Cell theory

Cell
Definition: Cells are the basic structural and functional units of all living organisms.

1. Cell Theory
All living organisms are composed of one or more cells.
The cell is the basic unit of life.
All cells arise from pre-existing cells.

2. Types of Cells
Prokaryotic Cells:
Lack a nucleus and membrane-bound organelles.
Example: Bacteria and Archaea.
Eukaryotic Cells:
Have a nucleus and membrane-bound organelles.
Examples: Animal cells, plant cells, fungal cells, and protists.

3. Cell Structure
Cell Membrane:
A phospholipid bilayer that controls the movement of substances in and out of the cell.
Cytoplasm:
The gel-like substance inside the cell where organelles are suspended.
Nucleus:
Contains genetic material (DNA) and controls cellular activities.
Organelles:
Mitochondria: Produce energy (ATP) through cellular respiration.
Ribosomes: Synthesize proteins.
Endoplasmic Reticulum (ER):
Rough ER has ribosomes and synthesizes proteins.
Smooth ER synthesizes lipids and detoxifies substances.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
Lysosomes: Contain digestive enzymes for breaking down waste materials.
Chloroplasts (in plant cells): Conduct photosynthesis to convert light energy into chemical energy.

4. Cell Functions
Metabolism: All biochemical processes occurring within a cell.
Reproduction: Cells can divide through processes like mitosis (for growth and repair) or meiosis (for sexual reproduction).
Communication: Cells communicate with each other through signaling molecules and receptors.

5. Cell Division
Mitosis: Process by which a eukaryotic cell divides to produce two identical daughter cells.
Meiosis: A specialized form of cell division that produces gametes (sperm and eggs) with half the number of chromosomes.

6. Cell Specialization
In multicellular organisms, cells can differentiate into various types with specific functions (e.g., muscle cells, nerve cells, blood cells).

7. Cell Transport Mechanisms
Passive Transport: Movement of molecules across the cell membrane without energy (e.g., diffusion, osmosis).
Active Transport: Movement of molecules against their concentration gradient, requiring energy (e.g., sodium-potassium pump).

8. Cell Communication
Cells communicate through chemical signals, hormones, and neurotransmitters to coordinate functions and responses.

These notes provide a foundational overview of cellular biology. If you need more specific information or have questions about a particular aspect of cells, feel free to ask!