Cell Organelles
The components of the cells which helps in construction and functioning of the crkl are called organelles. Infact organelles are the parts of the cell itself.
Different organekles perform different functions of the cell such as Ribosome synthesize protein, Mitochondrion provide energy to cell cell, Nucleus keep chromoso-
mes safe and separate from other substance and Golgi body or Golgi apparatus secrtes the hormones etc.
The major group of the cell organelles
1-Plasma membrane
2-Cytoplasm
3-Nucleus
Name of the cell organelles
Living parts of a cell
1-Plasma membrane
2-Cytplasm
i-Endoplasmic Reticulum (ER)
a-Smooth ER
b-Rough ER
ii-Mitochibdrion
iii-Golgi Apparatus
iv-Ribosomes
v-Lysosomes
vi-Centrioles
vii-Plastids
3-Nucleus
Non-living parts of the cell
i- Cell Wall (in plants only)
ii-Vacuoles
iii-Granules (Cell inclusions)
Plasmamembrane
Nature of Plasmamembrane
1- Each and every cell has an outer covering that is known as Plasma
-membrane.
2-Most of the organelles as Lysosomes, Nucleus, Peroxysomes, Mitochondria, Golgi
Apparatus, Endoplasmic reticulum (ER.) and chloroplast are beleagured by this plasmamembrane.
Structure of Plasmanembrane-
1-Plasmamembrane is selectively permeable. It means, it allows some specific substances to come inside the cell.
2-It is a thin, delicate,and elastic membrane.
3-Thethickness of the membrane is 70 ºA.
4-On using a somple microscope it looks like a single line.
5-If we use an Electron microscope we will find three layers in which one layer is of lipid that is beleagured by two protein layers.
6-The lipid layer is composed of lipid and phoshate, so called Phospholipid. In Plasma
membrane, phospholipid is found 75 %.
Fluid Mosaic Model of Plasmamembrane-
This model was given by two scientists Singer and Nicolson in 1972. They suggest that there is a bilayer of phospholipid (combinedly one layer) is covered by two upper and lower protein layers. Some molecules of Protein are embedded in yhis menbrane, called intrinsic protein and some molecules are outside the membrane
are called extrinsic protein, so we can describe the Fluid mosaic model as " a number of proteiny iceberges floating in the sea of liquid " The protein are not to give only strength to the membrane but it serves as (i) enzymes (catayse chemical reactions )(ii) transport proteins or permeases (for movements of water soluble ions) (iii) pumps (for active transport) (vi)receptor proteins (for endocytosis). Presence of lipids and proteins provide flexibility to the membrane. This property of the flexibility of yhe membrane helps in endocytosis.
Advantage of selective permeability-
1-The useful molecules enter yhe cell.
2-The metabolic intermediates remain within the cell.
3-Seccretion and wastes leave the cell.
Functoons of Plasmamembrane-
1-Some substances (molecules or ions) such as carbon dioxide, Oxygen, water etc. can move across the plasmamembrane through a process called diffusion.
Note- Diffusion is sn event in which molecules of the gases or substance of higher concentration go to the molecules of the low concentrations. Generally no membrane required for this process.
2-The movement of liquid take place through Osmosis.
Note-Osmosis is an event in which Molecules of the water or liquid move from higher concentrations to the lower concentration of the solution through the Plasmamembrane.
Nucleus-
Structure of Nucleus-
Nucleus is surrounded by double membrane.
The nucleus possess pore which allow the transfer of material from inside the nucleus to its outside.
Nucleus contains chromosomes which are visible as road like structure.
Chromosomes have information for inheritance of features from parents to next generation in the form of DNA molecules.
Chrimosomes are composed of DNA and proteins.
Nucleus plays an important role in cellular reproduction. In cellular reproduction the cell is divided ino two daughter cell.
In some organisms like bacteria nucleus is poorly defined, such a undefined region of nucleus containing nucleic acid is called a nucleoid.
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