CHAPTER 5. THE CHEMICAL INDUSTRY 5.4
the human diet. We cannot make our own food and so we either needto eat vegeta-
bles, fruits and seeds (allof which are direct plantproducts) or the meat ofother animals
which would have fed on plants during their life. So most of the nutrients that animals
need are obtained either directly or indirectly from plants. Table 5.2 summarises the
functions of some of themacronutrients in animals.
Table 5.2: The functionsof animal macronutrients
Nutrient Function
Carbon Component of organic compounds
Hydrogen Component of organic compounds
Oxygen Component of organic compounds
Nitrogen Component of nucleic acids and pro-
teins
Phosphorus Component of nucleic acids and
phospholipids
Potassium Helps in coordination and regulating
the water balance in thebodyMicronutrients also playan important function inanimals. Iron for example, is found in
haemoglobin, the bloodpigment that is responsible for transporting oxygen to all the
cells in the body.
Nutrients then, are essential for the survival oflife. Importantly, obtaining nutrients
starts with plants, whichare able either to photosynthesise or to absorbthe required
nutrients from the soil. It is important therefore that plants are always able to access the
nutrients that they needso that they will grow and provide food for otherforms of life.
The role of fertilisers ESCCN
Plants are only able to absorb soil nutrients in aparticular form. Nitrogen for example,
is absorbed as nitrates, while phosphorus is absorbed as phosphates. The nitrogen
cycle (Grade 10) describes the process that is involvedin converting atmospheric nitro-
gen into a form that canbe used by plants.
However, all these natural processes of maintaining soil nutrients take along time. As
populations grow and the demand for food increases, there is more and more strain
on the land to producefood. Often, cultivationpractises don’t give thesoil enough
time to recover and to replace the nutrients that have been lost. Today, fertilisers play
a very important role inrestoring soil nutrientsso that crop yields stayhigh. Some
of these fertilisers are organic (e.g. compost, manureand fishmeal), which means that
they started off as partof something living. Compost for example is often made up
of things like vegetablepeels and other organicremains that have beenthrown away.
Others are inorganic and can be made industrially. The advantage ofthese commercial
fertilisers is that the nutrients are in a form thatcan be absorbed immediately by the
plant.