Cells (1).pptx for class nineth - class 9

Cells class 9

1. Major contributions done by the Scientists towards the discovery of Cell and its components:

2. TIMELINE-CELL BIOLOGY

3. ROBERT HOOKE- MICROGRAPHIA How is cork made from the bark of the Cork Oak trees? A thin cross-section of the cork was taken and viewed under the microscope Cross-sectional view of Cork under the Microscope (Magnification-between 20-50X)

4. Describing a nearby lake, Berkelse Mere, he noted that its water was very clear in winter ‘but at the beginning or middle of summer it becomes whitish, and there are then little green clouds floating in it’. These clouds contained wispy ‘green streaks, spirally wound serpent-wise, and orderly arranged’—the beautiful green alga  Spirogyra . Then came Leeuwenhoek's first mention of little animals: ‘among these streaks there were besides very many little animalcules … And the motion of most of these animalcules in the water was so swift, and so various upwards, downwards and round about that ‘twas wonderful to see. ANIMALCULES (Protista) 70X-250X Magnification ANTON VAN LEEUWENHOEK- The letter concerning “animalcules” Spirogyra

5. Robert Brown W hile investigating the fertilization mechanisms of plants in the Orchidaceae and Asclepiadaceae families, he noted the existence of a structure within the cells of orchids, as well as many other plants, that he termed the “nucleus” of the cell.

6. Jan Evangelista Purkinje Purkinje found a juicy substance in every cell he examined. He coined the term “Protoplasm” to it.

7. Schleiden and Schwann-Cell Theory 1. All organisms are made up of one or more cells. 2. Cell is the fundamental living unit. Matthias Schleiden Theodor Schwann Worked extensively on plant cells. Worked extensively on animal cells.

8. Rudolf Virchow- Omnis Cellula e Cellula 3. Cells arise from pre-existing cells.

9. Amoeba Chlamydomonas Paramoecium Fungi Plants Animals Examples of some Unicellular and Multicellular organisms:

10. Cells whose shape can vary: Cells which have a distinct shape:

11. Division of labour within the cell: Link for onion peel experiment: https://youtu.be/EUXmC84aRFQ

12. Structural organization of cell: Any cell has these three basic components:

13. PLASMA MEMBRANE - Why is the cell membrane also called Plasma membrane? Plasma Membrane is a phospholipid bilayer. Each molecule has a hydrophilic head and hydrophobic tail.

14. PLASMA MEMBRANE IS SELECTIVELY PERMEABLE. How does plasma membrane facilitate the movement of substances? What physical processes drive the movement of these substances? Do these processes need energy to be initiated? Let’s try to answer these questions:

15. DIFFUSION: Net movement of molecules from a region of higher concentration to a region of lower concentration. Characteristics of diffusion

16. What would happen if the plasma membrane allows diffusion of all the molecules??

17. Diffusion of Carbon dioxide and oxygen within the biological membrane Significance of selectively permeable membrane : The membrane only allows the substances of specific size and composition.

18. CONCEPT OF SOLUTE, SOLVENT, SOLUTION: Identify the solute and solvent in the following solution: (A) Sugar solution (B) Air (C) Rainwater (D) Aerated drinks

19. OSMOSIS Osmosis: Osmosis  is the process where solvent molecules move through a selectively permeable membrane from a dilute solution into a more concentrated solution. Osmosis occurs gradually . Osmosis in egg: https://youtu.be/Zx7OpxQR1YY

20. Concept of Endo and Exo Osmosis: Osmosis in raisins: https://youtu.be/JKGKDMHAnwM

21. Unicellular freshwater organism- Paramoecium Link for the Video: https://youtu.be/MxbwiACd0Tw

22. How do stems sustain themselves?? How do roots absorb water??

23. Endocytosis in Amoeba Endocytosis in amoeba https://youtu.be/mv6Ehv06mXY

24. HAVE A RECAP OF ALL THINGS LEARNT!!!

25. CELL WALL Link for plasmolysis experiment https://youtu.be/VPwLN6U1spk

26. NUCLEUS

27. What if a well-defined nucleus is not present…. Nucleoid-irregular shaped region in a prokaryotic cell that comprises most of the genetic material. Prokaryotic cell and Eukaryotic cell-differences associated with nucleus and cell organelles.

28. CYTOPLASM

29. FLIPPED CLASSROOM- CELL ORGANELLES ( Poster Presentation ) 7 topics 5 groups 2 groups- 1+1 topic Rubrics Creativity of the poster Timing, flow and fluency while speaking Level of understanding the topics and answering the questions

30. Cell organelle No of membranes Structure Function Endoplasmic Reticulum It is a single membrane bound cell organelle. Large network of tubules and sheets Specific structures are either long tubules or round/ oblong bags. It forms a network system within the cell for transport of substances. It forms a cytoplasmic framework as a surface for biochemical activities in the cell. Golgi apparatus It is a single membrane bound cell organelle. It was first described by Camillio Golgi It consists of membrane bound vesicles/sacs. These vesicles are arranged parallel to each other in stacks called as cisterns. These are in close connection with the ER. Storage, modification, packaging of substances synthesized in the ER into vesicles. These vesicles are dispatched to various target sites inside and outside the cell. It can also make complex sugars from simple sugars It is involved in the formation of Lysosomes. Lysosomes It is a single membrane bound cell organelle. They are membrane bound sacs filled with digestive enzymes. Foreign materials like bacteria are completely digested by the lysosomes as they enter into the cells. This is done by the powerful digestive enzymes present within them. Lysosomes help in keeping the cells clean. If the cell is infected or damaged, the lysosomes burst and the enzymes digest the entire cell.

31. Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum It appears rough under the microscope. It appears smooth under the microscope. It appears rough due to the presence of ribosomes. It appears smooth due to the absence of ribosomes. These ribosomes of RER are involved in the process of protein synthesis. The SER is involved in lipid synthesis. Lipids are essential for cell function. Absence of this function. Lipids manufactured by SER are also involved in formation of Biological membranes. (Membrane Biogenesis) Absence of this function. SER in vertebrates is also involved in detoxification of toxins.

32. Cell organelle No of membranes Structure Function Mitochondria It is a double membrane bound cell organelle. Amongst the two membranes; The outer membrane is porous The inner membrane is folded. The inner membrane increases surface area for ATP production. The energy required for various chemical activities for the cell is manufactured by mitochondria in the form of ATP. ATP is the energy currency of the cell. The body utilizes ATP for Making new chemical compounds For mechanical work. Plastids It is a double membrane bound cell organelle. There are 2 types of plastids, chromoplast and leucoplast. Internal organization of chloroplast has numerous membrane layers embedded in stroma. Similar in structure with mitochondria. Plastids have their own DNA and ribosomes. Chromoplast are the coloured plastids. Green, yellow and orange pigments can be seen. Chloroplast has chlorophyll pigment involved in photosynthesis. Leucoplast are white/colourless plastids that store starch, oils and protein granules. Vacuoles It is a single membrane bound cell organelle. These are storage sacs for solid or liquid contents. Large in plant cells, smaller in animal cells. Occupy 50-90% cell volume in plant cells. In plant cells, vacuoles are filled with cell sap providing rigidity and turgidity to the cell. Vacuoles also stores amino acids, sugars, organic acids that are essential to plant cells. In amoeba, the food vacuole stores food items. In Paramoecium, the vacuole acts as an osmoregulatory organ.

33. Cell Division- Mitosis and Meiosis Cell division is the process through which new cells are produced. Cell division is of two types: Mitosis and Meiosis Mitosis occurs in somatic cells (normal body cells: skin cells, liver cells etc. Meiosis occurs in germ cells (reproductive cells): testis (males) and ovaries (females) to form gametes (egg and sperm).

34. Characteristic features of Mitosis:

35. Characteristic features of Meiosis:

36. Why is there a reduction in the number of chromosomes in meiosis process?? Reason: The ideal number of chromosomes to be present in a cell=46. If each gamete has 46 chromosomes, as the male and female gamete fuse during fertilization, they will have 92 chromosomes in the zygote. This leads to abnormalities. To avoid this, nature has devised a process to cut down the number of chromosomes to half in the male and female gametes formed, to 23 chromosomes in number. This ensures that when male and female gamete fuse, the resultant zygote will have 46 chromosomes (23+23) which is the right number of chromosomes to be present within any cell. This slide is only for your understanding.

37. Mitosis Meiosis Occurs in somatic cells. Occurs in germ/reproductive cells. Only one round of cell division is observed. Two rounds of cell-division is observed. Two daughter cells are formed at the end of the process. Four daughter cells (gametes) are formed at the end of the process Daughter cells formed are identical to mother cell. Daughter cells formed are not identical to mother cell. Daughter cells have the same number of chromosomes as the mother cell. Daughter cells have half the number of chromosomes as the mother cell. This process is essential for growth and repair of tissues. This process is essential for reproduction in the formation/production of gametes.

38. Diagrams of Cell Organelles: RER SER Golgi Apparatus

39. Vacuole: tonoplast is the wall of the vacuole Chloroplast (plastids) Individual disk like structures are called thylakoids. Grana is stacked thylakoids. Lysosomes Mitochondria

40. Chapter based questions (questions in blue and questions at the end of the chapter) Note: Kindly elaborate on the answers accordingly if they are given for more marks. Blue questions: Pg: 59 Blue questions: Pg: 61

41. Blue questions: Pg: 63 6. The two organelles with their own genetic material are mitochondria and plastids. Blue questions: Pg: 65

42. 1.Differences between plant cells and animal cells to be written by making the necessary corrections on your own. 2. Differences between prokaryotic and eukaryotic already given. 6. Lipids and proteins are synthesized in the Endoplasmic Reticulum . Exercise questions: Pg: 67

43. These answers have been taken from this page, if any answer is blurred, access it from here : https://byjus.com/ncert-solutions-class-9-science/chapter-5-fundamental-unit-of-life/

44. Please be thorough with the textbook for objectives and short answer questions. Be thorough with exchange of gases, osmosis and tonicity as well as nucleus along with cell organelles for long answer questions.