Cell Biology Lecture Notes

Basic Characteristics of Cells

Cells: Smallest living units of an organism.
Common features of all cells:
- Cell Membrane: Separates cell interior from the environment.
- Cytoplasm: Jelly-like fluid inside the cell.
- DNA: Genetic material of the cell.

Eukaryotic Cells
- Have organelles, including a nucleus.
- More advanced and complex; found in plants and animals.
Prokaryotic Cells
- No nucleus or membrane-enclosed organelles.
- Genetic material exists freely; unicellular organisms like bacteria.

Organelles: Specialized cell parts with unique functions.
- Nucleus: Control center containing DNA.
  - DNA dictates cell function and behavior.
  - Chromatin: Spread-out form of DNA inside nuclear membrane.
  - Chromosomes: Condensed DNA during cell division.
  - Nucleolus: Site where ribosomes are made.
- Ribosomes: Synthesize proteins.
  - Can be free in the cytoplasm or attached to the endoplasmic reticulum (ER).
- Endoplasmic Reticulum (ER):
  - Rough ER: Has ribosomes; involved in protein synthesis.
  - Smooth ER: Lacks ribosomes; involved in lipid synthesis.
- Golgi Apparatus: Processes and packages proteins.
  - Modifies proteins into usable forms with added lipids or carbohydrates.
- Vacuoles: Storage sacs for materials.
  - Central vacuole in plant cells stores water.
- Lysosomes: Break down cellular debris with enzymes.
- Mitochondria: Powerhouse of the cell, produces energy (ATP) via cellular respiration.
- Chloroplasts: Site of photosynthesis in plant cells, contains chlorophyll.
- Cytoskeleton: Maintains cell shape, includes microfilaments and microtubules.

Cell Wall: Provides shape, support, and protection in plant cells (absent in animal cells).
Cilia: Hair-like structures in respiratory tract cells, trap particles and assist movement.
Flagella: Tail-like structures for cell movement, present in some bacteria and sperm cells.

Eukaryotic vs. Prokaryotic Cells:
- Eukaryotic: Plants and animals, nucleus present.
- Prokaryotic: Unicellular, no nucleus.
Commonality: All cells have cell membrane, cytoplasm, and DNA.
Plant cells uniquely have chloroplasts; both plant and animal cells have mitochondria.