Protein and Amino Acids Overview

Overview of Protein

• Essential component of every living cell in plants, animals, and microorganisms.
• Composed of amino acids and nitrogen; these are the building blocks formed during protein digestion.

Amino Acids

• Joined by peptide bonds to create various proteins.
• Classified into essential and non-essential amino acids.
• Non-essential amino acids can be synthesized by the body, while essential amino acids (9 total) must be obtained through diet.

Types of Proteins by Structure

• Simple Proteins: Hydrolyze to yield only amino acids (e.g., Albumins, Globulins).
• Complex Proteins: Composed of simple proteins and additional non-protein groups (e.g., Glycoproteins, Phosphoproteins).
• Derived Proteins: Formed from degradation products like peptides.

Protein Sources

• Complete Proteins: Contain all essential amino acids; primarily from animal sources (e.g., meats, dairy).
• Partially Complete Proteins: Contain some essential amino acids but are insufficient for growth; examples include certain fish.
• Incomplete Proteins: Low in one or more essential amino acids; typically from plant sources (e.g., grains, cereals).

Functions of Proteins

• Tissue Building: Essential for repair and growth.
• Energy Source: Can be used when carbohydrates and fats are insufficient.
• Plasma Proteins: Maintain osmotic balance in blood (e.g., Albumin).
• Defense Mechanisms: Essential for immune response; antibodies are proteins.

Protein in Acid-Base Balance

• Proteins act as buffers by attracting and releasing hydrogen ions (H+) to maintain pH levels (normal range: 7.35 - 7.45).

Protein Transport Functions

• Some proteins carry nutrients and facilitate oxygen transport via hemoglobin.
• Lipoproteins transport lipids; other proteins can act as membrane pumps for transporting vitamins and minerals.

Fluid Balance Regulation

• Proteins generally remain in blood vessels; however, during illness or malnutrition, they may leak, attracting water and causing edema (swelling).

Digestion and Absorption of Proteins

• Begins in the stomach, where protein is hydrolyzed into polypeptides by HCL and enzymes; further cleaved by pancreatic enzymes.
• Amino acids are absorbed in the small intestine and can either enter circulation, convert to other amino acids, or provide energy.

Protein in Food

• Sources include casein in milk, albumin in egg whites, and gluten in wheat.

Protein Deficiency

• Protein-energy malnutrition (PEM): Insufficient dietary protein leads to conditions like Kwashiorkor and Marasmus.
• Kwashiorkor: Characterized by edema, muscle weakness, and brittle hair due to severe protein deficiency.
• Marasmus: Results from lack of energy and protein, leading to extreme weakness, muscle wasting, and growth retardation.

Health Implications of Protein Intake

• High animal protein intake may increase heart disease risk due to saturated fats.
• Plant proteins may lower risks of certain cancers, while high intakes of red and processed meats are linked to some cancers.
• High protein intake may increase calcium excretion, affecting bone health; a calcium-to-protein ratio of > 20:1 is deemed protective.
• High protein diets increase workload on kidneys, which could accelerate deterioration in those with chronic kidney disease.

Protein Recommendations

• Protein intake should constitute 10-35% of total energy.
• Recommended dietary allowance (RDA) for adults: 0.8 g/kg of body weight; higher for infants/children.

Protein Powders

• Commonly used by athletes to enhance muscle growth, but muscle building requires physical activity rather than supplementation alone; excessive protein does not necessarily yield greater muscle growth.

Explore the vital role of proteins in all living cells, including plants, animals, and microorganisms. Learn about amino acids, their classifications, and how they contribute to protein structure through peptide bonds. This quiz delves into essential and non-essential amino acids and their significance in biological processes.