PEROXISOME AND ITS FUNCTION

PEROXISOMES

1. P. Baudhuin coined the name peroxisome.

OCCURRENCE:- Peroxisome Occur in many  animal cells and in a wide range of plants. They are present in all photosynthetic cells of higher plants. It is also present in Protozoa, brown algae ,fungi etc.

STRUCTURE:- Peroxisomes are variable in size and shape. They have a single limiting unit membrane of lipid and protein molecules.

FUNCTIONS OF PEROXISOMES:-

1. Hydrogen peroxide metabolism- Peroxisome contain enzymes for peroxide formation called oxidase and peroxide destroying enzyme called catalase. Oxidase and catalase are the smallest and largest enzyme of peroxisome respectively. Catalase breaks hydrogen peroxide into water and oxygen.

2. Beta-oxidation- oxidation of fatty acids. They are capable of oxidizing fatty acyl coenzyme to acetyl coenzyme using molecular oxygen.

3. Photorespiration- In plants, Peroxisomes are found in photosynthetic cells and participates in photorespiration. For this, they are associated with chloroplast and mitochondria. Peroxisomes pick up glycolate from chloroplast and it is oxidised with the help of molecular oxygen to produce glyoxylate. Hydrogen peroxide is produced as a by product which is catalysed by catalase .

PIC:- PHOTORESPIRATION IN PEROXISOMES

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VARIOUS TYPE OF LYSOSOMES AND FUNCTIONS OF LYSOSOMES

VARIOUS TYPE OF LYSOSOMES AND FUNCTION OF LYSOSOMES

Lysosomes are of four types:-

1. Primary lysosome-These are newly pinched off vesicles from trans face of Golgi bodies. Enzymes are present in inactive form.

2. Secondary lysosomes-These are formed bye fusion of phagosome and primary lysosomes. Enzymes get activated, digestion occurs and Sajid digested food passes into cytoplasm.

3. Residual bodies- These are formed when digestion is over in secondary lysosomes. They contain only undigested food matter.

4. Autophagosome- These are formed when primary lysosomes fused with its own intracellular dead or degraded cell organelles.

PIC- VARIOUS TYPES OF LYSOSOMES

FUNCTIONS OF LYSOSOMES:-

1. The lysosomes digest the food contains of phagosome and pinosome. The lysosomes of leukocytes enable the latter to devour the foreign proteins , bacteria and viruses.
2. During the starvation the lysosomes digest the Stored food contains.
3. They digest extracellular material.
       Example- during fertilization Pounds discharge several enzymes. Which are the lysosomal enzymes that digest the limiting membranes of the ovum and for penetration path in oven for the sperms.

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LYSOSOME AND IT'S CHEMICAL COMPOSITION

LYSOSOME AND ITS CHEMICAL COMPOSITION

1. Earlier name is 'perinuclear dense bodies'.
2. Christian c Duve renamed this organelle as lysosome.

OCCURRENCE:-
1. It is present in most animal cells and few plant cells.
2. It is absent in bacteria and mature mammalian erythrocytes.
3. Leukocytes , especially granulocytes are a particularly rich source of lysosomes. Their lysosomes are so large that they can be observed under light microscope.

STRUCTURE:-
1. It is bounded by single unit membrane.
2. It is 0.2 to 0.5 micrometre In size .
3. It contains many enzymes.

EXAMPLE OF CELLS CONTAINING LYSOSOMES:-

A) Animal tissues- liver, kidney, Nerve cells, brain, intestinal epithelium, lung epithelium, macrophages, Gland, bone, urinary bladder.
B) Protozoa-leukocytes, amoeba.
C) Plants-onion seeds, corn seedlings, Yeast.
D) Tissue culture cells-HeLa cells, fibroblasts,chick cells.

ENZYMES OF LYSOSOMES:-
A)Proteases and peptidases-
     1. Collagenase
     2. Peptidase
B) Nucleases-
     1. Acid Ribonuclease
     2. Acid deoxyribonuclease
C) Phosphatases-
     1. Acid phosphatase
     2. Phospho-diesterase
D) Enzymes acting on carbohydrates-
     1. b-galactosidase
     2. a-glucosidase
E) Enzymes acting on glucoaminoglycans-
     1. Lysozymes
     2. Hyaluronidase

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RIBOSOMES

RIBOSOMES

1. In 1940 Albert Claude name it microsomes.
2. In 1952 George Emil Palade described it.
3. In 1958 R.B Roberts coined the name ribosomes.
4. It is present both in prokaryotic and Eukaryotic cell.
5. It is made up of rRNA, ribonucleoprotein, Mg2+, Ca2+ etc.
6. Ribosome is a complex molecular machine found inside the cell that means protein from amino acid in a process called transcription.

