Properties of cells & cell membrane

Prokaryotic cell structure and Properties
Eukaryotic cell structure and Properties

1. PROPERTIES OF CELLS AND CELL MEMBRANE Dr. Pulipati Sowjanya Professor & Head Vignan Pharmacy College Vadlamudi, Guntur ( Dt )

2. The Discovery of Cells All living things are made up of one or more cells. • A cell is the smallest unit that can carry on all of the processes of life. Hooke – In 1665, Robert Hooke discovered cells in slices of cork. • Leeuwenhoek – In 1673, Anton van Leeuwenhoek was the first to observe living cells in microorganisms; Leeuwenhoek called these organism animalcules~ we now call them protists .

3. Cell Diversity Cell Shape – A cell’s shape reflects its function.

4. Cell Diversity Cell Size – Cell size is limited by a cell’s surface area–to volume ratio.

5. Cell Diversity Cell Size • Unicellular organisms are made up of one cell • Multicellular organisms are made up of many cells that often specialize according to function - differentiation

6. OVERVIEW OF CELL STRUCTURE https://www.youtube.com/watch?v=URUJD5NEXC8&t=278s

7. Prokaryotic Cells Cells lack a nucleus and membrane bound organelles -Includes bacteria -Single, circular chromosome in nucleoid region -Surrounded by cell membrane and a cell wall made up of peptidoglycan

8. Prokaryote Structures Appendages - flagella, pili, fimbrae Cell envelope- glycocalyx, cell wall , cell membrane Cytoplasm - ribosomes, granules, nucleoid/chromosome.

9. Bacterial Appendages: • Pili (pl), pilus (s) – – only found in gram negative bacteria tubulare, hairlike structures of protein larger and more rare than fimbriae. • - - 2 types of pili at t ac h ment pilus - allow bacteria to attach to other cells sex pilus, - transfer from one bacterial cell to another- conjugation.

10. F i m b r i ae fimbriae (pl) fimbria (s) Adhesion to cells and surfaces Responsible for biofilms. Pathogenesis of gonococcus and E.coli Escherichia coli .

11. Fla g e l la Flagella (pl), flagellum(s) long appendages which rotate by means of a "motor" located just under the cytoplasmic membrane. bacteria may have one, a few, or many flagella in different positions on the cell. Advantages chemotaxis - positive and negative. motility All spirilla, half of bacilli, rare cocci.

12. Fla g e l la

13. F l age l l a Three morphological regions • – – Helical filament long outermost region; composes up to 90% of its length contains the globular (roughly spherical) protein flagellin arranged in several chains and form a helix around a hollow core – Hooked or curved area filament is attached; consists of a different protein • – – – Basal body terminal portion of the flagellum fix the flagellum to the cell wall and plasma membrane composed of a central rod inserted into a series of rings Gram negative - 2 pairs of rings • • Outer pair - fixed to the outer membrane and peptidoglycan layer Inner pair - fixed to the plasma membrane (SM ring) Gram positive - only inner pair is present

14. Motility • – – – Types of bacterial motility run or swim - when a bacterium moves in one direction for a length of time tumbles - periodic, abrupt random changes in direction swarming - rapid wavelike growth across a solid culture medium • Mechanism of flagellar movement - relative rotation of the rings in the basal body of the flagellum Antigenicity – flagellar or H antigen - useful in the serological identification of serotypes of Salmonella organisms

15. A rr an g e m e n t s Flagella vary in number and arrangement. Polar arrangment Monotrichious - 1 flagellum at one end Fastest; Pseudomonas -example Lophotrichious - tuft at one end Amphitrichious- bipolar Peritrichious - multiple flagella; randomly dispersed around the bacterial cell E. coli - example

16. Flagellar arrangements Monotrichous Lophotrichous A m phit r i c hou s Peritrichous Atrichous

17. Axial filaments

18. Axial filaments • tuft of fibrils that arise at the ends of the cell under the outer membrane and spiral around the cell • rotation an opposing of the outer membrane movement that propels the spirochetes by causing them to move like co rkscrews Found in Spirochetes and are similar to flagella, but are located between the cell wall and an outer membrane, and are attached to one end of the organism.

