Cell organelles and their functions is a topic of biology studied during higher education and graduate degree in science.
These cells are almost similar in all the organisms ranging from microbes to plants and animals.
A cell is a basic unit of life which carries out most of the physiological processes on its own. Except in higher animals and plants, cell of microbes like bacteria, protozoa are independent even in terms of search for food, reproduction, excretion etc..
But we can still say that a cell is independent entity and makes up the whole living system in the world.
A group of cells form a tissue, groups of tissues form an organ, groups of organs form an organism. So cell is a basic element of all the living organisms.
In microbes like amoeba, paramecium, bacteria etc. a single cell even carries out complex functions like eating, digestion, moving, sex, reproduction, excretion etc. through a few extra or modified cell organelles.
In larger animals and plants, this is not present and cells have same set of cell organelles inside.
Check Out: List Of Cells in Human Body
List of cell organelles in a typical cell:
- Cell membrane (plasma membrane)
- Golgi bodies
- Endoplasmic reticulum
- Centrosome (Centrioles)
A typical cell as shown in the image below
Plasma membrane: This is the outer covering of cell. In plant cells it is present just below the cell wall while in animal cell, it forms the outer most cover.
It encloses entire cell and its organelles. It is a selectively permeable, flexible layer of the cell. It is one of the largest organelle in a cell structure.
Mitochondria: These are sac like organelles inside the cells. They have their own single stranded DNA. Because of this DNA presence, mitochondria have ability to self replicate.
Hence mitochondria multiply within the cell even before cell divides. This is because they are worn out during the process of respiration. So, they form new ones to carry out the function non stop. Check for its structure Mitochondria structure .
Golgi bodies: These are the vacuoles or sac like structures. They occupy a considerable amount of cytoplasm. They are formed from the endoplasmic reticulum. They have two set of vesicles as Cis and Trans golgi networks. Cis-set is at the center while trans set is at the periphery of the apparatus. From these vesicles, lysosomes are formed.
Endoplasmic reticulum: This is also a sac like structure attached to nucleus and extend thereof like being suspended in the cytoplasm. It is of two types. Rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).
Lysosome: It is an organelle found mostly bound to the cell membrane. This organelle is found in all the cells and contains hydrolytic enzymes.
Peroxisome: These are vesicles which store enzymes of energy metabolism.
Centrosomes: These contain centrioles which form spindles and help in separation of genetic material in cell division.
Nucleus: This is the inner most and mostly centrally located organelle. It is the control center of the entire cell. They contain the cell’s genetic material.
Flagella: These are the organelles of locomotion. They are found in few cells like protozoans and in human cells sperms.
Cilia: These are the organelles which help in movement of particle near the membrane on outer surface.
Genetic material: This compromises DNA, chromosomes which assists in cell multiplication.This is not an organelle but is present in the nucleus and involves in cell multiplication.
Vesicles: These are small-sized sac like structures. They are of different types lysosomes, peroxisomes.
Vacuole: Vacuoles are pouches in the cell that store materials such as water, salts, proteins, and carbohydrates.
Micro-tubules: These are filamentous extensions in cytoplasm. They form the cyto-skeleton.
Cytoplasm: This is the fluid matrix of the cell. It encompasses the cell organelles, other solid substances, enzymes, water etc. Its volume is fixed and has a definite pH, tonicity depends on the ionic concentration
Cell wall: This is a non-living outer envelope of the cell. This is very characteristic and seen only in plant cells. Even bacteria possess cell wall and hence are sometime classified under plants. It is a rigid, firm, thick external covering of the cell. It is made of cellulose, mucopolysacharides and muco-peptides.
Cell organelles and their functions include:
Each cell organelle has a specific role to play in the cell’s physiology and growth.
Cell wall: Since plants are mostly non-motile, cell wall presence imparts rigidity, capacity to tolerate harsh conditions like wind, heat, wear and tear etc. It imparts definite shape to cell.
Cell membrane: This is a selectively permeable membrane and hence helps transport of desired substances into and outside the cell. In animal cells, the membrane is flexible and helps tolerate mechanical movements. It is made of glycoproteins, glycolipids etc.
Nucleus function: This is the key organelle which has the genetic material and is involved in multiplication of cell, growth and maintenance of cell. This nucleus is absent in prokaryotic cells. Nucleus has a nucleolus which produces ribosomes. These ribosomes pass out of nucleus and settle over endoplasmic reticulum to aid protein synthesis by translation.
Golgi bodies: They are helpful in storage and transport of substances in the cell.
Vesicles: These help in storage and release of substances as required by the cell. For example lysosomes help in cell digestion when cell dies. Vacuoles function is to store water.
Micro-tubules: These micro-tubules provide structural strength. Because of these micro-tubules, the cell has a fixed structure and does not collapse.
Also one comes across these cell organelles in botany. There are small differences in cell organelles and their function in between animal and plant cells. But largely similar. On the other hand most of the organelles are absent in red blood cells.
Specialized cell organelles: These are the cell organelles present in cells of special purpose. They are not common to all the cells. These include
1. Chloroplast: These are specialized cell organelles present in leaf cells and green algae. They contain chlorophyll pigment. They help in photosynthesis where in energy from sunlight is captured as carbohydrates.
2. Pilus: These are the organs present in bacteria. They small tubular structures anchoring out of the cell. They are meant for sexual reproduction.
3. Flagella: These are the organelles see only few types of bacteria. They are hair like structures helping in motion.
4. Eyespot: Seen in euglina (protozoa) and few algae. It helps detect the sunlight and move the cell towards light.
Reference:Essential Cell biology-Bruce Alberts.