Chapter 1: Cell Theory and Structure Comparison

1. CHAPTER 1 CELL AS A UNIT OF LIFE

2. LEARNING OUTCOME 1.1 CELL THEORY **Describe the cells as the smallest independent unit of life and form the basis of living organisms. 1.2 PROKARYOTIC AND EUKARYOTIC CELLS **Compare the structure of prokaryotic & eukaryotic cells 1.3 PLANT AND ANIMAL CELLS **Detailed structure ( plant and animal ) **Compare plant and animal cells 1.4 CELLS AS BASIC UNIT OF LIVING ORGANISMS **Specialized cells. a) plant – meristem,parenchyma,collenchyma,sclerenchyma b) animal – epithelium, nerves, muscle, connective tissue -(DESCRIPTION OF STRUCTURE FUNTION AND DISTRIBUTION)

3. CELL THEORY. THEORY; • All living organisms are composed of one or more cells. • Cells- basic units of structure and function in an organism. • cells have the same chemical composition. • Cells come only from reproduction of existing cells- mitosis • Genetic materials- pass to daughter cells during cell division. • P/S – virus/chloroplast/mitochondria have their own DNA

4. Prokaryotes • Pro = before; karyon = nucleus • Single celled organism • relatively small – 0.5 to 10 um • lack membrane-bound organelles • earliest cell type • No nucleus/ no nuclear envelope • E.g.; bacteria/cyanobacteria(blue –green algae) • Surrounded by cell wall(peptidolycan – modified sugar)

5. Eukaryotes • Eu = true; karyon = nucleus • 10-100 micrometer • contain membrane-bound organelles • Evolved from prokaryotes by endosymbiotic association of two or more prokaryotes • Include Protists, Fungi, Animals, and Plants ( cell wall made of cellulose) • E.g.; Protist/fungi/animal and plant

6. Features of Prokaryotic Cells

7. Features of Prokaryotic Cells • Cytoplasm • semi-fluid cell interior • no membrane-bound organelles • location for metabolic enzymes • location of ribosome for protein synthesis • Ribosome. • The smaller (70 S) type. • Nucleoid • region where naked DNA is found • Nucleoid (or Nuclear Zone) • The region of the cytoplasm that contains DNA. It is not surrounded by a nuclear membrane.

8. Features of Prokaryotic Cells • DNA. • Always circular, and not associated with any proteins to form chromatin – naked DNA • Plasmid. • Small circles of DNA, used to exchange DNA between bacterial cells, and very useful for genetic engineering. • Cell membrane. • made of phospholipids and proteins, - separates the cell from the environment

9. Features of Prokaryotic Cells • Mesosome. • A tightly-folded region of the cell membrane containing all the membrane-bound proteins required for respiration and photosynthesis. • Can also be associated with the nucleoid. • Cell Wall. • Made of murein (not cellulose), which is a glycoprotein (i.e. a protein/carbohydrate complex, also called peptidoglycan). • There are two kinds of cell wall, which can be distinguished by a Gram stain: Gram positive bacteria have a thick cell wall and stain purple, while Gram negative bacteria have a thin cell wall with an outer lipid layer and stain pink.

10. Features of Prokaryotic Cells • Cell Wall • rigid structure - maintain its shape (made of peptidoglycan) • Capsule (or Slime Layer). • A thick polysaccharide layer outside of the cell wall • Used for sticking cells together, as a food reserve, as protection against dehydration and chemicals, and as protection against phagocytosis.

11. Features of Prokaryotic Cells • Capsule • outer sticky protective layer • this is in NO way the same as the cell wall of a plant cell • Flagellum. • A rigid rotating helical-shaped tail used for propulsion(movement) • The motor is embedded in the cell membrane and is driven by a H+ gradient across the membrane. • Clockwise rotation drives the cell forwards, while anticlockwise rotation causes a chaotic spin. • This is the only known example of a rotating motor in nature.

12. Features of Eukaryote Cells

13. Features of Eukaryote Cells • Cytoplasm (or Cytosol). • This is the solution within the cell membrane. • contains enzymes -glycolysis (part of respiration) and other metabolic reactions together with sugars, salts, amino acids, nucleotides and everything else needed for the cell to function. • All living content excluding nucleus and plasma membrane

14. Features of Eukaryote Cells • Nucleus. • largest organelle. • Surrounded by a nuclear envelope-double membrane with nuclear pores - large holes containing proteins that control the exit of substances (RNA /ribosomes)from the nucleus. • The interior is called the nucleoplasm, which is full of chromatin- a DNA/protein complex in a 1:2 ratio containing the genes. • During cell division the chromatin becomes condensed into discrete observable chromosomes. • The nucleolus is a dark region of chromatin, involved in making ribosome.

15. Features of Eukaryote Cells • Mitochondrion (pl. Mitochondria). • sausage-shaped organelle (8µm long)-where aerobic respiration takes place in all eukaryotic cells. • Mitochondria are surrounded by a double membrane: the outer membrane is simple and quite permeable, while the inner membrane is highly folded into cristae-large surface area. • The space enclosed by the inner membrane is called the mitochondrial matrix, and contains small circular strands of DNA. • The inner membrane is studded with stalked particles, which are the site of ATP synthesis.

