Samacheer Class 11 Bio Botany - Cell The Unit of Life

• Fischer in 1894 & Hardy ( 1899 ) Proposed the Colloidal theory of Protoplasm (the physical basis of life)
• It is a colloidal system with water, many biological import things, glucose, fatty acids, amino acids minerals, vitamins hormones & enzymes are seen.
• Homogenous -These solutes are soluble
• Heterogenous – Solutes are not soluble – This Forms the basis for its colloidal nature.
• Protoplasm occur in 2 states but interconvertible

Prokaryotes
Eukaryotes
Size of cell
1-5 cm
10 -100 cm True Nucleus
Nuclear character
Nucleoid or incipient nucleus only (No nuclear membrane or Nucleolus
Nucleolus & Nuclear membrane present
DNA
Usually Circular without histone protein
Usually linear with histone proteins
RNA/ Protein synthesis
Couples in Cytoplasm
RNA Synthesis inside Nucleus / Protein synthesis in the cytoplasm)
Ribosomes
50 s +30 s (70s)
60s + 40s ( 80s)
Organelles
Absent
Numerous
Cell Movement
Flagella
Flagella & Celia
Organisation
Usually unicellular
Single, Colonial and multicellular
Cell division
Binary Fission
Mitosis & Meiosis
Example
Bacteria & Archae Bacteria
Fungi, Plants, and Animals

Plant Cell
Animal Cell
1.Usually they are large than animal cell
Usually smaller than plant cell
2. Cell wall present in addition to plasma membrane and consists of middle lamellae. Primary and secondary walls
Cell wall absent
3. Plasmaodesmata present
Plasmodesmata absent
4. Chloroplast present
Chloroplast absent
5. Centrioles absent except motile cells of lower plants
Vacuole small and temporary
6. Vacuole larger and pennanent
Tonoplast absent
7. Tonoplast present around vacuole
Centrioles present
8. Nucleus present along the periphery of the cell
Nucleus at the centre of the cell
9. Lysosomes are rare
Lysosomes present

* Jonathan Singer & Garth Nicolson (1972) proposed FM model.
* Plasma membrane made up of lipid (phospholipid), protein & little carbohydrate.
I. Phospholipid: Molecule has a hydrophobic tail(repel water) & hydrophilic head (water-loving)
II. Protein of membrane
* Globular in nature intermingles between lipid bipolar most perfect beyond Jt known
as (integral proteins)
Few are superficially attached on either surface of lipid bilayer (peripheral proteins)
* They are involved in transport of molecules across the membrane
* They acts as enzymes
* They acts as receptors or antigens.
III Carbohydrate
* They are short chain of polysaccharides.
(i.e) With protein glycoprotein With lipid glycolipids, glycocalyx
Flip Flapping:
* The movement of membrane lipids from one side of the membrane to the other side by vertical movement called flip-flap movement.
A- hydrolipid tail,
B-hydrophilic head,} lipid
C-intrisic protein
D-extrinsic protein
This movement is very slow than lateral diffusion of lipid molecules.
* Phospholipids can flip flop due to smaller polar regions.
* Proteins cannot do so because of extensive polar regions.

* The largest internal membrane (ER)
* Name given by K.R.Porter(1948)
Consists of Vesicles &Tubules, Cisternae
Cisternae:
* Long broad, flat sac-like structures arranged in stacks to form lamella.
* In between membrane is filled with fluid
Vesicles:
Oval membrane-bound vascular structure
Tubules:
Irregular shaped, branched, smooth-walled structure enclosing a space
Function:
* It is associated with nuclear membrane and cell surface membrane
* When ribosomes present on ER- it is known as (RER) Rough Endoplasmic Reticulum
* When ribosomes absent on ER- it is known as Smooth Endoplasmic Retiöulum(SER).

* 1st observed by A. Kolliker (1880)
* Altmann(1894) – named it as Bio-plasts
* Benda (1897) – named as Mitochondria
Structure
* Ovoid, rod-shaped, pleomorphic structures
* Double membrane
* Outer membrane smooth, & permeable- contain porins
2 compartments
1. outer chamber between 2 membranes
2. Inner chamber filled with matrix
Cristae – Infoldings of inner membrane:
* It contain enzymes for ETS(Electron Transport System)
* Inner membrane has FI particles or exosomes
* Each FI particle has a base, a stem & a rounded head
* Head has ATP synthetase to do oxidative phosphorylation content.
* 73% protein
* 25-30% lipids
* 5-7% RNA, DNA & enzymes(about 60 circular DNA &70’s Ribosomes.
* All enzymes of Kreb’s cycle are found in the matrix except succinate dehydrogenase.
* Mitochondria is a semi-autonomous body
* It’s inheritance is uniparental (i.e) maternal
* It is used to track recent evolutionary time because it mutates 5-10 times faster than DNA in the nucleus.

