Metabolism Of Food We Eat

Metabolism Of Food We Eat

Whenever we take a bite of our food, there is tons of work done by our body on that single bite to give us fuel that is energy to work. I hope everyone of you guys know the importance of food for our survival. But have you wondered what happens to food after that? How it is giving us energy to work.  How we get nutrients for our body from food? Let’s make you understand the process of giving us energy through your food we eat.

Our body gets energy from food through a process called Metabolism.

Metabolism Introduction

What is Metabolism?

Metabolism is sum total of all the chemical reactions take place inside our body. Metabolism of food gives us energy and nutrient we need for proper growth and functioning. We need energy for everything from thinking to walking to growing. Each of the chemical reaction in our body is coordinated with other body function. 

The source of energy:

  • Firstly, the green plants we eat takes up energy from sunlight. In presence of sunlight it converts water and carbon dioxide into glucose and oxygen with help of chlorophyll present in leaves. This phenomenon is known as photosynthesis. Chlorophyll is responsible for green color of leave. 10% of this energy is transferred in next tropic level. In basic language 10% of the total energy is transfer to the organism who has eaten the plant.
  • The plant eaten by herbivores or carnivores who eat animals who have eaten plant take this energy in form of sugar along with another necessary chemical. 
  • After eating food, these molecules are digested with the help of enzymes. Enzymes acts biological catalyst. Enzymes converts carbohydrates into simple sugar, proteins into amino acids, and fats into fatty acids. And these carbohydrates, fats and proteins can be used as source of energy by our body.
  • Then these compounds are absorbed by our blood. Blood carries the absorbed compounds to different parts of body. The energy from these compounds are then released for our body needs. The glucose produced from the food is convert into glycogen and stored in the liver.
Organic molecules have structures that give them lots of chemical energy in the form of ATP.

What Is A Ketogenic Diet

If you guys are here that means you are wanting to get in shape and you wanted to know more about Ketogenic Diet. Let’s start at the beginning.

Know more about Keto Diet

Nutrients of Metabolism 

Carbohydrates, lipids and protein are the main components of food we eat. These components further serve as fuels for the body. The process starts with digestion of food (carbohydrates, lipids and protein) into smaller compounds and then absorbed by the blood. The blood carries it throughout the body where each and every cell uses the digested product and makes energy for useful work.

The end products of digestion are monosaccharides (mainly glucose), monoacylglycerol and long fatty acid chains, and small peptides and amino acids. Different cell of the body metabolizes these compounds. And the process of production of ATP from glucose is known as respiration.

Mechanisms of ATP synthesis

Energy metabolism is vital for growth, repair, and reproduction of cells of the body. The cell uses this energy for various function. The metabolism of food occurs in two coupled processes- oxidation of nutrients and synthesis of high energy compound, ATP (which works as main source of energy for the cell). 

There are mainly two mechanism of ATP synthesis: – 

  1. Oxidative phosphorylation 
  2. Substrate level phosphorylation

In oxidative phosphorylation, there is synthesis of ATP from ADP and inorganic phosphate (Pi) which takes place in mitochondria. This is the reason why mitochondria are known as power house of the cell.

In substrate level phosphorylation, there is synthesis of ATP through transfer of high energy phosphoryl group from compound ADP. 

Oxidative Phosphorylation

The metabolism reaction involves oxidation and reduction reactions for ATP synthesis. The process starts as following: – 

  1. electrons are removed from fuel molecule by the process known as oxidation
  2. This electron is then transferred to two major electron carriers: – 

a) NAD+ (nicotinamide adenine dinucleotide)

b) FADH (flavin adenine dinucleotide)

  • NAD+ and FADH2 is converted into NADH and FADH2 by process known as reduction 
  • Oxidative phosphorylation depends on electron transport from NADH and FADH2 to oxygen which forms water.
  • The electron is transported via. Protein complexes in inner mitochondrial membrane.
  • Inner mitochondrial membrane has number of chemical groups required for accepting or donating electrons such as flavins, copper ions, etc.
  • These protein complexes are known as electron transport system (ETS).
  • The electron from NADH is transferred to oxygen via three protein complexes: – NADH dehydrogenase, cytochrome reductase and cytochrome oxidase.
  • The electron transport between the complexes is mediated by mobile electron carriers like ubiquinone and cytochrome c. 
  • During the reaction catalyzed by enzymes FAD is converted into FADH2, its electron is transferred to oxygen through cytochrome reductase and cytochrome oxidase.
  • The electron transfer through ETS is further associated with proton pumping from mitochondrial matrix to inner membrane.
  • The pumping of proton creates PMF (proton motive force) which further leads to formation of ATP from ADP and Pi in presence of ATP synthase complex.

Oxidation of Carbohydrates, Proteins and Fats (TCA Cycle)

Oxidation of food we eat is through the TCA cycle. TCA is tricarboxylic acid cycle. It is also known as Krebs’s cycle/citric acid cycle. It was discovered by Sir Hans Kreb in the flight muscles of Pigeon.

In Krebs’s cycle, 12 ATPs are gained in 1 turn. And this ATP is used up by our body in form of energy.

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