Page 266 - Biology_F5

Nutrition

5.2 Autotrophic nutrition normally acquired by these organisms
through oxidation reaction. For example,
Task 5.2 Iron bacteria called Ferrobacillus obtain
Search from library and internent their energy by oxidising ferrous to ferric ion,
sources the information on whereas sulphur bacteria called Thiobacillus
photosynthesis, then make short notes. thiooxidans (also known as Acidithiobacillus
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thiooxidans) found in hot springs containing
In this type of nutrition, organisms acquire hydrogen sulphide obtain energy by
energy from sunlight and utilise it to oxidising inorganic sulphur. Organisms
synthesise their food using carbon dioxide which obtain their energy from chemicals
(CO ) obtained from the atmosphere. The through oxidation reaction are called
2
organisms that are capable of utilising chemoautotrophs. The energy obtained by
sunlight or chemical energy to make their both photoautotrophs and chemoautotrophs
own food from simple inorganic materials is used to build food in form of complex
are referred to as autotrophs, which literally molecules, such as sugar, starch, protein,
mean self-feeders. Autotrophs, such as and lipids from carbondioxide.
plants, cyanobacteria, green algae, and
green sulphur bacteria use sunlight energy Photosynthesis
to manufacture their food. These are Photosynthesis refers to a process whereby
collectively called photoautotrophs. The organisms containing chlorophyll and
word photoautotroph is a combination of carotenoid pigments manufacture their
three Greek words: photos, auto, and trophos own food in the form of carbohydrates from
meaning ‘light,’ ‘self,’ and ‘nourishment simple inorganic substances (carbon dioxide
or feeders’ respectively. Therefore, the and water) using sunlight energy. Examples
term photoautotroph literally refers to an of photosynthetic organisms are plants, algae
organism capable of manufacturing its own and some bacteria with bacteriochlorophyll.
food using light energy. Photoautotrophs,
such as plants, cyanobacteria and algae However, photosynthesis in plants
contain green pigments, such as chlorophyll differs from that of bacteria in terms of
'a', 'b' and 'carotenoid'. These pigments are the products released. Unlike bacteria,
important in absorbing light energy, which is plants release oxygen as a by-product.
vital in the synthesis of food in plants by the In addition, photosynthesis in plants
process known as photosynthesis. Bacteria involves pigments, such as chlorophyll, and
contain bacteriochlorophyll, which performs carotenoids while bacterial photosynthesis
the same function as chlorophyll. Generally, uses bacteriochlorophylls in most cases.
the light absorbed by the chlorophyll in green Therefore, bacteria lack definite chloroplasts
plants is converted into chemical energy as opposed to plants, which contain definite
during photosynthesis. chloroplasts.

Besides light, inorganic chemicals are the Photosynthesis process in green plants,
alternative source of energy for the synthesis can be summarised by the following
of food. Energy from such chemicals is equation:

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