Anas Zoology

  Eukaryotic Cell Eukaryotic Cell The cells which contain true nuclei are called eukaryotic cells. Eukaryotic cells are found in animals, plants, algae and fungi. They are larger in size as compared to prokaryotic cells. The cells may vary in shape, size and physiology but they all have a typical structure with little variations in number and location of cellular organelles. The eukaryotic cell have a outer covering membrane called plasma membrane / cell membrane. Inside the cell a membrane-bound nucleus is present. Between the nucleus and plasma membrane, cytoplasm is present in which various cellular organelles like mitochondria, golgi complex, centrioles etc can be seen. ✱ Shape: Eukaryotic cells exhibit diversity. They can be spherical, triangular, tubular, cuboidal, polygonal, cylindrical, oval, rounded or elongated. Shape of cells may vary from organ to organ. A single organ may show variations in shape of cell. ✱ Size: Eukaryotic cells are microscopic. They are larger in s...

  (Image Source:  https://pmgbiology.files.wordpress.com/2015/10/chromosomes.jpg?w=300 ) Chromosomes are found inside the nucleus of the cell. The number of chromosomes differ from organism to organism. Humans have 23 pairs i.e. 46 chromosomes. Out of these 23 pairs, 22 pairs are autosomes and 1 pair is of sex chromosomes. Human female have XX as the sex chromosome and human male have XY as the sex chromosome. One set (23 chromosome) is inherited from the maternal (female parent) and another set from the paternal (male parent). Since two sets are present inside the cell, the cell is called as diploid (di=two, ploid=set). All somatic cells of the body are diploid. Gametes (sperm and ovum) contains only one set of chromosomes and hence are called haploid. The number of chromosomes in each somatic cell is the same for all members of a given species.  Chromosome Morphology: (Image Source:  https://microbiologynotes.org/wp-content/uploads/2020/07/types-of-Telomere.jpg ) C...

  Golgi Complex / Golgi Apparatus Golgi apparatus is found in all types of eukaryotic cells except the mammalian RBCs. It is absent in prokaryotes. Golgi apparatus are small sacs which are responsible for transporting, modifying and packaging proteins and lipids. The golgi apparatus was discovered by Camillo Golgi in 1898. He discovered them in the nerve cells. Golgi apparatus has a system of outer flattened cisternae which appears as parallel membranes in the form of an ellipse.  There are two faces known as cis and trans face of golgi apparatus. The cis face lies near the rough endoplasmic reticulum and the trans face lies near to the cell membrane. Substances from the rough endoplasmic reticulum enter through the cis face for processing and they exit from the trans face in the form of smaller vesicles. Functions: Packaging center of cell. Proteins are processed and sorted for their transport. Lipid processing. Secretory proteins like hormones are packed into secretory vesic...

  Endoplasmic Reticulum (ER) Endoplasmic Reticulum (ER) is a system of sac like structures and tubes found in all eukaryotic cells. They are known as sarcoplasmic reticulum in skeletal muscles, Nissl granules in neurons and myeloid bodies in retinal pigment cells. They are absent in RBCs, eggs and embryonic cells. Endoplasmic Reticulum arise by evagination of nuclear membrane. Endoplasmic Reticulum have three parts: Cisternae: It is a sac like, parallel tubules having ribosomes on their surface. It is unbranched. Tubules: It is tube like, irregular, branched and without ribosome. Vesicles: They are round or spherical, without ribosomes Parts of Endoplasmic Reticulum . There are two types of endoplasmic reticulum  Rough Endoplasmic Reticulum (RER): They have ribosomes on their surface. The 60S unit of ribosomes are attached to the ER by means of a protein ribophorin I and ribophorin II. Number of cisternae and tubules are more. They are abundant near the nuclear membrane. ...