• A vital organ of green plants.
• Double membrane-bound organelle peripheral space in between the membrane
• Inner chloroplast is filled with gelatinous stroma
• Inside the stroma interconnected sacs called Thylakoids
• Inner space of the thylakoid is the thylakoid lumen
• Thylakoids stacked together like piles of coins known as grana.
• Light is absorbed and converted into chemical energy (carbohydrates) in the granum
• Chloroplast genome encodes for approximately 30 proteins involved in photosystem I & II – cytochrome, b, f, complex and ATP synthase & also one of the subunits of RUBISCO is enclosed by it.
• RUBISCO- is the major protein component of the stroma single most abundant protein on earth
• The thylakoid contain small, rounded photosynthetic units called Quantosomes
• The chloroplast is semi-autonomous, divided by fission.

* 1953 – 1 observed by George Palade
* Dense particles in the EM not membrane-bound
Electron microscope observation
1. Made up of 2 round subunits one large layer & one small unit to form a complete unit
2. Mg++ is required for complete cohesion.
Biogenesis – denova formation, auto replication and nucleolar origin
Function – Sites of protein synthesis.
Content – consists of
* RNA 60%,
* Protein 40%
Polysemes:
In protein synthesizing cells, many ribosomes attached to single m RNA – to form polysomes’ main role in the formation of several copies of particular.

Chromoplast
Leucoplast
Nature
Coloured
Colourless
Types & occurence
Chloroplast:
occur in green algae& higher plants. Pigment chlorophyll a & b
Phaeoplast:
occur in brown algae & dinoflagelletes Pigment-fucoanthin
Rhodoplast:
Occur in red algae Stores protein
Pigment phycoerythrin
Amyloplast
Stores starch occur in storage parts Eg. Tapioca rootElaioplast Stores- lipids
Eg. Groundnut seeds
Aleuroplast or
proteoplast
Eg. Moon dhal

polypeptide Intracellular digestion:
They digest carbohydrates, proteins & lipids present in the cytoplasm
Autophagy:
During the adverse condition, they digest their own organelles like mitochondria ER
Auto lysis:
Causes self-destruction of cell on the insight of disease
Aging:
Have autolytic enzymes that disrupts intracellular molecules.

• Central hub, surrounded by nine triplet peripheral fibrils (tubulin) connected to the tubules by radial spokes (9 + 0) pattern Cilia or Flagella Spindle fibres
• Centriole is the basal body of Flagella, Lilia or, Spindle fibers.
• It is a nonmembranous organelle

Prokaryotes
Eukaryotes
Reserse material
Phosphate granules & Cyanophycean granules
Starch grains Glycogen granules
Organic materials
Poly (3 hydroxyl granules sulphur granules, carboxysomes &Gas vacuoles
Aleurone grains, flat droplets
Other secretions
…………………………….
Essential oil, resins, gums, latex and tannin
Inorganic inclusions
metachromatic granules- such as polyphosphate granules (volutin granules) & sulfur granules
Calcium carbonate crystals, Calcium oxalate crystals, Silica crystals Eg.cystolith- hypodermal cells of Ficus bengalensis (calcium carbonate)
Raphides- Eichhornia (calcium oxalate)
Prismatic crystals – dry scales ofAlliumcepa (calcium oxalate)

AUTOSOMES
ALLOSOMES
In human diploid cells out of 46, only 44 chromosomes are Autosomes
Only 2 chromosomes are Allosomes or Sex chromosomes
They are controlling somatic characteristics of an organism
They are involved in Sex determination

• Yes. It connects plasma membrane & nuclear membrane, giving support to the Cytosol so we can call it the endoskeleton of the cell.
• It also helps in the exchange of substances in and out of the cell.

