Cellular Respiration

             Energy is not produced directly by the Oxidation of complex molecules. It is produced when glucose or fatty acids are oxidised in the cells in a process called Cellular Respiration. Energy is released in several stages. Mitochondria present inside the cells use the oxygen entering inside for respiration and energy production. First step of the reactions is glycolysis, which after series of reactions under goes Krebs Cycle and then Electron transport resulting in the production of energy. Let's see the process of Cellular Respiration.
The first step of respiration is the conversion of glucose to pyruvic acid (Glycolysis) which is common for all the three types of respiration i.e., Aerobic, Anaerobic respiration and fermentation.
Let's see the fate of pyruvic acid in aerobic respiration.
Food In Intestine (absorbed by) ----> Blood ---> Liver (through blood) -----> tissues ----> Oxidation of food takes place

Mitochondria are the sites of cellular respiration. Oxidation of food materials takes place in them. The energy released through oxidation is utilised by the mitochondria to synthesis ATP (Adenosine Tri Phosphate) which are energy rich compounds.
ATP provides energy required for various metabolic functions and reactions of the organism.

About Mitochondria
Meaning and Named by
Elementary/F1 Particles
Mito = thread Chondrion = granule
Uniformly distributed in cytoplasm
Two membranes outer and inner
These are on the crests
Biological oxidation of food materials like glucose and fatty acids.
granular cytoplasmic organelle named by --> Benda
No. of Mitochondria varies with the type of the cell and its functional state width varies from 0.5 - 2 μ length is variable upto 40 μ shape – mostly granular
outer one is smooth inner one projects into crests inner chamber is filled with matrix
They are round stalked bodies They are molecules of ATP as enzymes They are responsible for oxidative Phosphorylation
Mitochondriaon synthesizes stores and releases the high energy ATP, so referred as power house of the cell

Cellular Respiration
O2, ADP + Pi (inorganic phosphate), Carbohydrates, fats are required for the respiratory activity in mitochondria.
Glycolysis: Conversion of one molecule of glucose into two molecules of pyruvic
Glucose + Pi
glucose - 6 - Phosphate + Pi Fructose - 1, 6 di phosphate 2 CH3COCOOH (Pyruvic acid)

Result of Glycolysis: 4 ATP and 2 NADH are formed 2 ATP molecules are used in this process. So, net gain is 2 ATP molecules.
Kreb's Cycle: Takes place in mitochondrial matrix.

2CH3COCOOH (In presence of O2)---->2Carbon Compounds Acetyl CoA ( CO2 Removed) ----> 4 Carbon Compounds Oxaloacetic acid ---->6 Corbon atoms citric acid

H+ ions of Acetyl Co A are transferred to NAD+ and FAD+ (Forming) ---> NADH and
FADH2 (large amount of energy is released).

Electron Transport
NADH and FADH2 are oxidised in the elementary particles of mitochondria where 1 Proton & 2 electrons are formed from each molecule of NADH and are ejected into the inner membrane of mitochondria. These electrons are transferred from one acceptor to another which are arranged in a chain (The energy released is used for production of ATP). These electrons and protons are finally transferred to oxygen to form water.
Note: ADP + Phosphate ( in presence of O2 Forms ) ---> ATP (Oxidative Phosphorylation)
  • A net gain of 38 ATP molecules are formed from the total oxidation of one glucose molecule through Glycolysis, Krebs Cycle and Electron transport.
  • Each ATP molecule gives 7,600 calories of energy.
  • 40% of the total energy present in the glucose molecule is converted into ATP energy.

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