PLASMA MEMBRANE

PLASMA MEMBRANE
OCCURRENCE OF PLASMA MEMBRANE
Plasma membrane or the cell membrane is usually found in all types. it is the outer most boundaries of the animals cells and inner to cell wall in plant cells.
CHEMICAL COMPOSITION OF PLASMA MEMBRANE
Cell membrane is chemically composed of lipoproteins as lipids (20-40%) and proteins (60-80%). In addition there is small quantity of carbohydrates and cholesterol is also present.
lipids present are phospholipids and sterol, the cholesterol in the animals cell are sterol and in that of plant cell are phytosterol.

STRUCTURE AND MORPHOLOGY:
The most acceptable model for the membrane structure was proposed by singer and Nicholson in 1972, this model is called as the fluid Mosaic model.
Fluid part refers to the phospholipids molecules and mosaic part refers to the proteins.
THE LIPIDS BILAYER (FLUID)
The membrane is composed of a lipid bilayer in which the proteins are sandwiched in a mosaic pattern. The outer surface of the lipids layer is hydrophilic and is glycerol. The inner surface is hydrophobic and is composed of water- insoluble fatty acid tail.
ARRANGEMENT OF PROTEINS (MOSAIC)
The protein does not form a layer on lipids bilayer layer but are arranged in a mosaic pattern.
TYPES OF PROTEINS:
There are two types of proteins.
EXTRINSIC PROTEINS:
The proteins that lie on the outer surface of the lipid bilayer are called the extrinsic proteins or perpheral proteins most of which are present on the cytoplasmic side.
INTRINSIC PROTEINS:
The proteins that are completely buried in the lipid layer are called the intrinsic proteins.

THE GLYCOCALYX
Carbohydrates attached to the proteins forms glycoproteins, and carbohydrates attached to the lipids forms glycolipids. These carbohydrates form a layer on above the membrane called glycocalyx

CELL WALL

CELL WALL

DISCOVERY
The cell wall was discovered by Robert Hooke in 1665.

OCCURRENCE
It is found in all plant cells, fungi, algae and bacteria, but absent in animals cell and protozoa. it is the outer most boundaries of the plant cells.

CHEMICAL COMPOSITION
Cell wall is composed of micro fibrils, these fibrils are cemented together by lignin pectin and other substances. Chemical composition of cell wall varies depending on the type of cell.

CELL WALL IN BACTERIA:
Bacterial cell wall is chemically composed of peptidoglycan.

CELL WALL IN PLANTS:
Cell wall of plants cell is composed of cellulose, hemicellulose, pectin and lignin.

STRUCTURE OF CELL WALL
The cell waLls have three fundamental parts.

MIDDLE LAMELLA
Middle lamella joins together the two adjacent cells. it is usually thin and about 1 um in thickness. Middle lamella is formed during cytokinesis by the cell plate during cytokinesis,

CHEMICAL COMPOSITION:
In woody tissue it is mainly composed of magnesium and calcium pectate. Middle lamella is commonly lignified.

PRIMARY WALL
Primary wall is the first wall formed during development. it is usually 1-3 um in thickness.

CHEMICAL COMPOSITION:
It is composed of cellulose, pectin mostly polysaccharides and hemicellulose.

SECONDARY WALL
It is laid down inside the primary wall. It is usually thick about 5-10 um. It is more or less rigid, both the wood and bark are the secondary cell walls. Secondary cell wall give rigidity to the plant.

CHEMICAL COMPOSITION:
Secondary cell wall is composed of hemicellulose (xylan) and lignin minerals (Ca,Mg)

PLASMODESMATA:
Plasmodesmata are small pores in the cell wall. Cells interact though plasmodemata with the protoplasts of adjacent cells across the wall.

IMPORTANCE OF CELL WALL/FUNCTIONS OF CELL WALL
*) Cell wall gives strength and rigidity to the cell.
*) Cell wall prevents the cell from osmotic lysis.
*) Cell wall limits the entry of larger molecules inside the cell.
*) Cell wall is porous and allow free passage of water and dissolved minerals.

