Biochemistry Foundations, Fermentation Science, and Galactosemia Notes

Introduction to Biochemistry and Macromolecules

• Definition of Biochemistry: Biochemistry is the branch of science dealing with large molecules composed of thousands of covalently connected atoms, known as macromolecules, and the biochemical processes these molecules undergo to yield products necessary for maintaining physiological homeostasis.
• Core Macromolecules: Biochemical systems rely on four primary categories of macromolecules:
  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acids
• Primary Objectives of Biochemistry:
  • Understand the fundamental importance of chemical reactions in living systems.
  • Trace and explain the historical development of biochemistry as a scientific field.
  • Understand the specific role of biochemistry in defining, understanding, and diagnosing diseases.

Historical Foundations and Discovery of Fermentation

• Yeast and Sugar Fermentation:
  • The discovery of biochemistry as a distinct science originated from observations surrounding yeast and the fermentation of sugar.
  • The human knowledge that yeast converts sugars into ethyl alcohol predates recorded history.
  • It was not until the early $20\text{th}$ century that studying this conversion process formally led to the emergence of biochemistry.
• Definition of Fermentation: Fermentation is a metabolic process through which an organism converts carbohydrates—such as starch or sugars—into an alcohol or an acid.
• Historical Controversy & The Buchner Discovery:
  • Pasteur's Assertion: The French microbiologist Louis Pasteur maintained that the process of fermentation could only occur within intact, living cells.
  • The Buchner Experiment ($1899$): The brothers Buchner proved Pasteur wrong by discovering that fermentation can indeed occur in cell-free extracts.
  • Mechanism of Discovery: Yeast extract was stored in a crock containing a concentrated sugar solution added as a preservative. Overnight, the contents of the crock fermented and spilled over the laboratory bench and floor, dramatically demonstrating that fermentation proceeds in the absence of an intact, living cell.

Mechanism, Environmental Factors, and Dynamics of Fermentation

• Biological Mechanism:
  • Fermentation requires the presence of yeast, which refers to a group of microscopic fungi that perform the biochemical work of converting sugar into alcohol.
  • Grape sugars are consumed by yeast cells; the yeast feeds on the sugars, digests them via metabolic pathways, and excretes alcohol as a product.
  • No wine exists without the activity of yeast.
• Byproducts of Fermentation:
  • Alcohol: Primary liquid product of sugar metabolic digestion.
  • Carbon Dioxide ($CO_2$): An important gas produced during fermentation; crucial for the production of sparkling wines. Requires continuous monitoring.
  • Heat: Thermal energy released during metabolic conversion. Requires continuous monitoring.
• Impact of Temperature on Fermentation:
  • Cooler Fermentations: Favored for fresh, fruitier white wines and rosé.
  • Warmer Fermentations: Favored for red wines requiring higher flavor concentration and elevated tannin levels. Warmer temperatures allow greater extraction of color and tannins from grape skins, but simultaneously cause a loss of delicate, fresh, and fruity flavors.
• Termination, Interruption, and Pause Controls:
  • Natural Completion: Fermentation stops naturally once all grape sugars are consumed by the yeast.
  • Spontaneous Interruption / Cessation: Fermentation can be interrupted and cease if:
    • The ambient temperature rises above $35^\bullet\text{C}$.
    • There is a lack of essential nutrients (aside from sugar) necessary to keep the yeast alive.
  • Stuck Fermentation: A situation where fermentation stops on its own before all sugars are converted to alcohol without the winemaker's involvement. Winemakers globally avoid this by utilizing commercial yeasts rather than relying on ambient yeasts.
  • Intentional Cessation (Preserving Residual Sweetness):
    • Yeast Elimination/Inhibition: Adding sulfur dioxide ($SO_2$) or grape spirit to the fermenting wine, or employing physical filtration methods.
    • Temperature Pausing: Chilling the fermenting wine below $5^\bullet\text{C}$.
• Fermentation Vessels:
  • Stainless Steel Tanks: The modern standard in winemaking. Easy to sanitize, available in a wide range of sizes, allows maximum temperature control, and provides an anaerobic environment (no oxygen) preferred for fresh, fruity, light wine styles.
  • Wooden Barrels / Oak Vats / Casks: Wood retains heat and its micropores allow controlled oxygen entry, adding complexity to specific wine styles.
  • Concrete Vats / Concrete Eggs (Amphorae): An ancient practice growing in modern popularity because concrete naturally maintains an even temperature effectively.

