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Cells

Cells. Wassily Kandinsky (1866-1944). Cell Theory: - all organisms are composed of cells - all cells come from other cells. Figure 4.1x. Scanning electron microscope (SEM). TEM. Figure 4.1B. Cell size and shape relate to function Minimum Maximum. Figure 4.2.

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Cells

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  1. Cells Wassily Kandinsky (1866-1944)

  2. Cell Theory: - all organisms are composed of cells - all cells come from other cells Figure 4.1x

  3. Scanning electron microscope (SEM) TEM Figure 4.1B

  4. Cell size and shape relate to function • Minimum • Maximum Figure 4.2

  5. A small cell has a greater ratio of surface area to volume than a large cell of the same shape 30 µm 10 µm Surface areaof one large cube= 5,400 µm2 Total surface areaof 27 small cubes= 16,200 µm2 Figure 4.3

  6. 2 kinds of cells: prokaryotic and eukaryotic Prokaryotic cells - “before nucleus” - small, relatively simple cells • Single-celled organisms

  7. Eukaryotic cells - functional compartments - true nucleus - larger: 10-100 microns - often multicellular - organelles surrounded by membranes - usually need O2

  8. What do these have in common? • HIV infection • Transplanted organs • Communication between neurons • Drug addiction • Cystic fibrosis • hypercholesteremia

  9. Plasma membrane • Contact between cell and environment • Keeps useful materials inside and harmful stuff outside • Allows transport, communication in both directions

  10. Plasma membrane components 1. Phospholipid bilayer polar head P – cytosol hydrophobic molecules hydrophilic molecules nonpolar tails

  11. 2. Cholesterol - adds rigidity Fluid mosaic model Glycoprotein Carbohydrate (of glycoprotein) Fibers of the extracellular matrix Glycolipid Phospholipid Cholesterol Microfilaments of the cytoskeleton Proteins CYTOPLASM Figure 5.12

  12. 3. Membrane Proteins - span entire membrane or lie on either side • Structural Support • Recognition • Communication • Transport

  13. How do molecules cross the plasma membrane? • Passive transport • Active transport • Endocytosis and exocytosis

  14. Diffusion and gradients • Diffusion = movement of molecules from region of higher to lower concentration. • Osmosis = diffusion of water across a membrane

  15. Molecule of dye Membrane EQUILIBRIUM • In passive transport, substances diffuse through membranes without work by the cell EQUILIBRIUM Figure 5.14A & B

  16. Osmosis = diffusion of water across a membrane Hypotonicsolution Hypertonic solution • water travels from an area of higher concentration to an area of lower water concentration Selectivelypermeablemembrane Solutemolecule HYPOTONIC SOLUTION HYPERTONIC SOLUTION Water molecule Selectivelypermeablemembrane Solute molecule with cluster of water molecules Figure 5.15 NET FLOW OF WATER

  17. Water balance between cells and their surroundings is crucial osmoregulation = control of water balance • Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution

  18. 10 microns isotonic solution hypertonic solution hypotonic solution net water movement into cells net water movement out of cells equal movement of water into and out of cells

  19. Passive transport = diffusion across membranes • Small nonpolar molecules - simple diffusion • Many molecules pass through protein pores by diffusion through channels. • Facilitated diffusion Solutemolecule Transportprotein Figure 5.17

  20. Active transport • against a concentration gradient • transport proteins needed • requires energy (ATP)

  21. FLUIDOUTSIDECELL Phosphorylated transport protein Transportprotein • Active transport in two solutes across a membrane • Na+/K+ pump • Protein shape change Firstsolute 1 First solute, inside cell, binds to protein 2 ATP transfers phosphate to protein 3 Protein releases solute outside cell Second solute 4 Second solute binds to protein 5 Phosphate detaches from protein 6 Protein releases second solute into cell Figure 5.18

  22. Exocytosis and endocytosis transport large molecules exocytosis = vesicle fuses with the membrane and expels its contents FLUID OUTSIDE CELL CYTOPLASM Figure 5.19A

  23. or the membrane may fold inward, trapping material from the outside (endocytosis) Figure 5.19B

  24. human immune system ingests whole bacteria

  25. Receptor-mediated endocytosis

  26. Cholesterol can accumulate in the blood if membranes lack cholesterol receptors Phospholipid outer layer LDL PARTICLE Receptor protein Protein Cholesterol Plasma membrane Vesicle CYTOPLASM Figure 5.20

  27. What do these have in common? • HIV infection • Transplanted organs • Communication between neurons • Drug addiction • Cystic fibrosis • hypercholesteremia

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