Animal Cell - Structure, Cell Organelles, and Functions

What is Animal Cell?

 

Animal cells are typical of the eukaryotic cell, enclosed by a plasma membrane and containing a membrane-bound nucleus (true nucleus) and other organelles.  Animals' cells are multicellular organisms.

Animal cell lacks a cell wall. The lack of a rigid cell wall allowed animals to develop a greater diversity of cell types, tissues, and organs with different shapes.

Eukaryotic cells, both animal and plant, cell size range between 1-100 micrometers, visible only with the aid of a microscope.

Check out the difference between animal cell and plant cell.

 

Animal Cell Diagram

 

Animal cells consist of various cell organelles, diagram is provided below- 

 

 

 

Animal Cell Organelles and Functions

 

Cell Organelles are- 

 

1. Cell membrane (Plasma membrane) 

 

All living organism cells have a cell membrane (plasma membrane), it is the outermost component of the cell that encloses all the cellular contents.

Its primary role is to protect the cell from its surrounding and separates the cytoplasm inside a cell from the extracellular fluid outside. These membranes also regulate the flow of molecules and materials in and out of the cells. 

 

2. Cytoplasm

 

The cytoplasm is jelly-like material, filling the cell, which suspended all the cell organelles, such as the endoplasmic reticulum, mitochondria, ribosomes enclosed within the cell membrane.

 The cytoplasm is responsible for giving its shape means helps keep the shape of the cell.  It is a place where many biochemical reactions take place for a cell's existence.

The cytoplasm consists of all the cellular content between the plasma membrane and nucleus, it has "two compartments"- cytosol and organelles (little organs).

 

3. Nucleus

The nucleus is a storehouse of genes, the brain of cells, and the largest organelle in a cell.

 

The nucleus carries the cell's hereditary material or genetic material of the cell (DNA), which contains hereditary units called genes. Its controls, coordinates and regulates all cellular activities within and outside the cell. It is also called the control center of the cell.  

 

The nucleus consists of – 

 

1. Nucleoplasm

2. Nucleolus

3. Nuclear Pore

4. Nuclear Envelope/ Nuclear Membrane 

 

4. Ribosome

 

The ribosome is the dumbbell-shaped minute particle, made up of ribonucleic acid and protein ribonucleoprotein (RNP).

There are two types of ribosomes - free and fixed. Free ribosomes are located in the cytosol. Fixed ribosomes are attached to the Rough Endoplasmic reticulum (rER).

Ribosome produce protein via a process called translation (the process of translating mRNA into protein). A ribosome is the site of protein synthesis, also called the protein factory of the cell.

 

 

5. Endoplasmic Reticulum

 

Endoplasmic reticulum (ER) is a network of membrane-encloses flattened sacs is made up of tubules, cisterns, and vesicles that connected to the nuclear envelope.

 

Depending upon the Presence or Absence of ribosomes, ER is two types –

 

1. Smooth endoplasmic reticulum (SER)

2. Rough endoplasmic reticulum (RER)

 

SER has a smooth membrane and doesn’t bear ribosomes. RER has rough membrane and bears ribosome (consisting of RNA) on its outer surface.

These are involved in the processing, modification, and folding of the synthesized proteins and transported out of a cell, detoxification of harmful metabolic by-products, and storage and release of calcium, ions.

 

6. Mitochondria 

 

Mitochondria are double-membrane-bound organelles found in eukaryotic cells.  It is involved in releasing energy from nutrients. This process is known as cellular respiration.

Mitochondria is a vital and major organelle of a eukaryotic cell and is called the powerhouse of the cell. It produces energy in the form of ATP (adenosine triphosphate) for various functions in the cell and body.

 

7. Golgi complex/ Apparatus 

 

Golgi Apparatus is also known as Golgi body or Golgi complex. The golgi body is a membrane-bound organelle of eukaryotic cells. It is made up of a series of flattened, stacked sacs or pouches called cisternae.

