Biology Chapter: The Unit of Life

Basic structural and functional unit of all living organisms.
Cells can exist as unicellular (single-celled) or multicellular (many-celled) organisms.

Prokaryotic Cells:
- Lack a defined nucleus.
- Typically smaller and simpler (e.g., bacteria and archaea).
- Genetic material is located in a nucleoid region.
Eukaryotic Cells:
- Have a defined nucleus and membrane-bound organelles.
- Generally larger and more complex (e.g., plant, animal, fungi, and protist cells).
- Organelles include mitochondria, endoplasmic reticulum, Golgi apparatus, etc.

Cell Membrane:
- Phospholipid bilayer that controls the movement of substances in and out of the cell.
Cytoplasm:
- Gel-like substance where cellular processes occur and organelles are suspended.
Nucleus:
- Contains genetic material (DNA); controls cell activities.
Organelles:
- Mitochondria: Powerhouse of the cell; site of ATP production.
- Chloroplasts (in plants): Site of photosynthesis.
- Ribosomes: Synthesize proteins.
- Endoplasmic Reticulum:
  - Rough ER: Has ribosomes; involved in protein synthesis and processing.
  - Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion.

Mitosis:
- Process of cell division resulting in two identical daughter cells.
- Phases: Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.
Meiosis:
- Production of gametes (sperms and eggs); results in four genetically diverse cells.
- Involves two rounds of division.

Metabolism:
- Sum of all chemical reactions within a cell, including catabolism (breaking down molecules) and anabolism (building up molecules).
Cell Communication:
- Cells communicate through signaling molecules; receptors on target cells receive signals.
Transport Mechanisms:
- Passive Transport: Movement across the cell membrane without energy (e.g., diffusion, osmosis).
- Active Transport: Movement against a concentration gradient requiring energy (e.g., sodium-potassium pump).

Understanding cells is crucial for studies in genetics, microbiology, physiology, and health sciences.
Discovery of the cell theory: all living organisms are composed of cells, which are the basic units of life.

The fundamental building block of all living organisms.
Exists in two forms: unicellular (single-celled) and multicellular (many-celled).

Prokaryotic Cells:
- Lack a defined nucleus.
- Smaller and simpler than eukaryotic cells.
- Examples include bacteria and archaea.
- Genetic material exists within a nucleoid region.
Eukaryotic Cells:
- Contain a defined nucleus and membrane-bound organelles.
- Typically larger and more complex than prokaryotic cells.
- Examples include plant, animal, fungi, and protist cells.
- Specialized organelles, such as mitochondria, endoplasmic reticulum, and Golgi apparatus, perform different functions.

Cell Membrane:
- Phospholipid bilayer that regulates the passage of substances in and out of the cell.
Cytoplasm:
- Gel-like substance where cellular processes occur and organelles are suspended.
Nucleus:
- Contains the cell's genetic material (DNA).
- Controls cellular activities.
Organelles:
- Mitochondria:
  - Powerhouse of the cell.
  - Site of ATP (energy) production.
- Chloroplasts (plants):
  - Site of photosynthesis.
  - Responsible for converting sunlight into energy.
- Ribosomes:
  - Synthesize proteins.
  - Essential for cellular function.
- Endoplasmic Reticulum:
  - Rough ER: Contains ribosomes.
    - Involved in protein synthesis and processing.
  - Smooth ER: Lacks ribosomes.
    - Involved in lipid synthesis and detoxification.
- Golgi Apparatus:
  - Modifies, sorts, and packages proteins and lipids for secretion.

Mitosis:
- Process of cell division that produces two identical daughter cells.
- Four stages:
  - Prophase
  - Metaphase
  - Anaphase
  - Telophase
- Cytokinesis completes the division.
Meiosis:
- Production of gametes (sperm and egg cells), resulting in four genetically unique cells.
- Two rounds of division occur.

Metabolism:
- Sum of all chemical reactions within a cell.
  - Catabolism: Breaking down molecules.
  - Anabolism: Building up molecules.
Cell Communication:
- Cells communicate through signaling molecules.
- Receptors on target cells receive signals.
Transport Mechanisms:
- Passive Transport:
  - Movement of substances across the cell membrane without requiring energy.
  - Examples include diffusion and osmosis.
- Active Transport:
  - Movement against a concentration gradient, requiring energy.
  - Example: Sodium-potassium pump.

Understanding cells is fundamental to many biological fields.
- Genetics
- Microbiology
- Physiology
- Health Sciences
The discovery of the cell theory revolutionized biology.
- All living organisms are composed of cells.
- Cells are the basic functional unit of life.