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This text discusses the structure, function, and growth of prokaryote and eukaryote cells, focusing on the cell cycle and mitosis. It covers the stages of the cell cycle, including interphase and mitosis, and discusses the control of the cell cycle and abnormal cell division. The text also explores the process of mitosis in detail, including the stages of prophase, metaphase, anaphase, telophase, and cytokinesis. Furthermore, it provides learning activities and resources for further study on cell division.
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Structure, function and growth of prokaryote and eukaryote cells • (ii) Cell growth and Cell cycle • Interphase • Mitosis • Mitotic index • Control of the cell cycle • Abnormal Cell division: cancer cells
Cell Cycle • When cells reach a certain size they must stop growing or divide. • The cell cycle is the period from the formation of a new cell until that cell divides itself • The length of the cycle depends on the cell – but is usually 8 – 20 hours
CK The Cell Cycle
Interphase… • G1 (First Gap Period) • Cell grows and increases in mass • Cell membrane (+ wall) are increased • Number of organelles increase • Chemical preparation for DNA Synthesis (enzymes, deoxyribose sugars, nucleotide bases and phosphates synthesised)
Interphase • S phase (synthesis) • Replication of DNA • Chromosomes held together by centromere • In animals centriole pairs duplicate
Interphase • G2 (Second gap phase) • Cell builds up energy reserves • Increased protein synthesis
Mitosis • Revision – complete the mitosis diagram (note this is from standard grade)
Mitosis • Compare this to your SG diagram. • Name the stages • Interphase • Prophase • Metaphase • Telophase • Cytokinesis • What features characterise each stage?
Joins onto spindle fibre Chromatids in condensed form Mitosis • Prophase • Chromosomes condense (coil and fold up) to become visible.
Mitosis – prophase cont… • Cytoskeleton disintegrates • (its components (microtubules) are used to begin spindle formation) • Spindle formation begins between centrosomes (aka Microtubule organising centres – MTOCs) • Nuclear Membrane starts to break up
Mitosis • Metaphase • Spindle continues to grow from centrosomes (which are now at the poles) • Chromosomes line up across the centre of the cell
Mitosis – metaphase cont.. • Chromosomes attach to the spindle fibre by the kinetochore in the centromere • The arrangement of the chromosomes across the equator is also known as the metaphase plate.
Mitosis • Anaphase • Centromeres divide • Sister chromatids separate and the chromosomes are pulled to the poles
Mitosis • Telophase • Chromosomes begin to de-condense • Nuclear membrane reforms • Spindle disassembles and reassembles as the cytoskeleton in the 2 new cells
Cytokinesis • Dividing of the cytoplasm and organelles • Animals • Cytoplasm is pinched by a ring of contractile microfilaments (made up of the proteins actin and myosin) • As the ring gets smaller it forms a cleavage furrow
Cytokinesis cont… • In plants • Membrane vesicles spread across the equator of the cell. • They merge to form plasma membrane • The new membranes lay down the cell wall between the two cells.
Mitotic Index • The fraction (or percentage) in a microscope field that contain condensed chromosomes (i.e. Undergoing mitosis)
Learning Activities • Look at web animations • www.biozone.co.uk/links.html • Cell biology – Mitosis / Meiosis – How cells divide • Posters • Card sort (pictures / names / descriptions) • Read Dart pg 9-14 and take notes • Use Scholar • Advanced Higher Questions