TYPES OF RIBOSOMES:-

1. PROKARYOTIC RIBOSOMES (70S)-  The molecular weight of it is 2.8*10^6 Dalton.

       a) Small subunit (30S)- The molecular weight of it is 1*10^6 Dalton. It is made up of 16 S rRNA and 21 types of protein.

      b) Large subunit (50S)- The molecular weight of it is 1.8*10^6 Dalton. It is made up of 5S and 23S rRNA and 31 types of protein.

2. EUKARYOTIC RIBOSOMES (80S)-the molecular weight of it is 4*10^6 Dalton.

       a) Small subunit(40S)- the molecular weight of it is 1.3*10^6 Dalton. It is made up of 18 S rRNA and 30 types of protein.

       b) Large subunit (60S)- the molecular weight of 8 is 2.7*10^6 Dalton. It is made up of 5S,5.8S and 28S rRNA and 40 types of protein.

Structure of ribosome:-the smallest sub unit of life doesn't contain a head, a base , a cleft and a platform. The largest have any content in ridge, a Central protuberance and is stalk.

Function of ribosome:-the main function of ribosome is to form polypeptide chain.

PIC:-STRUCTURE OF PROKARYOTIC RIBOSOME

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FUNCTION OF GOLGI APPARATUS

FUNCTIONS OF GOLGI APPARATUS

• GOLI FUNCTIONS IN PLANTS:-

1. Golgi apparatus is mainly involved in the secretion of materials of primary and secondary cell walls.

2. During cytokinesis it forms cell plate.

• Golgi functions in animals:-

1. In animals Golgi apparatus is involved in the packaging and exocytosis of following materials:

• Zymogen of exocrine pancreatic cells.
• Mucus secretion by Goblet cells of intestine.
• Lacto protein secretion by mammary gland cells.
• Secretion of compounds of thyroxine hormone by thyroid cells.
• Secretion of tropocollagen and collagen.
• Formation of Melanin.
• Formation of yolk and viteline membrane.
• Lipid secretion from liver cells.

More about the structure of Golgi apparatus click here

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SOME IMPORTANT NOTE ON GOLGI APPARATUS

SOME IMPORTANT NOTE ON GOLGI APPARATUS

• Golgi has two faces:-

I) Cis face- It is towards ER.
II) Trans face- It is towards plasma membrane.

• GERL REGION:- this is a region on which smooth endoplasmic reticulum, Golgi apparatus and lysosome constitued endomembrane system. To the trans face of Golgi is associated the trans reticular Golgi in which acid phosphatase enzyme make its first appearance.GERL is found to be involved in the origin of primary lysosomes.
• ZONE OF EXCLUSION:- a Golgi apparatus is surrounded by a differentiated region of cytoplasm where ribosomes, glycogen and organelles such as mitochondria and chloroplast are absent . This is called zone of exclusion . Even which endoplasmic reticulum lies in the zone lacks ribosome.

• Enzymes of Golgi apparatus:-

A) Glycosyl transferase :

      1. Sialyl transferase-- Transfer salic acid.

      2. Galctosyl transferase-- Transfer Galactose to lipids. 

B) Sulpho and glycotransferases : 

      1. Sulpho transferase--- Transfer sulphate.

      2. Lysolecithin acetyl transferase-- Transfer acyl group to phospholipid.

C) Oxido-reductase :

      1. NADH-cytochrome-c-reductase--- Add or remove H.

     

D) Phosphatases : 

     1. Glucose-6-phosphatase---- Remove phosphate.

     2. ATPase---- Removal or addition of phosphate.

    3. Acid phosphatase----- Removal of phosphate.

E) Kinase : 

      1. Casein phosphokinases----phosphorylation of casein.

Know about the structure of Golgi apparatus(click here)

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GOLGI APPARATUS AND IT'S STRUCTURE

Golgi apparatus

It was discovered by Camillo Golgi. He name it as internal reticular apparatus.

It has many other names such as Golgi bodies, Golgi complex, Golgi material.

Occurrence:-it is absent in prokaryotic cell, certain fungi, sperm cells, cells of bryophytes and pteridophytes, cell of mature sieve tubes and RBC.

Morphology:-

1. It is pleomorphic i.e. in some cell types it appears compact and Limited, in others spread out and netlike.
2. A group of cisternae is called dictyosome and a group of dictyosomes makes up the Golgi apparatus.

