Lecture Notes: Sales Structures and Processes

Overview

• Discussion on sales structures and processes as part of a core unit.
• Theme: Unity and Diversity.

Common Features of Living Cells

• Plasma Membrane: Semi-permeable layer made of phospholipids.
• Cytoplasm: Watery solution where metabolic reactions occur.
• DNA: Genetic material for all living organisms.
  • Note: Viruses may use RNA, are not considered living.

Classification of Cells

• Prokaryotic Cells

  • Simplistic, smaller (<10 micrometers), evolved first, ubiquitous.
  • Structure:
    • Lack a nucleus (DNA not membrane-bound).
    • Cell wall present, non-compartmentalized.
    • Ribosomes: 70S ribosomes.
    • Naked DNA (not associated with histone proteins).

• Eukaryotic Cells

  • Complex structure, compartmentalized.
  • Structure:
    • May have a cell wall (plants, fungi only).
    • Nucleus: Double membrane, contains DNA associated with histone proteins.
    • Ribosomes: 80S ribosomes, larger.
    • Presence of mitochondria in all eukaryotes.
    • Some may have other organelles like chloroplasts.

Functions of Life

• Metabolism: Enzyme-catalyzed reactions.
• Nutrition: Acquiring necessary nutrients.
• Excretion: Removal of waste.
• Growth and Reproduction: Increase in size/number of cells.
• Homeostasis: Regulation of internal conditions.
• Sensitivity: Response to environmental stimuli.

Unicellular vs. Multicellular Organisms

• Unicellular Organisms: Single cell performs all life functions (e.g., Paramecium, Chlamydomonas).
• Multicellular Organisms: Specialized cells perform distinct functions.

Examples of Unicellular Organisms

• Paramecium:

  • Cilia for movement.
  • Contractile vacuole for homeostasis.
  • Food vacuoles for nutrition.

• Chlamydomonas:

  • Flagella for movement.
  • Chloroplast for photosynthesis.
  • Contractile vacuole and eye spot for light detection.

Unity and Diversity in Cells

• Plastids: Found in plants only.
• Cell Walls: Present in fungi and plants.
• Vacuoles: Large in plants and fungi, small/absent in animals.
• Centrioles: Present in animal cells.

Exceptions to Cell Theory

• Red Blood Cells: Lack nucleus, no DNA.
• Phloem Sieve Tube Elements: Cytoplasm/nucleus removed, rely on companion cells.
• Skeletal Muscle Cells: Multinucleated.
• Aseptate Fungi: Lack division, no separate cell boundaries.

Identifying Cells in Micrographs

• Prokaryotic Cells: Rod, round, or spiral shape, less than 10 micrometers, naked DNA.
• Plant Cells: Geometrical shape, large central vacuole, presence of chloroplasts.
• Animal Cells: Varied shapes, absence of cell wall, no large vacuole or chloroplasts.