  Cytoplasm: Cytoplasm is the protoplasm present within the living cell, excluding nucleus. Cytoplasm is enclosed within cell membrane. Cytoplasm can be differentiated as: Cytoplasmic matrix / Cytosol / Hyaloplasm Cell inclusions Cell organelles Cytoplasmic Matrix: The Cytoplasmic matrix is the the gel like substance present in cytoplasm. It is more dense and viscous than the cytoplasmic fluid. Cytoplasmic matrix contains enzymes for synthesis of carbohydrates, fats, amino acids and proteins. Cell Inclusions: Cell inclusion are the non-living substances of cytoplasm. They may be in the form of reserve food, minerals, excretory and secretory products. Some of these are: 1) Starch grains: Exists as eccentric of concentric rings around proteinaceous hilum. It is stored in rhizomes, potato, rice, maize etc. Starch Grains around hilum 2) Fat droplets: They are present in animal cells in the form of adipocytes. Fat droplet in the cell 3) Glycogen granules: They are present in liver and m...

Nucleus: Nucleus is a membrane enclosed organelle that contains the chromosome. It is present inside the cell. The study of nuclei of cells is known as Karyology. Nucleus is present in all cells except mature RBC's and sieve cells of xylem. The shape of nucleus varies. It can be oval, disc shaped, lobular, irregular etc In prokaryotes the nucleus is not covered by well defined membranes. In prokaryotes it is called as prokaryon/genophore/nucleoid. Normally a cell contains one nucleus but their number varies in certain cells e.g. binucleate liver cells and cartilage, polynucleate in osteoblast and skeletal muscles etc. Nucleus is made up of four parts: Nuclear Membrane Nucleoplasm/Karyoplasm Chromatin Network Nucleolus Different parts of Nucleus 1) Nuclear Membrane: It is a perforated double membrane. The pores have pore complex to regulate the size of pore. It seems to separate the contents of nucleus from cytoplasm. The nuclear membrane is made up of phospholipid bilayer. 2) Nucl...

The specialized structures seen inside the living cells are called cell organelles. Different cell organelles present inside a cell are: Nucleus Ribosomes Endoplasmic Reticulum (Smooth and Rough) Cytoskeleton Golgi complex/apparatus Mitochondria Lysosomes Centriole Vacuoles

What are Lipids? A lipid is a class of organic compound which is a fatty acid or its derivative. They are insoluble in water but soluble in organic solvent. Major lipids in cell membrane are: Phospholipids  Cholesterol 1) Phospholipids: The lipid substances containing phosphorous and fatty acids are called phospholipids. There are different types of phospholipids present in cell membrane, they are as follows: Aminophospholipids Phosphatidylinositol Sphingomyelin Phosphatidylserine Phosphatidylcholine Phosphatidylglycerol Phosphatidylethanolamine The phospholipid molecules are arranged in two layers in cell membrane. A phospholipid molecule consist of two parts: head portion and tail portion. The head portion is made up of phosphate group and a glycerol atom and tail portion is made up of two fatty acid chains. Head portion is polar and hydrophilic (Strong affinity for water). The tail portion is non polar and hydrophobic (repelled by water/water fearing). Structure of Phospholipid ...

The stratified epithelium tissue consist of two or more layers of cells.  An epithelium tissue consist of cells that form membranes, which cover and line the body surfaces and glands.  The stratified epithelium tissue can be further classified in 4 types: Stratified Squamous Epithelium Stratified Cuboidal Epithelium Stratified Columnar Epithelium Transitional Epithelium 1) Stratified Squamous Epithelium: Description: There are several layers of cells which are cuboidal to columnar in shape. The apical cells are squamous and basal cells are cuboidal or columnar. Location: Forms superficial layer of skin (Keratinized form), lining of mouth, oesophagus, part of epiglottis and also covers the tongue. Function: Protection (against microorganisms and water loss) 2) Stratified Cuboidal Epithelium: Description: Several layer of cells in which the cells are cube shaped in both the apical surface and basal surface. Location: Pancreatic duct, Sweat glands. Function: Protection, absorptio...

