explain components of eukaryotic cell
Answers
Parts of Eukaryotic Cell
Cytoplasmic Membrane: It is also called plasma membrane or cell membrane. The plasma membrane is a semi-permeable membrane that separates the inside of a cell from the outside.
The polar, hydrophilic (water-loving) heads face the outside and inside of the cell. These heads interact with the aqueous environment outside and within a cell.
The non-polar, hydrophobic (water-repelling) tails are sandwiched between the heads and are protected from the aqueous environments.
Scientists Singer and Nicolson described the structure of the phospholipid bilayer as the ‘Fluid Mosaic Model’. The reason is that the bi-layer looks like a mosaic and has a semi-fluid nature that allows lateral movement of proteins within the bilayer.
It allows transport of molecules across the
Cell Wall: The cell wall is a non-living, rigid structure outside the plasma membrane in plant cells and fungi. It is absent in Eukaryotic cells of animals
Structure and composition: It is made of different components in different Eukaryotes:
Cellulose, hemicellulose, proteins, and pectin – in plants.
Protects the cell from injury, undesirable molecules and pathogens.
Endoplasmic reticulum (ER)
Description: It is a network of small, tubular structures. It divides the space inside of Eukaryotic cells into two parts – luminal (inside ER) and extra-luminal (cytoplasm).
Structure: ER can be of two types –
Smooth Endoplasmic Reticulum (SER) Rough Endoplasmic Reticulum (RER)
Smooth due to lack of ribosomes Rough due to the presence of ribosomes
The main site of lipid synthesis Site of protein synthesis.
Functions
SER is involved in lipid synthesis and RER is involved in protein synthesis.
RER helps in folding proteins and transports it to the Golgi apparatus in vesicles.
Golgi Apparatus
An important site for packaging material within the cell.
Proteins are modified in the Golgi.
An important site for the formation of glycolipide
Ribosomes
Description: These structures are not bound by a membrane. Ribosomes are also called ‘Protein factories’ since they are the main site of protein synthesis.
A Major site for synthesis of proteins and polypeptides (chain of amino acids).
Mitochondria: They are membrane-bound organelles, also known as ‘powerhouses of the cell’.
Structure: It has two membranes – outer and inner. The outer membrane forms a continuous boundary around the mitochondria. The inner membrane is semi-permeable and divided into folds called ‘cristae’. The membranes divide the lumen of the mitochondria into an inner and outer compartment. The inner compartment is called matrix and outer compartment forms the intermembrane space.
Functions
They produce energy (ATP) and therefore are called the ‘powerhouse of the cell’.
Helps in regulating cell metabolism.
Mitochondria possess their own DNA, RNA and components required for protein synthesis.
Lysosomes
The main function of lysosomes is to digest lipids, proteins, carbohydrates and nucleic acids.
Nucleus
Description: Nucleus is the main organelle of a cell. It is a double membrane structure with all the genetic information. Therefore, it is also called the ‘brain’ of a cell. The nucleus is found in all eukaryotic cells except human RBCs and sieve cells of plants.
It provides mechanical support, maintains the shape of the cell and helps in motility.
Cilia and Flagella
They are both responsible for the movement of a cell.
Cilia Flagella
Short, hair-like structures Long structures
There are many cilia per cell There are fewer flagella per cell
Plastids
: They are double membrane organelles found in plant cells. They contain pigments and are of three types:
Chloroplasts – They contain chlorophyll and are involved in photosynthesis, where light energy is converted to chemical energy. Chloroplasts contain compartments called stroma and grana. Grana contains structures called thylakoids that contain chlorophyll. Stroma contains enzymes needed for carbohydrate and protein synthesis.
Chromoplasts – These give plants yellow, red or orange colours because they contain pigments like carotene.
Leucoplasts – These are colourless plastids that store either carbohydrates (Amyloplasts), oils and fats (Elaioplasts) or proteins (Aleuroplasts).