Vacuoles: Definition, Types, Examples, Diagram, Functions

What is a Vacuole?

Vacuoles are organelles that have several cellular functions. They can store food or nutrients to keep a cell alive. They also store all the waste products and prevent the whole cell from contamination. The vacuoles of the plant cells are bigger than those of the vacuole in animal cells. More than 80% of the volume of the cell is occupied by plant vacuoles. They are one or numerous of them in number.

Vacuoles are considered an important part of cellular homeostasis and general cell function. Therefore, its knowledge is fundamental for students to gain a foundation in cell biology that will assist them in understanding more complex, higher-level cellular processes and structures.

Structure of Vacuole

The structure of vacuoles is surrounded by a membrane called the tonoplast and its internal contents are separated from the cytoplasm of the cell. The movement of molecules into and out of the vacuole is regulated by this membrane. This further controls the cell sap composition.

The cell sap, or the internal content of the vacuoles, consists of the ions, sugars, pigments and other water molecules. The functions performed include storing nutrients and waste materials and maintaining turgor pressure.

Types of Vacuoles

The types of vacuoles are discussed below:

Central Vacuoles

Plant cells have a large central vacuole, which occupy approximately 30 per cent of the cell volume. This central vacuole is important in the turgor pressure, storage of water, and nutrients, and the regulation of the pH of the cell's interior environment. It also allows for cell enlargement, thereby giving the plant structural support.

Contractile Vacuoles

Some protists, such as protozoa, have contractile vacuoles. It prevents flooding of the cell with water and prevents it from bursting. The vacuole does this by rhythmically contracting to pump excess water from the cell.

Food vacuoles

Food vacuoles develop during the process of phagocytosis, in organisms such as amoeba. A foreign organism or food particles that are engulfed become enclosed in the food vacuole. Digestive enzymes are then secreted into the food vacuole to break down the ingested material, after which it is absorbed by the organism for energy and growth.

Functions of Vacuole

The various functions of vacuoles are:

• Vacuoles function as storage compartments for nutrients, ions, sugar pigments and waste products.

• Vacuoles also store some substances that are potentially damaging to the cell, such as toxins or by-products of metabolism, keeping them away from the rest of the cell.

• These play a significant role in the development of a plant cell by helping to control cell expansion, enlargement, and differentiation.

• They also contain enzymes and an acidic environment that provides for the digestion of macromolecules and cellular waste products.

• The vacuole takes the substances through a process called endocytosis, after which the contents are digested and then excreted through exocytosis. The contents are stored within the cells and separated from the cytosol.

Formation and Life Cycle of Vacuoles

Vacuoles are produced in a cell through various mechanisms, but the most important one is the fusion of small vesicles formed from the Golgi apparatus and the endoplasmic reticulum. The vacuole lifecycle involves strongly controlled membrane dynamics, protein traffic, and organelle interaction, enabling the vacuole to play a role in maintaining cell homeostasis and growth.

Vacuoles and Cellular Homeostasis

They serve in the maintenance of cellular homeostasis by regulating the pH and detoxification processes. They regulate the pH by actively pumping ions into and out of the vacuole. Thereby adjusting acidity and alkalinity to maintain homeostasis in the cell's internal environment. This is very important in enabling the cell to maintain optimum conditions for enzymatic activities along with other biochemical processes. Also, they serve as stores for harmful substances, sequestering dangerous molecules and preventing their detrimental effects on the cell.

Importance in Biotechnology and Research

Vacuoles are quite prominent in genetic engineering research and biotechnology, concerning the manipulation of genes and the study of their functions in different organisms. Therefore, they can be targets of gene insertion or alteration for product production or a gene function study.

Moreover, the continued research in vacuole function in a multitude of organisms yields very useful information on cellular function, disease processes, and biotechnological potential that moves the edge of knowledge along a line from agriculture to medicine.

Vacuole NEET MCQs (With Answers & Explanations)

Important topics for NEET exams:

• Vacuoles in Plants

• Types of Vacuoles

Practice Questions for NEET

Q1. Which of the following statement is not correct for vacuoles

1. Contractile vacuoles help in excretion

2. Tonoplast facilitates the transport of ions against the concentration gradient into the cytoplasm

3. Food vacuoles are formed by engulfing the food particles

4. Sap vacuole is bound by single membrane

Correct answer: 2) Tonoplast facilitates the transport of ions against the concentration gradient into the cytoplasm

Explanation:

The tonoplast is the membrane surrounding the vacuole. The vacuole helps in maintaining cell volume and cell turgor; the regulation of cytoplasmic ions and pH. The tonoplast helps in the transport of ions and minerals against the concentration gradient into the vacuole utilizing energy in the form of ATP. Therefore statement 2 is wrong.

Hence, the correct answer is option 2) Tonoplast facilitates the transport of ions against the concentration gradient into the cytoplasm

Q2. When a number of primary lysosomes fuse to clear the worn out organelles, ____ are formed

1. Primary lysosomes

2. Secondary lysosomes

3. Autophagic vacuoles

4. Residual bodies

Correct answer: 3) Autophagic vacuoles

Explanation:

When some primary lysosomes fuse to clear the worn-out organelles, autophagic vacuoles are formed. When some primary lysosomes fuse to clear the worn-out organelles, autophagic vacuoles are formed. These vacuoles contain the damaged or old organelles that are targeted for degradation. The lysosomal enzymes inside the autophagic vacuole break down the organelle components into basic molecules, which can then be recycled by the cell. Autophagy is a vital cellular process for maintaining homeostasis, as it removes dysfunctional organelles and protects the cell from stress.

Hence, the correct answer is option 3) Autophagic vacuoles

Q3. Inclusion bodies of blue-green, purple, and green photosynthetic bacteria are:

1. Gas vacuoles

2. Centrioles

3. Microtubules

4. Contractiles vacuoles

Correct answer: 1) Gas vacuoles

Explanation:

• Green, purple, and blue-green (cyanobacteria) photosynthetic bacteria all have inclusion bodies called gas vacuoles.

• These gas-filled networks help the bacteria control their buoyancy, which allows them to position themselves in the water column in the most suitable potential way to absorb light during photosynthesis.

Hence, the correct answer is option 1) Gas Vacuoles.

Also Read:

• MCQs on Vacuoles

• Cell Membrane

• Semi Autonomous Organelles

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