SPECTROPHOTOMETRY, MICRO DISSECTION AND MICROMETRY

SPECTROPHOTOMETRY

DEFINITION
Spectrophotometry is the measure of amount of light that passes through the sample can be calculated that how much light was absorbed by the sample.
SPECTROPHOTOMETER
A spectropohtometer is a photometer that can measure intensity of wave length of light source.
OPTICAL DENSITY
Ability of specimen to absorb or block the passage of light.
FACTORS
The cell mass is directly proportional to the optical density. The amount of light passes through the solution is indicative of the concentration of certain chemicals that do not allow light to pass through.
APPLICATIONS
Spectrophotometry can be used to determined the wave length of light that take part 1 photosynthesis.

MICRO DISSECTION
It refers to a variety of techniques in which microscope is used for the dissection of cells or its organelles.
TYPES
Different kinds of techniques involve in micro dissection.
*) CHROMOSOME MICRO DISSECTION
To remove a portion from a complete chromosomes, a fine glass needle is being used under a microscope.
*) LASER MICRO DISSECTION
Use of a laser through a microscope for the dissection of selected cells.
*) LASER CAPTURE MICRO DISSECTION
Use of a laser through a microscope to cause selected cells to adhere to a film is called laser capture micro dissection.

MICROMETRY

DEFINITION
Measuring the size of microscopic objects is called micrometry.
This can be done by using specially designed scales.
(1) OCULAR MICROMETER
One of the scales is placed in eyepiece called ocular micrometer.
(2) STAGE MICROMETER
Other on the stage (stage micrometer) The micrometer have equally spaced divisions.
Before using the eyepiece micrometer to measure a particular structure, you will have to find out the real width of each unit on the scale at each magnification. In other words you have to calibrate the micrometer. This can be done by replacing the specimen with the stage micrometer, and to measure the eyepiece units at each magnification.

GEL ELECTROPHORESIS

GEL ELECTROPHORESIS

DEFINITION:
The techniques which is used for the separation of molecules on the bases of their size and charge in gel under the influence of electric field is called gel electrophoresis.

PROCEDURE:
In this techniques agarose gel act as molecular sieve and separate the molecules on the basis of their size and surface charge. The gel is poured into the plastic plates to form a viscous slab. Two ends of the slab are suspended in salt solution which are connected b electrodes to a power source. When voltage is applied the molecules start moving through the gel. Negatively charged molecule moves towards positive pole and positively charged molecules moves towards the negative pole.

TYPES OF ELECTROPHORESIS

*) ANAPHORESIS: (Separation of histone)

*) CATAPHORESIS: (Separation of DNA/RNA)

FACTORS AFFECTING THE SPEED OF MOLECULES:
Two factors affect the speed, with which charged molecule move towards an electrode.
a) The amount of charge (greater charge, faster movement and vice versa)
b) The size of molecule (smaller molecules, faster movement and vice versa)
c) Shape of DNA
d) Concentration of gel.

TYPES OF GEL:
Different gel types and conditions are used for different molecules and types of applications.

AGAROSE:
A common gel for separating large DNA fragments is made of agarose

POLYACRYLAMIDE:
For separation of small DNA fragments polyacrylamide gel is used.

APPLICATION:
Gel electrophoresis separates macro molecules such as Nucleic Acid and proteins on the basis of their rate of movement through an agarose gel in an electric field. The distance a DNA molecule travels is inversely proportional to its length or size.

CHROMATOGRAPHY

CHROMATOGRAPHY
Chromatography is the separation of sample components of a mixture based on differential affinity for a mobile versus a stationary phrase. separation involves two phrase.

MOBILE PHASE
The mobile phase is a liquid or gas with a mixture of substances to be separated.

STATIONARY PHASE
The stationary phase is a solid substance through which the mobile phase moves. The separation depends on chemical and physical properties of the molecules such as solubility and molecular mass.
ION EXCHANGE AND ABSORPTION CHROMATOGRAPHY
When the components are separated by ionic bonds the chromatography is ion exchange, and when the components are absorbed by stationary phase it is known as absorption chromatography.

PAPER CHROMATOGRAPHY
It is used for the separation of photosynthetic pigments, sugar or amino acids. In this type of chromatography paper is used as a stationary phase.

PROCESS
*) A mixture is dissolved in a liquid and spotted near one end of a paper strip.
*) The end of the paper nearest to spot is placed in the solvent in such a way that alcohol does not touch the spot.
*) Alcohol which moves through the paper by capillary action carrying the molecules with it, and results in the formation of bands on the paper.

DIAGRAM

TYPES

COLUMN CHROMATOGRAPHY
In column chromatography the stationary phase is a supporting phase is a supporting tube, with a paper or silica on the inner surface of the tube.