• Cisternae- it is sac like closed components which are held in parallel bundles. In each stack cisternae are separated by a space of 20 to 30 nm which may contain lot like elements or fibres. Each stack of cisternae form a dictyosome which may contain 5 to 7 Golgi cisternae in animal cells or 20 or more cisternae in plant cells.
• Tubules- It is like of endoplasmic reticulum's tubules . It is 30-50 nm diameter.
• Vesicles- It is 60 nm in diameter. It is of three types:- 

       I) Transitional vesicles- They are small membrane limited vesicles which are thought to form blebs from the transitional ER to migrate are converge to cis face of Golgi.

      II) Secretory vesicles- They are varied-sized membrane limited vesicles which discharge from margins of cisternae of Golgi. They often occur between the maturing face of Golgi and the plasma membrane. 

      III) Clathrin-coated vesicles- They are spherical protuberances , about 50 micrometre in a diameter and with a rough surface. They are found at periphery of the organelle, usually at ends of single tubules. The vesicles are known to play a role in intra-cellular traffic i.e. between ER and Golgi. 

PIC:- GOLGI APPARATUS

Know about endoplasmic reticulum (click here)

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FUNCTION OF ENDOPLASMIC RETICULUM

FUNCTIONS OF ENDOPLASMIC RETICULUM

• COMMON FUNCTIONS OF SER AND RER:-

     1. The endoplasmic reticulum provides an ultrstructure skeletal framework to the cell and gives mechanical support to cytoplasmic matrix.

    2. The Endoplasmic reticulum membrane has permeases and carriers for Osmosis diffusion and active transport process.

   3. The Endoplasmic reticulum contains many enzymes which perform various synthetic and metabolic activities.

   4. The endoplasmic reticulum membrane forms the new nuclear envelope after each nuclear division.

• Function of smooth endoplasmic reticulum:-

     1. Smooth endoplasmic reticulum performs synthesis of lipids and lipoproteins.

    2. Smooth endoplasmic reticulum is found related to glycogenolysis.

   3. The synthesis of cholesterol means 20 enzymes. 11 enzymes are bounded to SER membranes.

   4. SER is related to steroid hormone biosynthesis.

   5. SER is also involved in detoxification of toxic substances and drugs. i.e. xenobiotics in the liver cells by detoxifying enzymes including cytochrome p 450.

• Function of rough endoplasmic reticulum:-

     1. It is involved in folding of proteins, modification and transport.

   
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ENDOPLASMIC RETICULUM AND IT'S TYPES

ENDOPLASMIC RETICULUM

The name endoplasmic reticulum first coined by Poter in 1953.

Occurrence:-

1. It is present both in animal and plant cells.

2. It is absent in egg cells, embryonic cells and RBC of mammals.

3. Nuclear membrane is continuous with endoplasmic reticulum.

Morphology:-

1. Cisternae- The cisternae are long, flattened,sac-like, unbranched tubules having the diameter of 40 to 50 micrometre. They remain  arranged parallely in bundles or stake.

2. Vesicles-The vesicles are oval membrane bound vacuolar structure having the diameter of 25 to 100 micrometre. They often remain isolated in the cytoplasm and occur in most cells but especially abundant in SER.

3. Tubules- The tubules are branched structures forming the reticular system along with the cisternae and vesicles. They usually have the diameter from 50-190 micrometre.

Various type of Endoplasmic reticulum:-

• Smooth endoplasmic reticulum-

          1. It possesses  smooth walls.

          2. Ribosomes are absent in it.

          3. This smooth type of Endoplasmic Reticulum occurs mostly in those cells which are involved in the metabolism of lipids and glycogen.

          4. It is found in adipose cells, interstitial cells, glycogen storing cells of liver, spermatocytes and leukocytes.

• Rough endoplasmic reticulum-

       1. It possesses rough walls.

       2. Ribosomes are present in it.

       3. It is found in pancreatic cells, plasma cells, Goblet cells and liver cells.

       4. Ribosomes play a vital role in the process of protein synthesis.

• Sarcoplasmic reticulum- The smooth endoplasmic reticulum of the muscles cells is known as sarcoplasmic reticulum. It has a special receptor called Rheodyne receptor which is calcium sensing receptor. It releases Ca 2 + ion for muscle contraction.

Enzymes of Endoplasmic reticulum:-

1. The enzymes are present in endoplasmic reticulum membrane.

2. The enzymes are stearases, NADH-cytochrome c- Reductase, NADH diaphorase, glucose-6-phosphotase and mg2+ activated ATPase.

Pic- Endoplasmic reticulam

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Function of plasma membrane (endocytosis, Pinocytosis, junctions)

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FUNCTIONS OF PLASMA MEMBRANE

    PART-2 

CONTINUING FROM PART-1 

b) Endocytosis- It is of two types:-

      I) Phagocytosis- It is editing phenomenon where large particle like bacteria dead cell debris etc. are engulfed in by vesicle formed by plasma membrane. The vesicle is called phagosome. 

