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A Handbook of Biology

BÅSËD ØÑ FÜÑÇTÏØÑ, ËSSËÑTÏÅL ËLËMËÑTS ÅRË DÏVÏDËD ÏÑTØ 4

ÇÅTËGØRÏËS:

1. Components of biomolecules & structural elements of cells: E.g. Carbon,

hydrogen, oxygen & nitrogen.

2. Components of energy-related chemical compounds: E.g. Mg²⁺ in

chlorophyll and phosphorus in ATP.

3. Elements that activate or inhibit enzymes: E.g. Mg²⁺ an activator for

RuBisCO & phosphoenol pyruvate (PEP) carboxylase (critical enzymes

in photosynthetic carbon fixation). Zn²⁺ is an activator of alcohol

dehydrogenase, Mo activates nitrogenase during nitrogen metabolism,

and Fe activates catalase enzymes.

4. Elements that alter the osmotic potential of a cell: E.g. Potassium helps in

opening & closing of stomata.

RØLË ØF MÅÇRØ & MÏÇRØ ÑÜTRÏËÑTS

Essential elements have role in metabolic processes such as:



Permeability of cell membrane, maintenance of osmotic concentration

of cell sap, electron transport systems, buffering action, enzymatic

activity, constituents of macromolecules and co-enzymes.

ÑÏTRØGËÑ:

It is required by plants in the large amount. It is absorbed mainly

as NO^-3. Some are also taken up as NO2

– and NH4

+ ion. It is essential

for all plant parts, particularly the meristematic tissues and the

metabolically active cells.

It is the major constituents of amino acids, proteins, nucleic acids,

chlorophyll, vitamins and hormones.

The first stable product of fixation of atmospheric nitrogen in

leguminous plants is NO2

–. (NEET 2013)