Cell Biology Overview

Basic Characteristics of Cells

• Cells: smallest living units of organisms.
• Common features of all cells:
  • Cell Membrane: Separates inside of the cell from its environment.
  • Cytoplasm: 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.
• Genetic material is not contained within a nucleus.
• Typically unicellular organisms like bacteria.

Organelles and Their Functions

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

Nucleus

• Control Center: Contains DNA.
• Chromatin: Spread form of DNA inside nuclear membrane.
• Chromosomes: Condensed DNA during cell division.
• Nucleolus: Site where ribosomes are made.

Ribosomes

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

Endoplasmic Reticulum (ER)

• Rough ER: Has ribosomes.
• Smooth ER: Lacks ribosomes.
• Function: Transports materials like proteins.

Golgi Apparatus

• Receives proteins and materials from the ER.
• Customizes proteins by folding or adding lipids/carbohydrates.

Vacuoles

• Storage sacs for materials.
• Central Vacuole: Stores water in plant cells.

Lysosomes

• Break down cell parts with enzymes.
• Act as garbage collectors.

Mitochondria

• Powerhouse: Produces ATP through cellular respiration.
• Present in both plant and animal cells.

Cytoskeleton

• Structure: Maintains cell shape.
• Components: Microfilaments (protein threads) and microtubules (hollow tubes).

Chloroplasts

• In photoautotrophic organisms like plants.
• Responsible for photosynthesis.
• Contains chlorophyll, a green pigment.

Unique Cell Structures

• Cell Wall: Provides shape and protection; present in plant cells, absent in animal cells.
• Cilia: Hair-like projections in respiratory tract cells, help trap particles.
• Flagella: Tail-like structures aiding in cell movement; present in some bacteria and sperm cells.

Summary

• Eukaryotic Cells: Have nucleus and organelles, found in plants and animals.
• Prokaryotic Cells: Unicellular, no nucleus, found in bacteria.
• All cells have a cell membrane, cytoplasm, and genetic material.
• Both plant and animal cells have mitochondria, but only plant cells have chloroplasts.