Difference Between Vesicle and Vacuole

Main Difference – Vesicle vs Vacuole

Vesicle and vacuole are both membrane-enclosed organelles, containing fluids. Vesicles are enclosed by a phospholipid bilayer and serve as chambers for metabolism, temporary storage of food and enzymes, and transport molecules. Various types of vesicles are found in cells like lysosomes, transport vesicles, and secretary vesicles. The vacuole is also a type of vesicles. Plant cells contain a large, central vacuole, storing mostly water and nutrients. The main difference between vesicles and vacuole is that vesicle is designed to store different types of molecules whereas vacuole is a type of vesicle, mostly storing water.

This article studies, 

1. What is a Vesicle
      – Structure, Types, Functions
2. What is a Vacuole
      – Structure, Types, Functions
3. What is the difference between Vesicle and Vacuole

What is a Vesicle?

A vesicle is a membrane-enclosed small organelle inside the cell, containing different types of fluid. The vesicles are formed during exocytosis and endocytosis. On the other hand, liposomes are formed artificially. The membrane which encloses the vesicle is a phospholipid bilayer. Unilamellar liposomes contain a single phospholipid bilayer surrounding the vesicle. Multilamellar liposomes are enclosed by two phospholipid bilayers. Vesicles can fuse with plasma membrane as well as the organelles in the cell in order to release their contents. Structure of a liposome is shown in figure 1.

Figure 1: Liposome

Types of Vesicles and Their Function

Various types of vesicles are found in the cell, containing different types of constituents. Vesicles are involved in metabolism, temporary storage of food and enzymes, transport molecules and buoyancy control. They also serve as chemical reaction chambers. Vacuoles, lysosomes, transport vesicles, secretory vesicles and extracellular vesicles are the most common types of vesicles found in the cell.

Vacuoles

Vacuoles consist mostly of water. A large central vacuole is a characteristic feature of plant cells. It controls the osmotic balance of the plant cell and serves as a storage of nutrients. Some protists consist of contractile vesicles, regulating the osmotic balance of the cell.

Lysosomes

Lysosomes are an important type of vesicles involved in the digestion. Food vacuoles are fused with lysosomes, which contain enzymes to digest the food. Lysosomes are also involved in phagocytosis. On the other hand, lysosomes destroy damaged organelles in the process called autophagy.

Transport Vesicles

Transport vesicles contribute to molecular passages between locations inside the cell. For example, proteins are transported from rough endoplasmic reticulum to Golgi apparatus by vesicles. Secreted proteins and membrane-bound proteins, which mature inside the Golgi apparatus also travel to their destinations via transport vesicles. 

Secretory Vesicles

Substances which are to be excreted from the cell are contained in secretory vesicles. Cellular wastes and special chemicals made by the cell are stored in secretory vesicles and released when needed. Synaptic vesicles, which are located at the presynaptic terminals in neurons store neurotransmitters. When the signal comes to the axon, these synaptic vesicles are fused with the cell membrane, releasing the neurotransmitters to the synapse, the gap between presynaptic and postsynaptic neurons. These neurotransmitters are recognized by the receptor molecules on the next nerve cell. Hormone-producing cells store hormones in secretory vesicles.

Extracellular Vesicles

Almost all the life forms produce extracellular vesicles. Exosomes, microvesicles, membranous vesicles, and apoptotic vesicles are examples for extracellular vesicles. Extracellular vesicles are formed by pinching off the outer plasma membrane. 

What is a Vacuole?

A vacuole is a type of vesicles mostly containing water. Vacuole is a characteristic feature of plant cells, but it can be found in animal cells, bacterial cells, protist and fungal cell as well. It contains organic compounds including enzymes and inorganic compounds other than water. Vacuole is formed by the fusion of multiple vesicles. The size and the shape of a vacuole vary depending on the cell’s requirements.

Function of Vacuole

The function of vacuole varies with the type of cell, which contains the vacuole. Major functions of the vacuole are described below.

