Biochemistry: Acids, Bases, Salts, and Macromolecules

Acid-Base Balance and Buffers

• Neutralizing an acid requires lowering the hydrogen ion (H+) concentration to raise the pH.
• Buffers maintain a stable pH.

Salts and Macromolecules

• Salts readily dissociate into ions in water, crucial for life processes (e.g., electrolytes conduct electricity).
• Macromolecules include proteins, carbohydrates, lipids, and nucleotides.

Carbohydrates

• Carbohydrates include sugars and starches, categorized by size.
• Monosaccharides are simple sugars.
• Disaccharides are two simple sugars linked together.
• Polysaccharides are long chains of linked monosaccharides (e.g., glycogen).

Lipids

• Three main lipid types exist in the human body:
  • Neutral fats (triglycerides): Stored fat.
  • Phospholipids: Form cellular membranes (hydrophobic and hydrophilic parts).
  • Steroids: Lipid-based hormones, cholesterol, bile salts, and vitamin D.
• Saturated fats are solid at room temperature, with carbons saturated by hydrogen and zero double bonds.

Proteins

• Proteins are chains of amino acids (peptides), forming over half of the body's organic matter.
• They function as enzymes, hormones, and antibodies.
• Denaturation occurs when a protein's shape changes due to environmental changes (temperature, pH, ion concentration), making it non-functional.

Nucleotides

• DNA provides the blueprint for life and protein synthesis.
• Nucleotide bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T).
• RNA acts as an intermediary between DNA and protein.
• Nucleotide bases: Adenine (A), Guanine (G), Cytosine (C), Uracil (U).
• Adenosine triphosphate (ATP) is the chemical energy source for cells, releasing energy when high-energy phosphate bonds break.

Water

• Water is vital for organisms due to its properties:
  • Excellent solvent
  • Participates in chemical reactions
  • Absorbs and releases heat slowly
  • Requires significant heat to change from liquid to gas
  • Acts as a lubricant

Digestive System (GI Tract)

• The GI tract processes ingested food through ingestion, mechanical processing, digestion, secretion, absorption, and excretion (defecation).
• Organs and their functions:
  • Oral Cavity: Mechanical processing.
  • Salivary Glands: Produce saliva (parotid, submandibular, sublingual). Mumps affects the parotid glands.
  • Teeth: Canines tear food.
  • Pharynx: Passageway for digestive and respiratory systems.
  • Epiglottis: Covers the larynx during swallowing.
  • Esophagus: Moves food via peristalsis (bolus); lower esophageal sphincter.
  • Stomach: J-shaped organ; protein digestion begins (pepsinogen/pepsin, hydrochloric acid, mucus); chyme. Pyloric sphincter.
  • Small Intestine: (Duodenum, Jejunum, Ileum); primary site of nutrient absorption; Ileocecal valve.
  • Pancreas: Exocrine organ producing digestive enzymes (lipases, carbohydrases, proteinases) and buffers; endocrine organ producing insulin and glucagon. Pancreatic Duct.
  • Liver: (Hepatocytes) Largest organ; produces bile; common hepatic duct, common bile duct, cystic duct, (Jaundice, Hepatitis, Yellow Fever).
  • Gallbladder: Stores and concentrates bile for fat breakdown (bile emulsifies fats).
  • Large Intestine: Absorption of water, Vitamin K synthesis; composed of cecum, appendix, colon (ascending, transverse, descending, sigmoid), rectum, anus.

Absorption of Nutrients

• Carbohydrates: Basic units are simple sugars (monosaccharides). Digestive enzymes (carbohydrases) break bonds; digestion begins in the mouth (salivary amylase), continues in the duodenum (pancreatic amylase); absorbed into capillaries.

  • Lactose intolerance occurs without sufficient lactase.

• Proteins: Basic units are amino acids. Proteinases break protein bonds, chewing increases surface area and stomach acid activates pepsin (protein-splitting enzyme); digested in the duodenum and absorbed into capillaries.

