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Presentation on theme: "PROCARYOTİC &EUCARYOTİC CELLS Prof. Dr. Gönül KANIGÜR."— Presentation transcript:


2 Microorganisms can be divided into 2 groups : Single CellularMulti-cellular ProcaryoteBacteria - EucaryoteFungi Protozoa Algae Fungi Algae

3 CELLS The microscopic study of cells reveals 2 types of cells: prokaryotic and eukaryotic.

4 Two Main Classes of Cells Prokaryotic (Bacteria and Archaea) – Pro = “Before”; Karyon = “Kernel” – No nucleus, DNA coiled up inside cell Eukaryotic (Everything else) – Eu = “True” – DNA inside membrane bound organelle inside cell, the nucleus

5 Prokaryotic Cells are relatively simple 1. Bacteria are prokaryotic cells 2. 1-10 um in diameter, just visible with light microscopes. 3. Metabolically diverse. 4. No True Nucleus

6 MORPHOLOGY OF PROKARYOTIC CELLS Prokaryotes exhibit a variety of shapes – Most common Coccus – Spherical Bacillus – Rod or cylinder shaped

7 Cellular Structure A typical bacterial (procaryotic) cell has the following basic structures : (1)Cell Wall, (2)Cell Membrane, (3)Ribosomes, (4)Nuclear Region

8 CELL WALL Bacterial cell wall – Rigid structure – Surrounds cytoplasmic membrane – Determines shape of bacteria – Holds cell together – Prevents cell from bursting – Unique chemical structure Distinguishes Gram positive from Gram-negative

9 Cytoplasmic membrane A.Structure -A phospholipid bilayer with proteins -contains carbonhydrates -contains sterols B-Function -transport:simple diffusion,facilitated diffusion,osmosis and active transport -Endocytosis:phagocytosis and pinpcytosis

10 Cellular Structure (3)Ribosomes Small particles composed of protein and ribonucleic acid (RNA). A single cell may have as many as 10,000 ribosomes. Part of the translation apparatus, synthesis of cell proteins take place upon these structures.

11 INTERNAL STRUCTURE Ribosome – Involved in protein synthesis – Composed of large and small subunits Units made of protein 40% and ribosomal RNA 60% – Prokaryotic ribosomal subunits Large = 30S Small = 50S – Small than eukaryotic ribosomes Difference often used as target for antimicrobials

12 Cellular Structure (4)Nuclear Region Nuclear region is primitive in procaryotic cell, i.e. bacteria. Procaryotic cells DO NOT possess a true nucleus. The functions of the nucleus are carried out by a single long strand of deoxyribonucleic acid (DNA) The nuclear region where the DNA is present is sometimes known as a nucleoid, NOT a nucleus.

13 Bacterial chromosome is not directly intereact with the proteins such as histons DNA contents range from about 0.6 million to five milion bp.5000 proteins are coded from the chromosomal DNA Bacteria may also contain plasmids,double stranded DNA molecules.they are not essential for growth and reproduction.

14 Plasmids carry functional genes that give certain properties of the bacterial cell for ex.drug rezistance.some bacteria are rezistance to some antibiotics.

15 Movement Many bacteria are motile, able to move independently due to a special structure known as Flagellum (plural : Flagella)

16 PILI Rigid tubular structure made of pilin protein Found only in Gram negative cells Functions – Sexual pili—joins bacterial cells for DNA transfer (conjugation) – Common pili—adhesion


18 I. Organisms and general properties A. Organisms – 1. Microorganisms Fungi Protozoa Algae – 2. Other Higher plants Animals

19 I. Organisms and general properties, cont. B. General properties – More complex than procaryotes – Larger than procaryotes – Have a true nucleus – Have membrane-bound organelles

20 III. The cell wall and glycocalyx A. Cell wall – Rigid structure – Found on plant cells – Not made of peptidoglycan, but of long polysaccharide, e.g., cellulose B. Glycocalyx A carbohydrate-containing structure on the surface of a cell. – May strengthen membrane of animal cells. – Serves as an adhesin, i.e., holds adjacent cells together