19. Evidence of motility Two ways by which motility can be demonstrated: direct or microscopic hanging drop preparation or wet mount preparation by dark field mycroscope Distinguishes: Brownian movement - when the bacteria show molecular movement true motility - if a bacterium describes a rotatory, undulatory or sinuous movement indirect or macroscopic Stab inoculation of the semisolid media nonmotile - growth is limited at the point of inoculation motile - growth is diffuse or moves away from the line of inoculation; turbidity of the medium

20. Detection of Motility Direct • Indirect Presence mobile bacteria

21. 2. Bacterial Surface Structure cell envelope A. Glycocalyx - some extracellular material secreted by many bacterial cells in the form of: capsule - attached tightly to the bacterium and has definite boundaries. slime layer - loosely associated with the bacterium and can be easily washed off Compositions: - - layer of polysaccharide proteins - sometimes

22. Functions of the Capsule Protection Identification Vaccine preparation Tissue attachment Antibiotic barrier

23. Medical Importance - rapid serological identification of: Several groups of streptococci Meningococcus Hemophilus influenzae Klebsiella pneumoniae Some of the coliforms Yersinia and Bacillus specie

24. Cell wall peptidoglycan (polysaccharides + protein) Components of the peptidoglycan layer : – – – Repeating glycan chains ( N acetyl glucosamine and N acetyl muramic acid ) a set of identical tetrapeptide side chains attached to N- acetylmuramic acid a set of identical peptide cross bridges

25. Peptidoglycan

26. Differences in Cell Wall Structure Basis of Gram Stain Reaction Hans Christian Gram- 1884 Differential Stain Gram Positive vs Gram Negative Cells Gram Positive Cells- Thick peptidoglycan layer with embedded teichoic acids Gram Negative Cells- Thin peptidoglycan layer, outer membrane of lipopolysaccharide.

27. Gram Stain Reaction Hans Christian Gram- 1880s Divides bacteria into 2 main groups- Gram positive Gram negative Also- gram variable Gram nonreactive Gram positive bacteria many layers of peptidoglycan and teichoic acids. form a crystal violet-iodine-teichoic acid complex Large complex, difficult to decolorize

28. Gr a m p o s i t i v e b a cter i a

29. Gram negative bacteria Very thin peptidoglycan No teichoic acids Alcohol readily removes the crystal violet. Alcohol also dissolves the lipopolysaccharide of the cell wall. Gram variable cells Some cells retain crystal violet; some decolorize and take up the safranin 4 factors- Genetics- variable amount of teichoic acid. Age of culture- older cultures have variable amount of teichoic acid Growth medium- necessary nutrients not available Technique- smear not thin or evenly made. Staining procedure not done correctly- decolorizer left on too long. Gram Stain Reaction

30. Gram negative bacteria

31. G r a m s t ai n t e chniqu e

32. Maintenance of the shape (due to rigidity of peptidoglycan). Protects the cytoplasmic membrane cell contents Rigidity Cell wall is osmotically insensitive Hypotonic solution – cell burst. Hypertonic solution – cell shrank. Isotonic solution – bacteria is life. Function of Cell Wall

33. Cell membrane Peripheral Membrane Protein Integral Membrane Protein Peripheral Membrane Protein Phospholipid

34. Selective permeability to different molecules. Active transport aided by permease. Play a role in DNA replication. Cell wall biosynthesis. Mesosomes ----- cell division. Function of Cytoplasmic Membrane

35. Eukaryotic Cell

36. Cell Membrane

37. Functions of Cell Membrane The prime functions of the cell surface membrane are: To control what substances can enter and leave the cell - like passport / border control the cell surface membrane is a  selectively permeable barrier . To sense the environment. Chemicals can pass through the cell membrane by one of the following processes: Passive diffusion - passive since it requires no energy expenditure by the cell, two main types:              Active transport / pumping - uses energy supplied by the cell, e.g. in the form of ATP.