• Lipids (Triglycerides): Basic units are fatty acids and glycerol. Lipases separate fatty acids; bile emulsifies fats in the duodenum; pancreatic lipase further breaks triglycerides; absorbed via lymphatics (lacteals).

• Water and Ions: Absorbed primarily through osmosis, electrolytes like sodium chloride (promote water absorption).

• Vitamins: Water-soluble (C, B vitamins) and fat-soluble (A, D, E, K) vitamins absorbed differently.

Nutrient Transport and the Hepatic Portal System

• The liver monitors and adjusts circulating nutrient levels.
• Liver stores nutrients, produces bile, maintains normal blood glucose, amino acid, and fatty acid levels, and converts carbohydrates to lipids.

Metabolism and Nutrition

• Redox reactions are central to metabolism (oxidation=loss of electrons, reduction=gain of electrons).
• Metabolism involves catabolism (breaking down large molecules) and anabolism (building new molecules).
• Nutrient absorption is nearly complete 4 hours post-meal as blood glucose falls.
• Glucagon, lipolysis, and gluconeogenesis maintain blood glucose.
• Basal Metabolic Rate (BMR) is the rate of energy use at rest.
• Metabolism produces heat.

Protein Metabolism

• Essential amino acids must be consumed; nonessential are produced by the body.
• Protein breakdown occurs in the liver.

Lipid Metabolism

• Triglycerides (glycerol and 3 fatty acids). Skeletal muscle shifts from carbohydrate to lipid metabolism during rest.
• Essential fatty acids like linoleic, arachidonic, and linolenic acids are crucial for prostaglandins & cell membranes.

Carbohydrate Metabolism

• Cellular respiration: Glucose + oxygen → carbon dioxide + water + ATP
• Glucose converted to glycogen (liver and muscles) for storage.

Vitamins

• Vitamins are organic compounds required for metabolic functions.
• Antioxidants (A, E, C) protect cells.
• Vitamin D precursor formed in skin upon UV light exposure.
• Fat-soluble (A, D, E, K) vitamins stored in fat tissue.
• Water-soluble vitamins excreted readily.

Minerals

• Minerals like calcium (for bones) and sodium (for water absorption) are essential.
• Osteoporosis and hypertension are linked to mineral imbalances.

Body Temperature Regulation

• The hypothalamus controls body temperature. Heat loss promotion through blood vessel dilation, sweating, and increased breathing. Heat loss restriction through decreased skin blood flow. Heat production promotion through shivering and hormone release, increasing metabolic activity.

Eating Disorders

• Obesity involves more than 20% excess weight.
• Bulimia and anorexia nervosa are characterized by distorted body image, restrictive diets, and/or exercise and purging behaviours.

Cellular Respiration

• Cellular respiration breaks down glucose into energy (ATP), in 4 steps:

1. Glycolysis
2. Transition Reaction
3. Krebs Cycle
4. Electron Transport Chain

Glucose Metabolism

• Glucose-6-phosphate involved in glucose release, glycogen synthesis, and glycolysis.
• Pyruvic acid used for lactic acid, alanine production, and gluconeogenesis.
• Acetyl CoA used in the Krebs cycle and lipid synthesis.
• Glycogenesis, glycogenolysis, and gluconeogenesis are key processes in glucose metabolism.

Lipid Metabolism

• Lipogenesis (synthesis of triglycerides) and lipolysis (breakdown of triglycerides) are associated with energy levels.
• Ketones (from fatty acid catabolism) are a sign of fat metabolism.

Liver Disorders

• Cirrhosis, hepatitis, jaundice, are liver related diseases. Appendicitis, esophageal cancer, and peptic ulcers can also affect the digestive system.

Explore acid-base balance, the role of buffers, and the properties of salts in biological systems. Learn about the structure and function of macromolecules including carbohydrates and lipids. Understand the different types of carbohydrates and lipids found in the human body.