Question

1) Explain how the body metabolizes carbohydrates and protein in the fed state.

#2) Explain how the body metabolizes carbohydrates and fat in the fed state.

Answer 1

Metabolism of carbohydrate.

Glycolysis.

It is the main process in which the breaking down of glucose molecule into two pyruvate  molecules takes place. There is also occurance of storing of energy that is been released during this of breaking down of carbohydrate . This stored energy is in the form of process as ATP and NADH.Glycolysis is the very important method of energy production in most of the living beings.This pathway occures in help of both anaerobic and aerobic respiration.

Glycolysis is a mechanism with two phases.

1) During the first phase;

● the breakdown of two ATP molecules.

2) During the second phase;

● chemical energy converted into ATP and NADH.

● one molecule of glucose is broken down to form two molecules of pyruvate This pyruvate can be utilised for oxidation in later process.

Gluconeogenesis

*It is the reverse of glycolysis.

* It is the conversion of non-carbohydrate molecules into glucose.

* The non-carbohydrate molecules are pyruvate, lactate, glycerol, glutamine etc..

* This process tooks place when the glucose amount is too low. This occure in liver and the liver acts as the organ that breaks down the non-carbohydrate molecules and sends them out to other organs and tissues to be used in Gluconeogenesis.

* insulin and glucagon regulates the gluconeogenesis

Glycogenolysis

* it is the breakdown of glycogen in the liver, muscles, and the kidney, to provide glucose whenever necessary.

*single glucose molecule from glycogen, is transformed or converted into glucose-1-phosphate .

*Then is converted to glucose-6-phosphate.

* Glucose-6-phosphate will undergo glycolysis.

* Glycolysis requires one molecule of ATP when the glucose originates in glycogen.

* Alternatively, mechanism acts for the glucose-6-phosphate to be converted back into glucose in the liver and the kidneys, if necessary to  raise blood glucose levels.

Glycogenesis

* It is the process of synthesizing glycogen.

* excess glucose is converted to glycogen

* Glycogen consisting of glucose, in the form of glucose-6-phosphate, linked together.

* Glycogenesis occurs in the liver, skeletal muscles, and kidney

Protein metabolism

The steps :

-transcription

-translation

-post translational modifications.

● Transcription:  RNA polymerase transcribes a coding region of the DNA in a cell producing messenger RNA .

● mRNA sequence contains codons: 3 nucleotide long segments that code for a specific amino acid.

● Ribosomes translate the codons to the appropriate amino acids.

●Non-essential amino acids are synthesized in Citric Acid Cycle.

● The amino acids are joined by peptide bonds making a polypeptide chain. This polypeptide chain undergoes the post translational modifications.

●Dietary protein is broken down into individual amino acids by the helpof various enzymes and hydrochloric acid that is present in the gastrointestinal tract.

● Then it  further broken down to α-keto acids.

● Proteins can be broken down by enzymes known as peptidases or by the help of  denaturation.

Lipid metabolism

* It is the synthesis and degradation of lipids in cells

* It involves the breakdown or the storage of fats for energy.

* the synthesis of structural and functional lipids is also occured in this mechanism, like as the construction of cell membranes.

* Lipogenesis is the process of synthesizing the fats.

* The lipids in human body are triglycerides and cholesterol.

* Lipid metabolism is the digestion and absorption process of dietary

* There are two sources of fats : from consumed dietary fats and from stored fat.

* Lipid metabolism often begins with hydrolysis  which tooks place with the help of various enzymes in the digestive system.

* The second step is the absorption of the fatty acids into the epithelial cells of the intestinal wall.

* In the epithelial cells, fatty acids are packaged and transported to the rest of the body.