                Example-macrophages,kupffer cells in liver ,reticular cell in spleen ,histocytes in connective tissue, monocytes and neutrophils.

       II) Pinocytosis- It is the non specific uptake of small droplets of extracellular fluid by pinosome. It is a cell drinking phenomenon.

2) plasma membrane separates Protoplasm from external environment.

3) plasma membrane protect cell from injury.

4) plasma membrane forms sheat of cilia and flagella.

5) plasma membrane forms various types of in folding like:

   I) Microvillus:- It increases the surface area for absorption of digested food in small intestine and solutes in nephron.

  II) Mesosomes:-  It is found in Gram Positive Bacteria to perform molecular respiration.

  III)Lamelasome:- It is structurally and functionally similar to mesosome and found in blue green algae.

  IV)Lomasome:- It is in folding of plasma membrane in fungi which help in diffusion of substances during cell wall formation.

6) various type of junctions:-

     I) Tight Junction:- At this junction adjacent cell get fused. A protein band binds plasma membrane. 

                       Example:-  It is found in blood capillaries, collecting tubules and brain cells.

      II) Gap junctions:- At this junction adjacent cells have protoplasmic connections through special proteins called connexions.

                           Example:- Cardiac muscle cells.

        III) Desmosomes:- At this junctions , adjacent membrane possess disc shaped thickening.The disc possess tonofibrils.

                 Example:- Stratified squamous epithelia.

        IV) Terminal bar:- It is same to desmosomes but lack tonofibrils.

             

                 Example:- Stratified squamous epithelia.

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FUNCTION OF PLASMA MEMBRANE (ACTIVE TRANSPORT,PASSIVE TRANSPORT)

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FUNCTIONS OF PLASMA MEMBRANE

PART-1

1.The most important function of plasma membrane is transport of different substances into and out of the cell.

 

        Some types of transport:-

I) Passive transport- This type of transport do not require energy. It is 3 types:-

  a) Simple diffusion- Net movement of particles (Ions/Molecules) from any of their higher concentration towards an area of lower concentration that is along the concentration gradient.  

              Example- Movement of fats, oxygen, carbon dioxide and water to the Lipid portion of the membrane.

b) Osmosis- It is a diffusion of solvent molecules across a semipermeable membrane.

              Example- Movement of water into and out of the cell membrane.

c) Facilitated diffusion-Transport of particles is facilitated by some carrier protein e.g., permeases or translocases. Carrier protein bind to the substances with stereochemical specificity so highly selective.

            Example-Entry of glucose into RBC by D-hexose permease , entry of water through aquaporins in plasma membrane of cell.

II) Active transport-This type of transport require ATP. Movement of a particle against the concentration gradient by some carrier protein.

             Example- movement of most ions and amino acids by Na+-K+ ATPase , calcium ATPase, Proton pump.

III) Bulk transport- this type of transport figure ATP. It occurs with the help of vesicles. It is of three types- 

a) Exocytosis-secretion or ejection of particles from form a cell, particles being enclosed in a vesicle which fuses with the plasma membrane and release the content outside the cell.

                Example-secretions of neurotransmitter, hormones, mucus etc , ejection of cell waste.

REMAINING PART TOMORROW..... THANK YOU FOR READING.

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FLUID MOSAIC MODEL OF PLASMA MEMBRANE

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FLUID MOSAIC MODEL OF PLASMA MEMBRANE

1. It is the most acceptable model till date.

2. It was given by singer and nicolson in 1972.

3. Plasma membrane does not have uniform deposition of lipids and proteins.

4. Plasma membrane is not solid but semifluid. Nonpolar ends of phospholipids contain fatty acids which provides fluidity. Semifluid nature of lipids enable lateral movement of protein. The Semifluid nature of membrane is also important for cell growth, secretions, cell division, endocytosis, exocytosis and formation of intercellular junctions.

5. Plasma membrane is dynamic in nature due to transport ability, quick repair and ability to expand and contract.

6. In this model, proteins have been compared to icebergs floating in the sea of phospholipid bilayer.

7. At some place extrinsic protein and lipid of external surface of plasma membrane bears oligosaccharides forming glycoprotein and glycolipid. Glycoprotein and glycolipid costitute glycocalyx.

8. Glycocalyx present towards the extracellular side only.

PIC:- proteins are embedded in bilayer
                                ..........................

PIC:- Fluid mosaic model
                          ................................

