Anatomy and physiology of Cell, structure, cell cycle

Lecture

1. Unit-III The Cell By Muhammad Shahid PhD Nursing Scholar MSN, BSN, DPBCN, RN, BSc Assistant Professor & Principal SON-KGH Date: August 7 th 2024 Prepared by Muhammad Shahid 1

2. Objectives At the end of lecture students will be able to : Define cell. Understand the History of Cells & the Cell Theory. Discuss the types of cell. Describe the structure and function of cell. Explain in detail cell division. Define cell cycle. Discuss the stages of cell cycle. Prepared by Muhammad Shahid 2

3. Human Cell A cell is a minute jelly like mass of protoplasm containing a nucleus held together by a cell membrane. The cell is the structural and functional unit of living organisms. Human body is made up of 75 trillion cells. It was Robert hook who first coined the term cell in 1665. Cells can only be seen with the help of microscope. The study of cells is called histology. Human body begins as a cell Prepared by Muhammad Shahid 3

4. History First to View Cells In 1665, Robert Hooke used a microscope to examine a thin slice of cork (dead plant cells) What he saw looked like small boxes Prepared by Muhammad Shahid 4

5. Cont… Hooke is responsible for naming cells Hooke called them “CELLS” because they looked like the small rooms that monks lived in called Cells Prepared by Muhammad Shahid 5

6. Anton van Leeuwenhoek In 1673, Leeuwenhoek (a Dutch microscope maker), was first to view organism (living things) Leeuwenhoek used a simple, handheld microscope to view pond water & scrapings from his teeth. Prepared by Muhammad Shahid 6

7. Beginning of the Cell Theory In 1838, a German botanist named Matthias Schleiden concluded that all plants were made of cells Schleiden is a cofounder of the cell theory. Prepared by Muhammad Shahid 7

8. Beginning of the Cell Theory In 1839, a German zoologist named Theodore Schwann concluded that all animals were made of cells Schwann also cofounded the cell theory Prepared by Muhammad Shahid 8

9. Beginning of the Cell Theory In 1855, a German medical doctor named Rudolph Virchow observed, under the microscope, cells dividing He reasoned that all cells come from other pre-existing cells (by cell division) Prepared by Muhammad Shahid 9

10. CELL THEORY All living things are made of cells Cells are the basic unit of structure and function in an organism (basic unit of life) Cells come from the reproduction of existing cells (cell division) Prepared by Muhammad Shahid 10

11. Simple or Complex Cells Prokaryotes – The first Cells Cells that lack a nucleus or membrane-bound organelles Includes bacteria Simplest type of cell Single, circular chromosome 11 Prepared by Muhammad Shahid

12. Prokaryotes cell Nucleotide region (center) contains the DNA Surrounded by cell membrane & cell wall ( peptidoglycan ) Contain ribosomes (no membrane) in their cytoplasm to make proteins Prepared by Muhammad Shahid 12

13. Eukaryotes Cells that HAVE a nucleus and membrane-bound organelles Includes protists , fungi, plants, and animals More complex type of cells Prepared by Muhammad Shahid 13

14. Eukaryotic Cell Contain 3 basic cell structures: Nucleus Cell Membrane Cytoplasm with organelles Prepared by Muhammad Shahid 14

15. Two Main Types of Eukaryotic Cells Plant Cell Animal Cell Prepared by Muhammad Shahid 15

16. Structure of the cell The cell is mad up of the following structures. Cell membrane or Cell wall. It is a thin delicated semipermiable membrane which seprates the cell from environment. It is madeup of Protein, salt and water. 1. Proteins: 55% 2. Phospholipids: 25% 3. Cholesterol : 13% 4. Other lipids: 4% 5. Carbohydrates: 3% Prepared by Muhammad Shahid 16

17. Cell membrane 1. Permeable membrane: The membrane which allow all substances to pass through it. 2.Semipermeable membrane: That membrane that allows some substances to pass through it. 3.Nonpermeable membrane: The membrane which not allows any substance to pass through it. Prepared by Muhammad Shahid 17

