# Current Affairs 11th Class

#### Nucleic Acids

Nucleic acids are the polymers of nucleotide made up of carbon, hydrogen, oxygen, nitrogen and phosphorus and which controls the basic functions of the cell. These were first reported by Friedrich Miescher (1871) from the nucleus of pus cell. Altmann called it first time as nucleic acid. Nuclein was renamed nucleic acid by Altman in (1889). They are found in nucleus. They help in transfer of genetic information. Types of nucleic acids : On the basis of nucleotides i.e., sugars, phosphates and nitrogenous bases, nucleic acids are of two types which are further subdivided. These are DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid). (1) DNA (Deoxyribonucleic acids) : Term DNA was given by Zacharis.  (i) Types of DNA : It may be linear or circular in eukaryotes and prokaryotes respectively. Palindromic DNA : The DNA helix bears nucleotide in a serial arrangement but opposite in two strands. $-T-T-A-A-C-G-T-T-A-A.......$ $-A-A-T-T-G-C-A-A-T-T......$ Repetitive DNA : This type of arrangement is found near centromere of chromosome and is inert in RNA synthesis. The sequence of nitrogenous bases is repeated several times. Satellite DNA : It may have base pairs up to $160\,\,bp$and are repetitive in nature. Microsatellite has $16\,\,bp$and minisatellite has $1160\,\,bp.$ They are used in DNA matching or finger printing (Jefferey). In eukaryotes, DNA is deutrorotatory and sugars have pyranose configuration. (ii) Chargaff’s rule : Quantitatively the ratio of adenine (A) to thymine (T) and guanine (G) to cytosine (C) is equal. i.e., “Purines are always equal to pyrimidine”. (iii) C value : It is the total amount of DNA in a genome or haploid set of chromosomes. (iv) Sense and Antisense strand : Out of two DNA strand one which carries genetic information in its cistrons is called sense strand while the other strand does not carry genetic information, therefore, doesn’t produce mRNA. The non-functional DNA strand is called antisense strand. (v) Heteroduplex DNA : Hybrid DNA formed as a result of recombination is called heteroduplex DNA. It contains mismatched base pair of heterologous base sequence. X-Ray crystallography study of DNA : It was done by Wilkins. It shows that the two polynucleotide chains of DNA show helical configuration. Single stranded DNA (ssDNA) : It is single helixed circular. And isolated from bacteriophage $\phi \times 174$ by Sinsheimer (1959). It does not follow chargaff’s rule. The replicative form (RF) has plus – minus DNA helix. e.g., parvovirus. Double helical model of DNA: It is also known as Watson and Crick model. (2) RNA or Ribonucleic acid : RNA is second type of nucleic acid which is found in nucleus as well as in cytoplasm i.e., mitochondria, plastids, ribosomes etc. They carry the genetic information in some viruses. They are widely distributed in the cell. Genomic RNA was discovered by Franklin and Conrat (1957).

