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Cells

Cells. Chapter 3 Bio160. Plasma Membrane. Plasma membrane – flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell. Fluid mosaic model. Lipid bilayer. Membrane proteins. Plasma Membrane.

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Cells

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  1. Cells Chapter 3 Bio160

  2. Plasma Membrane • Plasma membrane – flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell. Fluid mosaic model Lipid bilayer Membrane proteins

  3. Plasma Membrane • Cytoplasm – Everything inside the cell including the fluid (cytosol) and organelles. The plasma membrane is selectively permeable, which means that only certain substances can enter or leave the cell

  4. Transport Across Membranes

  5. Transport Across Membranes

  6. Transport Across Membranes

  7. Transport Across Membranes

  8. Transport Across Membranes

  9. Tonicity • Isotonic – concentrations of solutes are the same on both sides of the membrane 0.9% NaCl solution (normal physiological saline) is isotonic for red blood cells (RBC) • Hypotonic – a solution that has lower concentration of solutes than the cytosol Lysis or hemolysis in RBC • Hypertonic – a solution that has greater concentration of solutes than the cytosol Crenation – cell shrinkage

  10. Nucleus • Nucleus – control center contains chromosomes - heredity material-called chromatin when cell is not dividing nucleolus - assembly plant for ribosomes surrounded by nuclear membrane which has pores in it through which substances enter and exit

  11. Ribosomes • Ribosomes - contain both rRNA and ribosomal proteins functions as the workbench for protein synthesis some ribosomes are free ribosomes - no attachment to organelles - concerned primarily with synthesizing proteins for use inside cell

  12. Ribosomes some ribosomes are attached to the endoplasmic reticulum (ER), hence rough ER, involved in the synthesis of proteins for insertion in the cell membrane or for export from the cell

  13. Endoplasmic Reticulum • Endoplasmic reticulum (ER) - system of membrane-enclosed channels continuous with nuclear membrane and Golgi complex rough ER - has attached ribosomes - proteins synthesized are stored by the ER and sugar groups may be added to form glycoproteins - then transported from ER to Golgi

  14. Endoplasmic Reticulum (2) smooth ER - no ribosomes attached - provides a surface area for chemical reactions • site of steroid, fatty acid, phospholipid synthesis (ex: in testis provides surface for enzymes involved in testosterone synthesis) • site of carbohydrate synthesis, detoxification of alcohol, pesticides, carcinogens (ex: liver synthesis of glycogen) • stores Ca++ in muscle (but called sarcoplasmic reticulum (SR) in muscle)

  15. Golgi Apparatus • Golgi apparatus - consists of stacks of flattened sacs (like pancakes) that can form vesicles for exocytosis, lysosomes, or for storage (vesicles are membrane bound sacs that are smaller than vacuoles) Golgi receives proteins, carbohydrates, lipids from vesicles made from ER and collects, sorts, packages as new vesicles, and delivers vesicles for storage, membrane use, or exocytosis, lysosomes

  16. Lysosomes • Lysosome - formed by Golgi and contain powerful digestive (hydrolytic) enzymes that: recycle monomers in a cell from polymers (proteins, carbohydrates, lipids, nucleic acids) destroy bacteria engulfed by white blood cells (WBC) when the phagocytic vesicle fuses with lysosome

  17. Mitochondria • Mitochondria - powerhouse of cell - double membraned - found in both animal and plant cells, but not in bacteria Major site of chemical reactions that release energy from certain nutrient molecules and transfer it to ATP, a chemical form the cell can use.

  18. Cytoskeleton • Cytoskeleton - elaborate network of protein structures = "bones and muscles" microfilaments - thin strands of actin - aid in cell movement (ex. amoeboid movement as in WBC), aid in cytokinesis • most highly developed in muscles

  19. Cytoskeleton microtubules - hollow tubes formed of globular proteins called tubulins • provide monorail system to move organelles/vesicles • also in centrioles, cilia, spindle fibers

  20. Centrosomes and Centrioles • Centrosomes – a structure near the Golgi and nucleus that contains two centrioles. • Centrioles - paired cylindrical bodies, each composed of microtubules Organize spindle fibers and asters during mitosis in animal cells (may not be necessary for this purpose because plants produce spindle fibers during mitosis but they lack centrioles)

  21. Centrosomes and Centrioles • Having centrioles at each pole in mitosis provides a vehicle for transmission of centrioles to all cells Form the bases of cilia and flagella

  22. Cilia/Flagella • Cilia/Flagella - Membrane bound sets of microtubules that move by means of ATP cannot produce cilia/flagella without centrioles • Cilia – tiny, hairlike structures that fringe the surface of some cells • Flagellum – long, usually single extension, ex. tail of a sperm

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