The simple epithelium tissue consist of a single layer of cells. An epithelium tissue consist of cells that form membranes, which cover and line the body surfaces and glands. The simple epithelium tissue can be further classified into 4 types: Simple Squamous Epithelium Simple Cuboidal Epithelium Simple Columnar Epithelium Pseudostratified Columnar Epithelium Simple Squamous Epithelium: Description: Single layer of cells with a centrally located nucleus. The cells are flat. Location: Lines the heart, blood vessels, bowman's capsule, air sacs of lungs and inner surface of the eardrum (tympanic membrane). Function: Filtration, diffusion and osmosis. Simple Squamous Epithelium Simple Cuboidal Epithelium: Description: Single layer of cells with a centrally located nucleus. The cells are cube shaped. Location: Surface of ovary, anterior surface of eye lens, lines the kidney tubules, found in the ducts of pancreas. Function: Secretion and absorption. Simple Cuboidal Epithelium Simple Col...

 It is the most accepted model of Plasma Membrane/Cell Membrane. It was proposed by Singer and Nicolson in the year 1972. Phospholipids form bilayer in the centre. their unsaturated fatty acids forms the tail and glycerol forms the head, which prevents the close packing of the molecules. Phospholipids show two types of movements: Transition and Flip-Flop movement. Transition: Molecules change their position in the same layer. Flip-Flop: Molecules interchange between two layers. There are two types of proteins in cell membrane/plasma membrane Extrinsic/Peripheral proteins - Form 30% of the total membrane protein, superficial, easily removed, some are covered by glycolipids/glycoproteins. They provide structural and functional specificity to the membrane. eg. ATPase, spectrin, acetycholinesterase etc. Intrinsic/Integral Proteins - Form 70% of the total membrane proteins, embedded in lipid bilayer, can be extracted by rupturing membrane, held in position by polar and nonpolar side of ...

A) Danielli - Davson Model / Sandwich Model / P-L-P Model: This model of plasma membrane was proposed by Danielli and Davson in the year 1935. According to this the plasma membrane is trilaminar, where lipids bilayer is sandwitched between the two protein layers. Hence it is also called as P-L-P model (P=protein, L=lipid). This model fails to explain functional specificity and active transport through membranes. B) Unit Membrane Model / Robertson Model: This model of plasma membrane was proposed by Robertson in the year 1959. According to Robertson, all membranes have the same basic structure but they have their own distinctive composition. Example: Internal organelles have more proteins than lipids in eukaryotic cells whereas plants and bacteria have more lipids than proteins. This model fails to explain the membranes stability and permeability. Related Articles: 1) Biomembranes https://anaszoology.blogspot.com/2022/08/biomembranes.html

Biomembrane/Biological Membrane is a semipermeable covering around the cell and organelles, which separated them from the external environment. Biomembrane which covers the cell is called a cell membrane/Plasmalemma, biomembrane which covers the organelle is called subcellular membrane. Composition of Biomembrane Biomembranes are tripartite or trilaminar i.e. made up of three layers Proteins : 59-75% fibrous or globular proteins Lipids : 20-40 % Phospholipid, sterol, glycolipid, sphingolipid Carbohydrates : 1-5% Hexose, hexamine, sialic acid Functions of Biomembranes: Helps to transport the solutes across the membrane. Biomembrane only allow certain types of molecules to enter the cell and organelle, they keep the toxins from entering into the cell. The receptors present on biomembranes helps the cells to communicate.

