Cell Biology Basics

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.
  - Smaller and simpler (e.g., bacteria).
- Eukaryotic Cells:
  - Have a nucleus.
  - More complex (e.g., plant and animal cells).

Nucleus:
- Contains genetic material (DNA).
- Controls cell activities.
Mitochondria:
- Powerhouse of the cell.
- Site of ATP (energy) production.
Ribosomes:
- Sites of protein synthesis.
- Can be free in the cytoplasm or attached to the endoplasmic reticulum.
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 delivery to other organelles.
Lysosomes:
- Contain digestive enzymes to break down waste materials and cellular debris.
Cell Membrane:
- Semi-permeable barrier that controls the movement of substances in and out of the cell.
- Composed of a phospholipid bilayer with embedded proteins.

Cell Division:
- Mitosis: Process by which a eukaryotic cell divides its nucleus and genetic material equally, resulting in two identical daughter cells.
- Meiosis: Produces gametes (sex cells) with half the chromosome number, involving two rounds of division.
Cellular Respiration:
- Process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water.
- Includes glycolysis, the Krebs cycle, and oxidative phosphorylation.
Photosynthesis (in plant cells):
- Conversion of light energy into chemical energy (glucose) using carbon dioxide and water, producing oxygen as a byproduct.
- Occurs in chloroplasts, involving chlorophyll.

Signal Transduction:
- Mechanism by which cells respond to external signals (e.g., hormones).
- Involves receptor proteins and secondary messengers.
Cell Junctions:
- Tight Junctions: Prevent leakage of molecules between cells.
- Gap Junctions: Allow direct communication between adjacent cells.
- Desmosomes: Provide structural support by anchoring cells together.

Cells can differentiate into various types (e.g., muscle cells, nerve cells) depending on their function.
Specialization allows for complex interactions and systems within multicellular organisms.

Cell Theory: Fundamental principles stating that all living organisms consist of cells, cells are the basic unit of life, and all cells originate from pre-existing cells.
Prokaryotic Cells: Characterized by the absence of a nucleus; examples include bacteria, which are smaller and simpler in structure.
Eukaryotic Cells: Defined by the presence of a nucleus; more complex cells such as those found in plants and animals.

Nucleus: Houses genetic material (DNA) and regulates cell activities.
Mitochondria: Known as the powerhouse of the cell, primarily responsible for ATP (energy) production.
Ribosomes: Sites for protein synthesis; can exist freely in the cytoplasm or be attached to the endoplasmic reticulum.
Endoplasmic Reticulum (ER):
- Rough ER: Contains ribosomes; involved in synthesizing and modifying proteins.
- Smooth ER: Lacks ribosomes; functions in lipid synthesis and detoxification processes.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or for transport to other organelles.
Lysosomes: Enzyme-containing organelles that digest waste materials and cellular debris.
Cell Membrane: Semi-permeable barrier regulating substance movement; consists of a phospholipid bilayer with embedded proteins.

Cell Division:
- Mitosis: Eukaryotic process ensuring equal division of the nucleus and genetic material, producing two identical daughter cells.
- Meiosis: Specialized division forming gametes (sex cells) with half the chromosome set; involves two rounds of division.
Cellular Respiration: Biochemical process converting glucose and oxygen into energy (ATP), producing carbon dioxide and water; includes glycolysis, the Krebs cycle, and oxidative phosphorylation.
Photosynthesis: Process in plant cells converting light energy into chemical energy in the form of glucose, using carbon dioxide and water, and releasing oxygen as a byproduct; takes place in chloroplasts, facilitated by chlorophyll.

Signal Transduction: Mechanism by which cells interpret and react to external signals (such as hormones) involving receptor proteins and secondary messengers.
Cell Junctions:
- Tight Junctions: Prevent leakage of molecules between cells.
- Gap Junctions: Facilitate direct communication between neighboring cells.
- Desmosomes: Offer structural support by anchoring adjacent cells together.

Capability of cells to differentiate into various types (e.g., muscle or nerve cells) based on functional roles, enabling complex interactions within multicellular organisms.