Cell Division and Differentiation

Cell Division

• Essential for: Growth, repair, and replacement of cells.
• Chromosomes: Carry genes with instructions for new cells and tissues. Humans have 46 chromosomes in 23 pairs.
• Cell Cycle: Includes DNA replication, mitosis, and cytokinesis.
• Mitosis: Produces two identical daughter cells from one parent cell, involves chromosome duplication and nucleus division.
• Genetic Identity: Daughter cells are genetically identical to the parent cell.
• Cell Cycle Length: Varies by organism and cell type.
• Observation: Visualizing cell division by microscopy.

Cell Differentiation

• Animal Cells: Differentiate early in life, becoming specialized and unable to change types as they mature.
• Plant Cells: Can differentiate throughout their life, especially in meristems (growth regions).
• Stem Cells (Animals): Become any needed cell type for growth and repair.
• Plant Cloning: Using mitosis for identical plant propagation from a small tissue sample.
• Meristems: Plant regions with actively dividing cells (roots and stems).
• Embryo Development: Early embryos undergo extensive mitosis for organism growth.
• Plant Growth Zones: Plant roots have division, elongation, and differentiation zones.
• Differentiation Importance: Allows cells to specialize for organism function.

Stem Cells

• Types: Stem cells can be embryonic or adult.
• Adult Stem Cells: Found in most tissues, replacing damaged cells.
• Medical Uses: Treat conditions like spinal injuries, diabetes, macular degeneration, potentially growing new organs/tissues.
• Plant Cloning: Using plant stem cells from meristems for fast and cost-effective plant reproduction.
• Ethical Concerns (Embryonic): Usage raises concerns about the source (e.g., aborted embryos).
• Alternative Sources: Stem cells from umbilical cord or amniotic fluid reduce ethical concerns.

Cell Structure and Levels of organization

• Basic Building Blocks: Cells are the fundamental units of living organisms.
• Tissues: Groups of cells with shared structure and function.
• Organs: Collections of tissues performing specific functions.
• Organ Systems: Groups of organs working together (e.g., digestive system).
• Digestive System (Overview): Muscular tube processing food from mouth to anus.
• Key Organs: Mouth, esophagus, stomach, liver, gall bladder, pancreas, small intestine, large intestine, rectum, anus.
• Digestive System Function: Exchange substances with the environment, breaking down food.
• Enzymes: Crucial for food breakdown.

Food Groups and Their Tests

• Carbohydrates: Made up of sugar units.
  • Simple sugars (one or two units): Turn Benedict's solution brick red upon heating.
  • Complex carbohydrates (long chains): Turn iodine solution blue-black.
• Lipids: Three fatty acid molecules bonded to a glycerol molecule. Detected using the ethanol test.
• Proteins: Long chains of amino acids. Detected using Biuret reagents (blue to purple).
• Food Tests: Iodine, Benedict's, Biuret, and Ethanol.

Enzymes

• Definition: Biological catalysts (proteins) that speed up metabolic reactions.
• Mechanism: Lower activation energy for reactions.
• Specificity: Each enzyme fits a specific substrate.
• Optimal Conditions: Enzymes work best at certain temperatures and pH.
• Denaturation: Enzymes lose function with extreme temperatures or pH.
• Importance: Crucial for breaking down and building molecules.
• Examples: Amylase, Lipase, Protease, Catalase.

Digestive System Detail

• Digestive Enzymes: Specialized cells in glands and digestive tract lining that catalyze food breakdown.
• Carbohydrate Digestion: Carbohydrases (e.g., amylase) break down carbohydrates into sugars.
• Protein Digestion: Proteases break down proteins into amino acids.
• Fat Digestion: Lipases break down fats into fatty acids and glycerol.
• pH Effects: Different enzymes function optimally at different pH levels.
• Stomach Acid: Maintaining low pH.
• Pancreatic Enzymes: Working best in an alkaline environment.

Historical and Safety Note

• Historical Context: Dr. William Beaumont's experiments on Alexis St Martin.
• Safety Note: Biuret solution is corrosive, ethanol is flammable and harmful.