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CELL STRUCTURE AND FUNCTION

CELL STRUCTURE AND FUNCTION

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CELL STRUCTURE AND FUNCTION

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  1. CELL STRUCTURE AND FUNCTION Despite the diversity among cells, three basic features are common to all cell types. All cells have outer boundary, an interior substance and a control region.

  2. CELL STRUCTURES

  3. Composition: phospholipid bilayer with embedded proteins. Function: selective passage of molecules into and out of cell PLASMA MEMBRANE

  4. Composition: nuclear envelope surrounding nucleoplasm, chromatin and nucleolus Function: storage of genetic information, controls metabolic functioning and structural characteristics of the cell. NUCLEUS

  5. Composition: protein and RNA in two subunits Function: Protein synthesis RIBOSOMES

  6. Composition: membranous saccules and canals Function: synthesis and /or modification of proteins and other substances, and transport by vesicle formation ENDOPLASMIC RETICULUM

  7. Composition: stack of membranous saccules Function: Processing, packaging, and distribution of molecules GOLGI APPARATUS

  8. Composition: membranous sac Function: storage and transport substances VACUOLE AND VESICLE

  9. Composition: membranous vesicle containing digestive enzymes Function: intracellular digestion LYSOSOME

  10. Composition: inner membrane (cristae) within outer membrane Function: cellular respiration MITOCHONDRION

  11. Composition: microtubles, actin filaments Function: shape of the cell and movement of its parts. CYTOSKELETON

  12. STRUCTURE OF THE CYTOSKELETON

  13. Composition: 9 + 2 pattern of microtubules Function: movement of cell CILIA AND FLAGELLA

  14. Composition: 9 + 0 pattern of microtubules Function: formation of basal bodies CENTRIOLE

  15. CHROMOSOME Chromosomes are rod-shaped structures made of DNA and proteins.

  16. Chromatid- the strand of a chromosome that becomes visible during meiosis or mitosis. Chromatin – the less tightly coiled DNA-protein complex Centromere – the region of the chromosome that holds the two sister chromatids together during mitosis. CHROMOSOME

  17. Sex chromosomes are chromosomes that determine the sex of an organism, and they may also carry genes for other characteristics. In humans, sex chromosomes are either X or Y. XX for female XY for male The autosomes are all the other chromosomes in an organism except for sex chromosomes. In humans two of the 46 are sex chromosomes, and the remaining 44 chromosomes are autosomes. SEX CHROMOSOMES & AUTOSOMES

  18. HUMAN KARYOTYPE

  19. The DNA in eukaryotic cells wraps tightly around proteins called histones. Histones help maintain the shape of the chromosomes and aid in the tight packaging of DNA. Nonhistone proteins are generally involved in controlling the activity of specific regions of the DNA HISTONE AND NON-HISTONE

  20. CELL CYCLE The cell cycle is an orderly set of stages that take place between the time a cell divides and the time the resulting daughter cells also divide.

  21. Interphase -the cell carries on its regular activities. The three stages: G1 phase S phase G2 phase. Mitotic Stage Stages of mitosis: karyokinesis (division of the nucleus) cytokinesis (division of the cytoplasm). CELL CYCLE STAGES

  22. STAGES: The old (parental) DNA strands unwind and “upzip” New complementary nucleotides pair with the nucleotides in the old strands. A pairs with T and C pairs with G. The enzyme DNA polymerase joins the new nucleotides forming new (daughter) complementary strands. When replication is complete, the two double helix molecules are identical. DNA REPLICATION

  23. PROTEIN SYNTHESIS Is the formation of proteins by using information contained in DNA and carried by mRNA

  24. TRANSCRIPTION- is the process of forming a nucleic acid by using another molecule as a template; particularly the process of synthesizing RNA by using one strand of a DNA molecule as a template. TRANSLATION- refers to the portion of protein synthesis that takes place at ribosomes and that uses the codons in mRNA molecules to specify the sequence of amino acids in polypeptide chains. PROTEIN SYNTHESIS

  25. CONTROL OF CELL DIVISION In eukaryotes, proteins regulate the progress of cell division at certain checkpoints.

  26. 1. Cell Growth Checkpoint. Proteins at this checkpoint control whether the cell will divide. Hint: if the cell is healthy and has grown to a suitable size during G1 phase, protein will initiate DNA synthesis (S phase). If conditions are not favorable for DNA synthesis, the cell cycle will stop at this point. CELL GROWTH CHECKPOINT

  27. 2. DNA Synthesis (G2) checkpoint. DNA repair enzymes check the results of DNA replication. If this checkpoint is passed, proteins will signal the cell to begin the molecular processes that will allow the cell to divide mitotically. DNA SYNTHESIS CHECKPOINT

  28. 3. Mitosis checkpoint. If a cell passes this checkpoint, proteins signal the cell to exit mitosis. The cell enters into the G1 phase, the major growth phase of the cell cycle, once again. MITOSIS CHECKPOINT

  29. PROKARYOTIC CELL DIVISION Most prokaryotes reproduce by binary fission, in which two identical cells are produced from one cell.