16. Features of Eukaryote Cells • Chloroplast. • Bigger/fatter than mitochondria, chloroplasts-site of photosynthesis,-only found in photosynthetic organisms (plants and algae). • enclosed by a double membrane, also have a third membrane (thylakoid membrane)-folded into thylakoid disks which then stacked into piles( grana) • The space between the inner membrane and the thylakoid is called the stroma. • The thylakoid membrane contains chlorophyll and other photosynthetic pigments arranged in photosystems, together with stalked particles, and is the site of photosynthesis and ATP synthesis. • Chloroplasts also contain starch grains, ribosomes and circular DNA.

17. Features of Eukaryote Cells • Ribosomes. • These are the smallest and most numerous of the cell organelles, and are the sites of protein synthesis. • They are composed of protein and RNA, and are manufactured in the nucleolus of the nucleus. • Ribosomes are either found free in the cytoplasm-site of proteins synthesis for the cell's own use, or they are found attached to the rough endoplasmic reticulum, where they make proteins for export from the cell. • They are often found in groups called polysomes. • All eukaryotic ribosomes are of the larger, "80S", type.

18. Features of Eukaryote Cells • Smooth Endoplasmic Reticulum (SER). • Series of membrane channels involved in Synthesizing and transporting materials, mainly lipids, needed by the cell. • Rough Endoplasmic Reticulum (RER). • Similar to the SER, but studded with numerous ribosomes, which give it its rough appearance. • The ribosomes synthesis proteins, which are processed in the RER (e.g. by enzymatically modifying the polypeptide chain, or adding carbohydrates), before being exported from the cell via the Golgi Body.

19. Features of Eukaryote Cells • Golgi Body (or Golgi Apparatus). • Another series of flattened membrane vesicles, formed from the endoplasmic reticulum. • F(x)transport proteins from the RER to the cell membrane for export. • Parts of the RER containing proteins fuse with one side of the Golgi body membranes, while at the other side small vesicles bud off and move towards the cell membrane, where they fuse, releasing their contents by exocytosis.

20. Features of Eukaryote Cells • Vacuoles. • These are membrane-bound sacs containing water or dilute solutions of salts and other solutes. • Most cells can have small vacuoles that are formed as required, but plant cells usually have one very large permanent vacuole that fills most of the cell, so that the cytoplasm (and everything else) forms a thin layer round the outside. • Plant cell vacuoles are filled with cell sap, and are very important in keeping the cell rigid, or turgid. • Some unicellular protoctists(protist) have feeding vacuoles for digesting food, or contractile vacuoles for expelling water.

21. Features of Eukaryote Cells • Lysosomes. • These are small membrane-bound vesicles formed from the RER containing a cocktail of digestive enzymes. • They are Used To Break Down Unwanted Chemicals, Toxins, Organelles Or Even Whole Cells, So That The Materials May Be Recycled. • They can also fuse with a feeding vacuole to digest its contents.

22. Features of Eukaryote Cells • Cytoskeleton. • This is a network of protein fibres extending throughout all eukaryotic cells, Used For Support, Transport And Motility. • The cytoskeleton is attached to the cell membrane and gives the cell its shape, as well as holding all the organelles in position. • There are three types of protein fibres (microfilaments, intermediate filaments and microtubules), and each has a corresponding motor protein that can move along the fibre carrying a cargo such as organelles, chromosomes or other cytoskeleton fibres. • These motor proteins are responsible for such actions as: chromosome movement in mitosis, cytoplasm cleavage in cell division, cytoplasmic streaming in plant cells, cilia and flagella movements, cell crawling and even muscle contraction in animals.

23. Features of Eukaryote Cells • Centriole. • This is a pair of short microtubules involved in cell division. • Before each division the centriole replicates itself and the two centrioles move to opposite ends of the cell, where they initiate the spindle that organises and separates the chromosomes.

24. Features of Eukaryote Cells • Undulipodium (Cilium and Flagellum). • This is a long flexible tail present in some cells and used for motility. • It is an extension of the cytoplasm, surrounded by the cell membrane, and is full of microtubules and motor proteins so is capable of complex swimming movements. • There are two kinds: flagella (no relation of the bacterial flagellum) are longer than the cell, and there are usually only one or two of them, while cilia are identical in structure, but are much smaller and there are usually very many of them.

25. Features of Eukaryote Cells • Microvillus (MICROVILLI) • These are small finger-like extensions of the cell membrane found in certain cells such as in the epithelial cells of the intestine and kidney, where They Increase The Surface Area For Absorption Of Materials. • They are just visible under the light microscope as a brush border. • Cell Membrane (or Plasma Membrane). • This is a thin, flexible layer round the outside of all cells made of phospholipids and proteins. • It separates the contents of the cell from the outside environment, and controls the entry and exit of materials. • The membrane is examined in detail later.