• In 1882- observed by Flemming in Oocytes of animal Salamander &Giant nucleus of unicellular Algae Acetabularia
• The highly condensed chromosomes form a chromosomal axis, from which lateral loops of DNA formed as a result of intense RNA synthesis

Light Microscope
Electron Microscope
Another name = compound microscope
1st introduced by Ernest Ruska & developed by G.Binnin & H. Roher (1981)
Principle
Principle
The transmission of visible light from the source of eye through a sample
It uses a beam of accelerated electrons as source of illumination.
Resolving power – Lesser
Resolving power – Higher
Magnification – Less
Magnification-1,00,000 times than the light
Purpose – studying in schools & college
Purpose Microscope Research purpose -can be seen in scientific laboratories
Pattern of working:
The microscope transmits visible light from eye through sample where
interaction occur and magnified image is visible.
The specimen to be viewed under EM should be dehydrated and impregnated with election opaque chemicals like gold, palladium for withstanding electrons & also for contrast.
Types:1 Only one
Types: 2 types TEM, SEM

NAME OF THE CELL WALL
FUNCTIONS OF THE CELL WALL
SHAPE
It gives definite Shape and Rigidity to the ceil
BARRIER
It prevents several molecules from entering the cells
PROTECTION
To the internal protoplasm against mechanical injury
MAINTAIN ANCE
It maintains osmotic pressure So, prevent bursting of cells
DEFENCE
They are acting as a source of defense for cells

* Cell transport is the main function
* PM act as a channel of transport for molecules
* PM is selectively permeable to molecules
It transported by
* Energy-dependent processes,
* Energy independent processes Membrane proteins involved processes
* Endocytosis & Exocytosis large quantity of solids and liquids are transported into a cell or out of cells.
I. Endocytosis 2 types
a) Phagocytosis particle is engulfed by membrance which fold around it forming vesicles, enzymes digest and products are absorbed.
b) Pinocytosis Fluid droplets are engulfed by forming vesicles.
II. Exocytosis -Vesicles fuse with the plasma membrane and eject contents.
-This may be a secretion in the case of digestive enzymes hormones or mucus.

The cell wall plays a vital role in holding several important functions given below.
* Offers definite shape and rigidity to the cell.
* Serves as barrier for several molecules to enter the cells.
* Provides protection to the internal protoplasm against mechanical injury.
* Prevents the bursting of cells by maintaining the osmotic pressure.
* Plays a major role by acting as a mechanism of defense for the cells.

• They are organs of Photosynthesis.
• Light reactions & dark reactions take place in the granum & stroma respectively.
• Chloroplast also play important role in the Photorespiration or C 2 cycle.

Jonathan Singer and Garth Nicolson (1972) proposed fluid model: It is made up of lipids and proteins together with a little amount of carbohydrate. The lipid membrane is made up of phospholipid. The phospholipid molecule has a hydrophobic tail and hydrophilic head. The hydrophobic tail repels water and water-loving polar molecule are called hydrophilic molecule. They have polar phosphate group responsible for attracting water. Water-hating non – polar molecule are called as a hydrophobic molecules. They have fatty acid which is non – polar which cannot attract water.
Hydrophilic head attracts water. The proteins of the membrane are globular proteins which are found intermingled between the lipid bilayer most of which are projecting beyond the lipid bilayer. These proteins are called as integral proteins. Few are superficially attached on either surface of the lipid bilayer which are called as peripheral proteins. The proteins are involved in the transport of molecules across the membranes and also act as enzymes, receptors or antigens.

GLYOXYSOMES
PEROXYSOMES
SPHAEROSOMES
Single membrane-bound &sub cellular organelle
Single membrane-bound & subcellular organelle
Single membrane-bound & subcellular organelle
Contain enzymes of the glyoxylate pathway
Contain enzymes and play important role in C 2 cycle or Photorespiration
They play important role in the storage of fats in the endoplasm cells of oilseeds
Beta oxidation of fatty acids occurs in the glyoxysomes of germinating seeds
Eg. Castor seeds
Eg. Occur in all green plants
Eg. Coconut Castor seeds

Functions of Golgi bodies:
* Glycoproteins and glycolipids are produced.
* Transporting and storing lipids.
* Formation of lysosomes.
* Production of digestive enzymes.
* Cell plate and cell wall formation
* Secretion of carbohydrates for the formation of plant cell walls and insect cuticles.
* Zymogen granules (proenzyme / pre-cursor of all enzymes) are synthesized.

