Cell Biology Basics

Prokaryotic Cells
- Lack a nucleus and membrane-bound organelles.
- 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).

Plasma Membrane
- Semi-permeable membrane that surrounds the cell.
- Composed of a phospholipid bilayer with embedded proteins.
Nucleus
- Contains genetic material (DNA).
- Site of transcription.
Cytoplasm
- Jelly-like substance between the plasma membrane and nucleus.
- Contains organelles and cytosol.
Organelles
- Mitochondria: Energy production through ATP synthesis (cellular respiration).
- Ribosomes: Protein synthesis; can be free in cytoplasm or attached to the rough endoplasmic reticulum (RER).
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes; synthesizes proteins.
  - Smooth ER: 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 waste processing.
- Peroxisomes: Break down fatty acids and detoxify harmful substances.
- Cytoskeleton: Provides structure and transport within the cell; includes microtubules, microfilaments, and intermediate filaments.

Mitosis: Process of somatic cell division resulting in two identical daughter cells.
- Stages: Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.
Meiosis: Process of gamete formation resulting in four genetically diverse cells.
- Involves two rounds of division (Meiosis I and II).

Cells communicate through chemical signals (hormones, neurotransmitters).
Receptors: Proteins on the cell surface or inside that bind to signaling molecules.
Signal Transduction Pathways: Series of molecular events triggered by receptor activation leading to a cellular response.

Catabolism: Breakdown of molecules to obtain energy (e.g., glycolysis, Krebs cycle).
Anabolism: Synthesis of complex molecules from simpler ones (e.g., protein synthesis).

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

Autocrine: Signals affect the same cell that releases them.
Paracrine: Signals affect nearby cells.
Endocrine: Signals (hormones) travel through the bloodstream to distant cells.
Juxtacrine: Direct contact between signaling and target cells.

Understanding cell structure and function is fundamental to all biological sciences.
Cell interactions and communications are crucial for maintaining homeostasis and coordinating physiological processes.

Prokaryotic Cells:
- Characterized by the absence of a nucleus and membrane-bound organelles.
- Generally smaller and simpler; examples include bacteria.
Eukaryotic Cells:
- Possess a nucleus and membrane-bound organelles.
- Larger and more complex; examples include plant and animal cells.

Plasma Membrane:
- A semi-permeable barrier made of a phospholipid bilayer embedded with proteins.
Nucleus:
- Contains DNA, serves as the site for transcription.
Cytoplasm:
- A jelly-like substance, housing organelles and cytosol.
Organelles:
- Mitochondria: Produce energy through ATP synthesis during cellular respiration.
- Ribosomes: Responsible for protein synthesis, may exist free or attached to the rough endoplasmic reticulum (RER).
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes for protein synthesis.
  - Smooth ER: Involved in lipid synthesis and detoxification processes.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or internal use.
- Lysosomes: Contain digestive enzymes to process waste.
- Peroxisomes: Break down fatty acids and detoxify harmful substances.
- Cytoskeleton: Composed of microtubules, microfilaments, and intermediate filaments; provides structural integrity and facilitates transport within the cell.

Mitosis: Somatic cell division producing two identical daughter cells, consisting of stages: Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.
Meiosis: Gamete formation yielding four genetically diverse cells; includes two rounds of division (Meiosis I and II).

Cells utilize chemical signals, such as hormones and neurotransmitters, to communicate.
Receptors: Proteins that bind signaling molecules, located on the surface or within the cell.
Signal Transduction Pathways: Series of reactions initiated by receptor activation that yield specific cellular responses.

Catabolism: The breakdown of complex molecules to release energy; includes processes like glycolysis and the Krebs cycle.
Anabolism: The synthesis of complex molecules from simpler ones, such as during protein synthesis.

Passive Transport: Molecules move across membranes without energy input (e.g., diffusion, osmosis).
Active Transport: Molecules are moved against their concentration gradient, requiring energy (e.g., sodium-potassium pump).

Cell Wall: A rigid exterior providing structural support and protection against environmental stress.
Chloroplasts: Organelles responsible for photosynthesis, containing chlorophyll for light absorption.
Central Vacuole: Large storage organelle that helps maintain turgor pressure in the cell.

Autocrine: Signals impact the same cell that released them.
Paracrine: Signals affect adjacent cells in the vicinity.
Endocrine: Hormonal signals travel through the bloodstream to reach distant cells.
Juxtacrine: Requires direct contact between signaling and target cells.

A comprehensive understanding of cell structure and functions is essential across biological sciences.
Cell interactions and communication play a vital role in maintaining homeostasis and physiological coordination.