Lecture Notes on An Enjoyable Day in the Science Lab

Memorable Day in Science Class

• Reminiscing on fun days in science classes:
  • Dissecting an earthworm.
  • Analyzing owl pellet (feathers, fur, bones).
  • Testing osmosis using eggs.
  • Observing fruit flies in genetic experiments.
• Unforgettable lesson in 9th grade:
  • Teacher brought pond water.
  • Observed a single drop on a slide.
  • Saw a single-celled amoeba.
• Impact of this lesson:
  • Fascination with the concept of life at microscopic levels.
  • Introduction to the amazing aspects of cell theory.

Modern Cell Theory

• Three main tenets:
  1. Cell is the smallest unit in all organisms.
  2. All living organisms are composed of one or more cells:
  • Amoeba: Single-celled organism (unicellular).
  • Humans: Multi-celled organisms (multicellular).
  3. All cells arise from pre-existing cells.

Inside the Cell

General Features

• Cells contain their own mini-world:
  • Genetic material.
  • Ability to divide.
  • Organelles performing various functions.

Types of Cells

• Prokaryotic Cells:
  • Include bacteria and archaea.
• Eukaryotic Cells:
  • Include plants, animals, fungi, protists.

Similarities Between Prokaryotic and Eukaryotic Cells

• Both have:
  • Genetic material.
  • Cytoplasm.
  • Ribosomes: Small organelles that manufacture proteins.
  • Cell membrane: Regulates the movement of substances.

Differences Between Prokaryotic and Eukaryotic Cells

• Prokaryotes:
  • Lack a nucleus; genetic material in the cytoplasm.
  • Lack membrane-bound organelles.
• Eukaryotes:
  • Have a nucleus containing genetic material.
  • Have membrane-bound organelles like mitochondria, Golgi apparatus.

Tour Inside the Eukaryotic Cell

• Start by crossing the cell membrane (plasma membrane):
  • Selectively permeable.
  • Maintains internal environment stability.
• Inside the cell is the cytoplasm:
  • Gel-like substance housing organelles.
  • Present in both prokaryotic and eukaryotic cells.
• Organelles in the cytoplasm are underpinned by the cytoskeleton:
  • Provides structure and support.
  • Aids in cellular movement.
• Ribosomes:
  • Not membrane-bound.
  • Found in both cell types.
  • Essential for protein synthesis.
  • Can be free-floating or bound to the rough endoplasmic reticulum (RER).

Membrane-Bound Organelles in Eukaryotic Cells

• Nucleus:
  • Contains genetic material (DNA).
  • Controls cell activities.
  • Houses the nucleolus: Site of ribosome production.
• Endoplasmic Reticulum (ER):
  • Connected to the nuclear envelope.
  • Rough ER (RER): Studded with ribosomes, involved in protein synthesis and transport.
  • Smooth ER (SER): Lacks ribosomes, involved in detoxification and lipid synthesis.
• Golgi Apparatus:
  • Packaging and distributing center of the cell.
  • Modifies proteins and lipids received from the ER.
  • Targets molecules to their destinations.

Energy and Additional Organelles

• Mitochondria:
  • Powerhouse of the cell.
  • Produces ATP via cellular respiration.
  • Utilizes glucose and oxygen.
• Vacuoles:
  • Storage organelles.
  • Large central vacuole in plant cells; multiple small vacuoles in animal cells.
• Chloroplasts (in plant cells):
  • Involved in photosynthesis.
  • Contain chlorophyll, giving them a green color.
• Cell Wall (in plant cells):
  • Provides an additional layer of protection.
  • Maintains cell shape.

Protein Production and Export in Cells

• Protein Synthesis:
  • Directed by genetic instructions (DNA) in the nucleus.
  • Carried out by ribosomes, possibly attached to RER.
• Protein Transport:
  • RER sends proteins in vesicles to the Golgi apparatus.
  • Golgi modifies and packages proteins for export.
  • Vesicles transport proteins to the plasma membrane for release from the cell.

Conclusion

• Understanding cell structure and function is fundamental.
• Many fascinating organelles like mitochondria and chloroplasts weren’t covered here.