Golgi bodies, ER, Lysosomes, Ribosomes.pdf

Golgi Complex/Golgi bodies/Dalton’s complex/Lipochondrion  It was discovered by Camillo Golgi in 1898 It is complex cytoplasmic structure made up of cisternae, network of tubule with vesicle and vacuole (golgian). It is absent in prokaryotic cell, sieve tubes of plants, antherozoide...

Golgi Complex/Golgi bodies/Dalton’s complex/Lipochondrion  It was discovered by Camillo Golgi in 1898 It is complex cytoplasmic structure made up of cisternae, network of tubule with vesicle and vacuole (golgian). It is absent in prokaryotic cell, sieve tubes of plants, antherozoides of bryophytes and pteridophytes and RBC of mammals. It is made up of unconnected unites called dictyosomes. Dictyosome : 2-5 µm. Number: one in algae to 15000 in rhizoidal cell of Chara but a plant cell generally consists of 10-20 dictyosomes.  Structure Four kinds of structure cisternae, tubules, vesicles and golgian vacuoles are the structure found in golgi complex. Cisternae are flattened sac like unbranched structure aranged parallel(4-8). Cisternae are interconnected by a network of branched tubules towards perifery. Small sac like structure called vesicle are attached at the end of tubules. Golgi body has two surface convex or forming surface and concave or maturing surface or concave surface. Tubules of maturing surface produce large vesicle known as golgian vacuoles. Functions: The golgi body collects ,processes and sorts molecules It synthesizes carbohydrates such as mucilage, cellulose etc In plants ,enzymes in the golgi body converts sugars into cell wall components. It give rise primary lysosome. It forms acrosomes of sperms.it is an important part of tip of animal sperms which help in digestion of egg membrane during fertilization. The production of hormones by endocrine glands is mediated through golgi apparatus. Endoplasmic reticulum  ER is a three dimensional complicated channels. It was discovered by Porter and Tompson (1945). It is present in all eukaryotic cell except eggs, mature RBC of mammals and embryonic cell. Structure  ER is made up of 3 types of elements I. Cisternae – flattened sac like structure having 40-50 nm diameter. They lies parallel to each other. Outer surface has ribosomes. II. Vesicle – they are rounded or oval membrane bound structure having 25-250 nm diameter and found isolated in cytoplasm. III. Tubules - tube like irregular , branched forming net like structure along with cisternae. Having 50-100 nm diameter.  Types of ER 1. RER [Rough endoplasmic reticulum] 2. SER [Smooth endoplasmic reticulum] RER RER is called rough endoplasmic reticulum because it is covered with many tiny organelles called ribosomes These are just visible as black dots. Ribosomes are the sites of protein synthesis. They can be found free in the cytoplasm as well as on the RER. Proteins formed by ribosomes on the RER enters the sac and move through them. Small sacs called vesicles can break off from the ER and join together to form golgi bodies.  SER SER is often attached with cell membrane. SER has a smooth appearance because it lacks ribosomes. It mainly consist of cisternae and few tubules. It has a completely different function to RER. It makes lipids and steroids, such as cholesterol and the reproductive hormones oestrogen and testosterone. Difference between SER and RER  Functions It gives mechanical support. It also help in intracellular transportation of materials. It also involve in synthesis of glycogen , lipid , steroids and proteins. It forms cell wall ,cell membrane, and nuclear membrane. It produces enzymes of primary lysosomes.  LYSOSOME Lysosome are single membrane bound vesicle containing hydrolyzing enzymes. They are the site of cellular digestion and help in intracellular digestion of food. so they are commonly called suicidal bag. The enzyme of lysosome are synthesized in ER and packed in golgi body. Occurance : lysosomes are present in all animal cells except mammalian RBCs. They are also found in protists, fungi, and Root tip of the maize ,cotton, pea seeds etc. Shape and size : They are generally rounded and may be irregular. Structure: It is single membranous structure containing hydrolytic enzymes. About 40 different types of hydrolytic enzymes are found in lysosome. Types of Lysosomes  Type : They exist in more than one morphological forms. This phenomenon is called polymorphism. Depending upon the content and their function , they are categorised into 4 types Primary : primary lysosome are newly formed from golgi complex which contain hydrolytic enzymes. , Secondary ( digestive vacuole or heterophagosomes): Primary lysosome fuse with food vacuole to form secondary lysosome. Residual body: The digested food material are diffused into cytoplasm and cytoplasm remaining undigested food residues in lysosome. So lysosome having residue are called residual body. Autophagic vacuole: When primary lysosome fuses with intracellular organelle from autophagic vacuoles. Lysosome digested the cell organells through autophagy or autodigestion Functions: Lysosome digest the intracellular and extracellular food. Lysosome of WBC destroy foreign protein , pathogenic microorganism and toxic substances. Lysosome of sperm help to dissolve limiting membrane of egg during fertilization. Autolysis: Self destruction of cell tissue or organ by lysosome is called autolysis.  Ribosomes Ribosome are small sub-spherical granular organelles which are not enclosed by membrane. It is also called ‘Protein factory of cell’. It was discovered in plant cell by Robinson and brown (1953) but the term was given by Palade (1955) who discovered ribosome in animal cells. Ribosome are found in all kinds of cells except mammalian RBCs. Each ribosome is sub spherical in shape and size of ribosome is measured in Svedberg unit or sedimentation coefficient.  Structure Each ribosome is made up of two unequal sub unites. A larger subunit is dome shaped and smaller is ellipsoidal. Both are made up of rRNA and protein so it is also called ribonucleoprotein. The two sub unites binds only at the time of protein synthesis in presence of Mgᶧᶧ.  Types Based on sedimentation coefficient they are of two types; 70s type: it is found in both prokaryotic and eukaryotic cell. Sub unit of 70s ribosome are 30s and 50s.it is occurs in mitochondria and chloroplast. 80s type : it is found in eukaryotic cell. its smaller subunit is 40s and larger subunit s 60s. It is occurs in cytoplasm so it is called cytoplasmic ribosome. Function It is the site of protein synthesis.ie all kinds of protein synthesize in it. All the enzyme and few hormones such insulin are produced on ribosome.