Cell organelles - different organelles of plant cell

 STRUCTURE OF PLANT CELL

cell wall

·        -A plant cell wall has 3 parts – Middle lamella , Primary cell wall , Secondary cell wall

·        -Plant cells are joined together by the middle lamella which is made up of Ca2+ and Mg2+ salts giving it the property of adhesion

·       - Primary cell wall lie between the middle lamella and the middle lamella and the plasma membrane

·       - Function of cell wall is provide support to the plant cell

Cell membrane / plasma membrane

·        -Cytoplasm is surrounded on outerside by thin and flexible membrane called Plasmalemma

·        -It is made up of lipids and proteins , protein content of about 40% and lipid content of 60%

·        -Phospholipids found in the cell membrane are Lecithin and Cephalin

·       - Plasma membrane provides flexibility to the cell , and acts as selectively permeable/semipermeable  membrane helping in transport of nutrients in and out of the cell

Microtubules

·        -They are found in association with spindle fibres helping in giving orientation to newly synthesized Cellulose microfibrils in the cell

·       -- It is made up of protofilaments (13 in  number ) ,made up of tubulin

·        Provide structural framework to the cell

Lysosomes 

       - Known as the” suicidal bags of the cell”

       - Term Lysosome was given by Duve in 1955

       - It is single membrane bound organelle identified by presence of Digestive enzymes
     -They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria

Peroxisome and Spherosome

·        -Both are single membrane bound organelles

·        -Peroxisome oxidise various fatty acids and produce H2O2

·       -- Peroxisomes are associated with glycolate mechanism in photosynthesis

·       -- Spherosomes are associated with the storage of Lipids and acid phosphatase enzyme is found in them

Golgi bodies

·        --It is a double membrane bound organelle

·        -first described by Cammillio Golgi in nerve cells of Cat in 1822

·       -- Golgi bodies are said to arise from the Endoplasmic reticulum

·        --Major function – Protein sorting and packaging of food materials to different cells

Mitochondria

·        --It is a Double membrane bound organelle

·        -Term mitochondria was given by Benda

·        --Mitochondria is made up of 70% protein , 25-30% lipids , RNA&DNA in small quantities

·        -Inner membrane / cristae is the site of Krebs Cycle / ETC

·        -Mitochondria is called the “Power house of the cell” due to its role in respiration

Chloroplasts

·        -Double membrane bound organelle

·        -It is roughly made up of 35% Protein , 30% lipids ,6% Chlorphyll , 5% Carotenoids and 2-3%  nucleic acid

·        -It has circular / ring shaped DNA

·        -2 membranes – Grana (made up of thylakoids) . Inner membrane Stroma ( enzymes of dark reaction)

·        -Main functions are – Photosynthesis ( Chloroplyll pigment ) , Proplastid differentiation ,Cytoplasmic inheritance

Ribosomes

·        -These are the main  sites of protein synthesis

·        --It is a membrane less organelle

·        --It contain 40-70% RNA

·        --Size/weight of ribosome is measured  in terms of Sverdberg(S) units

·        -In prokaryotes it is 70S(Chloroplasts) and Eukaryotes it is 80S

Endoplasmic reticulum

·       -- Double membrane bound organelle

·        -It consnist of Tubules , Vesicles and Cisternss

·        -It is of 2 Types – Rough Endoplasmic Reticulum ( having ribosomes emdedded) ,  -Smooth Endoplasmic Reticulum (lipid metabolism)

·        -It act as intercellular transport system , helps in passage of mRNA from nucleus to -cytoplasm , Protein synthesis(RER)  ,Lipid metabolism (SER)

Nucleus

·        -Called the “brain house of the cell”

·        --Discovered by Robert Brown in 1833

·        --Double membrane bound nuclear envelope found

·        --It is the store house of genetic information , produces m-RNA , t-RNA , ribosomes

·        -Nucleus is made up of Nuclear envelope , nucleolus and chromatin fibres

·        -Nucleolus is involved in production and organisation of the ribosomes

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