Respiration is an energy releasing and enzymatically controlled catabolic process which involves a step-wise oxidative breakdown of organic substances inside living cells. In this statement about respiration explain the meaning of
(a) Step-wise oxidative breakdown
(b) Organic substances (used as substrates).
(a) Respiration is a stepwise oxidation of organic molecules in a cell involving main three steps.
(i) Glycolysis (ii) Krebs' cycle (iii) Electron transport chain
Glucose passes through series of enzymatically controlled reactions and is finally converted into $\mathrm{H}_2 \mathrm{O}+$ ATP $+\mathrm{CO}_2$.
(b) Organic substances are the molecules normally found in living systems. They are usually composed of carbon atoms in rings or long chains to which other atoms such as hydrogen, oxygen and nitrogen are attached. e.g., glucose, fatty acids, amino acids etc. These molecules burnt as substrate to produce energy. Respiration of glucose and fatty acids is called floating respiration and respiration of protein and amino acids are called protoplasmic respiration.
The figure given below shows the steps in glycolysis. Fill in the missing steps $A, B, C, D$ and also indicate whether ATP is being used up or released at step $E$ ?
Process of glycolysis is summarised as follow
Glucose is the favourite sulphate for respiration as carbohydrates are first converted into glucose. Prior to used for respiration. Fats are acetyl CO-A are broken down into glycerol and fatty acid which is further degraded into acetyl Co-A, while protein is degraded into, smaller units anino acids. Respiratory process involves the breaking down of substrate is catabolic proceses. Sometime the fatty acid is required them synthesis of it occurs by withdrawing acetly Co-A. This synthesising phase is the anabolic process.
Thus, respiratory pathway involves the catabolic process (break down) and anabolic pathway synthesis of molecules using respiratory intermediates frant link, it is called as an amphibolic pathway.
