Recording-2025-03-17T14:39:33.980Z

Microscopy Basics

• Purpose of Microscopy

  • Essential for observing cells, as they are mostly invisible to the naked eye.

  • Some visible exceptions: frog eggs and fish eggs are large enough to be seen.

• Importance of Staining

  • Most cells lack natural color; staining allows visualization.

  • Key skin cells with pigmentation include skin cells (melanocytes) and red blood cells (hemoglobin).

  • Melanin protects against ultraviolet light; hemoglobin's red color is due to iron oxidation.

  • Staining provides contrast, aiding cell visibility under a microscope.

• Staining Techniques

  • Various techniques available for staining either the cell or its background.

  • Resulting images can vary based on the stain used.

Types of Microscopes

• Light vs. Electron Microscopes

  • Light microscopes use visible light; resolution is limited.

  • Electron microscopes utilize particle beams, enabling higher resolution and detailed observations (can see individual atoms).

• Key Factors Affecting Resolution

  • Magnification increases resolution, but wavelength of light (or particles in electron microscopy) is a secondary factor.

Cell Types

• Two Major Cell Types:

  1. Prokaryotic Cells

     • Lack a nucleus and membrane-bound organelles.

     • Usually have a single circular DNA chromosome, ribosomes, and may have features like cell walls and flagella.

  2. Eukaryotic Cells

     • Contain a true nucleus enclosed by a nuclear membrane, and membrane-bound organelles.

     • Multiple linear chromosomes.

• Eukaryotic Kingdoms:

  • Animalia, Plantae, Fungi, and Protista.(Note: Protista has become less defined due to molecular evidence).

Essential Cell Features (Both Prokaryotic and Eukaryotic)

• Common Structures:

  • Plasma membrane to control entry/exit of substances.

  • Cytoplasm where cellular reactions occur.

  • Ribosomes for protein synthesis.

  • Chromosomes carrying genetic information (genes).

• Differences in Chromosome Structure:

  • Prokaryotes: Single circular chromosome.

  • Eukaryotes: Multiple linear chromosomes (humans have 23 pairs).

Function of Cell Organelles

• Nucleus:

  • Encloses eukaryotic genetic material, separates it from cytoplasm, reducing errors during DNA processes.

• Key Organelles in Eukaryotes:

  • Endoplasmic Reticulum (Rough and Smooth): Protein synthesis and lipid production.

  • Golgi Apparatus: Modifies, sorts, and packages proteins.

  • Mitochondria: Sites of aerobic respiration.

  • Lysosomes: Contain digestive enzymes for breaking down molecules.

  • Peroxisomes: Break down toxic hydrogen peroxide.

  • Flagella/Cilia: Movement (in some cells).

  • Microvilli: Increases surface area for absorption (e.g., intestinal cells).

Differences Between Animal and Plant Cells

• Plant Cells have:

  1. Cell walls

  2. Large central vacuole (for storage and maintaining turgidity)

  3. Chloroplasts (for photosynthesis)

  • Note: Plant cells still have mitochondria for cellular respiration.

• Animal Cells lack cell walls and chloroplasts.

Cell Size and Efficiency

• Surface Area to Volume Ratio:

  • Smaller cells are more efficient as volume increases faster than surface area.

  • A high surface area allows for adequate nutrient and waste exchange (homeostasis).

  • Large cells could have a lower metabolic rate or could be specialized, like egg cells that store nutrients for the developing organism.

Conclusion: Understanding Cells

• Cells have diverse structures and functions.

• Microscopy techniques (staining, magnification) are crucial for studying cells, aiding in biology and medical fields.

• Eukaryotic and prokaryotic cells exhibit fundamental differences while sharing shared properties essential for life.