Introduction to Cells

Basic Characteristics of All Cells

Cells: smallest living units of an organism
Common features of all cells:
- Cell membrane: separates internal environment from external
- Cytoplasm: jelly-like fluid inside the cell
- DNA: genetic material

Eukaryotic Cells
- Have organelles including the nucleus
- Examples: Plant and animal cells
Prokaryotic Cells
- No nucleus or membrane-enclosed organelles
- Genetic material not in nucleus
- Examples: Unicellular organisms like bacteria

Nucleus
- Control center containing DNA
- Chromatin: spread-out form of DNA inside the nuclear membrane
- Chromosomes: condensed DNA structures during cell division
- Nucleolus: produces ribosomes
Ribosomes
- Synthesize proteins
- Located freely in cytoplasm or on the endoplasmic reticulum (ER)
Endoplasmic Reticulum (ER)
- Passageway for transporting materials
- Rough ER: has ribosomes, involved in protein synthesis
- Smooth ER: no ribosomes
Golgi Apparatus (Golgi Body)
- Modifies, sorts, and packages proteins
Vacuoles
- Storage sacs
- Central Vacuole (Plant Cells): stores water
Lysosomes (Animal Cells)
- Contain enzymes to break down waste
Mitochondria
- Powerhouse of the cell
- Generates ATP through cellular respiration
Cytoskeleton
- Maintains cell shape
- Composed of microfilaments and microtubules
Chloroplasts (Plant Cells)
- Site of photosynthesis
- Contains chlorophyll
Cell Wall (Plant Cells)
- Provides shape, support, and protection

Cilia
- Microscopic, hair-like projections
- Help trap inhaled particles and expel them
- Found in respiratory tract cells
Flagella
- Tail-like structure aiding in movement
- Found in some bacteria and human sperm cells

Eukaryotic Cells: Plant and animal cells with a nucleus and organelles
Prokaryotic Cells: Unicellular organisms without a nucleus
Common features of all cells: cell membrane, cytoplasm, and DNA
Both plant and animal cells have mitochondria; only plant cells have chloroplasts