Cell Biology Study Notes

Cell Theory
- All living organisms are composed of cells.
- The cell is the basic unit of life.
- All cells arise from pre-existing cells.
Types of Cells
- Prokaryotic Cells
  - Lack a nucleus and membrane-bound organelles.
  - Examples: Bacteria and Archaea.
  - Simple structure, generally smaller.
- Eukaryotic Cells
  - Contain a nucleus and organelles.
  - Examples: Animal cells, plant cells, fungi, and protists.
  - More complex structure, generally larger.
Cell Structure
- Plasma Membrane
  - Semi-permeable barrier controlling the entry and exit of substances.
  - Composed of a phospholipid bilayer with embedded proteins.
- Nucleus
  - Contains genetic material (DNA).
  - Site of transcription (RNA synthesis).
- Cytoplasm
  - Jelly-like fluid inside the cell where organelles are suspended.
  - Site of various metabolic processes.
- Organelles
  - Mitochondria: Powerhouse of the cell, site of ATP production via cellular respiration.
  - Ribosomes: Sites of protein synthesis.
  - Endoplasmic Reticulum (ER):
    - Rough ER: Studded with ribosomes; involved in protein synthesis and modification.
    - Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.
  - Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use in the cell.
  - Lysosomes: Contain digestive enzymes for breaking down waste.
  - Chloroplasts: (in plant cells) Site of photosynthesis, converting light energy into chemical energy.
Cell Division
- Mitosis: Process of cell division that results in two identical daughter cells for growth and repair.
- Meiosis: Specialized form of cell division for the production of gametes (sperm and eggs), leading to genetic diversity.
Cell Communication
- Cells communicate through signaling molecules and receptors.
- Types of signaling:
  - Autocrine (self-signaling)
  - Paracrine (signaling to nearby cells)
  - Endocrine (hormones affecting distant cells)
Cell Transport Mechanisms
- Passive Transport
  - Movement of substances across the membrane without energy (e.g., diffusion, osmosis).
- Active Transport
  - Movement against the concentration gradient, requiring energy (e.g., sodium-potassium pump).
Cell Metabolism
- Anabolism: Constructive metabolism; building up molecules (e.g., protein synthesis).
- Catabolism: Destructive metabolism; breaking down molecules (e.g., glucose breakdown for energy).
Stem Cells
- Undifferentiated cells with the potential to develop into different cell types.
- Types:
  - Embryonic stem cells: Pluripotent (can become any cell type)
  - Adult stem cells: Generally multipotent (limited differentiation potential).

Cell Theory

All living organisms are composed of cells.
Cells are the basic unit of life.
All cells arise from pre-existing cells.

Types of Cells

Prokaryotic Cells
- Lack a nucleus and membrane-bound organelles
- Examples include bacteria and archaea
- Generally smaller and simpler in structure
Eukaryotic Cells
- Contain a nucleus and membrane-bound organelles
- Examples include animal cells, plant cells, fungi, and protists.
- More complex structure and generally larger

Cell Structure

Plasma Membrane
- Acts as a semi-permeable barrier that controls the entry and exit of substances.
- Composed of a phospholipid bilayer with embedded proteins.
Nucleus
- Contains genetic material (DNA)
- Site of transcription (RNA synthesis)
Cytoplasm
- Jelly-like fluid inside the cell where organelles are suspended.
- Site of various metabolic processes.

Organelles

Mitochondria
- Powerhouse of the cell
- Site of ATP production through cellular respiration
Ribosomes
- Sites of protein synthesis
Endoplasmic Reticulum (ER)
- Rough ER: Studded with ribosomes, involved in protein synthesis and modification
- Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification
Golgi Apparatus
- Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
Lysosomes
- Contain digestive enzymes for breaking down waste.
Chloroplasts (present in plant cells)
- Site of photosynthesis, converting light energy into chemical energy

Cell Division

Mitosis
- Process of cell division that results in two identical daughter cells.
- Used for growth and repair.
Meiosis
- Specialized form of cell division for the production of gametes (sperm and eggs).
- Leads to genetic diversity.

Cell Communication

Cells communicate through signaling molecules and receptors.
Types of signaling:
- Autocrine: Self-signaling
- Paracrine: Signaling to nearby cells
- Endocrine: Hormones affecting distant cells (through the bloodstream)

Cell Transport Mechanisms

Passive Transport
- Movement of substances across the membrane without requiring energy, such as diffusion and osmosis.
Active Transport
- Movement against the concentration gradient, requiring energy. Example: Sodium-potassium pump.

Cell Metabolism

Anabolism: Constructive metabolism; building up molecules (example: protein synthesis).
Catabolism: Destructive metabolism; breaking down molecules (example: glucose breakdown for energy).

Stem Cells

Undifferentiated cells with the potential to develop into different cell types.
Types of Stem Cells:
- Embryonic Stem Cells: Pluripotent, meaning they can become any cell type
- Adult Stem Cells: Generally multipotent; limited differentiation potential, meaning they can become a more limited range of cell types.