Pregled metabolizma proteina

Protein Metabolism Overview

• Protein metabolism encompasses the breakdown, synthesis, and utilization of proteins in the body.
• Proteins are vital for numerous bodily functions, such as structural support, enzymatic catalysis, and transport.
• Protein metabolism involves both catabolic and anabolic processes.
• Catabolic processes break down proteins into amino acids.
• Anabolic processes synthesize proteins from amino acids.

Protein Breakdown (Catabolism)

• Deamination: Removal of the amino group from amino acids.
• Transamination: Transfer of the amino group from one amino acid to another.
• Oxidative deamination: Amino acids are broken down, releasing nitrogen as ammonia.
• Urea cycle: Converts ammonia to urea, a less toxic nitrogenous waste product, for excretion.
• Carbon skeletons: The remaining part of the amino acid after deamination, further metabolized into carbohydrate and lipid intermediates.
• Fate of the carbon skeletons: Used for energy production, gluconeogenesis, or ketogenesis.

Protein Synthesis (Anabolism)

• Amino acid pool: A collection of amino acids circulating in the blood used for protein synthesis.
• Genetic code: Dictates the sequence of amino acids in proteins.
• Transcription and translation: Cellular processes converting genetic information into proteins.
• Protein folding: The process by which a polypeptide chain folds into its three-dimensional structure.
• Regulation of protein synthesis: Controlled by hormones, growth factors, and amino acid availability.

Protein Turnover

• Continuous process of protein synthesis and degradation.
• Crucial for maintaining cellular function and adapting to physiological needs.
• Rate of protein turnover differs among tissues and proteins.
• Damaged or unneeded proteins are degraded via the ubiquitin-proteasome system.

Amino Acid Classification

• Essential amino acids: Cannot be synthesized by the body and must be obtained from the diet.
• Non-essential amino acids: Can be synthesized by the body.
• Conditional amino acids: Non-essential, but become essential under specific conditions (like illness or stress).

Protein Digestion

• Proteins are initially broken down into smaller polypeptides by enzymes in the stomach and small intestine.
• Peptidases: Enzymes hydrolysing peptide bonds to release individual amino acids.
• Absorption of amino acids occurs in the small intestine.

Protein Metabolism Disorders

• Phenylketonuria (PKU): A genetic disorder affecting phenylalanine metabolism, causing phenylalanine buildup in the blood.
• Maple syrup urine disease (MSUD): A genetic disorder affecting branched-chain amino acid metabolism, leading to branched-chain amino acid accumulation.
• Other inherited metabolic disorders: Numerous inherited disorders can affect specific steps in protein metabolism, causing varied symptoms.

Hormonal Regulation

• Hormones impact protein metabolism through various mechanisms influencing synthesis, breakdown, and amino acid utilization.
• Insulin: Promotes protein synthesis and inhibits degradation.
• Glucagon: Stimulates protein degradation and gluconeogenesis.
• Growth hormone: Influences protein synthesis and growth.
• Cortisol: Affects both protein breakdown and synthesis depending on conditions.

Importance of Adequate Protein Intake

• Crucial for tissue growth, repair, and maintenance.
• Contributes to immune function, enzyme activity, and hormone production.
• Necessary for various bodily functions.

Special Considerations

• Nitrogen balance: Measures nitrogen intake versus excretion, reflecting protein status.
• Positive nitrogen balance: Synthesis exceeds degradation.
• Negative nitrogen balance: Degradation exceeds synthesis.
• Protein requirements vary by age, activity level, and health conditions.