Different Parts of a Plant Cell

Plant cells are classified into three types, based on the structure and function, viz. parenchyma, collenchyma and sclerenchyma. The parenchyma cells are living, thin-walled and undergo repeated cell division for growth of the plant. They are mostly present in the leaf epidermis, stem pith, root and fruit pulp. Mature collenchyma cells are living, and provide stretchable support to the plant. Lastly, sclerenchyma cells (e.g. fiber cells) are hard, non-living and give mechanical support to plants. Now, let us see the different parts of a plant cell with their significant roles.

Cell WallCell wall is the outermost tough and rigid layer, which comprises cellulose, hemicellulose, pectin and at other times, lignin. As expected, it remains connected with the cell walls of other cells. The prime functions of cell wall are protection, giving structural support and helping in the filter mechanism.

Cell MembraneCell membrane, also called plasma membrane, is present inside the cell wall and surrounds the cytoplasm. It connects the intracellular components (organelles and cytoplasm) with the extracellular environment, and helps in protection and transportation. The cell membrane is permeable to specific substances only.

PlasmodesmataPlasmodesma (plural plasmodesmata) is a small opening, which connects plant cells with each other. Present only in some types of algal cells and plants cells, this connecting channel enables transport of materials and allows communication between the cells. In a single plant cell, about 1,000-100,000 plasmodesmata are present.

Nuclear MembraneThe nuclear membrane and the nuclear envelope mean one and same thing. As the name reveals, it is the outer covering of the nucleus. It separates the cytoplasmic contents from the nuclear contents. Nonetheless, minute pores (nuclear pores) are present for exchanging materials between the nucleus and cytoplasm.

NucleusNucleus is a specialized organelle, which contains the plant's hereditary material i.e. DNA (Deoxyribonucleic Acid). Inside the nucleus, a dense, spherical body called nucleolus is present. The nucleus contains structures, which regulates the cell cycle, growth, protein synthesis and reproductive function.

VacuoleVacuoles are large membrane-bound compartments, which store water and compounds. They function as storage, excretory and secretory organelles. The membrane surrounding a vacuole is called tonoplast. A mature plant cell has a single vacuole at the near center of the cell (central vacuole), which contributes to about 30-80 percent of the cell's volume.

CytoplasmCytoplasm is filled up by cytosol, which is a gelatinous and semitransparent fluid. All the organelles of the plant cell are present in this cytoplasm. This part of the plant cell is the site for cell division, glycolysis and many other cellular activities. Also, the cytoskeleton elements (microtubules and microfilaments) are present in the cytosol.

Plastid (Chloroplast)Plastids are organelles responsible for photosynthetic activity, manufacturing and storage of chemical compounds in plants. Chloroplast is an important form of plastid containing chlorophyll pigment, which helps in harvesting light energy and converting it to chemical energy. Likewise, chromoplast and other plastids are present in a plant cell.

MitochondriaMitochondria (singular mitochondrion) are oblong shaped organelles, which are also known as 'the powerhouse of the cell'. They are responsible for breaking down complex carbohydrate and sugar molecules to simpler forms, which the plants can use. Other than this, mitochondria are crucial for cell signaling, cycle, division, growth and death.

Endoplasmic ReticulumThe endoplasmic reticulum (ER) organelle plays a major role in manufacturing and storage of chemical compounds, like glycogen and steroids. It is also involved in translation and transportation of protein. ER is also connected to the nuclear membrane, so as to make a channel between the cytoplasm and the nucleus.

Golgi ApparatusGolgi apparatus also known as golgi complex and golgi body. It is an organelle responsible for processing of macromolecules (like carbohydrates, proteins and fats) and packaging them into membrane-bound vesicles for transportation purposes. Golgi bodies are present near to the nucleus of the plant cell.

RibosomeRibosomes are organelles, which are made up of 60% RNA (Ribonucleic Acid) and 40% protein, and play an important role in protein translation. It won't be wrong to say that the main site of protein synthesis is ribosome. Endoplasmic reticulum having ribosomes is referred to as rough endoplasmic reticulum (RER).

MicrobodiesMicrobodies are single, membrane-bound, globular shaped organelles, which are found in the cytoplasm. They range in size from 0.5-1 micrometer, and contain degradative enzymes. Many kinds of microbodies are present in a plant cell, of which the two most common types are peroxisomes and glyoxysomes.

