Describe the structure and functions of various cell organelles
Answers
Cell Organelle
A small organ-like structure present inside the cell is called a cell organelle. It has a particular structural makeup and performs a specific function. Depending upon the presence or absence of membrane, cell organelles can be classified into three categories, namely:
Without membrane: Some cell organelles like ribosomes are not bounded by any membrane. They are present in prokaryotic as well as eukaryotic organisms.
Single membrane-bound: Some organelles are bounded by a single membrane. For example, vacuole, lysosome, Golgi Apparatus, Endoplasmic Reticulum etc. They are present only in a eukaryotic cell.
Double membrane-bound: Cell organelles like mitochondria and chloroplast are double membrane-bound organelles. They are present only in a eukaryotic cell.
Learn more about Cell Division and Cell Cycle here.
Structure and Functions of Cells
Structure and functions of different cell inclusions are as follows-
Cell Organelle Occurrence/ Characteristic & Structure Function
Cell Membrane/ Plasma Membrane
Present in both plant cell and animal cell.
Selectively Permeable: Allows the materials in and out of the cell according to the requirement of the cell.
Made up of bilipid layer and protein (Fluid Mosaic Model)
Encloses the contents of the cell.
Provides shape: animal cell.
Allows transport: by Diffusion and Osmosis.
Cell Wall
Present only in a plant cell.
Hard and rigid.
Fully permeable.
Made up of Cellulose in plant and peptidoglycan in bacteria.
Protection
Gives shape and turgidity.
Cytoplasm
Contains 80-90% water and many organic and inorganic compounds.
Colloidal, Viscous, Jelly like fluid inside the cell.
Contains enzymes responsible for all the metabolic activity taking place inside the cell.
Nucleus
(Director/ Brain of the Cell)
Covered by a double membranous nuclear membrane in a Eukaryotic Cell.
Contains DNA, RNA, Protein, nucleolus, and Chromatin network.
Controls the activity of the cell.
Starts cell division.
It has the chromosomes or DNA which controls the hereditary characters
Mitochondria (The Power House of The Cell / Storage Batteries)
Double membranous structure.
Autonomous body as contains its own DNA.
Self-duplicates
The main seat of respiration.
Stores energy in the form of ATP molecules.
Golgi Bodies
(Shipping Department of Cell)
Discovered by Camillo Golgi in 1898.
Originates from RER.
Contains Sac like Cisternae and Vesicles.
Has two faces – cis face or receiving face and trans face or supplying face.
Modification, Packaging, and transport of materials
Synthesis of lysosomes, plasma membrane
Endoplasmic Reticulum
(Framework of Cell)
A network of membranes.
RER bears ribosomes and appears rough
SER does not have ribosomes
Forms the skeletal framework of the cell.
Transport of materials from one cell to other.
Provides a surface for the synthesis of material – Proteins in RER and Lipids in SER.
Formation of lysosomes, Golgi bodies and vacuoles
Membrane Biogenesis
Detoxification of harmful substances in the liver.
Vacuole
Arise from ER and GB
Surrounded by tonoplast and filled with cell sap
Store cell sap which may be liquid or solid food, toxic byproduct.
Provide rigidity and turgidity to plant cell
Lysosomes (Suicidal bags of Cell, natural scavenger, cellular housekeeper)
Membrane-bound organelles
Present in all animal cells and few plant cells
Tiny circular single membrane-bound structures filled with digestive enzymes
Intracellular digestion of food in unicellular organisms.
Ribosomes (Protein Factories)
Without a membrane
Consist of two subunits – 60S and 40S in eukaryote both made up of RNA
Synthesis of Proteins
Plastids
Double membrane-bound
Types-
Leucoplast –Colourless plastid;
Chromoplast –Coloured Plastid – blue, red, yellow
Chloroplast – Green plastid
Autonomous self-duplicating body
Chloroplast – Perform Photosynthesis – Helps in the release of oxygen
Chromoplast – impart colour to flowers which help in pollination
Leucoplast – Storage
Amyloplast –Store starch
Aleuroplast – Store Protein
Elaioplast – Store fat
Answer:
The structures and functions of various cell organelles in a cell are:
- The nucleus - It is a double membrane organelle found in all eukaryotic cells. It is the largest organelle. It is carrier of genetic material of the cell.
- Endoplasmic reticulum (ER) - It is a large network of membranes responsible for the production of proteins, metabolism and transportation of lipids, and detoxification of poisons. It is situated surrounding the nucleus and also provide structural strength to the cell.
- Mitochondria - They are called the powerhouses of the cell as they produce energy-rich ATP molecules for the cell.
- Ribosome - Ribosomes are small organelles in all cells that make protein. Ribosomes are made of both protein and ribosomal RNA (rRNA).
- Vacuoles - It is membrane-bound air sap organelles that can be found in both animals and plants. In a way, they're specialized lysosomes. That is to say that their function is really to handle waste products, and by handle, mean take in waste products and also get rid of waste products.
- Lysosome - It is single membrane bound organelle which are the suicidal bag of the cell as it recycles the waste material of the cell by destroying it in itself by its digestive enzymes.
- Golgi Apparatus - It is also termed as Golgi Complex. It is a membrane-bound organelle, which is mainly composed of a series of flattened, stacked pouches called cisternae. The Golgi apparatus, or complex, plays an important role in the modification and transport of proteins within the cell.