This document provides in-depth knowledge with a step-by-step explanation of each and every concept regarding the Cytology notes for CELL ORGANELLES to enhance your knowledge
CELL ORGANELLES
1 HISTORY
(i) The branch of biology which deals with the study of cell is known as
Cytology.
(ii) Robert Hooke discovered cell and described it in his book
Micrographia.
(iii) Beedle and Tatum proposed “One gene one Enzyme” hypothesis
(iv) R.Virchow stated “Omnis cellula ecellula” which means all cells arise
from a pre-existing cell.
(v) Kari Nageli showed that cells in plants arise by the division of pre-
existing cell.
(vi) Robert Hooke coined the term “Cellula”for honey comb like structure
of bottle cork.
(vii) Living cell was discovered by Leeuwenhock.
2 FATHER
(i) Father of Microbiology is Antoni von Leeuwenhock.
(ii) Father of Microscopic Anatomy is Marcello Malpighi.
(iii) Father of cytology is Robert Hooke.
(iv) Father of modern cytology is C.P. Swannson
(v) Father of Indian cytology is Dr A.K. Sharma
3 GENERAL FACTS REVEALED WITH CELLS
(i) Longest cell is nerve cell of Giraffe which is more than 1 metre (90cm in
man)
(ii) Largest egg is the egg of ostrich (17cm X 13.5cm).
(iii) Smallest cell is PPLO (Pleuro Pneumonia Like Organism).
(iv) Smallest plant cell is mycoplasma laidlawii (0.1µ).
(v) 60 Billion cells are found in human body.
(vi) 10 Billion cells are found in human brain.
(vii) In India, the centre of cellular and molecular biology is at Hyderabad.
,4 CELL THEORY
(i) Cell theory was proposed by Schleden (in plant cell) and Schwann (in
animal cell).
(ii) According to cell theory all living things are made up of cells. Cell is
structural and physiological unit of living beings. Cell has the power of
reproduction.
(iii) Cell theory is not applicable to viruses.
5 STAINING
Sno Stain Final Color Suitable for
(i) Janus green Greenish blue Mitochondria
(ii) Brazlin Red DNA
(iii) Aurantia Yellow Mitochondria
(iv) Toludin-Blue Sky blue RNA
(v) Para Rosalin Purple DNA
(vi) Fuelgen stain Red Purple DNA
(vii) Methylene Blue Nucleus
(viii) Sudan black Black/Red Lipid
(ix) Iodine solution Blue/Red Starch/Glycogen
(x) Eosine Red/Pink Cytoplasm/Cellulose
Cell Coat (Glycocalyx)
1. Position:- It is found outside the plasma membrane in many
protestants and animal cells.
2. Function:-
(i) It provides the cell a definite shape.
(ii) It helps in recognition of microbes for defense.
(iii) It protects the underlying plasma membrane.
(iv) It plays an important role in cancer, blood grouping and
rejection.
, CELL WALL
1. INRTODUCTION
(i) Each plant cell is surrounded by a rigid wall which is called cell wall
(ii) Cell wall was first studied by Robert Hooke in cork cells.
(iii) Due to the presence of cell wall, plant cells can be differentiated from
animal cells.
(iv) It is a secretary substance of the protoplasm which protects the cell.
2. STRUCTURE OF THE CELL WALL
(i) Generally, it is made up of cellulose however the cell wall of fungi is
made up of fungus cellulose or chitin and the cell wall of bacteria and
Blue Green Algae (BGA) is made up of DAPA and mumaric acid.
(ii) Numerous thread-like fibrils are found in this wall.
(iii) One fibril is formed of about 250 micro fibrils.
(iv) One micro fibril is also formed of about 20-22microfibrils which is called
elementary Fibril or Micelle.
(v) One micelle is formed of about 100 chains of cellulose molecules.
(vi) Approximately 3000 chains of glucose molecules are found in one
molecule of cellulose.
(vii) Matrix is found between the micro fibrils, this matrix is a gel like
substance in which pectin, lignin etc are found.
(viii) The cell wall is made up of four layers which are as follows:
2.1 Middle Lamella
(i) It is formed by the division of nucleus in two parts during the cell
division.
(ii) In this division the minute drops of some substances of protoplasm
become aligned at the equatorial plate and forms cell plate.
(iii) By some physical and chemical changes in this cell plate, an amorphous
substance is formed which is called middle lamella.
(iv) It is formed of calcium and magnesium pectate.
(v) It functions as cementing between two cells.
, 2.2 Primary Wall
(i) Protoplasm deposits some substances on the middle lamella due to which
a soft, delicate, plastic primary wall is formed.
(ii) This wall consists of the following substances
(a) Pectic substance, Arabinose, Galactose, Galacturonic acid
(b) Cellulose-Glucose
(c) Hemicellulose – Mannose, Xylose, Gluconic acid
(iii) Root hairs, parenchymatous cells and merismatic cells are formed of only
primary wall.
2.3 Secondary Wall
(i) This wall is made up of cellulose and hemicelluloses and is situated
inside the primary wall.
(ii) Generally lignin, leutin and suberin are deposited.
(iii) This wall is non-elastic and thick (5-10µ)
(iv) It is formed of the following three layers in most of the cells:
(a) Outer layer
(b) Middle layer
(c) Inner layer
2.4 Tertiary Layer
(i) After sometime cellulose wall is formed on the secondary wall which is
called the tertiary wall
(ii) Tertiary wall and secondary wall are commonly known as secondary
thickenings.
(iii) Additional substances do not accumulate on each area and leave the
deposition on the cell wall, these spaces are called primary pit fields.
(iv) Micro fibrils of protoplasm reaches from one cell to another cell by these
paces, these fibrils are called plasmodesmata.
(v) The main function of these plasmodesmata is in conduction of substances
and stimuli.
(vi) Due to the presence of plasmodesmata, entire protoplasm is found in the
form of continuous system or large continuity which is called symplast.
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