PIC:- A phospholipid structure
                           .............................

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CHEMICAL COMPOSITION OF PLASMA MEMBRANE

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                          CELL MEMBRANE

It is the outermost layer of an animal cell and second outermost layer of plant cell.

It was also called cytoplasmic membrane, plasmalemma.

The term cell membrane first coined by C.Nageli.

CHEMICAL COMPOSITION :- it is made up of mainly lipid, protein, carbohydrate, and some enzymes.

1) LIPID:- phospholipids, sphingolipids, glycolipids and sterols are present in cell membrane.

                        Phospholipids are two types:- 

I) Acidic(20%) - Example sphingomyelin.

II) Neutral (80%)- Example  phosphotidyl choline , phosphotidyl serine.

2) PROTEIN:- There are two types of protein intrinsic protein, extrinsic protein. Both of the proteins may be ectoprotein (lying outside), endoprotein (lying inside).

3) CARBOHYDRATES:-They are present as short unbranched or branched Chains of sugars attached either to exterior ectoproteins(forming glycoproteins) or to the polar ends of phospholipids at the external surface of the plasma membrane(forming glycolipids). The 6 principle sugars:

D-galactose, D-mannose ,L-fucose, N-acetyl neuraminic acid, N-acetyl-D-glucosamine and N-acety-D-galactosamine.

SOME IMPORTANT ENZYMES OF PLASMA MEMBRANE:-
1.Acetyl phosphatase
2.Acetyl cholinesterase (Ectoenzyme of RBC)
3.Acid phosphatase
4.Adenosine triphosphate
5.Mg2+ ATPase (Endoenzyme)
6.Na+-K+ ATPase(Ectoenzyme of RBC)
7.RNAase
8.NAD-ase (Ectoenzyme of RBC)

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EUKARYOTIC & PROKARYOTIC CELLS

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    EUKARYOTIC CELLS

Eukaryotic cells are such cells that contain a nucleus surrounded by a membrane and whose DNA is bound together by proteins into chromosomes. It also contains all the cell organelles.

Some characteristics of Eukaryotic cell:-

1) true nucleus is present.

2) histone protein is present.

3) cell size is very large.

4) all the cell organelles are present.

5) Protein synthesis occur in cytoplasm mitochondria and chloroplast.

6) ribosome of cytoplasm is 80S type where as that in mitochondria and chloroplast is 70S type.

7) cytoskeletal structures are present

8) exocytosis and endocytosis are present (in animals).

9) cell division occur by Amitosis, Mitosis and Meiosis.

Examples of Eukaryotic cell:-

All the plant cell and Animal cell.

..................................................

    PROKARYOTIC CELLS

Prokaryotic cells are cells that do not have a true nucleus and membrane bound cell organelles. Organisms that have prokaryotic cells are unicellular and called prokaryotes.

Here is a some  characteristics of prokaryotic cells:- 

1) True nucleus is absent only nucleoid is present . It contains single DNA molecule that is circular DNA.

2) Histone protein is absent.

3) Nuclear envelope and nucleolus absent.

4) Typically prokaryotic cells range from 0.1 to 5 micrometres in diameter and are significantly smaller than Eukaryotic cells.

5) Membrane bound organelles are absent.

6) Protein synthesis occur in cytoplasm.

7) Ribosome is 70s type.

8) Cytoskeletal structures are absent.

9) Exocytosis and endocytosis and absent.

10) Cell division occur by amitosis, mitosis and meiosis are absent.

Some examples of prokaryotic cells:-

Bacteria, archaea.

.....................................................

        MESOKARYOTIC CELLS

Mesokaryotic cells are cells that have both prokaryotic and Eukaryotic properties.

1)Prokaryotic property:- Histone protein is absent.

2) Eukaryotic property:-Nuclear envelope and nucleolus are present.

In mesokaryotes nuclear envelope and nucleolus are present even during cell division, chromosome remains condensed throughout the cell cycle.

Example of mesokaryotic cell:- Dinoflagellates.

Pic of a Dinoflagellate

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CELL , CELL THEORY

                             CELL AND CELL THEORY

Cell is the basic unit of life. It is the fundamental structural and functional unit of an organism.

CELL THEORY- in 1838 and 1839 Schleiden and Schwan formulated cell theory and state that:-
I) cell is the basic unit of the life.
II) all the living things are composed of cells and cell products.

Later Rudolf Virchow in 1855 first explained that cells divided and new cells are formed from preexisting cells (omnis cellula ecellula) .

cells are of three types:-

1) prokaryotic cell
2) mesokaryotic cell
3) Eukaryotic cell

Tomorrow we will talk about the three types of cells.