Cell Biology Lecture Notes

Basic Characteristics of Cells

• Cells are the smallest living units in organisms.
• All cells share three common components:
  • Cell Membrane: Separates the inside of the cell from the external environment.
  • Cytoplasm: A jelly-like fluid inside the cell.
  • DNA: Genetic material of the cell.

Categories of Cells

• Eukaryotic Cells
  • Have organelles, including a nucleus.
  • Found in complex organisms like plants and animals.
• Prokaryotic Cells
  • Lack a nucleus or membrane-enclosed organelles.
  • Unicellular organisms, such as bacteria.

Organelles and Their Functions

• Organelles: Specialized cell parts, each with unique functions.

Nucleus

• Acts as the control center of the cell.
• Contains DNA, which dictates cell activities.
• Chromatin: Spread-out form of DNA.
• Chromosomes: Condensed DNA structures during cell division.
• Nucleolus: Produces ribosomes.

Ribosomes

• Synthesize proteins.
• Can be free in the cytoplasm or attached to the endoplasmic reticulum (ER).

Endoplasmic Reticulum (ER)

• Rough ER: Has ribosomes; transports proteins.
• Smooth ER: Lacks ribosomes.
• Transports materials in vesicles to the Golgi apparatus.

Golgi Apparatus

• Customizes proteins by folding and adding other materials (e.g., lipids, carbohydrates).

Vacuoles

• Sac-like structures storing various materials.
• Central vacuole in plant cells stores water.

Lysosomes

• Contain enzymes to break down cellular debris.

Mitochondria

• "Powerhouse" of the cell, produces ATP through cellular respiration.
• Present in both plant and animal cells.

Cytoskeleton

• Maintains cell shape.
• Includes microfilaments and microtubules.

Chloroplasts (Plant Cells Only)

• Site of photosynthesis.
• Contains chlorophyll, giving green color.

Cell Wall (Plant Cells Only)

• Provides shape, support, and protection.

Unique Cell Structures

• Cilia: Hair-like projections in the respiratory tract, trap particles.
• Flagella: Tail-like structures aiding cell movement (e.g., sperm cells).

Summary

• Eukaryotic Cells: Have nucleus and membrane-enclosed organelles.
• Prokaryotic Cells: Lack nucleus, unicellular.
• All cells contain cell membrane, cytoplasm, and genetic material.
• Both plant and animal cells have mitochondria, but only plant cells have chloroplasts.