#### Cell Division / Cell Reproduction / Cell Cycle

It is the process by which a mature cell divides and forms two nearly equal daughter cells which resemble the parental cell in a number of characters. In unicellular organisms, cell division is the means of reproduction by which the mother cell produces two or more new cells. In multicellular organism also, new individual develop from a single cell. Cell division is central to life of all cell and is essential for the perpetuation of the species. Discovery : Prevost and Dumans (1824) first to study cell division during the cleavage of zygote of frog. Nagelli (1846) first to propose that new cells are formed by the division of pre-existing cells. Rudolf Virchow (1859) proposed “omnis cellula e cellula” and “cell lineage theory”. A cell divides when it has grown to a certain maximum size which disturb the karyoplasmic index (KI)/Nucleoplasmic ratio (NP)/Kernplasm connection. Cell cycle : Howard and Pelc (1953) first time described it. The sequence of events which occur during cell growth and cell division are collectively called cell cycle. Cell cycle completes in two steps: (1) Interphase,                  (2) M-phase/Dividing phase (1) Interphase : It is the period between the end of one cell division to the beginning of next cell division. It is also called resting phase or not dividing phase. But, it is actually highly metabolic active phase, in which cell prepares itself for next cell division. In case of human beings it will take approx 25 hours. Interphase is completed in to three successive stages. G1 phase/Post mitotic/Pre-DNA synthetic phase/gap Ist : In which following events take place. (i) Intensive cellular synthesis. (ii) Synthesis of rRNA, mRNA ribosomes and proteins. (iii) Metabolic rate is high. (iv) Cells become differentiated. (v) Synthesis of enzymes and ATP storage. (vi) Cell size increases. (vii) Decision for a division in a cell occurs. (viii) Substances of G stimulates the onset of next S – phase. (ix) Synthesis of NHC protein, carbohydrates, proteins, lipids. (x) Longest and most variable phase. (xi) Synthesis of enzyme, amino acids, nucleotides etc. but there is no change in DNA amount. S-phase/Synthetic phase (i) DNA replicates and its amount becomes double $(2C-4C).$ (ii) Synthesis of histone proteins and NHC (non-histone chromosomal proteins). (iii) Euchromatin replicates earlier than heterochromatin. (iv) Each chromosome has 2 chromatids. G2-phase/Pre mitotic/Post synthetic phase/gap-IInd (i) Mitotic spindle protein (tubulin) synthesis begins. (ii) Chromosome condensation factor appears. (iii) Synthesis of 3 types of RNA, NHC proteins, and ATP mole. (iv) Duplication of mitochondria, plastids and other cellular macromolecular complements. (v) Damaged DNA repair occur. (2) M-phase/Dividing phase/Mitotic phase : It is divided in to two phases, karyokinesis and cytokinesis.      Duration of cell cycle : Time period for ${{G}_{1}},S,{{G}_{2}}$ and M-phase is species specific under specific environmental conditions. e.g., 20 minutes for bacterial cell, 8-10 hours for intestinal epithelial cell, and onion root tip cells may take 20 hours. ${{\mathbf{G}}_{\mathbf{0}}}\mathbf{-}$phase (Lajtha, 1963) : The cells, which are not to divide further, do more...

#### Metabolically Inactive Cell Inclusions

Within the cytoplasm of a cell there occur many different kinds of non-living structures which are called inclusions or ergastic / Deutoplasmic substances. (1) Vacuoles : The vacuole in plants was discovered by Spallanzani. It is a non-living reservoir, bounded by a differentially or selectively permeable membrane, the tonoplast. The vacuole is filled with cell sap or tonoplasm. They contain water, minerals and anthocyanin pigments. Some protozoans have contractile vacuoles which enlarge by accumulation of fluid or collapse by expelling them from the cell. The vacuoles may be sap vacuoles, contractile vacuoles or gas vacuoles (pseudo vacuoles). Function of vacuoles : Vacuole maintains osmotic relation of cell which is helpful in absorption of water. Turgidity and flaccid stages of a cell are due to the concentrations of sap in the vacuole. (2) Reserve food material The reserve food material may be classified as follows : (i) Carbohydrates : Non-nitrogenous, soluble or non- soluble important reserve food material. Starch cellulose and glycogen are all insoluble. (a) Starch : Found in plants in the form of minute solid grains. Starch grains are of two types : Assimilation starch : It is formed as a result of photosynthesis of chloroplasts. Reserve starch : Thick layers are deposited around an organic centre called hilum. (b) Glycogen : Glycogen or animal starch occurs only in colourless plants like fungi. (c) Inulin : It is a complex type of polysaccharide, soluble and found dissolved in cell sap of roots of Dahlia, Jaruslem, Artichoke, Dandelion and members of compositae. (d) Sugars : A number of sugars are found in solution of cell sap. These include glucose, fructose, sucrose, etc. (e) Cellulose : Chemical formula is ${{({{C}_{6}}{{H}_{10}}{{O}_{5}})}_{n}}.$The cell wall is made up of cellulose. It is insoluble in water. (ii) Fats and Oils : These are important reserve food material. These are always decomposed into glycerol and fatty acids by enzymatic action. Fat is usually abundant in cotyledons than in the endosperm. e.g., flax seed produce linseed oil, castor produce castor oil, cotton seeds produce cottonseed oil, etc. (iii) Proteins and Amides (Aleurone grains) : Storage organ usually contain protein in the form of crystalline bodies known as crystalloids (potato). Proteins may be in the form of aleurone grains as in pea, maize, castor, wheat, etc. (3) Excretory Products : The organic waste products of plants are by-product of metabolism. They are classified as : (i) Resins : They are believed to be aromatic compounds consisting of carbon, hydrogen and oxygen and are acidic in nature. Sometimes they are found in combination with gums and are called gum resin. e.g., Asafoetida (heeng). (ii) Tannins : They are complex nitrogenous compounds of acid nature having an astringent taste. Presence of tannin in plants makes its wood hard durable and germ proof. (iii) Alkaloids : These are organic, basic, nitrogenous substance. They occur in combination with organic acids and most of them are poisonous. From plants, cocaine, hyoscine, morphine, nicotine, quinine, atropine, strychnine and daturine etc. are extracted. (iv) Glucosides more...

