Cell cycle.pptx

Captioning Statement Video and audio content at the University uses closed captions generated by automatic speech recognition (ASR). The ASR process is based on machine learning algorithms which automatically transcribe voice to text. According to our technology providers this process is approximate...

Captioning Statement Video and audio content at the University uses closed captions generated by automatic speech recognition (ASR). The ASR process is based on machine learning algorithms which automatically transcribe voice to text. According to our technology providers this process is approximately 70-90% accurate depending on the quality of the audio, and consequently video and audio closed captions may include some transcription errors. It is therefore important to recognise that the original recording is the most accurate reflection of the content, and not the captions. If you require accurate captions as part of your reasonable adjustments, please contact the Inclusion Centre to discuss your requirements 26/04/24 1 The cell cycle NU1303/NU1401 This topic relates to: Learning outcome: 1 Describe anatomy, physiology and homeostatic mechanisms of human development from conception to old age. Formative and summative assessment Any topic within this module could potentially have a question(s) in the exam paper Links with other topics in the module The cell is the fundamental building block of the whole body. This links with genetics, homeostasis, endocrinology. Links with other modules and stages It is important to understand the cellular level of life for pathophysiologies and psychopathophysiologies. Links to nursing and paramedic practice Many pathophysiologies/psychopathophysiologies and their treatment are linked to the cellular level. 26/04/24 3 Chapter 3 – The Cell CHARLES J. WELSH 2021 HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fourteenth Edition 26/04/24 4 3.4: The Cell Cycle Cell Cycle: The series of changes a cell undergoes from the time it is formed until it divides Main phases are interphase, mitosis, and cytokinesis (division of the cytoplasm) Daughter cells might then undergo changes to become specialized Whether the cell cycle progresses at certain times, called checkpoints, is controlled by interaction of special proteins A restriction checkpoint determines fate of cell: to continue cell cycle and divide, to enter a non-dividing stage as a specialized cell, or to die Most cells do not divide continually. Cells have a maximum number of times they can divide, because of built-in “clocks” (telomeres) on the tips of chromosomes, which shorten with each cell division Phases of the Cell Cycle Interphase Interphase: Phase of the cell cycle, before cell division begins, in which the cell grows and synthesizes new molecules, membranes, DNA, and organelles This is a time of great synthetic activity, rather than a time of rest During the G1 and G2 (“gap” or “growth”) phases of interphase, the cell grows, and structures other than DNA are duplicated During the S (“synthesis”) phase of interphase, the DNA of the cell is replicated in preparation for cell Cell Division 2 types of cell division: Meiosis: Only used for sperm & egg cell production Ensures that mature gametes have ½ the normal number of chromosomes as normal body cells Cell Division (Mitosis + Cytokinesis): More common type of cell division, used to increase number of cells Mitosis is division of the nucleus Cytokinesis is the division of the cytoplasm Regulated carefully, so that each of two daughter cells receives an exact copy of the original cell's genetic material (DNA) Stages of Mitosis 1 Mitosis is described as a series of four stages, but the process is actually continuous: 1. Prophase: The first stage of mitosis DNA condenses into visible chromosomes (each consisting of two chromatids connected by a centromere) Centrioles migrate to opposite poles Microtubules of the cytoskeleton organize into spindle fibers The nuclear membrane and nucleolus disassemble Stages of Mitosis 2 2. Metaphase: Spindle fibers attach to centromeres on the chromosomes Chromosomes randomly align midway between centrioles 3. Anaphase: Sister chromatids are pulled apart Chromatids are now considered individual chromosomes Chromatids are pulled along the shortening spindle Stages of Mitosis 3 4. Telophase: The final stage of mitosis Begins when the chromosomes have completed their migrations to opposite sides A nuclear envelope and nucleolus assemble for each forming cell The spindle fibers disassemble The chromosomes unwind, and take back their chromatin form Stages of Mitosis 4 (a–e): Ed Reschke Cytokinesis (Cytoplasmic Cytokinesis: Division) Cytoplasmic division Begins during anaphase of mitosis, when cell membrane constricts around middle of cell Constriction, called the cleavage furrow, continues throughout telophase; it eventually pinches the daughter cells apart Contractile ring of microfilaments attaches to inside of cell membrane; it divides the cytoplasm The two daughter cells may have slightly different amounts of cytoplasm and organelles, but they share identical genetic information Cell Differentiation Differentiation: The process by which a cell develops/specializes into a specific type of cell with specialized functions Humans have >290 types of differentiated cells Cell differentiation allows cells to specialize by using different parts of the complete genome that is present in each cell; in each type of cell, some genes are “turned on” while others are “turned off” Stem cells retain the ability to divide without specialization; their presence in the cell allows for continuous growth and renewal Progenitor cells are daughters of stem cells that are partially specialized Stem and progenitor cells allow cells to retain the ability to produce cells that will become the differentiated cells in each area of the body Stem and Progenitor Cells Cell Death Not all cells divide or differentiate; some die Apoptosis is a form of programmed cell death that is a normal part of development, rather than from injury or disease Removes overgrown tissues, damaged cells, extra cells in fetus Steps of apoptosis: Cell becomes rounded and bulges Nuclear membrane breaks down Chromatin condenses and enzymes cut up the chromosomes Cell shatters into many membrane-bound pieces Scavenger cells engulf and destroy the fragments