Cell Structures and Organelles: Functions and Differences in Prokaryotes and Eukaryotes

Cell Membrane (Plasma Membrane)

Surrounds the cell to keep its contents in and protect the inner-cell components from the outside environment. Selectively permeable to allow passage of specific contents, found in all life (prokaryotes and eukaryotes).

Cell Wall

An additional rigid layer surrounding the cell membrane for structural support and protection. Very common in prokaryotes. NOT found in animal cells.

Cytoplasm

A water-based gel-like fluid within all cells (prokaryotes and eukaryotes).

Ribosomes

Makes proteins and is found in large quantities in the cytoplasm (prokaryotes and eukaryotes) and on rough endoplasmic reticulum (eukaryotes only).

Nucleus

Organelle in cytoplasm with a double membrane that contains DNA. Found in all eukaryotes.

Smooth Endoplasmic Reticulum (SER)

Organelle made up of a network of interconnected membranes in the cytoplasm where lipids such as cholesterol, phospholipids, or lipid-containing hormones are made, processed, stored, and/or broken down. NOT found in prokaryotes.

Rough Endoplasmic Reticulum (RER)

Organelle made up of a network of interconnected membranes in the cytoplasm and connected to the nuclear membrane. Contains many ribosomes and is a site for making and processing proteins.

Golgi Apparatus

Organelle made up of layers of membrane-bound sacs where the proteins in the RER vesicles come in for further processing before being sent via vesicle to their final destination. NOT found in prokaryotes.

Vesicles

Small fluid-filled sacs enclosed by a membrane that are used for transporting cellular material to places in the cell or can be secreted to other cells.

Vacuoles

Membrane-bound organelle in cytoplasm acting as a large enclosed, isolating compartment in the cell serving multiple purposes such as containing enzymes, water, waste products, or large solids that have been engulfed.

Cytoskeleton

Highway/road systems extended throughout the cytoplasm for transporting vesicles and provides the cell with its structure and shape.

Flagella

Long, whipping organelle outside the cell that helps propel the cell for movement. Found only in certain motile cells in prokaryotes and eukaryotes.

Cilia

Short, hair-like organelle outside the cell that beats quickly back and forth to help with cell movement or help move stuff across tissue lining.

Lysosomes

Membrane-bound organelle in cytoplasm with enzymes that digest and breakdown material in the cell, such as recycling damaged cell parts or digesting infectious particles that enter the cell. NOT found in prokaryotes.

Peroxisomes

Membrane-bound organelle in cytoplasm with enzymes that catalyze redox reactions to detoxify and breakdown harmful substances.

Mitochondria

Double membrane-bound organelle in cytoplasm that produces energy (ATP) for the cell. Contains DNA and 70S ribosomes. NOT found in prokaryotes.

Chloroplasts

Double membrane-bound organelle in cytoplasm used in photosynthesis to produce organic molecules for the cell. Contains its own DNA and 70S ribosomes.