BackCellular Structure: Cytoplasm and Organelles
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Cytoplasm
Definition and Components
The cytoplasm is the cellular material located between the plasma membrane and the nucleus. It serves as the site for most cellular activities and contains various components essential for cell function.
Cytosol: The fluid portion of the cytoplasm, composed mainly of water with dissolved solutes such as proteins, salts, and sugars.
Organelles: Specialized structures within the cytoplasm that perform distinct metabolic functions. Organelles can be membranous or nonmembranous.
Inclusions: Non-living substances found in the cytoplasm, which vary by cell type. Examples include glycogen granules, pigments, lipid droplets, vacuoles, and crystals.
Cytoplasmic Organelles
Classification of Organelles
Organelles are classified based on the presence or absence of surrounding membranes. This compartmentalization is crucial for cellular organization and function.
Membranous Organelles | Nonmembranous Organelles |
|---|---|
Mitochondria | Cytoskeleton |
Peroxisomes | Centrioles |
Lysosomes | Ribosomes |
Endoplasmic Reticulum | |
Golgi Apparatus |
Mitochondria
Structure and Function
Mitochondria are double-membrane organelles with an inner membrane folded into shelflike cristae. They are often referred to as the "powerhouses" of the cell due to their role in energy production.
ATP Production: Mitochondria generate most of the cell's ATP through aerobic cellular respiration, a process that requires oxygen.
Genetic Material: They contain their own DNA, RNA, and ribosomes, allowing them to replicate independently by a process called fission.
Evolutionary Origin: Mitochondria are similar to bacteria, supporting the endosymbiotic theory of their origin.
Key Structures
Outer mitochondrial membrane
Inner mitochondrial membrane with cristae
Matrix: The innermost compartment containing enzymes and mitochondrial DNA
Equation for Cellular Respiration
The overall reaction for aerobic cellular respiration is:
Ribosomes
Structure and Function
Ribosomes are small granules composed of protein and ribosomal RNA (rRNA). They are the site of protein synthesis in the cell.
Free Ribosomes: Located in the cytosol; synthesize proteins that function within the cytosol or other organelles.
Membrane-bound Ribosomes: Attached to the rough endoplasmic reticulum (ER); synthesize proteins destined for incorporation into membranes, lysosomes, or for export from the cell.
Endoplasmic Reticulum (ER)
Types and Functions
The endoplasmic reticulum is a network of interconnected tubes and parallel membranes enclosing fluid-filled spaces called cisterns. It is continuous with the outer nuclear membrane and exists in two forms:
Rough ER: Studded with ribosomes; involved in protein synthesis and modification.
Smooth ER: Lacks ribosomes; involved in lipid synthesis, detoxification, and calcium storage.
Example: Protein Synthesis Pathway
Proteins synthesized by ribosomes on the rough ER are processed and transported to the Golgi apparatus for further modification and sorting.
Additional info: The smooth ER also plays a role in carbohydrate metabolism and steroid hormone production in certain cell types.
