CELLS AND CELL DIVISION

1. CELLS AND CELL DIVISION Kani Shiwani, Vee Duong, Vilma Arceo B2

2. Cell Division • Process in which the parent cell distributes its DNA and other genetic material into two daughter cells • Cell Cycle – the series of events that take place leading to cell division that produces two daughter cells • Interphase: G1, S, G2 • Mitosis – genetic material of cell divides • Cytokineses – cell membrane/ wall divides Human melanoma cell dividing

4. Types of cell division • Mitosis - process of making new body cells • Repairing of damaged cells • Growth • Meiosis – used to create gametes (egg and sperm cells)

6. Mitosis • Used for growth and repair • Chromosomes are duplicated and then separated into two identical daughter cell • each with its own nucleus • Stages: • Prophase – DNA condenses, centrioles appear to form mitotic spindle • Prometaphase – chromosomes join together at the centromeres • Metaphase – sister chromatids line up along the metaphase plate • Anaphase – sister chromatids are separated by kinetochores • telophase - nucleus separates, nuclear envelope regenerates, chromosomes decondense

8. Mitosis

9. Meiosis • Used to make sex cells • Parent cell divides to form cells with half their genetic material • Produces haploid cells that are not identical to each other or the parents. • Two phases: Meiosis I & Meiosis II

11. Meiosis I • Prophase I – synapsis occurs (joining of homologous chromosomes along their length); crossing over occurs at chiasmata -> genetic variation • Metaphase I – genetic variation when homologous chromosomes randomly line up (independent assortment) • Anaphase I – homologous chromosomes separate • Telophase I – homologous chromosomes separate and gather at opposite poles

12. Meiosis I

13. Meiosis II • Prophase II – spindle reforms • Metaphase II – sister chromatids arranged along metaphase plate randomly • Anaphase II – sister chromatids are pulled apart from each other • Telophase II – chromosomes move to opposite ends and nuclei reappear

14. Meiosis II

15. Mitochondria • A membrane-bound organelle found in most eukaryotic cells. • Take part in cellular metabolic processes • Supply energy for the cell • Double bound organelle • Made of phospholipid double layers & proteins • Have their own genome

16. Golgi Apparatus • Modify, sort and package proteins • Transport of lipids • Receives substances from ER • Collection of flattened membrane sacks called cisternae

17. Cell wall • Rigid and strong • Protects the cell • Made of cellulose

18. Endoplasmic Reticulum • Manufactures substances • Smooth ER: contains enzymes, manufactures fats and steroids • Rough ER: has ribosomes, manufactures proteins • Transports substances to be exported

20. Lysosome • Sac like structures • Digest substances • Release enzymes to break down complex molecules

22. FRQ 2011 FRQ During an investigation of a freshwater lake, a sad AP biology student discovers a previously unknown microscopic organism. Further study shows that the unicellular organism is eukaryotic. http://apcentral.collegeboard.com/apc/public/repository/ap11_biology_scoring_guidelines.pdf a. Identify FOUR organelles that should be present in the eukaryotic organism and describe the function of each organelle b. Prokaryotic cells lack membrane-bound organelles found in eukaryotes. However, prokaryotes must perform many of the same functions as eukaryotes. For THREE of the organelles identified in part (a) explain how prokaryotic cells carry out associated functions. c. According to the endosymbiotic theory, some organelles are believed to have evolved through a symbiotic relationship between eukaryotic and prokaryotic cells. Describe THREE observations that support the endosymbiotic theory.

23. Scoring Key • Identify organelle (1 point for listing 4); describe corresponding function (1 point for each function) = 5 points maximum • Organelles identified in part a – 1 point for each associated function = 3 points maximum • General description of endosymbiotic theory – 1 point; Observations for endosymbiotic theory – 1 point for each = 4 points maximum

24. 2006 FRQ A major distinction between prokaryotes and eukaryotes is the presence of membrane-bound organelles in eukaryotes. http://apcentral.collegeboard.com/apc/public/repository/_ap06_biology_sg.pdf a. Describe the structure and function of TWO eukaryotic membrane-bound organelles other than the nucleus. b. Prokaryotic and eukaryotic cells have some non-membrane-bound components in common. Describe the function of TWO of the following and discuss how each differs in prokaryotes and eukaryotes. • DNA • Cell wall • Ribosomes c. Explain the endosymbiotic theory of the origin of eukaryotic cells and discuss an example of evidence supporting this theory.

25. Scoring Key • Organelle Structure – 1 point for each (2 organelles – 2 points total); Organelle Function – 1 point for each (2 points total) = 4 points max • Common component between prokaryotes and eukaryotes (2); Function – 1 point for each; Difference between prokaryotes and eukaryotes – 1 point = 4 points max • Explanation for the endosymbiotic theory – 1 point; Evidence supporting the theory – 1 point = 2 points max

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