Cell Structure Basics

Plasma membrane: semi-permeable membrane that separates the cell from its environment
- Composed of phospholipid bilayer with embedded proteins
Cytoplasm: jelly-like substance inside the cell membrane
- Site of many cellular activities, including metabolism and protein synthesis
Nucleus: control center of the cell
- Contains DNA, the genetic material
Mitochondria: energy-producing organelles
- Site of cellular respiration, generating ATP
Endoplasmic reticulum (ER): network of membranous tubules and cisternae
- Involved in protein synthesis, lipid synthesis, and detoxification
Golgi apparatus: complex of flattened sacs and tubules
- Responsible for protein modification, sorting, and transport
Lysosomes: membrane-bound sacs containing digestive enzymes
- Involved in cellular digestion and recycling
Cytoskeleton: network of filaments that provides structural support and shape
- Composed of microtubules, microfilaments, and intermediate filaments

Passive transport: movement of molecules from high to low concentration
- Includes diffusion, osmosis, and facilitated diffusion
Active transport: movement of molecules from low to high concentration
- Requires energy input, often through ATP hydrolysis
Types of membrane transport:
- Simple diffusion: movement of molecules through the phospholipid bilayer
- Facilitated diffusion: movement of molecules through transport proteins
- Active transport: movement of molecules through pumps and carriers
- Endocytosis: uptake of molecules through vesicle formation
- Exocytosis: release of molecules through vesicle fusion

Signal transduction pathways: series of molecular events that transmit signals
- Involves receptors, signaling molecules, and response elements
Types of cell signaling:
- Autocrine signaling: signaling within the same cell
- Paracrine signaling: signaling between nearby cells
- Endocrine signaling: signaling between distant cells through hormones
- Direct signaling: direct interaction between cells through gap junctions
Receptors: proteins that bind to signaling molecules
- Seven-transmembrane receptors: G-protein coupled receptors
- Tyrosine kinase receptors: receptors with enzymatic activity

Cell cycle: series of stages that a cell goes through to replicate and divide
- Includes interphase (G1, S, G2) and mitosis (M)
Mitosis: process of cell division that results in two daughter cells
- Includes prophase, metaphase, anaphase, and telophase
Cytokinesis: process of cytoplasmic division
- Occurs after mitosis, resulting in two separate cells
Regulation of the cell cycle: controlled by checkpoints and regulators
- Ensures that DNA replication and division occur accurately and efficiently

Plasma membrane: semi-permeable membrane that separates the cell from its environment, composed of phospholipid bilayer with embedded proteins
Cytoplasm: jelly-like substance inside the cell membrane, site of many cellular activities, including metabolism and protein synthesis
Nucleus: control center of the cell, contains DNA, the genetic material
Mitochondria: energy-producing organelles, site of cellular respiration, generating ATP
Endoplasmic reticulum (ER): network of membranous tubules and cisternae, involved in protein synthesis, lipid synthesis, and detoxification
Golgi apparatus: complex of flattened sacs and tubules, responsible for protein modification, sorting, and transport
Lysosomes: membrane-bound sacs containing digestive enzymes, involved in cellular digestion and recycling
Cytoskeleton: network of filaments that provides structural support and shape, composed of microtubules, microfilaments, and intermediate filaments

Passive transport: movement of molecules from high to low concentration, includes diffusion, osmosis, and facilitated diffusion
Active transport: movement of molecules from low to high concentration, requires energy input, often through ATP hydrolysis
Types of membrane transport:
- Simple diffusion: movement of molecules through the phospholipid bilayer
- Facilitated diffusion: movement of molecules through transport proteins
- Active transport: movement of molecules through pumps and carriers
- Endocytosis: uptake of molecules through vesicle formation
- Exocytosis: release of molecules through vesicle fusion

Signal transduction pathways: series of molecular events that transmit signals, involves receptors, signaling molecules, and response elements
Types of cell signaling:
- Autocrine signaling: signaling within the same cell
- Paracrine signaling: signaling between nearby cells
- Endocrine signaling: signaling between distant cells through hormones
- Direct signaling: direct interaction between cells through gap junctions
Receptors: proteins that bind to signaling molecules
- Seven-transmembrane receptors: G-protein coupled receptors
- Tyrosine kinase receptors: receptors with enzymatic activity

Cell cycle: series of stages that a cell goes through to replicate and divide, includes interphase (G1, S, G2) and mitosis (M)
Mitosis: process of cell division that results in two daughter cells, includes prophase, metaphase, anaphase, and telophase
Cytokinesis: process of cytoplasmic division, occurs after mitosis, resulting in two separate cells
Regulation of the cell cycle: controlled by checkpoints and regulators, ensures that DNA replication and division occur accurately and efficiently