Cell Growth & Division PDF

Summary

These notes cover the topic of cell growth and division, including the stages of the cell cycle, DNA replication, cell senescence, and apoptosis. The lecture material originates from the University of Bradford.

Full Transcript

Cell Growth and Division Dr Humaira Khan [email protected] Session Aims By the end of today’s lecture, you should be able to: ✓ Understand the significance of cell growth and division ✓ Describe the stages of the cell cycle ✓ Explain the process of DNA...

Cell Growth and Division Dr Humaira Khan [email protected] Session Aims By the end of today’s lecture, you should be able to: ✓ Understand the significance of cell growth and division ✓ Describe the stages of the cell cycle ✓ Explain the process of DNA replication ✓ Understand the significance of cell senescence and apoptosis ✓ Describe the signals which induce somatic cell division ✓ Look at cell cycle disruption and its pathological implications Self-Directed Study ✓ Lecture slides and notes- annotate effectively ✓ Core textbooks ✓ Additional sources of information- Review articles, Governmental citations (Cancer Research UK, National Cancer Institute, WHO) 3 Cell Division ▪The cell cycle is the orderly sequence of events required for the duplication of a eukaryotic cell into two genetically identical daughter cells. ▪The cell undergoes nuclear division (mitosis) and a cytoplasmic division (cytokinesis) ▪Essential process to replace dead/injured cells from wear & tear, stress, chemical damage and adds new ones in tissue growth ▪A human being goes from 1 cell to around 75 trillion Cell Division is tightly controlled Cell division must be a controlled sequence of events Cells have a finite number of divisions Controlled by activation of ‘suicide genes’ Between 50 and 70 billion cells die each day due to apoptosis in the average human adult **There must be a delicate balance between cell division and cell death** Cell Growth vs Cell Death ATROPHY- tissue waste away as a result of the degeneration of cells. DYSPLASIA- the presence of additional cells of an abnormal type within a tissue, which may signify a stage preceding the development of cancer. HYPERPLASIA- the enlargement of an organ or tissue caused by an increase in the reproduction rate of its cells, often as an initial stage in the development of cancer Cell Division- Mitosis Cells must first replicate all their homologous (same relation, relative position or structure) chromosomes Cell replication has 2 main stages: ✓ Interphase (when the cell is not dividing) ✓ The mitotic (M) phase when a cell is dividing Interphase ▪ It is the phase between two successive mitotic divisions ▪ During this phase the cell grows and prepares itself for division ▪ Subdivided into – *G1 phase- Gap 1 or presynthesis stage – S phase and- synthesis stage – *G2 phase- Gap 2 or postsynthesis stage ▪ Busiest time in the cell cycle; longest ▪ *important checkpoints here ▪ Most cells only spend a small amount of time dividing ▪ An interphase cell in G0 is not dividing or preparing to divide e.g. neurons G1 phase- initiation stage ✓ Cells do not pass G1 without growth factors ✓ Strictly controlled; one of the important check points ✓ Lasts for about 8-10 hours of a 24 hour ✓ cycle ✓ High rate of metabolism, protein synthesis and growth ✓ Duplicates most organelles S phase- DNA replication ✓ Lasts for about 8 hours ✓ DNA replicates ✓ Precise and accurate DNA replication is necessary to prevent genetic abnormalities which often lead to cell death or disease. G2 Phase ✓ It lasts for 4-6 hours ✓ Synthesis of enzymes and proteins essential for cell division ✓ Replication of centrioles completed (form the spindle apparatus associated with the movement of DNA) http://essayweb.net/biology/images/celldivision/interphase.png Mitotic phase Characterised by: – Karyokinesis: Division of nucleus and – Cytokinesis: Division of cytoplasm It is a continuous process but for the sake of convenience is described in four phases. – Prophase – Metaphase – Anaphase and – Telophase LASTS

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