Lecture_3.pdf

CSU1879-Biology for Engineers Lecture 3 – Classification of Cells  Topics to be covered today 1.Introduction to cell classification 2. categories comes under classification – prokaryotes and eukaryotes – plant and animal cells...

CSU1879-Biology for Engineers Lecture 3 – Classification of Cells  Topics to be covered today 1.Introduction to cell classification 2. categories comes under classification – prokaryotes and eukaryotes – plant and animal cells – unicellular and multicellular organisms – Some examples 3. Cells with in an organisms 4. Different levels of cellular organisation 5. Homework  Cell Classification On the basis of nature of nucleus, Doughtery classified cells into two categories:- 1. Prokaryotic cells 2. Eukaryotic cells  Cellular Diversity We know all cells have similar basic structure and function region but they vary greatly in their shape, size, number, life span and activities. Cell shape :- shape of cells varies not only in different organism but also in different parts of same organisms. In the case of amoeba and WBCs of blood, shape of cells is not fixed due to pseudopodia to engulf the materials. These may be flat(cheek cells and epithelium cells of lungs) or cuboidal( germ cells of gonads) or columnar (intestine) or polygonal(liver cells) or rounded( fat cells), slipper shaped(Paramecium). Oval shaped(Hens egg),branched(chromatophores or pigment cells) or long thread like(mucle fibres or nerve fibres). The shape of cell may vary with the function they perform 3 Cells come in all shape and size 4  1. Prokaryotic cells 1. Occurrence:- are placed in kingdom Monera  These include bacteria, cyanobacteria, PPLOs. are characterized by the absence of nucleus and the presence of one enveloped system of organisation. 2. Size:- bacteria vary greatly in their size. Smallest bacteria is 0.15- 0.3µm in size. 3. shape:- basically there are four shapes of bacteria:- 1. coccus:- are spherical shaped bacteria 2. Bacillus:-are rod shaped bacteria 3. Spirrilum:- are spirally coiled and flagellated 4. Vibrio:- are comma shaped and flagellated  2. Eukaryotic cells It is characterized by having true All the protists, plants and animals nucleus having nuclear envelope, and fungi have eukaryotic cellular typical chromosomes and mitotic organisation apparatus. These cells vary greatly in their size which may be in range of 10 um to 500um. Structural Difference  Difference between prokaryotes and eukaryotes Prokaryotes Eukaryotes 1. Bacteria, 1. Protozoa, fungi ,plant and animals 2. It is double membrane system 2. It is single membrane system 3. Cell wall is made up of polysaccharides 3. Cell wall is made up of peptidoglycan 4. Cytoplasm contain many membrane 4. Cytoplasm do not contain ER bounded organelles 5. Mitochondria are absent, oxidative 5. Cells contain mitochondria which is site phosphorylation is associated with of oxidative phosphorylation plasmalemma 6. Contain microtubules 6. Cytoplasm does not have any 7. Ribosomes are of 80S in type microtubules 8. Endo and exo-cytosis occur in many 7. Ribosomes are of 70 S type protists and animals 8. Endo and exo-cytosis does not occur  Difference between prokaryotes and eukaryotes Prokaryotes Eukaryotes 1. Cell cycle is short, takes about 20-60 m 1. Cell cycle is of longer duration. Takes 2. Spindle apparatus is not formed during about 12- 24hr cell division 2. Spindle apparatus is formed 3. Chromosomes are attached to 3. Chromosomes are attached to nuclear plasmalemma membrane 4. Meiosis does not take place 4. Meiosis takes place 5. Cells are haploid 5. Cells are diploid 6. All the ribosomes are free in cytoplasm 6. Ribosomes are attached to ER 7. Transcription and translation occur in 7. Transcription and translation takes place cytoplasm in nuclear and cytoplasm respectively 8. The mRNA does not processing 8. The mRNA needs processing  Difference between plant cell and animal cell Animal cell Plant cell 1. Cell wall is absent 1. Cell wall is composed of dead cellulose 2. Consists of large vacuoles cell wall 3. Nucleus is located in the centre of the cell 2. Vacuoles are absent 4. Centrosome are present 3. Nucleus is pushed to one side of the cell 5. Plastids are absent 4. Centrosome absent 6. Numerous mitochondria are present 5. Plastids are mostly present 7. Cytoskeleton possesses intermediate 6. Few mitochondria are present fibers 7. Intermediate fibers are present 8. Crystals are lacking 8. Tubular cristae are present 9. May change form and move about 9. Does not change form and location 10. Incapable of synthesizing all amino acids, 10. Can synthesized all amino acids, and vitamins vitamins etc.  Difference between plant cell and animal cell Animal cell Plant cell 1. Divides by cell furrow method 1. Divides by cell plate method 2. Cells burst during hypertonic solution 2. Cell do not burst due to presence of cell 3. Glyoxysomes not present wall if placed in hypertonic solution 4. Stores carbohydrates as glycogen 3. Glyoxysomes may be present 5. Generally smaller, not exceeding 100um 4. Stores carbohydrates a s glycogen 5. Generally larger, exceeding 100um  Difference between unicellular and multicellular organism unicellular multicellular 1. Composed of single cell 1. Composed of large number of cells 2. Only some specialized external cells are 2. Whole body is exposed to environment exposed 3. Internal environment is not constantly 3. Internal environment is present present 4. A cell represents only an extremely small 4. A single cell representing the whole fraction of organisms organism 5. The size is varies 5. Cell size is generally large 6. Injury or death has no significant effect on 6. Injury leads to death of the cell the activity of organisms 7. Distinct reproductive organs are absent 7. Present 8. The organisms reproduce only once 8. It can reproduce several times 9. The cell is virtually immortal as there is 9. All the cells age and undergo natural no ageing death Thank you Geetansh School of Bioengineering and Food Technology Shoolini University Village Bhajol, Solan (H.P) 9805985357(Mob No.) [email protected]