Prokaryote Cell Structure

Prokaryotes

• Lack a true nucleus and membrane-bound organelles
• Have a simple cellular structure, typically 1-10 microns in diameter
• Are single-celled (unicellular) and can be filamentous (strings of single cells)
• Have a capsule (slimy outer coating), cell wall, cell membrane, cytosol, and cytoplasm
• Contain a single, large loop of DNA (nucleoid)
• Have pili (for sticking to things), flagella (for swimming), and ribosomes (for building proteins)

Prokaryotic Lifestyle

• Can be unicellular (alone) or form colonies (a film) or filaments (a chain of cells)
• Can be photosynthetic (energy from sunlight), chemosynthetic (inorganic compounds as energy source), disease-causing (feed on living things), or decomposers (feed on dead things)

Eukaryotes

• Have a true nucleus and membrane-enclosed organelles with specialized functions
• Are larger and more complex in structure than prokaryotes
• Can be multicellular and include animals, plants, fungi, and protists (algae and protozoans)
• Have organelles, chromosomes, and a cytoskeleton that controls cell shape and movement
• Have mini organs (organelles) with unique structures and functions located in the cytoplasm

Cell Components

Plasma Membrane

• Acts as a gatekeeper, separating the cell from its external environment
• Is selectively permeable and protects the cell, providing stability

Cytoplasm

• Is a gel-like substance that dissolves substances like salt
• Is involved in osmotic regulation and contains organelles

Nucleus

• Is the control center of the cell, containing the DNA
• Directs cell metabolism and cell reproduction

Other Organelles

• Endoplasmic Reticulum: a transport system that carries materials throughout the cell
• Ribosome: a protein factory that produces protein
• Golgi Apparatus: a protein packaging system that temporarily stores protein for transportation
• Lysosome: a suicidal bag of the cell that breaks down worn-out organelles or food
• Mitochondria: the powerhouse of the cell, releasing energy from food molecules
• Vacuoles: storage boxes that store materials like food, water, minerals, and waste products
• Peroxisomes: vesicles that contain enzymes for detoxifying potentially harmful molecules
• Intermediate Filaments: intertwined protein fibers that provide support and strength

Genetics

• A gene can consist of a single DNA molecule (common in prokaryotes) or multiple DNA molecules (common in eukaryotes)
• DNA molecules are packaged into chromosomes, which consist of chromatin (a complex of DNA and protein) in eukaryotes
• Somatic cells have two sets of chromosomes, while gametes (reproductive cells) have half as many chromosomes
• The centromere is the narrow waist of the duplicated chromosome, where the two chromatids are most closely attached

Learn about the characteristics and components of prokaryote cells, including their size, shape, and organelles. Discover the functions of the capsule, cell wall, cell membrane, cytosol, and cytoplasm.