Biology: Understanding Proteins and Amino Acids

Overview of Protein

• Fundamental component of all living cells: plants, animals, microorganisms.
• Constructed from amino acids and nitrogen, end products of protein digestion.

Amino Acids

• Join together via peptide bonds to form proteins.
• Classified into essential and non-essential amino acids.
• Essential amino acids: 9 that must be obtained through diet as the body cannot synthesize them.

Types of Proteins

• Simple Proteins

  • Yield amino acids upon hydrolysis.
  • Examples: Albumins, Globulins, Enzymes.

• Complex Proteins

  • Composed of simple proteins and non-protein groups.
  • Examples: Glycoprotein, Phosphoprotein, Lipoprotein, Chromoprotein (e.g., hemoglobin).

• Derived Proteins

  • Formed from the degeneration products of primary and secondary protein structures.

Protein Sources

• Complete Proteins

  • Contain all essential amino acids.
  • Typically derived from animal sources: meats, dairy, eggs.

• Partially Complete Proteins

  • Lack required amounts of essential amino acids.
  • Example: some fish types lacking methionine.

• Incomplete Proteins

  • Low in one or more essential amino acids.
  • Common in plant sources like grains; can be combined to form a complete profile.

Functions of Protein

• Tissue repair and building.
• Energy source.
• Growth stimulants.
• Creation of plasma proteins (e.g., Albumin) to maintain osmotic balance.
• Defense system (antibodies).

Protein in Acid-Base Regulation

• Proteins act as buffers by accepting/releasing hydrogen ions, maintaining blood and body fluid pH (normal range 7.35 - 7.45).

Transport Functions of Proteins

• Carry nutrients in body fluids.
• Hemoglobin transports oxygen; lipoproteins transport lipids.
• Some transport vitamins and act as cellular pumps.

Fluid Balance Regulation

• Proteins mainly reside in cells and plasma; their leakage during illness can cause edema (fluid accumulation).
• Causes of edema include excessive protein loss, inadequate protein synthesis, and dietary deficiency.

Protein Digestion and Absorption

• Proteins are broken down into amino acids and peptides in the stomach and small intestine.
• Absorption occurs in the small intestine with three fates for amino acids: enter circulation for enzymes, convert to other amino acids, or oxidize for energy.

Protein in Food Sources

• Examples include Casein (milk), Albumin (egg white), Gluten (wheat).

Protein Deficiency

• Protein-energy malnutrition (PEM) encompasses conditions from inadequate protein and energy:
  • Kwashiorkor: Severe protein deficiency, signs include edema, diminished muscle tone, brittle hair.
  • Marasmus: Severe energy and protein deficiency, symptoms include general weakness, growth retardation, and muscle wasting.

Health Implications Related to Protein

• Heart Disease: High animal protein intake linked to increased saturated fats, correlating with heart disease risk.
• Cancer: High red and processed meat intake risks certain cancers; legumes and fish may reduce risk.
• Bone Loss: High protein may increase calcium excretion; adequate calcium-to-protein ratio (20:1) needed for bone health.
• Kidney Disease: Increased kidney workload from high protein may accelerate chronic kidney disease; dietary restriction can slow its progression.

Recommended Protein Intake

• 10-35% of total food energy.
• RDA: 0.8 grams per kg for adults, higher for infants/children.

Protein Powders

• Common in athletic circles, yet do not effectively enhance muscle growth; adequate muscle work is key. Excess protein intake does not further muscle benefits.

This quiz covers the fundamental concepts of proteins and amino acids, exploring their significance in living cells and their classification into essential and non-essential amino acids. Test your knowledge on how proteins are formed and their vital roles in biology.