03 Diffusion, osmosis, and cell division
- 2. A cell can’t just keep growing and growing. - As cell gets larger, surface area to volume ratio decreases - Less surface area for passage of nutrients and waste across the membrane - Substances would take too long to diffuse to where they are needed in the cell DIFFUSION
- 3. Diffusion: Substances move from areas of high concentration to areas of low concentration. DIFFUSION
- 4. Osmosis: Diffusion of water Water can diffuse into and out of cells based on concentration of solute inside and outside a cell. OSMOSIS
- 5. Water can move in or out of a cell, causing it to expand or shrink, based on the type of solution it is placed in: Hypotonic – lower solute concentration outside the cell Isotonic – same solute concentration outside the cell Hypertonic – higher solute concentration outside the cell OSMOSIS
- 6. A hypotonic solution can swell an animal cell to the point of lysis, but plant cells have cell walls to prevent this. OSMOSIS
- 7. Passive transport: Movement of substance across a membrane without using energy Passive transport relies on diffusion and concentration gradients. PASSIVE TRANSPORT
- 8. Active transport: Movement of substances across a membrane using energy against concentration gradient. PASSIVE TRANSPORT
- 10. Why do cells need to divide? -To allow an organism to grow -To pass on genetic material -To assist an organism’ survival CELL DIVISION
- 11. 3 stages of cell cycle: Interphase Mitosis (division of nuclear material) Cytokinesis (division of cytoplasm) CELL DIVISION
- 12. Interphase - Cell is not dividing but also not dormant - Cell is active and growing and also preparing for division - Sometimes called resting phase but this is inaccurate (real resting phase is G0) - DNA/chromosomes not visible (unwound) INTERPHASE
- 13. Interphase: 4 stages Gap 0 (G0): - Cell rest cycle - may be temporary or permanent (where cells are functional but no new cells are produced (i.e. neuron) G0 INTERPHASE
- 14. Interphase: 4 stages Gap 1 (G1): - Rapid growth (4hr) - cell takes in nutrients for energy, growth, repair - Cells either go into S or G0 after G1 G0 INTERPHASE
- 15. Interphase: 4 stages S phase (S): - 10 hrs - DNA synthesis/ replication - the cell duplicates its genetic material to make an identical copy of its DNA G0 INTERPHASE
- 16. Interphase: 4 stages Gap 2 phase (G2): - 3-4hr - second period of growth in preparation for cell division -cell grows larger in size G0 INTERPHASE
- 17. S phase (S): Let’s take a closer look DNA replication Normally DNA duplication After duplication INTERPHASE
- 18. Mitosis: - A process by which somatic cells grow and divide - Cells come from pre-existing cells - Parent cell divides to produce two new identical daughter cells - asexual reproduction (offspring from one parent) - 4 phases: MITOSIS
- 19. Prophase - nuclear membrane breaks down - chromosomes shorten and thicken - Other structures important for mitosis are also forming (i.e. the centrioles) MITOSIS: PROPHASE
- 20. Prophase - A centromere holds two copies of the same chromosome together - Each copy of a chromosome is called a chromatid MITOSIS: PROPHASE
- 21. Mother’s side Prophase - A centromere holds two copies of the same chromosome together - Remember, every chromosome has been duplicated during the S phase of interphase. - Recall this: Mitosis Mother’s side Mother’s side Colors are not accurate MITOSIS: PROPHASE centromere
- 23. Metaphase - Microtubules (spindle fibres) attach at the centromeres and the chromosomes move to the centre (the metaphase plate) MITOSIS: METAPHASE metaphase plate
- 25. Anaphase - Paired chromosomes separate at the kinetochores and move to opposite sides of the cell MITOSIS: ANAPHASE
- 26. Telophase - Chromatids arrive at opposite poles of cell - New membranes form around the daughter nuclei - Chromosomes disperse and are no longer visible under the light microscope - spindle fibres disperse MITOSIS: TELOPHASE
- 27. Cytokinesis - Animal cells: the cell membrane pinches (forming a cleavage furrow) into two daughter cells, each with one nucleus CYTOKINESIS: ANIMAL CELLS
- 28. Cytokinesis - In plant cells, a cell plate (made of rigid cellulose) is synthesized between the two daughter cells. CYTOKINESIS: PLANT CELLS
- 29. Mitosis and cytokinesis: Review MITOSIS & CYTOKINESIS