Cell biology is one of the interesting branches of science that educates students on basic parts of the body, mostly on the cells and its functioning.
Cell is the basic yet important part of living organism. We all know that, to do any construction first bricks are laid and then slowly complete structure is formed. Likewise, cells are the building blocks that help in further formation and progress of the body. Cells are important since they carry all the physical and chemical process of the system. The structure of cell varies in plant and animals. It has protoplasm enclosed within membranes that consist of many proteins and nucleic acid. These cells are numerous in number and every now and then they undergo renewal process, so as to maintain their cycle and the number.
Animal cell have quite different shape in comparison to other living being on the earth. It consists of different organelles, like that of cell membrane, lysosomes, nucleus, and many more. The function and structure of each of these organelles are briefly described below:
1. Cell membrane: it is an outer membrane that surrounds the cell. It is semi permeable in nature and allows only some of the substance to pass inside and out of the cell. It is made up of lipid and proteins that acts as the selective barrier for the important substances. Here, both lipid and protein serve quite different function. Proteins checks all the chemical processes including the entry and exit of the substance whereas lipid maintains cells shape and flexibility. In animal cell, cell membrane is the first and outermost structure whereas in the plant cell, it is the second structure after cell wall. Lipid that makes this cell wall, are of different types. It has phospholipids that form the bilayer for entry of the substance, whereas cholesterol helps to keep the membrane stiff. Finally is the glycolipids that helps in recognisation of surrounding cells. Like the lipid, proteins are also of different types. One is the structural protein that provides cell shape, other is the receptor proteins that carries the communication process with external and internal environment, thirdly is the transport protein that assist in transport of molecules and finally is the glycoprotein that help in communication of two or more cells along with transport of molecules. This way, cytoplasm, the main component of cell checks for entry and exit of substances thus, maintain the balance between outer and interior environment of the cell.
2. Cytoplasm: it is the portion of cell that is present outside the nucleus. It is jelly like where many cell organelles are present that are essential for functioning of the cell.
3. Golgi bodies: this lies in the cytoplasm of the nucleus. It helps in packaging of proteins and lipids for transportation in or out of the cell. Therefore, Golgi bodies can be more or less in a cell depending upon the secretion and its function. It is a sac like structure that has many cisternae. It has two different faces; one end is cis phase that receives the substances whereas the other face is trans face from where the substance exist for further processing. The substances that leaves the ER enters cisternae of Golgi complex where they are modified and then send to further compartments thus exiting from the trans face and sending the modified substances to respective organelles. Beside, proteins Golgi apparatus is also involved in modification of lipids. Thus, helping in proper processing of every substance.
4. Mitochondria: it is a semi- autonomous organelle also called power house of the cell. It is rod shaped organelles made up of two layers, outer and inner. Outer membrane is smooth whereas inner layer is folded to form cristae. These fold are not only structural portion for mitochondria, rather they increase surface area increasing the production of cellular respiration. It is a site for cellular respiration along with involvement in cell division and cell death. It has its own DNA called mitochondrial DNA and this organelle helps in conversion of stored energy to the useable form.
5. Lysosomes: it is round in structure and is also called as digestive enzyme. It digest any of the unnecessary materials whether food particles, viruses or bacteria, thus also called hydrolytic enzyme that keeps the cell free of unnecessary substances. The natural environment of lysosomes is acidic thus helping to digest, proteins, nucleic acid and any other used substances. Beside this, it is also involved in programmed cell death. Improper functioning of lysosomes makes individual suffer from various types of dangerous diseases.
6. Centrosome: it is also called microtubule organizing centre, a small tubule located near the nucleus. It produces microtubule of the cell that is a key component of cytoskeleton. In animal cell, only a single centrosome is present.
7. Ribosomes: these are the important organelles that are found in the living cells. They are the site of protein synthesis. They can be found freely or attached to any membrane in a cell. They have two units the larger subunit and the smaller subunit. On the basis of function and their presence, they are of three types, tRNA, mRNA and rRNA that helps in the translation process and hence production of protein.
8. Endoplasmic Reticulum: it is a system of interconnected network located in the cytoplasm. It has many folding that forms cisternae. It is of two types based on the structure and function:
9. Nuclear membrane: it is the membrane that surrounds the nucleus and hence divides nuclear content form cytoplasm.
10. Nucleolus: it is the organelle that lies inside the nucleus and can vary in number, i.e. some cells have only one nucleus and others have more than one nucleus.
11. Nucleus: it is the main portion of the cell. It has DNA and thus, nucleus controls and maintains all the activity of the cell.
12. Vacuole: it is a fluid filled cavity where digested food and waste product that are in the path of excretion gets filled up.
13. Cilia and flagella: these are the protrusion form the body surface that helps in movements and locomotion. Cilia are small in length but numerous in numbers whereas flagella are less in number but longer in length.
These are some of the most important cell organelles in animal cell. These cell organelles together helps in functioning and progress of their body system.
Cell organelle seems like a single chapter from a biology textbook, but it is not so. In fact, it is a complete field where students can grab knowledge on differences of plant cell from that of animals. They can study about each organelle in detail and these studies helps in treatment of various diseases and introduction of several drugs that will keep human beings and animals away from any problem in their system. Beside this, we can even design drugs for human use if studied about each organelle in details and thus eliminate or avoid several unexpectedly increasing diseases.
Beside the details study on cell organelles this field of biology also deals with cell cycle in animals and all the effects that results from any disturbance in this cycle. Cell cycle in animal is quite complex, since they are eukaryotes with nucleus, cell undergo round of replication process along with division of cells, so as to form daughter cells. This cell division takes place via, mitosis and meiosis. Mitosis is the process where cell divides in equal number whereas in case of meiosis the cell number reduces to half. This is not yet the simple process, many enzymes and different molecules with varying steps takes part in this process. Mitosis is divided into prophase, metaphase, anaphase and telophase whereas meiosis has two round of division. DNA replication in this case, occurs only once whereas cell divide twice. Beside these two steps, one more type of division called binary fission helps in division of cells and hence formation of daughter cell. These divisions’ takes place in animal cell and are studied in detailed way in animal cell biology. Animal cell biology is a vast subject that has lots of information and this depth information helps students to establish a successful career in research field or a lectureship.
As we all know that science is all about hard work, therefore this subject is completely based on students understanding and patience that makes them master of this field.