38. CELL TRANSPORT https://www.youtube.com/watch?v=ufCiGz75DAk

39. Endoplasmic Reticulum It is originated from outer membrane of nuclear membrane . It is of two types - the rough endoplasmic reticulum (RER), the smooth endoplasmic reticulum (SER). The RER consists of interconnected membranous sacs ( cisternae ) - unit membrane enclosing a fluid-filled lumen. The function of the RER is the synthesis, storage and transport of proteins around the cell. The proteins are manufactured by the ribosomes ,  that stud the outside the RER cisternae . The RER is continuous with the smooth endoplasmic reticulum (SER) - a network of branching membranous tubes that may fill much of the cytoplasm. The SER is responsible for the synthesis, storage and transport of lipids and carbohydrates and also the storage of calcium ions.

40. Golgi Complex/ Apparatus

41. Golgi Complex/ Apparatus The Golgi apparatus (Golgi body or Golgi complex) is the cell's 'post office'. It consists of stacks of 4-8 fluid-filled membranous disc-like sacs ( cisternae , singular cisterna ). The Golgi apparatus above has been sectioned down the middle. One face (the  cis ) face points towards the nucleus and RER (the top face in this diagram). Fluid-filled spherical membranous globules, called  vesicles , bud-off from the RER, carrying synthesised proteins as cargo. These vesicles travel to the  cis -face of the Golgi complex and fuse with it, delivering their protein cargo (along with the lipids from the membrane of the vesicle).  Inside the Golgi cisternae the proteins (and lipids) are sorted and labeled by attaching carbohydrate chains (chains of sugar molecules bonded together) to the proteins (a process called  glycosylayion ). The proteins and their attached carbohydrate chains may also be  sulphated  - sulphur may be added to them, giving them a negative charge. They may also be  phosphorylated  (by addition of phosphate). These carbohydrates may be required for the final function of the protein (now a glycoprotein, protein + carbohydrate chain = glycoprotein) or they may serve as address labels.

42. Nucleus It is enclosed in a double unit membrane - the  nuclear envelope  (NE). The nuclear envelope is continuous with the endoplasmic reticulum (ER). The nuclear envelope encloses the  nuceloplasm . The nucleoplasm is mostly occupied by  chromatin . Each chromosome consists of a single DNA molecule coiled around proteins called  histones . The nuclear  envelope is perforated by pores called  nuclear pores . The nuclear pores allow materials to enter and exit the nucleus

43. Ribosomes Ribosomes  are factories that manufacture proteins for cells. They are small (diameter about 10 nm or 10 millionths of a millimetre )  ribonucleoprotein enzymes . A ribonucleoprotein is a structure consisting of protein and RNA (ribonucleic acid ). In eukaryotes the ribosome is 80S and made of a 60S large subunit + a 40S small subunit. Eukaryotic chloroplasts and mitochondria contain prokaryote-like 70S ribosomes .

44. Mitochondria Site of cellular respiration (Energy from the breakdown of organic molecules isused to phosphorylate ADP to produce ATP)  “powerhouse of the cell”  More metabolic activity= more mitochondria

45. Chloroplast  Found in plants and eukaryotic algae  Site of photosynthesis  Contain the green pigment chlorophyll ChloroplastStructure  Thylakoids • Grana = stacks of thylakoids • (Light Dependent Phase)  Stroma • Fluid outside the thylakoids

46. Cytoskeleton  Maintains shape of cell  Responsible for movement of cell and movement of organelles within cell Made of three types of protein fibers :  Microtubules, microfilaments & intermediate filaments Components of Cytoskeleton:  Microtubules – 25 nm diameter  Intermediate Filaments – 8 – 12 nm diameter  Microfilaments – 7 nm diameter Microtubules: Hollow tubes made up of A- and B tubulin responsible for cell motility

47. Thank you