RESOLUTION
MAGNIFICATION
Ability of lenses to show the finest details between two points form Resolution R
It is the size of the image seen with eye, magnified by the microscope
Formula =
\(R=\frac{0.61 \lambda}{(\mathrm{NA})}\)
where,λ -wavelength of light
NA-numerical aperture
Formula =
Size of image seen with microscope
Size of image seen with normal eyes

• Short cellular-numerous microtubule bound projections of plasma membrane.
• Each Cilium has membrane-bound structures, basal body,rootlets, basal plate shaft
• Shaft (axoneme) consists of nine pairs of microtubule doublets, arranged in a
• circle along the periphery with a two central tubules (9+2) arrangement of microtubules is present.
• Microtubules – made up of tubulin.
• Motor protein dynein – connects the outer microtubules pair & links them to the central pair.
• Nexin – links the peripheral doublets of microtubules.

PROKARYOTES
MESOKARYOTES
Nucleoid no true nucleus
Nucleus with nuclear membrane
1-5µm
5- 10µm
DNA usually circular without
DNA linear but without
histone proteins
histone proteins
Ribosomes 50S+30S
60S+40S
Organelles absent
Organelles present
Eg. bacteria & archaea
Eg. Dinoflagellate, Protozoa

There are three types of centromere in Eukaryotes. They are as follows:
* Point Centromere: The type of centromere in which the kinetochore is assembled as a result of protein recognition of specific DNA sequences. Kinetochores assembled on point centromere bind a single microtubule. It is also called a localized centromere. It occurs in budding yeasts.
* Regional Centromere: In regional centromere where the kinetochore is assembled on a variable array of repeated DNA sequences. Kinetochore assembled on regional centromeres bind multiple microtubules. It occurs in fission yeast cell, humans and so on.
* Holocentromere: The microtubules bind all along the mitotic chromosome. Example: Caenorhabditis Elegans (transparent nematode) and many insects.

NAME OF THE CELL WALL
FUNCTIONS OF THE CELL WALL
SHAPE
It offers definite Shape and Rigidity
BARRIER
It prevents the entry of several molecules into the cell
PROTECTION
Protects internal protoplasm against mechanical injury
Prevents cell from bursting
lit maintains osmotic pressure and prevent cell from bursting
DEFENSIVE DEVICE
It plays a major role by acting as a defensive device

PRIMARY WALL
SECONDARY WALL
First formed
Formed later
Thin elastic, extensible
Thick inelastic
Matrix made up of Hemi cellulose-bind micro, fibrils with matrix Pectinase- filling material, Glycoprotein-control orientation of microfibrils Water
Here cellulose & pectin compactly arranged with different orients giving a laminated structure to give strength to the cell wall.
Only one layer
Has three sub-layers s 1,s 2,s 3.
Does not determine shape of cell
Determine shape of cell

TEM
SEM
It has a high resolving power
Resolving power Comparatively lower
Most commonly used
Occasionally used depending on the study
2-dimensional image is provided
3D image is provided
Magnification 1-3 lakhs times
Magnification 2 lakhs times
Resolving power 2-10A°
Resolving power 5-20 nm

There are different types of mounting based on the portion of a specimen to be observed.
* Whole-mount: The whole organism or smaller structure is mounted over a slide and observed.
* Squash: This is a preparation where the material to be observed is crushed/squashed onto a slide so as to reveal its contents. Example: Pollen grains, mitosis, and meiosis in root tips and flower buds to observe chromosomes.
* Smears: Here the specimen is in the fluid (blood and microbial cultures etc) are scraped, brushed, or aspirated from the surface of the organ. Example: Epithelial cells.
* Sections: Freehand sections from a specimen and thin sections are selected, stained, and mounted on a slide. Example: Leaf and stem of plants.

DEFINITION:
* It is a process by which a cell receives information from outside and respond to it is called signal transduction
* Nitric oxide → is the main signally molecule
* Cell membrane → site of chemical interaction of signal transduction

S.No
Stain
Colour of staining
Affinity
1.
Eosin
Pink or red
Cytoplasm, Cellulose
2.
Methylene blue
Blue
Nucleus
3.
Saffranine
Red
Cell wall(lignin)
4.
Janus green
Greenish blue
Mitochondria

If a chromosome has centromere activity distributed along the whole surface of the chromosome during mitosis (i.e) microtubules distributed all along the mitotic chromosome.
Eg. Caenorhabditis Elegans (transparent nematode) & many insects.

POINT CENTROMERE
REGION AL CENTROMERE
The kinetochore is assembled as a result of protein recognition of specific DNA sequences
Kinetochores assembled on point centromere bind a single microtubule localized, Centromere
Eg. Budding Yeasts
The kinetochore is assembled on a variable array of repeated DNA sequences
Kinetochore assembled on regional centromeres, bind multiple microtubules
Eg. Fission yeast cells, Human cells