Lecture 3 & 4: Cellular Forms of Life (PDF)

 Lecture 3 & 4 CELLULAR FORMS OF LIFE Kingdom: Prokaryotae Division: Bacteriophyta Common Features of bacteria -The term bacterium was derived from the Greek word bakterion, which means a small stick. -Bacteria are widely distributed in nature; bei...

 Lecture 3 & 4 CELLULAR FORMS OF LIFE Kingdom: Prokaryotae Division: Bacteriophyta Common Features of bacteria -The term bacterium was derived from the Greek word bakterion, which means a small stick. -Bacteria are widely distributed in nature; being found almost everywhere. ‫موجودة فى كل مكان‬ -They cause diseases, other bad changes, such as food spoilage, souring of milk, deterioration‫ تحلل االقمشة‬of textiles, and corrosion of metal pipes. The vast majority is harmless. ‫معظمها‬ ‫مفيدة وقليل ضارة‬ -They range in size from between 0.2 and 10 micrometer. - Bacterial cells have very high ratios of surface area to volume (900:1). This reflects high metabolic activity. ‫لو أخدت صندوق قسمته ألتنين هيشيل نفس الحجم لكن هزود عدد الوجوه ف دا معناه اني بزود مساحة السطح‬. ‫ف بالتالي بيزيد النشاط‬ ~1~ Morphology of Bacterial Cells 1. Spherical (cocci), which are arranged ‫المدورة‬ a. Singly: e.g. genus Micrococcus b. in pairs: e.g. genus Diplococcus c. in chains: e.g. genus Streptococcus d. in cubes: e.g. genus Sarcina e. irregular: e.g. genus Staphylococcus 2. Rod (bacilli), ‫العصوية‬ 3. Spiral ( helical)‫حلزوني‬Ex spirochaete or Vibrio ‫الصور دي للتوضيح مش أكتر عشان تعرف أشكال البكتريا مش عليك غير االشكال الرئيسية‬ ~2~ Bacterial cell structure A-Invariant structures B-Variant structures found in all cells ‫فى كل البكتريا‬ found in some cells ‫فى بعض البكتريا‬ Ex : cell wall, cytoplasmic such as flagella, capsules, membranes, ribosomes, nuclear endospores, slime layer... etc. region. ~3~ Invariant Structures: 1. Cytoplasmic (Plasma) membrane 1-The thin structure that completely surrounds the cytoplasm of the cell. 2-It is composed of protein and phospholipids forming phospholipid bi-layer. 3-Function : It's selectively permeable membrane, ‫النفاذية‬ ‫األختيارية‬permits the passage of some molecules and prevents others. & a tight barrier : regulates the passage of molecules into and from the cell. 4- It plays a key role in cell respiration, as the enzymes responsible for respiration are part of the membrane. ‫ألن البكتريا‬ ‫معندهاش ميتوكوندريا‬ 2. Cell Wall 1-one of the most important structural features of the prokaryotic cell 10 - 40 % of dry weight. 2-confers rigidity as well as shape and protects the cell against osmotic stress shock 3-The cell wall contains murein, or peptidoglycan. This layer is not found in any eukaryotic organism 12‫الخميس‬ ~4~  Characteristics Gram +ve Gram -ve Thick (15-80nm), thin (10-15nm), Structure monolayer triple layer 5-20% 90% peptidoglycan, peptidoglycan, Composition low lipids (1-4%) higher lipids (11- 22%) Physical More resistance less resistance disruption Penicillin ‫مضاد حيوي‬ More susceptible less susceptible Lysozyme More susceptible less susceptible ‫االنزيمات المحللة‬ ‫دول نوعين من البكتريا واحدة فيهم بتمسك فى الصبغة وواحدة فيهم آل اللي بتمسك بوستيف واللي أل‬ ‫ والرسمة دي مهمة‬.. ‫نيجاتيف‬ ~5~ 3. Cytoplasm  Cytoplasm is granular in appearance and rich in RNA  It contains most of the enzymes and aqueous solutions of salts, sugars, amino acids, vitamins... etc. 4. Mesosomes 1-are folded invaginations in the plasma membrane of bacteria 2-play role in cell division,. And metabolic processes (Phosophorylation = ATP generation) ‫انتاج ال‬ATP and secretion of enzymes from the cell. 5. Ribosomes ribosomal nucleic acid (rRNA) + protein 1-Ribosomes are the sites of protein synthesis 2-The size of a ribosome is measured in Svedberg units (S) that depend on both the mass and shape of the ribosome ‫دي وحدة القياس يعني‬ 3-Ribosomes of prokaryotes are relatively smaller (70S) than those of eukaryotes (80S). ~6~ 6. Bacterial chromosome  a single large circular macromolecule of double- stranded DNA. 7. Reserve Material‫المواد التخزينية واألخراجية‬  They include lipid like molecules, volutin (polyphosphate) granules, glycogen, starch, polyphosphate granules, sulfur granules... etc  They are not bounded by membranes. Variant Structures 1. Photosynthetic Membranes In green bacteria In Cyanobacteria cylindrically- shaped they occur within the vesicles attached to the cytoplasm and are not cytoplasmic membrane bounded by a membrane, and known as thylakoids ‫فيها شبه من اللي فى البالستيدات بتاعة‬ ‫النبات يعني‬ ~7~ 2. Plasmids 1-small circular macromolecules of DNA 2-exist in some bacterial cells and contain a limited amount of specific genetic information 3-replicate independently 4- Episomes : When integrated into the chromosomes of bacteria and replicate under the control of chromosome. 3. Flagella 1-long, thread-like appendages of uniform diameter. 