#### Nucleus

The nucleus also called director of the cell. It is the most important part of the cell which directs and controls all the cellular function. Discovery : The nucleus was first observed by Robert Brown (1831), in orchid root cells. Nucleus plays determinative (in heredity) role in cell and organism, that was experimentally demonstrated by Hammerling (1934) in surgical experiments with green marine unicelled algae Acetabularia. Occurence : A true nucleus with definite nuclear membrane and linear chromosome, is present in all the eukaryotes except mature mammalian RBCs, sieve tube cell of phloem, tracheids and vessels of xylem. The prokaryotes have an incipient nucleus, called nucleoid or prokaryon or genophore or false nucleus. Number : Usually there is a single nucleus per cell i.e., mononucleate condition, e.g., Acetabularia. (1) Anucleate (without nucleus) : RBCs of mammals, phloem sieve tube, trachids and vessels of xylam. (2) Binucleate : e.g., Ciliate, Protozoans like Paramecium. (3) Polynucleate : e.g., fungal hyphae of Rhizopus, Vaucheria. Polynucleate condition may be because of fusion of a number of cells. i.e., syncytium, coconut endosperm or by free nuclear divisions without cytokinesis i.e., coenocyte. Shape : It varies widely, generally spherical e.g., cuboidal germ cells, oval e.g., columnar cells of intestine, bean shaped  in paramecium, horse-shoe shaped in Vorticella, bilobed, e.g., WBCs (acidophils), 3 lobed e.g., basophil, multilobed e.g., neutrophils, long and beaded form (moniliform) e.g., stentor and branched in silk spinning cells of platy phalyx insect larva. Size : The size of nucleus is variable i.e., $530\mu .$ In metabolically active cells size of the nucleus is larger than metabolically inactive cells. Chemical composition Proteins $=80%,\text{ }DNA=12%,\text{ }RNA=5%,\text{ }Lipids=3%$ Enzymes like polymerases are abundantly present and help in synthesis of DNA and RNA. Ultrastructure : The nucleus is composed of following structure. (1) Nuclear membrane : It is also called nuclear envelope or nucleolemma or karyotheca, was first discovered by Erclab (1845). Structure : It is a bilayered envelope. Each membrane is about 60-90Å thick lipoproteinous and trilaminar. Outer membrane, called ectokaryotheca (with ribosome) and inner membrane is called endokaryotheca (without ribosome). Two membranes are separated by a fluid-filled intermembranous perinuclear space (about $100-300{AA}$). Nuclear membrane is porous and has $1,000-10,000$ octagonal nuclear pores. Each nuclear pore is about $400-1,000\text{ }{AA}$ in diameter (average size is $800\text{ }{AA}$). Callan and Tamlin (1950) first to observe nuclear pore in nuclear membrane. The nuclear pares are enclosed by circular structure are called annuli. The pore and annuli together are called pore complex or pore basket.     Origin : It is formed by the fusion of ER elements during the telophase of cell division. Functions (i) It regulates the nucleo-cytoplasmic interactions. (ii) It allows the passage of inorganic ions, small organic molecules, ribosomal subunits, RNAs and proteins through nuclear pores. (iii) It maintains the shape of the nucleus. (2) The nucleolus (Little nucleus plasmosome) : It was first observed by Fontana (1781) in the skin cells of an eel. Bowman (1840) more...