THIN LAYER CHROMATOGRAPHY (TLC) When the stationary phase is cellulose or thin silica then it is called as thin layer chromatography.
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TISSUE CULTURE

TISSUE CULTURE

DEFINITION
The in-vitro culturing of cell, tissue or organ of an organisms in highly aseptic environment on artificial medium is called tissue culture.
Plants cells unlike most of the animals cells have copies of many functional genes and thus they can be propagated from a cell, and have the same genotype (genetically identical plants.)

HOW TISSUE CULTURE IS DONE

APPARATUS

*) Centrifuge
*) Water bath
*) Sterilizer
*) Liquid nitrogen freezer
*) Hemacytometer, this device is used for counting cells
*) Incubator, a device that maintains humididty, temperature and gas concentration.
*) Cell culture hood that provides a hygienic environment.
*) Broth, or agar growth medium

PROCEDURE

a) PROCUREMENT OF EXPLANT: Plant tissue cultures are initiated from explants, which are complete organs or small sections of tissue or a single cell removed from an intact plant.

b) STERILIZATION: Before tissue culture, glassware and explants are sterilized in chemical solutions (sodium or calcium hypochlorite, solutions).
c) PREPARATION OF A GROWTH MEDIUM: A suitable growth medium is prepared with all the essential element, organic nutrients, vitamins and plant hormones.

d) INOCULATION: Explant are allowed to grow in growth medium. Inoculation is performed in laminar flow hood that provides a germ free-sterile environment.

e) DEVELOPMENT OF CALLUS: The growing explants from a mass of undifferentiated cells called callus.

f) DEVELOPMENT OF PLANTLETS: As roots and shoots appear from tghe callus these are planted in soil to produces individual plants, due to chnages in hormones concentration.

WHAT IS CELL

CELL

DEFINITION
The cell is the basic structural and functional unit of all living organisms. it is the smallest unit that can carry out all activities of life.

TYPES OF CELL
There are two main types of cells; Prokaryotic cell and Eukaryotic cell.
Eukaryotic cells have a proper nucleus and double membrane- bounded organelle. Prokaryotes in contrast, do not have a nucleus. They have a region called nucleoid in which the genetic material is located

CELL HISTORY
Ancient Greek philosophers such as Aristotle concluded that "all animals and plant are constituted of a few elements which are repeated in each of them." The elements now days called cells
Further growth and development of cell biology is associated with the development of optical lenses and to the combination of these lenses in the construction of the compound microscopes.
Robert Hooke (1635-1703) was proposed the term cell (Latin, Cella = holloow space) in 1665 He examined a thin slice cut from a peice of dried cork under the compound microscope which were built by him by using 30 multiply microscope.
Leeuwenhoek was the first to observe free-living cells such as human sperm cells etc. Robert Brown (1773-1858) discovered and named the nucleus in plant cells.n
In 1838, a German botanist Mathias Jacob Schleiden (1804-1881) put forth the idea that cells were the units of structure in the plants. In 1839, his coworker a German Zoologist Theodor Schwann (1810-1882) applied Schleiden's idea to the animals.Later, both of them postulated that the cell is the basic structural and functional unit of all living organisms.

DIAGRAM

CELL THEORY
Credit for developing cell theory is usually given to three scientists: Theodor Schwann, Matthias Jacob Schleiden, and Rudolf.
MAIN FEATURES
This theory has the following points.
*) All living organisms are composed of one or many cells.
*) All new cells arise from division of pre-existing cells.
*) Cells contain the hereditary material of an organisms which is passed from parent to daughter cells.
*) All metabolic processes take place within cells.
*) Basic chemical compostion of cells within similar species is same.

HOW ARE THE CELLS STUDIED
There are several different techniques to study cells such as:
Microscopy (includes simple light microscope, compound light microscope) differential staining, centifugation, cell/tissue culture,chromatography, electrophoresis etc.
THE EARLIEST MICROSCOPE
The simple microscope was invented by Antony Van Leeuwenhoek in 1670. This microscope was composed of only one lense and able to magnify an object up to 250 times.
Robert hook developed a microscope called the compound microscope with two set of lenses called the ocular lens and the objective lens, in this type the image magnified by the objective lense is magnified a second time by the ocular lens. These microscope rely on the light.