Cell Organelles and Their Functions

Nucleus
- Contains genetic material (DNA).
- Controls cell activities and gene expression.
Mitochondria
- Powerhouse of the cell; site of ATP (energy) production.
- Involved in metabolic processes and cellular respiration.
Ribosomes
- Sites of protein synthesis.
- Can be free in cytoplasm or attached to the endoplasmic reticulum (ER).
Endoplasmic Reticulum (ER)
- Rough ER: Studded with ribosomes; involved in protein synthesis and processing.
- Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies certain chemicals.
Golgi Apparatus
- Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
Lysosomes
- Contains digestive enzymes; breaks down waste materials and cellular debris.
Peroxisomes
- Breaks down fatty acids and detoxifies harmful substances.
Cytoskeleton
- Provides structural support and shape to the cell.
- Involved in cell movement and division.
Plasma Membrane
- Semi-permeable barrier that regulates entry and exit of substances.

Composed of a phospholipid bilayer with embedded proteins.
Functions:
- Protects the cell’s interior and provides structure.
- Regulates transport of materials (selective permeability).
- Facilitates communication through receptor proteins.
- Maintains homeostasis by controlling ion concentrations and nutrients.

Refers to all biochemical reactions occurring within a cell.
Major pathways:
- Catabolism: Breakdown of larger molecules to release energy (e.g., glycolysis, Krebs cycle).
- Anabolism: Synthesis of larger molecules from smaller ones, requiring energy (e.g., protein synthesis).
Metabolic pathways are interconnected and regulated by enzymes.
ATP is the primary energy currency of the cell, produced mainly in mitochondria.

Process by which cells communicate with each other to coordinate activities.
Types of signaling:
- Autocrine: Signals act on the same cell that produces them.
- Paracrine: Signals affect nearby cells.
- Endocrine: Hormones released into the bloodstream affect distant cells.
Key components:
- Receptors: Proteins on cell surface or inside that bind to signaling molecules (ligands).
- Second messengers: Molecules that relay signals inside the cell (e.g., cAMP, calcium ions).
Importance:
- Regulates cellular processes such as growth, metabolism, and immune responses.
- Essential for maintaining homeostasis and responding to environmental changes.

Nucleus houses DNA and directs cellular activities.
Mitochondria produce ATP, essential for energy via cellular respiration.
Ribosomes are the sites of protein synthesis, located in cytoplasm or on endoplasmic reticulum.
Rough ER is ribosome-studded, involved in protein synthesis and processing; Smooth ER synthesizes lipids and detoxifies substances.
Golgi Apparatus modifies, sorts, and packages proteins/lipids for export or delivery to organelles.
Lysosomes contain enzymes for digesting waste and cellular debris.
Peroxisomes break down fatty acids and detoxify harmful substances.
Cytoskeleton provides cellular structure, shape, and facilitates movement and division.
Plasma Membrane is semi-permeable, regulating substance entry/exit and maintaining homeostasis.

Encompasses all biochemical reactions in cells.
Catabolism breaks down molecules to release energy; examples include glycolysis and the Krebs cycle.
Anabolism builds larger molecules from smaller ones and requires energy; includes protein synthesis.
Metabolic pathways are interconnected and enzyme-regulated.
ATP, generated mainly in mitochondria, is the main energy currency of the cell.

Cells communicate to coordinate activities through signaling processes.
Autocrine signaling acts on the originating cell, paracrine affects nearby cells, and endocrine affects distant cells via hormones.
Receptors, located on cell surfaces or inside, bind to signaling molecules (ligands).
Second messengers, like cAMP and calcium, transmit signals within the cell.
Cell signaling is crucial for regulating growth, metabolism, immune responses, and maintaining homeostasis in response to environmental changes.