#### Micromolecules

These are molecules of low molecular weight and have higher solubility. These include minerals, water, amino acid, sugars and nucleotides. All molecules or chemicals functional in life activity are called biomolecules. (1) Elements : On the basis of presence and requirement in plants and animals, they are grouped into major $(Ca,P,Na,Mg,S,K,N)$ and minor $(Fe,Cu,Co,Mn,Mo,Zn,I)$ bioelements. On the basis of function, they may be of following types :– (i) Framework elements : Carbon, oxygen and hydrogen. (ii) Protoplasmic elements : Protein, nucleic acid, lipids, chlorophyll, enzymes, etc. (iii) Balancing elements : Ca, Mg and K. (2) Biological compounds (i) Inorganic compounds : Water 80%, inorganic salts 1-3%. (ii) Organic compounds : Carbohydrates (1.0%), Lipids (3.5%), Proteins (12.0%) Nucleotides (2.0%), Other compounds (0.5). (3) Cellular pool : Aggregated and interlinked  various kinds of biomolecules in a living system. So cell is called cellular pool. It includes over 5000 chemicals. Inorganic chemicals are present mostly in aqueous phase while organic in both, aqueous and non-aqueous. Cellular pool comprises of both crystelloid and colloidal particles. Hence called as crystal colloids. (4) Water : Liquid of life, major constituent of cell (about 60-90%) and exists in intracellular, intercellular and in vacuoles. In cells it occurs in free state or bound state (KOH, CaOH etc.). Properties of water : It is colourless, transparent, tastless and odourless, neutral (pH-7) liquid.  It is universal solvent, as it can dissolve both polar and non-polar solutes. High boiling point due to hydrogen bonding. Shows high degree of cohesion and adhesion. It can undergo three states of matter i.e., solid$\rightleftharpoons$liquid$\rightleftharpoons$gas.  It is dense and heaviest at 4C and solid below it. (5) Carbohydrates : e.g., sugars, glycogen (animal starch), plant starch and cellulose. Source of carbohydrate : Mainly photosynthesis. It exists only in 1% but constitutes 80% of the dry weight of plants. Composition : It consists of carbon, hydrogen and oxygen in the ratio ${{C}_{n}}{{H}_{2n}}{{O}_{n}}.$ It is also called saccharide and sugars are their basic components. Classification of carbohydrates are : (i) Monosaccharides : These are single sugar units which can not be hydrolysed furthur into smaller carbohydrates. General formula is ${{C}_{n}}{{H}_{2n}}{{O}_{n}},$e.g., Trioses-3C, (Glyceraldehyde, dihydroxyacetone etc.), tetroses-4C, pentoses-5C, hexoses-6C etc. Important Hexoses Glucose : ${{C}_{6}}{{H}_{12}}{{O}_{6}}.$ Grape sugar is dextrose. Grape is sour due to presence of tartaric acid. Fructose is called fruit sugar (sweetest among natural sugars) and glucose is called "sugar of body" (blood sugar). Normal level of blood glucose is 80-120mg/100ml. If it exceeds then condition is called "glucosuria". Fructose : Occurs naturally in fruit juices and honey. Hydrolysis of cane sugar in body also yields fructose. Galactose : It is called as brain sugar. It's an important constituent of glycolipids and glycoproteins. Properties of monosaccharide
• Monosaccharides are colourless, sweet tasting, solids and show oxidation, esterification and fermentation.
• Due to asymmetric carbon, they exist in different isomeric forms. They can rotate polarized light hence they are dextrorotatory and laevorotatory.
• D-glucose after reduction gives rise to a mixture of polyhydroxy alcohol, sorbitol or mannitol.
• more...

#### Macromolecules

Macromolecules are polymerisation product of micromolecuels, have high molecular weight and low solubility. They include mainly polysaccharide, protein and nucleic acids. (1) Polysaccharide : They are branched or unbranched polymers of monosaccharides jointed by glycosidic bond.  Their general formula is ${{({{C}_{6}}{{H}_{10}}{{O}_{5}})}_{n}}.$ Polysaccharides are amorphous, tasteless and insoluble or only slightly soluble in water and can be easily hydrolysed to monosaccharide units. Types of polysaccharides (i) On the basis of structure Homopolysaccharides : These are made by polymerisation of single kind of monosaccharides. e.g., starch, cellulose, glycogen, etc. Heteropolysaccharide : These are made by condensation of two or more kinds of monosaccharides. e.g., chitin, pectin, etc. (ii) On the basis of functions Food storage polysaccharides : They serve as reserve food. e.g., starch and glycogen. Structural polysaccharides : These take part in structural framework of cell wall e.g., chitin and cellulose. Description of some polysaccharides Glycogen : It is a branched polymer of glucose and contain 30,000 glucose units. It is also called animal starch. It is also found as storage product in blue green algae, slime moulds, fungi and bacteria. It is a non-reducing sugar and gives red colour with iodine. In glycogen, glucose molecule are linked by $14$ glycosidic linkage in straight part and $16$ linkage in the branching part glycogen has branch points about every $8-10$ glucose units. Starch : Starch is formed in photosynthesis and function as energy storing substance. It is found abundantly in rice, wheat, legumes, potato (oval and ecentric shaped), banana, etc. Starch is of two types. Straight chain polysaccharides known as amylose and branched chain as amylopectin. Both composed of $D$glucose units jointed by $\alpha -1-4$ linkage and $\alpha -1-6$ linkage. It is insoluble in water and gives blue colour when treated with iodine. Inulin : Also called “dahlia starch”(found in roots). It has unbranched chain of 30 – 35 fructose units linked by $\beta -2-1$ glycosidic linkage between 1 and 2 of carbon atom of D– fructose unit. Cellulose : An important constituent of cell wall $(2040%),$ made up of unbranched chain of $6000\,\beta D$glucose units linked by 1 – 4 glycosidic linkage. It is fibrous, rigid and insoluble in water. It doesn’t give any colour when treated with iodine. It is a most abundant polysaccharide. Chitin : It is a polyglycol consisting of $N-$acetyl$D$glucosamine units connected with $\beta -1,\,4$ glycosidic linkage. Mostly it is found in hard exoskeleton of insects and crustaceans and some times in fungal cell wall. Second most abundant carbohydrate. It is a most abundant heteropolysaccharide. Agar-Agar : It is a galactan, consisting of both D and L galactose and it is used to prepare bacterial cultures. It is also used as luxative and obtained from cell wall of red algae e.g., Gracilaria, Gelidium etc. Pectin : It is a cell wall material in collenchyma tissue may also be found in fruit pulps, rind of citrus fruits etc. It is water soluble and can undergo sol $\rightleftharpoons$ gel transformation. It contain arabinose, galactose and galacturonic acid. Neutral more...

