Cell Biology Study Notes

Cell Theory: Fundamental principles stating that:
- 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.
  - Smaller and simpler (e.g., bacteria).
  - DNA is circular and located in the nucleoid region.
- Eukaryotic Cells:
  - Have a nucleus.
  - Larger and more complex (e.g., plant and animal cells).
  - Contain membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum).

Nucleus: Contains genetic material (DNA); controls cellular activities.
Mitochondria: Powerhouse of the cell; site of ATP (energy) production.
Ribosomes: Sites of protein synthesis; can be free-floating or attached to the rough endoplasmic reticulum.
Endoplasmic Reticulum (ER):
- Rough ER: Studded with ribosomes; synthesizes proteins.
- 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 enzymes for digestion; break down waste materials and cellular debris.
Peroxisomes: Break down fatty acids and detoxify harmful substances.
Cell Membrane: Phospholipid bilayer that controls the movement of substances in and out of the cell.

Cell Division:
- Mitosis: Process of cell division resulting in two identical daughter cells; involved in growth and repair.
  - Stages: Prophase, Metaphase, Anaphase, Telophase.
- Meiosis: Process of cell division that produces gametes (sperm and eggs); involves two rounds of division and results in four non-identical cells.
Cellular Respiration: Process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water.
- Glycolysis, Krebs cycle, and Electron Transport Chain.
Photosynthesis: Occurs in plant cells; converts light energy into chemical energy (glucose) using carbon dioxide and water.
- Key stages: Light-dependent reactions and Calvin cycle.

Signal Transduction: Process by which cells respond to external signals through receptors, leading to a cellular response.
Cell Adhesion: Mechanisms that allow cells to adhere to each other and their environment, essential for tissue formation.

Passive Transport: Movement of substances across a cell membrane without energy input (e.g., diffusion, osmosis).
Active Transport: Movement of substances against their concentration gradient, requiring energy (e.g., sodium-potassium pump).
Endocytosis and Exocytosis: Processes for transporting large molecules into (endocytosis) and out of (exocytosis) cells via vesicles.

Homeostasis: Maintenance of a stable internal environment within cells.
Cell Differentiation: Process by which cells become specialized for specific functions.
Stem Cells: Undifferentiated cells with the potential to develop into various cell types.

Cell Theory: Defines the role of cells in living organisms, emphasizing that all life forms consist of cells, the cell is the fundamental unit of life, and cell division leads to new cells.
Prokaryotic Cells: Simple cellular structures without a nucleus; examples include bacteria; DNA is in a circular form located in the nucleoid region.
Eukaryotic Cells: More complex with a defined nucleus; examples include plant and animal cells; contain various membrane-bound organelles for specialized functions.

Nucleus: Stores DNA and orchestrates cellular activities.
Mitochondria: Key organelles in ATP production, known as the powerhouse of the cell.
Ribosomes: Responsible for protein synthesis; can exist freely in the cytoplasm or attached to the rough endoplasmic reticulum.
Endoplasmic Reticulum (ER):
- Rough ER: Ribosome-studded, primarily involved in protein synthesis.
- Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification processes.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for delivery or secretion.
Lysosomes: Digestive organelles containing enzymes to breakdown waste and debris.
Peroxisomes: Organelles tasked with fatty acid breakdown and detoxification of harmful substances.
Cell Membrane: Composed of a phospholipid bilayer, regulates entry and exit of substances.

Cell Division:
- Mitosis: Yields two identical daughter cells; stages include prophase, metaphase, anaphase, and telophase.
- Meiosis: Produces gametes through two rounds of division resulting in four genetically varied cells.
Cellular Respiration: Converts glucose and oxygen into energy (ATP), carbon dioxide, and water; includes glycolysis, Krebs cycle, and electron transport chain.
Photosynthesis: A process in plants that transforms light energy into glucose using carbon dioxide and water; consists of light-dependent reactions and Calvin cycle.

Signal Transduction: Mechanism for cells to respond to external signals through receptor activation, initiating a cellular response.
Cell Adhesion: Essential for tissue formation, facilitating binding between cells and to their extracellular environment.

Passive Transport: Involves substance movement across cell membranes without additional energy; examples include diffusion and osmosis.
Active Transport: Requires energy to move substances against their concentration gradient, such as in the sodium-potassium pump.
Endocytosis and Exocytosis: Processes for bulk transport of larger molecules; endocytosis brings substances into the cell, while exocytosis expels them.

Homeostasis: The ability of cells to maintain a stable internal environment, crucial for optimal function.
Cell Differentiation: The process through which generic cells develop into specialized cells with unique functions.
Stem Cells: Cells that are not yet differentiated and possess the potential to become various types of cells within the body.