Biochemical Basis of Health and Disease

• World Health Organization (WHO) Definition of Health:
  • Health is a state of complete physical, mental, and social well-being, and not merely the absence of disease and infirmity.
• Biochemical Perspective on Health:
  • From a biochemical standpoint, health means all the many thousands of intracellular and extracellular chemical reactions occurring in vivo are proceeding at rates commensurate with the organism's survival under pressure from both internal and external challenges.
  • Maintaining health requires the proper and optimal intake of dietary chemicals, including vitamins, amino acids, fatty acids, minerals, and water.
  • Nutritional intake directly impacts health states; for example, overconsumption of fatty foods can lead to atherosclerosis.
• Biochemical Etiology of Diseases:
  • Diseases are not caused exclusively by infectious organisms or environmental pollutants.
  • Pathological conditions frequently result from abnormalities in genes, structural or enzymatic proteins, and biochemical processes.
  • Disturbances in human biochemistry responsible for disease or debilitating conditions include:
    • Abnormal nutrient ingestion or absorption.
    • Enzyme deficiencies.
    • DNA-based genetic disorders.
    • Hormonal imbalances.
    • Electrolyte imbalances.

Galactosemia: Pathophysiology, Symptoms, and Management

• Definition and Metabolic Cause:
  • Galactosemia is a rare genetic metabolic disorder in which infants are born without the ability to convert the milk sugar, galactose, into glucose (the sugar form utilized by the body for energy).
  • Enzymatic Etiology: Classic galactosemia occurs when the liver enzyme galactose-1-phosphate uridyltransferase ($\text{GALT}$) is missing or non-functional.
  • Enzymatic Function: $\text{GALT}$ is responsible for breaking down galactose (a byproduct of lactose found in breast milk, cow's milk, and dairy products) into glucose.
  • Pathophysiology: When galactose cannot be converted into glucose, galactose and its intermediate byproducts—such as galactose-1-phosphate—accumulate in tissues and the bloodstream, adversely affecting multiple organ systems.
• Genetics and Mode of Inheritance:
  • Galactosemia is inherited as an autosomal recessive disorder.
  • An affected child must inherit two defective copies of the gene (one from each parent) to manifest the disease.
• Initial Clinical Presentation (Newborn Period):
  • Signs develop within the first few days to weeks of life following exposure to lactose in breast milk or baby formula:
    1. Refusal to feed / eat
    2. Spitting up or vomiting
    3. Yellowing of the skin (jaundice)
    4. Lethargy
    5. Cataracts
    6. Sepsis (systemic infection)
• Prognosis and Unmanaged Progression:
  • Infants diagnosed with galactosemia must be placed on a special lactose-free diet shortly after birth to prevent severe multiorgan failure and death.
  • If dietary intervention is initiated after the first $10$ days of life, the majority of infants with severe or classic galactosemia die from a generalized infection.
  • Infants who survive past the first month without treatment are highly likely to develop liver cirrhosis.
• Long-Term Complications and Late-Emerging Symptoms:
  • Even with early dietary treatment, developmental delays and impairments commonly emerge:
    1. Learning and Speech Disabilities:
       • General learning disabilities.
       • Delay in language acquisition.
       • Speech disorders (present in the majority of children with classic galactosemia).
       • Difficulty with fine and gross motor skills.
       • Difficulty with mathematics and reading.
    2. Neurological Impairments (affecting a minority of patients):
       • Gait and balance disturbances.
       • Ataxia (inability to coordinate voluntary movements).
       • Tremors (involuntary muscle contractions and fine motor tremors).
       • Dysmetria (inaccurate estimation of distance during muscular activity).
    3. Ovarian Failure:
       • Almost all females with severe or classic galactosemia develop Premature Ovarian Insufficiency (POI), in which ovaries stop releasing eggs earlier than normal.
       • Galactose or its metabolic byproducts are believed to exert direct toxic effects on the ovaries.
       • Results in premature loss of ovarian function resembling early menopause, leaving most affected females unable to conceive children.
• Therapeutic and Dietary Management:
  • Dietary Restrictions: The sole treatment for galactosemia is complete avoidance of foods containing lactose and galactose, managed alongside a physician and metabolic dietitian.
  • Prohibited Dairy Foods: Cow's milk, butter, yogurt, cheese, and ice cream.
  • Prohibited Ingredients (Infancy): Casein, curds, whey, and whey solids (found in foods or drugs).
  • Safe Foods: Solid foods can be introduced around $4$ to $6$ months of age. Safe foods include beef, poultry, eggs, and most types of fruits, vegetables, and grains.
  • Nutritional Supplements:
    • Daily calcium supplements are required to compensate for the complete restriction of dairy products.
    • Vitamin D supplements are recommended in addition to calcium.
  • Multidisciplinary Therapies:
    • Speech Therapy: Improves communication skills and addresses speech disorders.
    • Targeted Educational Sessions: Employed to overcome specific learning difficulties.
    • Physical Therapy: Increases mobility and muscle strength while helping the child work within functional limitations.
    • Behavioral Therapy: Focuses on managing emotional and behavioral problems, and equips families with coping strategies for the anxiety and frustration associated with following a severely restricted lifelong diet.