26. Features of Eukaryote Cells • Cell Wall. • This is a thick layer outside the cell membrane used to give a cell strength and rigidity. • Cell walls consist of a network of fibers, which give strength but are freely permeable to solutes (unlike membranes). • A wickerwork basket is a good analogy. • made mainly of cellulose, also contain hemicelluloses, pectin, lignin and other polysaccharides. -built up in three layers > primary cell wall, the secondary cell wall and the middle lamella. • There are often channels through plant cell walls called plasmodesmata, which link the cytoplasms of adjacent cells. • Fungal cell walls are made of chitin (poly-glucosamine). • Animal cells do not have a cell wall, though they do have a layer of carbohydrate outside the cell membrane called the cell coat, or glycocalyx.

27. Microscopic structures of plant and animal cells

28. COMPARISON- PROKARYOTIC& EUKARYOTIC CELLS

29. PLANT CELL

30. Tissue and Organs in plant: • Dermal Tissue System (epidermis)-forms the outer layer of a plant. • Ground Tissue System (parenchyma/collenchyma/sclerenchyma)-(makes up the bulk of roots and stems • Vascular Tissue ( xylem& phloem)-transports water and food throughout the plant. • The FOUR Plant Organs are ROOTS, STEMS, LEAVES AND FLOWERS.

31. Specialized cell : Plant Meristem • Meristems- cells that undergo repeated division. • These are the cells from which all other cells in the plant originate. • No undergoes differentiation. • 2 types of meristem : 1) apical>shoot and root 2) lateral>cambia-vascular cambium -cork cambium • three types : primary, secondary, and pericycle. • The primary meristems give rise to primary tissues in the plant, which elongate the plant by either shoots or roots. • Secondary meristems form the basis of secondary tissues that enlarge the diameter of the stem or root. • the pericycle is a specialized meristem-found only in the root system-gives rise to branch roots.

32. Meristem, parenchyma, collenchyma, sclerenchyma, xylem, and phloem tissues

33. Specialized cell : Plant Parenchyma • Unspecialized and are found in all organs of plant. • Can divide and give rise to more specialized cells. • Living at maturity • Isodiametrical/ polyhedral(many sided)-capable 4 cell division • Thin 1st cell wall and without 2nd cell walls • Loosely packed • Involved in food storage. • Involved in apoplast pathway 4 movement of water and minerals. • Divide to 4 type: 1) epidermis 2) mesophyll 3) endodermis 4) pericycle Collenchyma • thicker primary walls. • Polygonal shape • f(x) : mechanical support • Form bundles underneath epidermis. • Flexible support to immature regions of the plant.

34. Sclerenchyma Sclerenchyma cells have thick secondary walls impregnated with lignin. Most are non living. More rigid than collenchyma cells Most cells death at functional maturity Can be divided into 2 types: a) fibres- elongated b) scelereids( stone cells ) - spherical - can be found in the cortex, pith and phloem * Function – supporting element of the plant

36. Specialized cell : Plant Xylem • Xylem transports water and minerals from the roots to the leaves. • Tracheids • elongated, with tapered ends and have lignified walls • Matured cells death with empty lumen • Pits in end walls. • Vascular rays • Fibers • Vessel Elements • Larger, with perforated plates in their end walls. • Long ,narrow tube formed

37. Xylem

38. Specialized cell : Plant Phloem • Phloem transports sucrose and other organic compounds from the leaves to the roots. • Sieve-tube members are conducting cells. • Contain cytoplasm but no nuclei. • Channels in end walls. • Plasmodesmata extend from one cell to another through sieve plate. • Companion cells- contain nucleus, vacuoles, ribosomes and mitochondria

39. Phloem

40. SUMMARY OF SPECIALISED PLANT CELLS: FUNCTION & DISTRIBUTION

42. Specialized cell : Animal Epithelial cell/ epithelium • One of the simplest tissues. • However, it can be built up into tissues of varying complexity. • Lining tissues : in it simplest form, it consists of a single layer of cells covering the surface of the body and the organs within it.

43. Specialized cell : Animal Epithelial cell • Also lines various spaces and tubes ( in which situation it is usually referred to as endothelium). • Typically the individual cells : firmly attached to each other.

44. Specialized cell : Animal Epithelial cell • rest on a basement membrane. • have a free surface • The main function of epithelial tissues is protection.

45. Specialized cell : Animal Epithelial cell • Other functions: • To increase the surface area for the reabsorption of materials/which absorption can take place. • Exchange materials by diffusion. • As a gland ; secrete mucus or enzyme.

46. Types of Epithelial Tissues

47. Simple Epithelial Tissues • Simple squamous epithelial tissues. • Simple cuboidal epithelial tissues. • Simple columnar epithelial tissues.

48. Simple squamous epithelial tissues • Cells are flattened. • Disc- shape nucleus • The sheet of cell is delicate, thin and leaky.

49. Simple squamous epithelial tissues • Functions:  exchange of material/protect underlying tissues  lubricates the movement between adjacent surface./facilitated diffusion of gaseous across alveoli • Distribution:  the linings of blood vessels.  alveoli  mouth cavity  Bowmann capsule

50. Simple cuboidal epithelial tissues • Cells are cubical in shape. • View from free surface are polygonal. • Specialized for secretion. • Make up the epithelia of kidney tubules and many glands – thyroid and salivary glands.