Eukaryotic vs. Prokaryotic Cells: Key Differences
Eukaryotic Cells
Eukaryotic cells are characterized by the following:
- Enclose their DNA within a nucleus
- Possess more than one chromosome
- Are typically multicellular
- Are generally larger and more complex than prokaryotic cells
- Separate their genetic material from the rest of the cell
Prokaryotic Cells
Prokaryotic cells are characterized by the following:
- Do not enclose their DNA within a nucleus
- Have one circular chromosome, not a true chromosome, but plasmids
- Are unicellular
- Are generally smaller and simpler than eukaryotic cells
- Do not separate their genetic material within a nucleus
- Grow, reproduce, and respond to the environment
Key Organelles and Structures in Eukaryotic Cells
Nucleus
The nucleus is a large, membrane-enclosed structure that contains the cell’s genetic material in the form of DNA. It controls many of the cell’s activities.
Structure
- The nuclear envelope is dotted with thousands of nuclear pores, allowing material to move in and out of the nucleus.
- Chromosomes, which carry genetic information, are located within the nucleus.
- Chromosomes are typically spread out as chromatin.
- Most nuclei contain a small, dense region called the nucleolus, where ribosome assembly begins.
Function
The nucleus contains nearly all of the cell’s DNA, which holds the coded instructions for making proteins and other important molecules.
Ribosomes
Ribosomes are responsible for protein synthesis. They are small particles of RNA and protein found throughout the cell. They produce proteins by following instructions encoded in DNA. Cells typically contain a large number of ribosomes.
Structure
Ribosomes are often attached to the endoplasmic reticulum.
Endoplasmic Reticulum (ER)
The endoplasmic reticulum is an internal membrane system where lipid components of the cell membrane are assembled, along with proteins and other materials.
Rough ER
Rough ER is involved in protein synthesis. It is named “rough” because ribosomes are found on its surface. Newly made proteins leave these ribosomes and are inserted into the rough ER. Proteins made on the rough ER include those that will be released, or secreted, from the cell, as well as many membrane proteins and proteins destined for lysosomes and other specialized locations within the cell.
Smooth ER
Smooth ER lacks ribosomes on its surface. It contains collections of enzymes that perform specialized tasks, such as synthesizing membrane lipids and detoxifying drugs.
Golgi Apparatus
Proteins produced in the rough ER move into the Golgi apparatus, which appears as a stack of flattened membranes.
Function
The Golgi apparatus modifies, sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or release outside the cell.
Cytoskeleton
Eukaryotic cells are given their shape and internal organization by a network of protein filaments known as the cytoskeleton.
Function
The cytoskeleton helps the cell maintain its shape and is also involved in movement.
Structure
The cytoskeleton is made up of microfilaments, responsible for movement, and microtubules, which maintain cell shape. Centrioles, located near the nucleus, help organize cell division.
Cell Membrane
The cell membrane regulates what enters and leaves the cell. It also protects and supports the cell.
Structure
The cell membrane consists of a lipid bilayer, a double-layered sheet that provides a flexible structure.
Vacuole
Vacuoles are large, saclike, membrane-enclosed structures.
Function
Vacuoles store materials like water, salts, proteins, and carbohydrates. Many plant cells have a single, large central vacuole filled with liquid.
Vesicles
Vesicles are smaller, membrane-enclosed structures.
Function
Vesicles store and move materials between cell organelles and to and from the cell surface.
Lysosomes
Lysosomes are small organelles filled with enzymes.
Function
Lysosomes break down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell. They are also involved in breaking down organelles that have outlived their usefulness.
Mitochondria
Nearly all eukaryotic cells, including plant cells, contain mitochondria.
Function
Mitochondria are the power plants of the cell. They convert the chemical energy stored in food into compounds that are more convenient for the cell to use.