18. 2. Cytoplasm It is the part around the nucleus and is made up of complex proteins consisting of following structure. a. Mitochondria: it is rod shape structure looking like pieces of thread, function is respiration of cell . b. Golgi Apparatus: Mass of twisted rod forming canal like structure. Function is secretion of cell. c . Centrosome: Lies near the nucleus and function is cell division Prepared by Muhammad Shahid 18

19. Cont… d. Vacuoles: Spaces with in the cytoplasm containing food or waste. Function is storage . 3. Nucleus: Lies in the center of the cell containing following structures. a. Nuclear membrane : Separate nucleus from cytoplasm. Prepared by Muhammad Shahid 19

20. Cont… b. Chromatin: it is thread like network. c. Nucleoli: Lies in the center of the cell. Function of nucleus is to control the cell and its activities. Without nucleus cell would die. It controls growth, reproduction and transmission of hereditary factors. Prepared by Muhammad Shahid 20

21. Characteristics of the cell 1.Ingestion and assimilation of nourishment: Cell use and absorb food. 2. Growth and repair: With the help of nourishment cells grow and repair worn out parts. 3 . Reproduction or cell division: This process is called mitosis and meiosis. 4 . Respiration: Cells respire through its Semipermeable membrane. Prepared by Muhammad Shahid 21

22. Conti… 5 . Excretion: Waste products are eliminated. 6. Motion: Some cells have power of movements eg . Blood cells 7. Secretion: Some cells produce secretions. Eg . Stomach cells produce juices. 8. Irritability and conductivity: Cells respond to stimuli 9 . Metabolism: Cells breakdown food and energy is released which is used for heat and other function. Prepared by Muhammad Shahid 22

23. Functions of the cell A cell performs these major functions essential for the growth and development of an organism. Important functions of cell are as follows: Provides Support and Structure Facilitate Growth Mitosis Allows Transport of Substances Energy Production Aids in Reproduction Prepared by Muhammad Shahid 23

24. Animal Cell Prepared by Muhammad Shahid 24

25. Mitosis or Cell Division Stages of cell division: 1.PROPHASE: a. Centrosomes divides into two b. each more away from each other but are still attached by thread like structure. 2. METAPHASE: Divides into two stages. 1 st stage of metaphase: Chromosomes which are thread like structure disappear inside the nucleus. There are 46 chromosomes in human cell. Their number is different in animal cells. Prepared by Muhammad Shahid 25

26. Stages of cell division: 2 nd stage of metaphase: a. Nuclear membrane disappear b. Chromosome arrange themselves around the center of cell. c. They appear to be attached to the thread like structure of the centrosome. Each centrosome is now at the ends of the cell. 3. ANAPHASE: Also divides into two stages: 1 st stage of anaphase: a. Chromosomes divide longitudinally into two equal parts. Prepared by Muhammad Shahid 26

27. Stages of cell division: 2 nd stage of anaphase: The two groups of chromosomes are more away to each end of the cell. They arrange themselves around the centrosome. The thread like structure joining the structures. 4. TELOPHASE: A Cell body becomes narrow at the centers. Thread like structure disappear Two nucleus membrane appear. 5 . FORMATION OF TWO DAUGHTER CELLS: Cell divides into two Chromosomes disappear inside nucleus Daughter cells will grow and each will divide again by mitosis. Prepared by Muhammad Shahid 27

28. Cell Cycle The cell cycle is the process a cell will go through to replicate all of its material and divide itself from one cell into two identical cells. we will look at the different stages of the cell cycle and what happens in each stage. We will also consider the regulation of the cell cycle, and look at some examples of when this goes wrong. Prepared by Muhammad Shahid 28

29. Phases of the Cell Cycle The Cell Cycle is a 4-stage process consisting of Gap 1 (G1), Synthesis, Gap 2 (G2) and Mitosis . An active eukaryotic cell will undergo these steps as it grows and divides. After completing the cycle, the cell either starts the process again from G1 or exits the cycle through G0. From G0 , the cell can undergo terminal differentiation. Prepared by Muhammad Shahid 29