1. Storing water in plants
2. Regulating internal turgor pressure
3. Regulating internal pH
4. Storing small molecules
5. Isolating harmful materials to the cell
6. Storing waste products temporary and exporting them when needed
7. Supporting structural rigidity in plant cells
8. Increasing the size quickly by just using water
9. Storing proteins, which are required by germination

Types of Vacuole

Bacterial Vacuoles

The three genera of the filamentous sulfur bacteria, Thioploca, Thiomargarita and Beggiatoa contain large vacuoles, reducing the space to the cytosol. Bacterial vacuoles are highly rich in nitrate ions. Some species of Cyanobacteria contains gas vacuoles, controlling the buoyancy of the organism.

Plant Vacuoles

The plant vacuole usually occupies around 30% of the cell’s volume. The plasma membrane, which surrounds the plant vacuole, is called the tonoplast and the fluid inside the vacuole is called the cell sap. Tonoplast regulates the movements of ions. The vacuole in plants isolates harmful materials, stabilizes the pH and acts as a chamber to degenerative enzymes to function in the cell. A vacuole in a plant cell is shown in figure 2.

Figure 2: Plant Vacuole

Fungi Vacuoles

Fungi contain more than one vacuole per cell, consisting of same functions as in plant vacuoles. Yeast vacuole is a dynamic structure with rapidly modifying morphology. It is involved in homeostasis of the pH, osmoregulation, and storage of ions, amino acids, and polypeptides.

Animal Vacuoles

Animal vacuoles are small and more than one vacuole occur per cell. They are mainly involved in exocytosis and endocytosis. The process of extrusion of lipids and proteins from the cell is known as exocytosis. Things to be extruded are first absorbed into secretory vesicles and transported into Golgi apparatus. When needed, they are transported to the cell membrane and extruded. The reverse of exocytosis is called endocytosis. Phagocytosis is the most common example for endocytosis. The engulfment of solutions into the cell is called pinocytosis. 

Difference Between Vesicle and Vacuole

Definition

Vesicle: A vesicle is a membrane-enclosed small organelle inside the cell, which contains different types of fluid.

Vacuole: A vacuole is a type of vesicles, mostly containing water.

Size

Vesicle: Vesicle is small in size.

Vacuole: Vacuole is comparatively large in size.

Presence

Vesicles: Vesicles are found in eukaryotic cells.

Vacuole: Vacuoles are found in both prokaryotic and eukaryotic cells.

Composition

Vesicle:  Vesicles are composed of water, nutrients, enzymes, wastes, harmful compounds and ions.

Vacuole: Vacuole is mostly composed of water.

Role

Vesicle: Vesicles are involved in metabolism, temporary storage of food and enzymes, transport molecules and buoyancy control. They also serve as chemical reaction chambers.

Vacuole: Vacuoles are involved in storing substances, mostly water, contributing to the structural support to the cell.

Types

Vesicle: The most common types of vesicles are vacuoles, lysosomes, transport vesicles, secretory vesicles and extracellular vesicles.

Vacuole: Bacteria, fungi, plant and animal cells contain vacuoles.

Conclusion

Vesicles and vacuoles are membrane-enclosed organelles, containing different types of substances stored in them. Vacuoles are a type of vesicles, mostly containing water. Vesicles are involved in the temporary storage of food and enzymes, metabolism, transport molecules and buoyancy control. They also serve as chemical reaction chambers for digestive reactions. Various types of vesicles are found, storing different substances. Vesicles store water, nutrients, enzymes, wastes, harmful compounds, and ions. Vesicles are small in size and found in large number per cell. Usually, a single, large vacuole is contained by cells. This is the difference between vesicle and vacuole.

Reference:
1. “Vesicle (biology and chemistry).” Wikipedia. Wikimedia Foundation, 25 Jan. 2017. Web. 19 Mar. 2017.
2. “Vacuole.” Wikipedia. Wikimedia Foundation, 16 Oct. 2017. Web. 19 Mar. 2017.

Image Courtesy:
1. “Liposome scheme-en” By SuperManu – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Plant cell structure svg vacuole” By Mariana Ruiz LadyofHats, labels by Dake, modified by smartse – (Public Domain) via Commons Wikimedia