Essential Biochemistry: Proteins, Lipids, and Metabolic Pathways

Proteins: Structure, Function, and Classification

Proteins are complex molecules made up of amino acids. They perform various essential functions in the body, such as:

• Structural Support (e.g., collagen)
• Enzymatic Activity (e.g., lactase)
• Transport (e.g., hemoglobin)
• Defense (e.g., antibodies)

Classification of Proteins

Proteins are classified based on their structure and function.

Classification Based on Structure

• Fibrous Proteins: (e.g., collagen)
• Globular Proteins: (e.g., enzymes, antibodies)

Classification Based on Function

• Enzymes
• Hormones
• Structural Proteins
• Transport Proteins
• Defense Proteins

The Urea Cycle and Ammonia Removal

The urea cycle is a series of biochemical reactions that occur in the liver to remove excess ammonia from the body. This process is vital for detoxification.

Key Reactions of the Urea Cycle

1. Ammonia Conversion: Ammonia is converted into urea through a series of enzyme-catalyzed reactions.

Key Enzymes Involved

• Carbamoyl Phosphate Synthetase
• Ornithine Transcarbamylase
• Argininosuccinate Synthetase
• Argininosuccinase
• Arginase

Disorders of the Urea Cycle

Genetic defects in enzymes involved in the urea cycle lead to ammonia accumulation in the blood, resulting in serious health issues.

Common Symptoms

• Vomiting
• Lethargy
• Seizures
• Developmental Delays

Lipids: Roles in Energy and Cell Structure

Lipids are biomolecules that include fats, oils, phospholipids, and steroids. They play crucial roles in the body:

• Energy Storage
• Cell Membrane Structure
• Hormone Production
• Insulation and Protection

Ketogenesis: Producing Ketone Bodies

Ketogenesis is a metabolic process that occurs in the liver when glucose levels are low. It produces ketone bodies from fatty acids.

Mechanism of Ketogenesis

1. Low Glucose Levels: When glucose is scarce, the liver breaks down fat for energy.
2. Fatty Acid Breakdown: Fatty acids are converted into acetyl-CoA.
3. Ketone Body Production: Acetyl-CoA is then converted into three types of ketone bodies:
   • Acetoacetate
   • Beta-hydroxybutyrate
   • Acetone

Disorders of Lipid Metabolism

Disorders related to lipid metabolism can significantly impact cardiovascular health and cellular function.

• Hyperlipidemia: High levels of lipids in the blood, increasing cardiovascular risk.
• Familial Hypercholesterolemia: Genetic disorder causing high cholesterol.
• Lipid Storage Diseases: Disorders (like Gaucher's disease) where lipids accumulate in cells.
• Ketosis: Excessive ketone production, often seen in diabetes or low-carb diets.