30. Phases of the Cell Cycle G1 phase Cell increases in size Cellular contents duplicated S phase DNA replication Each of the 46 chromosomes (23 pairs) is replicated by the cell G2 phase Cell prepares for cell division M phase Mitosis followed by Cytokinesis (cell separation) Formation of two identical daughter cells Prepared by Muhammad Shahid 30

31. Phases of Mitosis The M phase involves Mitosis which is the process of cell division. It is composed of: Prophase: Nucleolus disintegrates Nuclear membrane breakdown Spindle fibres appear Prometaphase: Spindle fibres attach to chromosomes Chromosomes condense Metaphase: Chromosomes align at the metaphase plate Prepared by Muhammad Shahid 31

32. Continue Anaphase Centromeres divide Sister chromatids move to opposite poles Telophase Nuclear membrane reforms Chromosomes decondense Spindle fibres disappear Cytokinesis: Is the process of the parent cell becoming 2 daughter cells. These daughter cells contain identical genetic information. Cytokinesis also involves a division of the cytoplasm. It is considered a separate step to mitosis. Prepared by Muhammad Shahid 32

33. Cell division Prepared by Muhammad Shahid 33

34. Cell cycle In eukaryotic cells, or cells with a nucleus, the stages of the cell cycle are divided into two major phases:  interphase  and the  mitotic (M) phase . During  interphase , the cell grows and makes a copy of its DNA. During the  mitotic (M) phase , the cell separates its DNA into two sets and divides its cytoplasm, forming two new cells. Prepared by Muhammad Shahid 34

35. Interphase G phase. During G phase, also called the first gap phase, the cell grows physically larger, copies organelles, and makes the molecular building blocks it will need in later steps. S phase.  In S phase, the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome. The centrosomes help separate DNA during M phase. Prepared by Muhammad Shahid 35

36. Continue.. G2 phase.  During the second gap phase, or phase, the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis. G2  phase ends when mitosis begins. The G, S, and G2 phases together are known as  interphase . The prefix  inter - means between, reflecting that interphase takes place between one mitotic (M) phase and the next. Prepared by Muhammad Shahid 36

37. M phase During the mitotic (M) phase, the cell divides its copied DNA and cytoplasm to make two new cells. M phase involves two distinct division-related processes: mitosis and cytokinesis. In  mitosis , the nuclear DNA of the cell condenses into visible chromosomes and is pulled apart by the mitotic spindle, a specialized structure made out of microtubules. Mitosis takes place in four stages: prophase (sometimes divided into early prophase and prometaphase), metaphase, anaphase, and telophase. Prepared by Muhammad Shahid 37

38. M phase In  cytokinesis , the cytoplasm of the cell is split in two, making two new cells. Cytokinesis usually begins just as mitosis is ending, with a little overlap. Importantly, cytokinesis takes place differently in animal and plant cells. Prepared by Muhammad Shahid 38

39. Cell Cycle Prepared by Muhammad Shahid 39

40. Cell division Prepared by Muhammad Shahid 40

41. Prepared by Muhammad Shahid 41

42. Regulation The progression of cells through the cell cycle is controlled by checkpoints at different stages. These detect if a cell contains damaged DNA and ensure those cells do not replicate. The Restriction point (R) is located at G1 and is a key checkpoint. If damaged DNA is detected at any checkpoint, activation of the checkpoint results in increased protein production is a tumour suppressor gene that stops the progression of the cell cycle and starts repair mechanisms for the damaged DNA. If this DNA cannot be repaired, then it ensures the cell undergoes apoptosis and can no longer replicate. Prepared by Muhammad Shahid 42

43. Cell division and Cell cycle Cell division is just one of several stages a cell experiences during its lifetime.  The cell cycle is a repeating series of events including growth, synthesis of DNA, and division of the cells. Prepared by Muhammad Shahid 43

44. References Anne Waugh, et al. (2006). Ross & Wilson: Anatomy and Physiology in Health and Illness, 11 th edition. Retrieved from https:// www2.le.ac.uk/projects/vgec/highereducation/topics/cellcycle-mitosis-meiosis on10-02-2021 Prepared by Muhammad Shahid 44