2-Longer than the organism & made of protein subunits called flagellin ‫ مرات‬3 ‫اطول من الخلية‬ 3-not seen by the light microscope. 4- chemotaxis : movement bacteria by flagella toward nutrients‫ الغذاء‬or away from a stress‫الخطر‬ ~8~ Flagella Arrangement‫الجدول دا مهم جداااااااااا‬ Arrangement Definition Shape Monotrichous 1) a single polar flagellum. 2) a cluster of flagella at Lophotrichous one end. 3) either one or cluster of Amphitrichous flagella at both ends. 4) a cluster of flagella Peritrichous arranged over the whole bacterial cell. 4. Pili  short hair-like appendages on the surface of some bacteria  They serve for attachment process / found in motile & non motile bacteria  The F or sex pilus is involved in bacterial mating & is found in donor cells.‫هناخدها قدام دي أتقل‬  They are half the thick of flagella –shorter.& thinner ~9~ 5-Capsule and Slime Layer Capsule Slime layer form a capsule external to the loosely attached; they form a cell wall ( firmly ) diffuse layer around cells. composed of polysaccharides and/or proteins. S-colonies bacteria ( smooth ) = colonies of capsulated bacteria Glycocalyx ‫اسم تاني ليها‬ Other type uncapsulated colonies called R colonies. Protect cells against dehydration Protect cells against phagocytes and loss of nutrients. Associated with virulence Slime layer may act to bind cells Determine pathogenicity together. Reservoir of stored food Attachment to solid surface (dental plague). ~10~ 6-Bacterial Endospore  Bodies produced within the cells as a defense mechanism for unfavorable conditions. ‫وسيلة دفاع تقوم بها البكتريا لتحمي نفسها من الظروف‬ ‫الصعبة‬  The position of the spore in the cell may be central, subterminal, or terminal.  The structure of the spore is much more complex than that of the vegetative cell, and it is a complex seven layered structure. Questiones ( true or false ) 1-Flagella are short hair-like projections composed of protein subunits 2- when plasmid have the ability to become integrated into the chromosomes it called rebosome 3- Bacterial chromosome is a single large circular macromolecule of double- stranded RNA. 4-Variant structures is found in some cells. 5-Gram +ve bacteria ‘s cell walls have 90% peptidoglycan, low lipids (1-4%). 1-true 2-false 3-false 4-true 5-true ~11~ Reproduction of bacteria -No sexual reproduction ‫اليوجد اعضاء تناسلية‬ -Bacteria multiply by the asexual process of binary fission >>>direct -It involves chromosomal DNA duplication -after which the bacterial membrane and cell wall grow inward to meet one another and divide the cell into two daughter cells. Gene transfer in bacteria Bacteria can exchange genes. it may occur within bacteria of different families by three mechanisms : (1) Conjugation: (2) Transduction:‫مش عليكم‬ (3) Transformation:‫مش عليكم‬ ~12~ (1) Conjugation: Conjugation process requires cell-to-cell contact. from F+ to F- by help of F pilus ‫هل اللي فوق دا يعتبر تكاثر جنسي وال ال و لماذا ؟؟‬ Importance of bacteria: 1) Decomposition of dead organisms, thus recycling nutrients in the soil. 2) Fix atmospheric nitrogen into compounds utilizable by plants. 3) Many bacteria that live in the intestinal tracts of animals synthesize certain vitamins that benefit the animals. 4) Manufacture of butter and cheese through souring of milk. ~13~ 5) Industrial fermentations. 6) Some bacterial strains can be used as feed or food. 7) Can be used for the production of biogass (methane). 8) Recovery of petroleum and heavy metals from polluted environments. 9) Wastes and waste water treatments. - Decomposition/ Fix nitrogen/ intestinal tracts/ cheese/ fermentations strains / biogass/ polluted environments ‫متحفظهمش لكن اقراهم وافهم كل واحدة يعني ايه والسطر اللي فوق دا ملخصهم‬ KINGDOM: PROKARYOTAE DIVISION: CYANOPHYTA (BLUE-GREEN ALGAE) Cells Prokaryotic Color blue-green Nutrition Photosynthetic Pigments Chlorophyll a Phycocyanin blue & phycoerythrin red Stored food Cyanophycean starch Morphology Unicellular, colonial or filamentous - Lack flagella - In many filamentous species, the ~14~  chains of cells are interrupted by large cells known as heterocysts. These cells lack photosynthetic pigments and they are concerned with the fixation of atmospheric nitrogen. - Sections between heterocysts are called hormogonia. Reproduction - No sexual reproduction - Reproduce asexually: - Unicellular forms reproduce by binary fission - Colonial and filamentous forms can reproduce by Fragmentation, - Cultivation of rice: increase soil fertility by Conversion of atmospheric nitrogen into a usable form Importance such as nitrate (nitrogen fixation by heterocysts) - Production of organic matter ‫يعني النيتروجين الموجود ف الهواء الجوي يتحول لصورة‬ ‫يمكن أستخدامها لتصنيع األمينو أسيد‬ ‫انا مش حاطط اسئلة كتير في المحاضرة دي عشان كبيرة هيبقى في شيت اسئلة هينزلك على جزء الميدترم كله‬ ‫والميدتيرم في السيستماتك هيقف لحد هنا‬ ~15~