#### Chromosome (Gr. chroma = colour soma = body)

Chromosome were discover by Hofmeister (1848) in filament of pollen mother cells of tradescantia (Rhoeodiscolour) studied by strasburger (1875) and given the persent name by Waldeyer (1888). During interphase, chromatin threads are present in the form of a network called chromatin reticulum. At the time of cell division, these thread like structures of chromatin become visible as independent structures, called chromosomes. The haploid set of chromosomes is define as genome. Structure : Each chromosome consists of two coiled filaments throughout its length called chromonemata by Vejdovsky. These have bead like structures called chromomeres which bear genes. Chromatid is a half chromosome or daughter chromosome. The two chromatids are connected at the centromere or primary constriction. Primary constriction (centromere) and secondary constriction gives rise to satellite. The secondary constriction consists of genes which code for ribosomal RNA and nucleolus hence it is called as “nucleolar organizer region”. Chromosomes having satellite are called SAT chromosomes. The ends of chromosomes are called “telomeres” (which do not unite with any other structure). In 1928 Emile Heitz developed a technique for stainning of chromosomes. Staining property of chromosomes is called as heteropycnosis. Chromosomes can be stained with basic dye like janus green there are two types of regions are seen :– (1) Heterochromatin : It is formed of thick regions which are more darkly stained than others areas. It is with condensed RNA which is transcriptionally inactive and late replicating. It generally lies near the nuclear lamina. It is of two type : (i) Constitutive hetrochromative : Occurs in all cells in all stages. e.g., Centromere. (ii) Facultative hetrochromative : Formed by inactivation of some gene in some cell in some stages. e.g., Barr body.  (2) Euchromatin : It is true chromatin and is formed of thin, less darkly stained  areas. It is with loose DNA which is transcriptionally active and early replicating. Chemical chomposition : DNA - 40%. Histone – 50%. Other (acid) Proteins – 8.5%. RNA – 1.5%. Traces of lipids, Ca, Mg and Fe. Histone are low molecular weight basic proteins which occur alongwith DNA in ratio. Nonhistone chromosomal or NHC proteins are of three types– structural, enzymatic and regulatory. Structural NHC proteins form the core or axis of the chromosome. They are also called scaffold proteins.

#### Types Of Cells

Chatton gave the term prokaryote and eukaryote. Depending upon the nature of nucleus cells are classified. Incipient nucleus is present in prokaryotes, where as in eukaryotes well organised nucleus is present.   Differences between prokaryotic and eukaryotic cell more...

