Protein Metabolism

Protein Metabolism

# Protein in the body

Proteins are large organic molecules made up of chains of amino acids (aa) linked together. The human body contains 20 different aa, each of which shares the -CO- and -NH- groups.

# Types of protein in the body

Protein exists in many different forms in the body and plays an important role in many functions:

• Transport proteins in the blood: Includes aa, plasma proteins such as albumin, globulin, and fibrinogen.

• Structural proteins: The main components that make up the shape and structure of the body, such as muscles, cell nuclei.

• Reserve proteins: Stored in cells, releasing aa when the body is deficient.

# Transport proteins in the blood

• Amino acids: Ion form, average concentration in the blood is 35-65 mg%. Only a small amount of aa is absorbed into the blood at a time, then transported to the liver and cells in the body by carriers.

• Plasma proteins: Includes albumin, globulin, and fibrinogen.

• Albumin, fibrinogen, and 80% of globulin are synthesized in the liver.

• 20% of globulin is produced in lymphoid tissues.

# Structural proteins

• Function: Building the shape and structure of the body.

• Location: Present in muscles, cell nuclei.

• Role: Determines the human body shape, creating differences between individuals.

# Reserve proteins

• Function: Store aa for the body.

• Location: In all cells.

• Role: When the body is deficient in aa, proteins in the cell nucleus are broken down into aa to supply the body. Reserve protein is the main aa store in cells.

# Role of protein

• Energy supply: Does not directly provide energy but indirectly through the process of breaking down aa into ketoacids, which are then converted into acetyl CoA, participating in the Krebs cycle to produce ATP.

• Structure and body formation: The main role of protein.

• Main component of antibodies and enzymes: Proteins participate in the immune system and chemical reactions in the body.

• Participate in gene activity: Proteins play an important role in the process of heredity.

# Protein requirement

• Requirement: Accounts for 12-15% of the total Kcal requirement per day.

• Protein loss: Each person loses about 20-30g of protein per day due to the process of breaking down protein into aa, then deamination and oxidation.

• Supplement: It is recommended to supplement with 50-60g of protein per day and eat a variety of proteins from different animal sources.

# Essential amino acids

Of the 20 aa, the body cannot synthesize itself or synthesize in quantities that are too low compared to the demand, need to be supplemented from the outside. These are essential aa:

• Phenylalanine

• Tryptophan

• Histidine

• Arginine

• Threonine

• Valine

• Leucine

• Isoleucine

• Lysine

• Methionine

# Regulation of protein metabolism

Protein metabolism is regulated by two mechanisms:

• Neural mechanism: The hypothalamus acts on protein metabolism.

• Humoral mechanism: Growth hormone (GH), sex hormones, T3, T4 (in the development phase) promote the transport of aa from the blood into cells to synthesize protein. Conversely, T3, T4 (in adulthood), cortisol have the opposite effect.

Summary

Protein is an important component of the body, playing a variety of roles in many functions. Understanding protein metabolism helps us to have a reasonable diet, ensuring a healthy body and good development.