MicrotubulesMicrotubules are straight, hollow, tubular cylinders, which are major elements of the cytoskeleton. These plant cell structures are involved in synthesizing cell wall. Function wise, they are crucial for structural support, cell division and transport of vesicles. Microtubules in a plant cell are simpler, as compared to those of an animal cell.

MicrofilamentsMicrofilaments are thin, filament like structures found in the cytosol, which contain actin subunits. These along with the microtubules make up the cytoskeleton of plants cells. Similar to the microtubules, the microfilaments are responsible for giving structural support, flexibility and shape to the cell.

In the overall functioning of a plant cell, the above cell parts coordinate in a specific manner. As you have seen, lysosomes are absent in plant cells. While vacuole is large and single in a plant cell, the animal cell houses smaller vacuoles in larger numbers. Likewise, for understanding the differences between plant and animal cells, you can study the cells separately along with the types of organelles present in them

Animal Cell: Structure

The structure of an animal cell differs slightly from a plant cell, in terms of shape, protective covering and organelles. Like for instance, in the labeled animal cell diagram, it is near circular in shape and lacks outer cell wall; while the plant cell resembles rectangular shape and possesses a rigid cell wall. In short, the outer layer of an animal cell is the flexible membrane. Other features that differentiate an animal cell from a plant cell are the presence of smaller vacuoles and absence of plastids.

Animal Cell: Parts and Functions

Animal cell functions and organelles are linked to each other. In fact, the collective work of the animal cell parts is responsible for overall functioning of the cell. Let's take an example of ribosome organelle, which does the main function of protein production. Likewise, mitochondria are centers for releasing energy. And it is because of the lack of cell wall that makes animal cell a more diverse type. Animal cell functions with respect to its specific parts are explained below.

Cell Membrane: As you refer to the animal cell model, you will notice that this cell is lined by a double-layered cell membrane. This membrane not only separates the inner cell content from outside, but also allows transportation of substances between the cell and surrounding.

Cytoplasm: An animal cell is basically divided into two types, nucleus and cytoplasm. The latter is the space that occupies maximum part of the cell and where the cell organelles are present. Filled with a material that is similar to the consistency of jelly, the cytoplasm function in a cell is to support the internal parts.

Nucleus: The cell nucleus is the control center for all types of animal cells. It houses the genetic material or more precisely, the chromosomes. The nucleolus is located at the near center of the nucleus and is crucial for protein synthesis in animals.

Ribosome: As the name signifies, ribosomes are made up of ribonucleic acid (RNA) and protein. They are present freely in the cytoplasm, or attached to the endoplasmic reticulum. As far as importance of ribosomes in animal cell functions is concerned, they are crucial for making proteins.

Endoplasmic Reticulum: The endoplasmic reticulum (abbreviated as ER) is crucial for synthesis, metabolism and transportation of compounds. It resembles a closed network with sac-like structures. There are rough ER (RER) and smooth ER (SER), with the former bearing ribosomes and helping in protein synthesis.

Mitochondria: In animal cell functions, the mitochondria (singular form, mitochondrion) are found in the cytoplasm. They are the powerhouse of the animal cell, performing the major function of converting nutrients and oxygen directly into energy sources.

Golgi Apparatus: Known by different names, golgi bodies and golgi complex, it is an organelle having sac-like structure. The golgi apparatus function is packaging cellular substances, which are then transported out of the cell with the help of vacuoles.

Lysosomes: The lysosomes are sometimes called vesicles, and are nearly circular shape. Containing digestive enzymes, you can predict lysosomes function. In the animal cell functions, lysosomes contribute by helping in digesting wastes and throwing them out of the cell.

Centrioles: The centrioles are present only in an animal cell. Comprising bundles of microtubules (nine in number), there are two centrioles located near the nucleus. They are cylindrical organelles, which play a role in orientation of cells during mitotic cell division.

Cilia and Flagella: These are present in unicellular animal and plants. In single-celled eukaryotes, the functions of cilia and flagella are attributed to locomotion of the organism from one place to another. Structurally, they are hair-like and present in the cell membrane.

With this brief information on animal cell functions and structures, I hope you are thorough with the concept of cell functioning and how organelles play their part in the cell. Had there been any defect in the cell parts, the cell functioning will not be normal. For thorough understanding, you can make a comparison between plant cell functions with that of an animal cell and point out the basic differences between them.