#### Ribosome

The ribosomes are smallest known electron microscopic without membrane, ribonucleo–protein particles attached either on RER or floating freely in the cytoplasm and are the sites of protein synthesis.  Discovery : In 1943 Claude observed some basophilic bodies and named them as microsome. Palade (1955) coined the term ribosome (form animal cell). Ribosomes in nucleoplasm were observed by Tsao and Sato (1959). First isolated by Tissieres and Watson (1958) from E. coli. Ribosomes found in groups are termed as polyribosomes or ergosomes (Rich and Warner 1963 observed first time polyribosomes). Occurrence : In prokaryotes ribosomes are found only in free form in the cytoplasm. While in the eukaryotes the ribosomes are found in two forms in the cytoplasm, free form and bind form (bound on RER and outer nuclear membrane). These are also reported inside some cell organelles like mitochondria and plastids respectively called mitoribosomes and plastidoribosomes. Types of ribosomes (1) 70S ribosomes : Found in prokaryotes, mitochondria and plastid of eukaryotes. (2) 80S ribosomes : Found in cytoplasm of eukaryotes. (3) 77S, 60S and 55S ribosomes : Levine and Goodenough (1874) observed 77S ribosomes in fungal mitochondria 60S ribosomes in animal mitochondria and 55S in mammalian  mitochondria. Structure : Each ribosome is formed of two unequal subunits, which join only at the time of protein synthesis. In 70S and 80S ribosomes, 50S and 30S, 60S and 40S are larger and smaller subunits respectively. Larger subunits is dome shaped and attached to ER by glycoproteins called “ribophorins”.     Smaller subunit is oval shaped and fits as a cap on flat side of larger subunit. Ribosomes are attached to ER through hydrophobic interactions. Chemical composition : Ribosomes are chemically composed of rRNA and proteins Ribonucleo-Protein (RNP). 70S ribosomes has 60-65% rRNA and $35-40%$ proteins (ratio is 1.5:1). rRNAs are of three types : 23S type and 5S type rRNAs in 50S and 16S type rRNA in 30S sub-units. 80S ribosome has 45% rRNA and 55% proteins (ratio is about 1 : 1). r-RNA are of four types : 28S, 5S and 5.8S types of rRNAs in 60S and 18S type rRNA in 40S sub-units. A $1\times {{10}^{-3}}\,(0.001M)$ molar concentration of $M{{g}^{++}}$ is needed for the structural cohesion of ribosomes i.e., for holding the two subunits together. If this concentration is increased by ten folds, two ribosomes unite to form a dimer. By decreasing the $M{{g}^{++}}$ conc. to normal, the dimer breaks into monomers (single ribosomes). Biogenesis of ribosome (1) In eukaryotes the ribosomal RNAs like 18S, 5.8S and 28S are synthesized by nucleolus and 5S RNA out of the nucleus.   (2) In prokaryotes both rRNA and its protein are synthesized as well as assembled by cytoplasm. Polyribosomes or Polysomes : When many ribosomes (generally $68$) are attached at some mRNA strand. It is called polysome. The distance between adjacent ribosomes is of 90 nucleotides. These are functional unit of protein synthesis. Functions (1) Ribosomes are also called protein factories of the cell or more...

#### Protoplasm (Proto = First, Plasm = Fluid)

Protoplasm is a complex, granular, elastic, viscous and colourless substance. It is selectively or differentially permeable. It is considered as “Polyphasic colloidal system”. Discoveries (1) J. Huxley defined it as “physical basis of life”. (2) Dujardin (1835) discovered it and called them “sarcode”. (3) Purkinje (1837) renamed it as “Protoplasm”. (4) Hugo Von Mohl (1844) gave the significance of it. (5) Max Schultz (1861) gave the protoplasmic theory for plants. (6) Fischer (1894) and Hardy (1899) showed its colloidal nature. (7) Altman (1893) suggested protoplasm as granular.   Chemically Composition
 Prokaryotic cell Eukaryotic cell It is a single membrane system. It is a double membrane system. Cell wall surrounds the plasma membrane. Cell wall surrounds the plasma membrane in some protists, most fungi and all plant cell. Animal cell lacks it. Cell wall is composed of peptidoglycans. Strengthening material is murein. It is composed of polysaccharide. Strengthening material is chitin in fungi and cellulose in others plants. Cell membrane bears respiratory enzymes. It lacks respiratory enzymes. Cytoplasm lacks cell organelles e.g., Mitochondria, ER, Golgi body etc. Cytoplasm contains various cell organelles. Ribosomes are only 70 S type. Ribosomes are both 80 S and 70 S type. There are no streaming movements of cytoplasm. Cytoplasm show streaming movements.
Water 75 - 85% Carbon 20%
Proteins 10 - 25% Oxygen 62%
Lipids 2 - 3% Hydrogen 10%
Inorganic Materials 1% Nitrogen 3%
Trace elements 5% (Ca, P, Cl, more...

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