Most of the proteins synthesized by ribosomes attached to the rough endoplasmic reticulum are ultimately transported to golgi Apparatus and exported to targeted destinations.

 

Ribosome - Rough Endoplasmic Reticulum - Transport Vesicles - Golgi Complex - Secretory vesicles -  Exocytosis

 

8. Lysosomes

 

Lysosomes are tiny sphere-shaped sac-like structures, bounded by a single membrane. It is filled with hydrolytic enzymes that have the capability to break down a variety of biomolecules and ability to destroy foreign particles and digest cells and unwanted materials.

 

Lysosomes are generated by the Golgi apparatus/ complex.

 

9. Peroxisome

 

Peroxisomes are organelles found in the eukaryotic cell. It is single membrane-bound organelles. New peroxisomes bud from pre-existing ones Peroxisomes.

Peroxisome vesicle contains oxidases and catalase that decompose hydrogen peroxide. It converts hydrogen peroxide to water and oxygen and neutralizes the toxicity.

 

10. Cytoskeleton

 

Cytoskeleton is the internal supporting network of cells. It laced all of the material within a cell. It provides the shape of the cells and gives the ability to carry out coordinated cellular movements and cell division.

The eukaryotic cytoskeleton consists of three main types of protein filaments-

 

1. Microfilaments/actin filaments

2. Intermediate filaments

3. Microtubules

 

11. Cilia and Flagella

 

Somebody cells have projections for moving the entire cell known as flagella. It is long, hair-like structures.

Moving substance along the surface of the cell is known as cilia. It is short, hair-like structures. Cilia are shorter and more numerous than flagella.

 

12. Centrosome and Centriole

 

Centrosomeis an organelle found in the cytoplasm near to nucleus. It contains a pair of centrioles embedded in a pericentriolar material (PCM, pericentriolar matrix). 

Centriole aids in organizing the mitotic spindle and completes the process of cytokinesis.

Centrosomes and Centriole, both are necessary for cell division, for cells to divide into two new identical daughter cells.

 

 

13. Proteasomes

 

Proteasomes are large protein complexes that degrade or destroy unneeded or damaged proteins of cells by a process called proteolysis (protein broken down into small peptides into amino acids) with the help of enzymes proteases. These resemble tiny barrel structures.

 

14. Microvilli

 

Microvilli are microscopic cellular membrane protrusions, cylindrically shaped extensions of the plasma membrane about 0.5-1 micrometer in length, and have a minute opening. They are not motile.

Microvilli are present in the intestine, kidney, and other areas of the body.  Absorption is an important function of microvilli, it increases the surface area for diffusion.

The function of microvilli is to increase the surface area of the cells and the efficiency of absorption for ingested food and water molecules.

 

15. Vacuole

 

A vacuole is a membrane-bound cell organelle. They look similar to vesicles and form when multiple vesicles fuse together.

Vacuole helps in-store waste products and export unwanted various substances from the cell, so that cell is protected from contamination.

Vacuoles also stored the food or any variety of nutrients that cells might need to survive. It helps in maintaining internal hydrostatic pressure or turgor within the cell.

 

In-plant cells, Vacuoles are filled with water, which helps to maintain water balance.

 

16. Secretory Vesicles

 

Secretory vesicles form from the trans-Golgi network (TGN). It is a major secretory pathway of the Golgi network.

Secretory vesicles play a vital role in the export of molecules outside of the cell, through a process called, exocytosis and from an organelle to specific sites at the cell membrane.

For example, hormones or neurotransmitters.

 

17. Cell Inclusion

 

Also called cytoplasmic inclusions or inclusions bodies or elementary bodies.

Cell Inclusions are stored nutrients, chemical substances, secretory products, and pigment granules. Chemical substances are usually either food material or stored products of cellular metabolism. Chemical substances are produced by cells or taken in by the cell.

 

These are not permanent components of the cell, constantly being destroyed and replaced. 

Examples are - pigments such as melanin and glycogen, fat, triglyceride, haemoglobin.