydrogen is H and the formula for oxygen is
O. The formula for water is written as H2O. Water is a
polar molecule which enables the formation of weak
hydrogen bonds, resulting in the molecules forming a
strong lattice framework. The hydrogen bonds also result
in water having a high heat of vapourisation. This means
a lot of energy is required to turn water into a vapour. Water being polar allows hydrogen bonds to
form as it is a charged molecule. The nucleus of the oxygen atom is negatively charged as it gains 2
electrons from both hydrogen atoms to form a full shell of electrons. The electrons are not shared
evenly as hydrogen has a lower electronegativity level than oxygen.
The properties and importance of water
A property of water is that it is a good solvent as it is charged due to it being polar. Being polar is
important as water sticks together allowing for Columns of water in the xylem of the plant. Water
sticking together is known as cohesion which is the lattice framework formed because of the weak
hydrogen bonds. Cohesion is vital for the growth of plants as it allows water molecules to stick
together and travel up the plant. Around 95% of a plant cells mass is water. Another property of
water is that it has a high specific heat capacity which means a significant amount of energy is
required to break the bonds. An advantage of this is that our bodies can maintain a constant
temperature as the temperature of our blood stays the same and does not fluctuate. 78% of the
human body is made up of water and approximately 70% of a human cell is water. Another
advantage is that there is no harm caused to animals that live in water as the temperature stays the
same. This is important as 75% of planet Earth is covered in water. Water is also a buffer which
means water can gain and lose H+ ions. This allows a constant PH to be maintained in human body
tissues. Intracellular electrolyte concentration is maintained as water molecules can travel in and out
of cells due to osmosis. This is important as it allows nutrients and oxygen to be distributed to cells
around the body. Another function of water is that it helps flush out waste products which should
not be stored in our body as it can cause harm. Water also helps in the creation of saliva which fights
germs in your mouth and has proteins and minerals that protect your teeth and prevent tooth
decay.
The importance of carbohydrates
Carbohydrates are particularly important in the human body and
have many different roles. Carbohydrates are important as they
provide the body with energy which can be either stored as glycogen
or used up in many different processes such as physical exercise,
structural support or digestion of food. If the body does not have
enough carbohydrates your metabolism will slow down as the body
now stores the extra energy as fat. Another importance of
carbohydrates is that they prevent the breakdown of protein as an
energy source. This means protein is no longer being used as a fuel
source. Carbohydrates are the body's main source of energy and the
brains preferred energy source. Carbohydrates are broken down into glucose by the enzyme
amylase. Glucose is a sugar which is absorbed into the blood and with the help of the hormone
insulin, glucose is transported into your body cells to fuel your tissues and organs. The formula for
glucose is C6H1206. Glycogen is a polysaccharide of glucose that is a storage of glucose in your liver
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