Cell Biology Overview

Cell Biology

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.
  - Genetic material is in a nucleoid region.
- Eukaryotic Cells
  - Have a nucleus and membrane-bound organelles.
  - Examples: Plant cells, animal cells, fungi, and protists.
  - More complex structure.
Cell Structure
- Nucleus
  - Contains genetic material (DNA).
  - Controls cell activities.
- Cell Membrane
  - Phospholipid bilayer that regulates the movement of substances in and out of the cell.
  - Contains proteins for transport and communication.
- Cytoplasm
  - Jelly-like fluid that fills the cell.
  - Site of many metabolic processes.
- Organelles
  - Mitochondria: Powerhouse of the cell; site of ATP production.
  - Ribosomes: Protein synthesis.
  - Endoplasmic Reticulum (ER):
    - Rough ER: Studded with ribosomes; synthesizes proteins.
    - Smooth ER: Lacks ribosomes; synthesizes lipids.
  - Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
  - Lysosomes: Contain digestive enzymes for waste breakdown.
  - Chloroplasts (in plants): Site of photosynthesis.
Cell Division
- Mitosis: Process of cell division resulting in two identical daughter cells.
  - Phases: Prophase, Metaphase, Anaphase, Telophase.
- Meiosis: Specialized form of cell division that produces gametes.
  - Results in four non-identical daughter cells with half the chromosome number.
Cell Communication
- Cells communicate through signaling molecules.
- Types of signaling:
  - Autocrine: Signals act on the same cell.
  - Paracrine: Signals act on nearby cells.
  - Endocrine: Hormones travel through the bloodstream to distant cells.
Cell Transport Mechanisms
- Passive Transport: Movement of molecules without energy expenditure (e.g., diffusion, osmosis).
- Active Transport: Movement of molecules against a concentration gradient, requiring energy (e.g., sodium-potassium pump).
Cell Metabolism
- Catabolism: Breakdown of molecules to release energy.
- Anabolism: Synthesis of complex molecules from simpler ones, requiring energy.
Cell Cycle Regulation
- Controlled by checkpoints to ensure proper division and function.
- Key proteins involved: Cyclins and cyclin-dependent kinases (CDKs).
Stem Cells
- Undifferentiated cells with the potential to develop into various cell types.
- Types of stem cells:
  - Embryonic stem cells: Pluripotent; can become any cell type.
  - Adult stem cells: Multipotent; limited to specific cell types.

These notes encapsulate the essential concepts within cell biology, providing a foundational understanding of the subject.

Cell Theory

All living organisms are made of cells; the cell is the fundamental unit of life.
Cells originate only from pre-existing cells.

Types of Cells

Prokaryotic Cells
- Do not have a nucleus or membrane-bound organelles.
- Examples include bacteria and archaea.
- Genetic material located in a nucleoid region.
Eukaryotic Cells
- Contain a nucleus and membrane-bound organelles.
- Examples include plant cells, animal cells, fungi, and protists.
- Exhibit a more complex structure compared to prokaryotic cells.

Cell Structure

Nucleus
- Stores genetic material (DNA) and governs cell activities.
Cell Membrane
- Composed of a phospholipid bilayer; regulates substance movement in/out.
- Contains proteins that facilitate transport and communication.
Cytoplasm
- Jelly-like substance filling the cell; where many metabolic activities occur.
Organelles
- Mitochondria: Known as the powerhouse of the cell; key site for ATP production.
- Ribosomes: Responsible for synthesizing proteins.
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes; primarily synthesizes proteins.
  - Smooth ER: Lacks ribosomes; involved in lipid synthesis.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for transport.
- Lysosomes: Contain digestive enzymes for breaking down waste.
- Chloroplasts: Found in plant cells; site for photosynthesis.

Cell Division

Mitosis: Cell division resulting in two identical daughter cells; consists of prophase, metaphase, anaphase, and telophase.
Meiosis: Specialized division creating gametes; results in four non-identical daughter cells, each with half the chromosome count.

Cell Communication

Cells interact using signaling molecules.
Types of Signaling:
- Autocrine: Signals affect the originating cell.
- Paracrine: Signals influence adjacent cells.
- Endocrine: Hormones circulate in the bloodstream to target distant cells.

Cell Transport Mechanisms

Passive Transport: Movement of molecules without energy (e.g., diffusion, osmosis).
Active Transport: Requires energy to move molecules against their concentration gradient (e.g., sodium-potassium pump).

Cell Metabolism

Catabolism: Process of breaking down molecules to release energy.
Anabolism: Building complex molecules from simpler ones, which requires energy input.

Cell Cycle Regulation

Cell division is regulated through checkpoints ensuring proper timing and functionality.
Key regulatory proteins include cyclins and cyclin-dependent kinases (CDKs).

Stem Cells

Undifferentiated cells capable of developing into various cell types.
Types of Stem Cells:
- Embryonic Stem Cells: Pluripotent; can differentiate into any cell type.
- Adult Stem Cells: Multipotent; have limited differentiation potential, usually to specific lineages.