Tuesday, September 15, 2020

Respiration in Plants - Notes | Class 11 | Part 1: Breathing in Plants

14. RESPIRATION IN PLANTS 

Oxidation of food materials (breaking of C-C bonds of complex molecules) within the cell to release energy for ATP synthesis is called cellular respiration.
This energy is used for absorption, transport, movement, reproduction, breathing etc.

Ultimate source of food that is respired is photosynthesis.

The compounds that are oxidized during respiration are called respiratory substrates. E.g. Carbohydrates (most common), proteins, fats and organic acids.

The energy released is not used directly but is used to synthesize ATP. When energy is needed, ATP is broken down. Hence, ATP acts as energy currency of the cell. 
 

BREATHING IN PLANTS


For respiration, plants get O2 and give out CO2.

In plants, gas exchange occurs via stomata & lenticels.

Plants need no specialized respiratory organs because
  • Each plant part takes care of its own gas-exchange needs. So gas transport is very limited.
  • Very low gas exchange as compared to that of animals.
  • Leaves are adapted for maximum gas exchange during photosynthesis. During this, O2 is released within the cell.
  • Most living cells have contact with air. They are located close to plant surface. In stems, living cells are organized in thin layers beneath the bark. They also have lenticels. In leaves, stems & roots, parenchyma cells are loosely packed that provides interconnected air spaces. 
Complete combustion of glucose yields energy most of which is given out as heat.

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy 

This energy is utilized to synthesize other molecules.

During the glucose catabolism, not all the liberated energy goes out as heat. Glucose is oxidised in several small steps. It enables some steps to couple released energy to ATP synthesis.

During respiration, oxygen is utilized, and CO2, water & energy are released.

Certain organisms are adapted to anaerobic conditions. Some are facultative anaerobes. Others are obligate.
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