21 Eukaryotic Cells Components Cell Wall – contains cellulose – support and protection Cell membrane / Plasma membrane – Phospholipid bilayer with embedded proteins – boundary layer and transport Nucleus – nuclear envelope, nucleoplasm, chromatin, nucleoli – storage and synthesis of genetic material. Nucleolus – Ribosome formation

22 IV. The cytoplasmic membrane A. Structure – A phospholipid bilayer with proteins – Contains carbohydrates – Contains sterols B. Function – Transport: simple diffusion; facilitated diffusion; osmosis; and active transport – Endocytosis: phagocytosis; and pinocytosis

23 VI. Organelles Organelle A membrane-enclosed structure. A. Nucleus – Has a double membrane with pores – Contains nucleoli where ribosomal RNA is synthesized – Contains chromatin: DNA + histones (basic proteins) – Chromosomes divide by mitosis.

24 İts diameter is aprox. 5um İt contains genetic material of the cell. The Dna content is l.5 x10 – 7 to 5xl0 -9 bp 30.000 protein are coded. The nucleus is the site of DNA replication and RNA synthesis.

25 V. Cytoplasm The substance outside the nucleus and inside the plasma membrane Similar in composition to that of procaryotes, but has a cytoskeleton that provides shape, support, and transport within cell Cytoskeleton consists of: – Microfilaments – Intermediate filaments – Microtubules

26 VI. Organelles, cont. B. Endoplasmic reticulum (ER) – Membrane network from nucleus to plasma membrane – Rough ER Has ribosomes attached Site of protein synthesis – Smooth ER No ribosomes attached Site of lipid synthesis

27 VI. Organelles, cont. C. Golgi apparatus – Stacks of membranes in cytoplasm – Receives proteins & lipids from ER – Ends pinch off forming secretory vesicles – Transports proteins & lipids within cell

28 D. Ribosomes – The site of protein synthesis – In cytoplasm: 80S variety consisting of 60S & 40S subunits – In mitochondria:70S variety consisting of 50S & 30S subunits

29 G. Lysosomes – Contains hydrolytic enzymes – Especially important in phagocytes

30 . Organelles, cont. H. Vacuoles - membrane bound cavities – Diverse functions: Store proteins, sugars, etc. Store metabolic waste Store water (plant cells)

31 Organelles, cont. E. Mitochondria – The site of respiration – Has 2 membranes: Outer one has sterols Inner one has no sterols, Has DS circular DNA – Has 70S ribosomes – Replicates autonomously

32 VI. Organelles, cont. F. Chloroplasts – The site of photosynthesis – In algae and other plant cells – Contain 70S ribosomes – Contain DS DNA – Replicate autonomously

33 An endosymbiotic orijin for these organels mitochondria,chlor oplast) is now generally accepted

34 I. Centrioles – Near nucleus – Functions: cell division, and formation of cilia and flagella

35 II. Structures external to the cell wall A. Flagella – Surrounded by the cytoplasmic membrane. – Contains microtubules in a 2 + (2 x 9) arrangement – Function: motility – Found on some protozoa and algae – Only a few per cell

36 VII. Comparisons EUCARYOTE Larger Simple wall structure Sterols in membrane 2 + (9x2) flagella True nucleus Histones PROCARYOTE Smaller Peptidoglycan wall No sterols in memb. Flagellin in helix No nucleus No histones

37 VII. Comparisons, cont. EUCARYOTES Several chromosomes Membrane-bound organelles 80S ribosomes PROCARYOTES One chromosome No membrane-bound organelles 70S ribosomes

38 VII. Comparisons, cont. PROCARYOTES 1 chromosome No membrane-bound organelles 70S ribosomes Replicates autonomously MITOCHONDRIA Multiple copies no membrane-bound organelles 70S ribosomes Replicates autonomously

39 VII. Comparisons, cont. PROCARYOTES About 1- 8  m Peptidoglycan wall No sterols in membrane No nucleus No histones MITOCHONDRIA About 1  m No wall No sterols in inner membrane No nucleus No histones



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