Cell Biology: Basic Cell Structure and Organelles

Cell Membrane:
- Semi-permeable barrier.
- Composed of phospholipid bilayer with embedded proteins.
Cytoplasm:
- Gel-like substance inside the cell.
- Contains organelles and cytosol (fluid component).
Nucleus:
- Contains genetic material (DNA).
- Surrounded by nuclear envelope with pores.

Mitochondria:
- Powerhouse of the cell.
- Site of ATP production through cellular respiration.
Ribosomes:
- Sites of protein synthesis.
- Can be free-floating 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 use within the cell.
Lysosomes:
- Contain digestive enzymes for breaking down waste materials and cellular debris.
Centrioles:
- Involved in cell division; help organize the mitotic spindle.
Chloroplasts (in plant cells):
- Site of photosynthesis.
- Contain chlorophyll, which captures sunlight.

Prokaryotic Cells:
- Lack a nucleus and membrane-bound organelles.
- Generally smaller and simpler (e.g., bacteria).
Eukaryotic Cells:
- Have a nucleus and membrane-bound organelles.
- Larger and more complex (e.g., plant and animal cells).

Mitosis:
- Process of cell division resulting in two identical daughter cells.
- Stages: Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.
Meiosis:
- Special type of cell division for producing gametes (sperm and eggs).
- Involves two rounds of division, resulting in four genetically diverse cells.

Cellular Respiration:
- Process of converting glucose and oxygen into ATP, carbon dioxide, and water.
- Involves Glycolysis, Krebs Cycle, and Electron Transport Chain.
Photosynthesis (in plants):
- Conversion of light energy into chemical energy (glucose).
- Occurs in chloroplasts; involves light-dependent and light-independent reactions.

Passive Transport:
- Movement of substances across the cell membrane without energy (e.g., diffusion, osmosis).
Active Transport:
- Movement of substances against their concentration gradient, requiring energy (e.g., sodium-potassium pump).
Endocytosis and Exocytosis:
- Endocytosis: Process of engulfing substances into the cell.
- Exocytosis: Process of expelling materials from the cell.

Signal Transduction Pathways:
- Series of molecular events initiated by the binding of signaling molecules (ligands) to receptors.
- Can result in changes in gene expression or cellular behavior.
Types of Cell Signaling:
- Autocrine (self-signaling), Paracrine (neighboring cells), Endocrine (long-distance signaling via hormones).

Understanding cell structure and function is crucial for:
- Advancements in medicine (cancer treatment, regenerative medicine).
- Biotechnology (genetic engineering, synthetic biology).
- Environmental science (impact of pollutants on cell function).

Cell Membrane: Semi-permeable barrier made of a phospholipid bilayer with embedded proteins, regulating the entry and exit of substances.
Cytoplasm: Gel-like fluid within the cell, containing organelles and cytosol, crucial for cellular processes.
Nucleus: Encloses genetic material (DNA), surrounded by a nuclear envelope with pores for molecular exchange.

Mitochondria: Known as the powerhouse of the cell; responsible for ATP production via cellular respiration.
Ribosomes: Sites of protein synthesis, can exist freely in the cytoplasm or be attached to the endoplasmic reticulum.
Endoplasmic Reticulum (ER):
- Rough ER: Covered with ribosomes; involved in the synthesis and modification of proteins.
- Smooth ER: Lacks ribosomes; participates in lipid synthesis and detoxification processes.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for either secretion or use within the cell.
Lysosomes: Contain digestive enzymes that break down waste materials and cellular debris.
Centrioles: Play a pivotal role in cell division by organizing the mitotic spindle.
Chloroplasts (plant cells): Site of photosynthesis, containing chlorophyll to capture sunlight for energy conversion.

Prokaryotic Cells: Lack a nucleus and membrane-bound organelles, generally smaller and simpler structures (e.g., bacteria).
Eukaryotic Cells: Possess a nucleus and membrane-bound organelles, larger and more complex (e.g., plant and animal cells).

Mitosis: Cell division resulting in two genetically identical daughter cells; consists of Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.
Meiosis: Specialized cell division for gamete production (sperm and eggs); includes two rounds of division leading to four genetically diverse cells.

Cellular Respiration: Converts glucose and oxygen into ATP, carbon dioxide, and water, involving Glycolysis, Krebs Cycle, and Electron Transport Chain.
Photosynthesis: In plants, transforms light energy into chemical energy (glucose), occurring in chloroplasts and involving both light-dependent and light-independent reactions.

Passive Transport: Movement across the cell membrane without energy input (e.g., diffusion, osmosis).
Active Transport: Requires energy to move substances against their concentration gradient (e.g., sodium-potassium pump).
Endocytosis and Exocytosis:
- Endocytosis: Engulfing materials into the cell.
- Exocytosis: Expelling materials out of the cell.

Signal Transduction Pathways: Initiated by ligand binding to receptors, leading to molecular events that can alter gene expression and cellular activities.
Types of Cell Signaling:
- Autocrine: Cells signal to themselves.
- Paracrine: Signaling to nearby cells.
- Endocrine: Long-distance signaling through hormones.

Vital for advancements in medicine, including cancer treatment and regenerative medicine.
Essential in biotechnology for processes like genetic engineering and synthetic biology.
Beneficial in environmental science by studying the impact of pollutants on cell function.