  An important tool of molecular biology is DNA fingerprinting. It is a way to distinguish individuals as it is unique for every living being (except clones) and cannot be altered by any process. Applications of DNA Fingerprinting: Paternity Test - The DNA fingerprint of child is matched with the prints of parents to determine family relationships. In parental disputes this technique is used to determine the true parents of the child. Criminal identification - DNA fingerprint from blood/hair/semen of suspect is picked up from the scene of crime, prepared and compared with the sample collected from scene. Many cases have been solved by this technique. Study Evolution - It is helpful in finding out genetic relationship between different races of man. Related Articles: DNA Fingerprinting:  https://anaszoology.blogspot.com/2022/08/dna-fingerprinting.html

An important tool of molecular biology is DNA fingerprinting. It is a way to distinguish individuals as it is unique for every living being (except clones) and cannot be altered by any process. All segments of DNA do not code for protein. Some segments have regulatory function, others are Introns (Interviewing sequence/IVS) still others are repetitive DNA sequences/Mini satellite sequences . The most important segment for DNA fingerprinting are short repetitive nucleotide sequences which vary from person to person. These are also called Variable number tendem repeats (VNTR). To prepare a DNA fingerprint a small amount of saliva/blood/hair/semen or any other cell of the body is required. Steps of DNA fingerprinting are as follows: Extract the DNA from the sample. If DNA is not sufficient, amplify it using PCR i.e. make more copies of DNA using PCR. Cut DNA with restriction endonucleases. The cut segments possess DNA of different length in different individuals called restriction length ...

 The organisms whose cells contain a membrane bound nucleus and membrane bound organelles are called a eukaryotes. Structure of Eukaryotic Cell Characteristics of Eukaryotic Cell: Cell size and volume depend on the activities performed by it (5 - 100 μm). Cellulosic cell wall is present only in plant cells. Capsule is absent. Mesosome is absent. Well organized nucleus is present. Mononucleate condition is more common. DNA is linear and is covered by histonic protein (except in mitochondria and plastid). Monocistronic DNA is more common. Three kinds of RNA polymerase are present. One for each - rRNA, mRNA, tRNA. Transcription occurs in the nucleus and translation in the cytoplasm. Extranuclear chromosome are absent. Ribosome is 80S (60S + 40S). Protein synthesis is inhibited by cyclohexamide. All organelles are present. Cilia and flagella show characteristic 9+2 arrangement of microtubule and are made up of protein tubulin. Microfilaments are present. True sap vacuoles are common in...

A prokaryote is a single celled organism that lacks a true nucleus and other membrane bound organelles. Structure of Prokaryotic Cell Characteristics of Prokaryotic Cells:  Cell is small in size (0.1 - 5 micrometers). Cell wall is made up of muramic acid (amino acid derivative of peptidoglycan). In many cells mucopolysaccharide capsule is present. Mesosomes controls cellular respiration and cell division. An organised nucleus is absent. DNA is circular and naked. Usually polycistronic DNA is present. Only one kind of RNA polymerase is present. Transcription and translation both occurs in the cytoplasm. Extracellular chromosomes are present in the form of plasmid or episome. Ribosome id 70S (50S + 30S) Cytoplasm lack cell organelles. If flagella is present, it is made up of single stranded protein called flagellin. Microfilaments - Actin and myosin are absent. Sap vacuoles are absent instead they have gas vacuoles. Endocytosis and exocytosis are absent. They divide by amitosis or si...

PROKARYOTES: Cell is small in size (0.1 to 5 μm) Cell wall is made of non cellulosic material. They generally contain muramic acid (amino acid derivative-peptidoglycan). Mucopolysaccharide capsule is present in many cells. Cell membranes infolds to form mesosomes that controls cellular respiration and cell division. An organized nucleus is absent. Here chromatin network is in direct contact with cytoplasm. It is called nucleoid / genophore. Mostly prokaryotes have multiple nucleoids. DNA is circular and naked. Usually polycistronic DNA is present. Only one kind of RNA polymerase is present. Both transcription and translocation occurs in the cytoplasm. Generally extranuclear chromosomes are present either in the form of plasmid or episome. Ribosome is 70S (50S + 30S) Protein synthesis is inhibited by chloramphenicol. Cytoplasm lacks membrane bound organelles. Flagella if present is mad up of single stranded protein, flagellin. Microfilaments - Actin and Myosin are absent. Sap vacuoles a...