Mitochondria: Mitochondria are founding the cytoplasm of eukaryotic cells and are characterized by specific morphological, bio chemical and functional properties. Mitochondria are generally rod shaded elongated structures commonly known as power house of the cells they are the sites of ATP production in the cell. Mitochondria consist of two membranes and the space surrounded by inner membrane is called mitochondrial matrix. Mitochondria are self replicating and can synthesize some of their own proteins and membrane material cristae of FI par tides of oxysomes are small staked sphere like stretchers containing an enzyme, ATPase that is involved in oxidative phosphorylation.
Mitosis
The cell division takes place only once. Mitosis takes place in the somatic cells of the body. Occurs in both sexually as well as a sexually, reproducing organism. The two chromatics of a chromosome do not exchange segments during prophase. The chromosomes no remains constant at the end of mitosis. The genetic constitution of the daughter cells is identical to that of parent cells.
Meiosis
There are two cell divisions, the first and the second meiotic divisions. Meiosis takes place in the germ cells. Occurs only in sexually reproducing organisms. Chromatics of two homologous chromosomes exchange segments during crossing over. The chromosomes number is reduced fro the diploid to the haploid. The genetic constitution of the daughter cells differs from that of the parent cell. The chromosomes of daughter cells usually contain a mixture of material and paternal genes.
Parenchyma
Parenchyma are living, isodiametric, oval, round, polygonal or elongated cells within their walls and vacuolated protoplasm and have intercellular spaces. These Parenchymatous cells perform the most important vital functions like preparation of food and storage of nutritive material like starch, proteins, mineral and water. Respiration process is carried out by parenchymatous cells. These cells retain the ability to divide and even mature and can be induced to divide under special cultural conditions. Each Parenchymatous cell is enclosed by a cell wall that provides structural support to the plant.
Sclerenchyma
These cells are very long narrow thick walled and lignified cells with pointed ends. There are no intercellular spaces among the cells and cells have no protoplast. These tissues are specially structured to give strength to the parts of the plants that have stopped growing in length. Sclereids are of four types. Brachysclereids, MacroSclereids, Osteosdereids, Asterosdereids.
Starch
Starch is a mixture of two homo-polysaccharids-amylose and amyl pectin. In amylase, about 100-100 units of glucose are linked together linearly by an @ 1-4 glycoside linkage. The amylase chain has a helical stretcher. Amylopectin is a highly branched molecule consisting of abuts 50,000 monomeric units. Like glycogen, glucose molecules in amyl pectin are linked linearly by @1-4 glycosidic linkage and make branch points by @1-6 glycosidic linkages.
Secondary Struchere of Protein- The Secondary Struchere of a Protein is formed by the folding of a polypeptide chain. The folded chain is held together by hydrogen and disulphide bonds. Hydrogen bonding interactions between peptide bonds are responsible for regular folding pattern like @ helix and B sheets. In an @ helix such as in @ keratin fibres and myoglobin the chain itself turns regularly to make a rigid cylinder. The tightly coiled polypeptide main chain forms the inner part of the rod and the side chain extends outward in a helical array. The helix is stabilized by hydrogen bonds between residue one and five of the amino acids.
In a B sheets such as in silk fibroin and parts of immunoglobulin, the polypeptide chain itself folds back and forth. In B pleated sheets, all peptide linkages participate in the formation of hydrogen bonds to provide stability. Many B sheets are slightly twisted, which are known as beta turns.
Centromere and Telomere. During the prophase, each chromosome consists of two identical units termed as sister chromatics each of which contains identical daughter DNA molecules that were produced in bathe S-phase advance the chromatics become more condensed owing in to the packing of the nucleoprotein fibres. Sister chromatics are held together at their centromeres.
Golgi apparatus: Golgi complex is structurally similar in both plant and animal cells but in plant cells it is more evident and is called as dicytysomes which are stack like or plate like bodies. The Golgi complex consists of a steak of flattened sacs or epistemic, small rounded transport vesicles, larger vacuoles filled with amorphous or granular material. Golgi apparatus is composed of at least three types of sacks which contain different types of enzymes.
Animal Cells: Cell wall is absent, centrioles are present, chloroplasts are absent, lysosomes are usually present, and vacuoles are absent or small in size.
Plant Cells: Cell wall is present, centrioles are absent. Chloroplast are present and helps in photosynthesis, plant cell contains equivalent stretchers called spherosomes, usually a single large vacuoles in mature cells.
Second Messenger: When a cell surface receptor binds to a signal molecule on the cell exterior it undergoes a reversible conformational change. This leads to the generation of an intracellular signal that alerts the behavior of the target cell. These intracellular signaling molecules are referred to as second messengers.
Gap Junctions: Gap Junctions are the communicating junctions widely present in all animals; they allow small water soluble molecules and ions to pass directly from one cell to another. Gap Junctions are formed in the adjacent plasma membranes the two cells. These channels are construed from protein molecules that extend out from the plasma membrane and are called connexons. Gap Junctions allow only smaller molecules such as inorganic ions, sugars, amino acids, nucleotides, vitamins etc. to pass between the cells. Where as larger molecules such as proteins, nucleic acids, and polysaccharides etc cannot pass through them.
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