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CELLS

CELLS. The basic living, structural, and functional unit of all organisms. Basic Cell Structure. Cell (Plasma) Membrane Cytosol Organelles Nucleus. Basic Cell. Basic Cell Structures. Cytosol. The semi-fluid component of cytoplasm or intracellular fluid 75% - 95% water

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CELLS

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  1. CELLS The basic living, structural, and functional unit of all organisms.

  2. Basic Cell Structure • Cell (Plasma) Membrane • Cytosol • Organelles • Nucleus

  3. Basic Cell

  4. Basic Cell Structures

  5. Cytosol • The semi-fluid component of cytoplasm or intracellular fluid • 75% - 95% water • May contain organelles, large carbohydrates, fat, and protein molecules

  6. Function of Cytosol • Location of chemical reactions (anaerobic energy metabolism) • Synthesis of cellular substances • Packaging of chemicals for transport • Facilitates excretion of waste material

  7. The Cell (Plasma) Membrane • Thin structure that separates the internal cellular components from the external environment.

  8. Cell Membrane

  9. Structure of the Cell Membrane • Phospholipid bilayer • Hydrophilic phosphoric heads face outward • Hydrophobic fatty acid tails face inward • Carbohydrates assist in cell identification/communication • Cholesterol increases strength of cell membrane

  10. Cell Membrane Proteins • Integral Proteins are proteins imbedded in the phospholipid bilayer • gates or channels are transport proteins • receptor sites for hormones • enzymes • cellular identity markers • Peripheral Proteins are loosely bound to plasma membrane • function not completely understood

  11. Cell Membrane Structures

  12. Cell Membrane Proteins

  13. Functions of the Cell Membrane • Flexible boundary • Facilitates contact with other cells and environment • Receptor sites - hormones, enzymes, neurotransmitters, nutrients, antibodies • Selectively permeable - mediates entrance and exit of material into and out of cell.

  14. Factors Influencing Permeability of Plasma Membrane • Size of molecules • Solubility in lipids • Charge on ions • Presence of carrier molecules

  15. Movement Across the Cell Membrane

  16. Intracellular Fluid • Fluid found in living cells • Comprises > 66% of body’s total water • Mostly water • may also contain potassium, phosphates, magnesium, chloride, and other ions

  17. The Extracellular Environment • Interstitial Fluid (Intercellular Fluid) • Fluid found in the microscopic spaces between cells • Plasma • Extracellular fluid within blood and lymph vessels

  18. Movement Across the Plasma Membrane • Passive Processes • No energy expenditure • Moves down a concentration gradient • High →low concentration • Active Processes • Requires energy expenditure • Moves against a concentration gradient • Low → high concentration • May utilize 40% of cells ATP supply

  19. Movement Across the Cell Membrane

  20. Passive Transport • Diffusion • Facilitated Diffusion • Osmosis • Dialysis • Filtration

  21. Diffusion • The movement of molecules from a higher concentration to a lower concentration. Does not require energy. • Ex: perfume, electrolytes

  22. Osmosis

  23. Facilitated Diffusion • Facilitated diffusion is the process of diffusion through the protein channels of the cell membrane. • Ex: glucose

  24. Facilitated Diffusion

  25. Dialysis • Dialysis is the diffusion of small solute particles through a selectively permeable membrane resulting in the separation of large and small solutes. • Example: Kidney dialysis

  26. Filtration • Filtration is the process of removing particles from a solution by allowing the liquid to pass through a membrane. It is influenced by gravity and hydrostatic pressure. • Example: Filtration in the glomerulus of the kidney nephron.

  27. Active Transport Processes • 1. Endocytosis occurs when the molecules are too big to enter the cell by diffusion or active transport, a vesicle is formed from the cell membrane. • Example: Phagocytosis or cell eating.

  28. 2. Exocytosis • Any remaining particles from phagocytosis may be expelled from the cell when the vesicle joins with the cell membrane and the contents are removed from the cell.

  29. Active Transport • Active Transport • Uses energy • Ions move against a concentration gradient • Na+/K+ pump • Estimated 40% ATP use in the body • Cytosis (Bulk Transport) • Endocytosis • Phagocytosis - cell eating • Pinocytosis - cell drinking • Receptor mediated endocytosis • Exocytosis

  30. Na+/K+ Pump

  31. Effects of Osmosis • Isotonic Solutions • Hypotonic Solutions • Hypertonic Solutions

  32. Tonic Solutions

  33. Nucleus • The “control center” of the cell • Usually the largest structure in the cell • Contains genetic information • Controls cellular function and structure

  34. Nuclear Structures • Nuclear Membrane • Nucleoplasm • Nucleolus • site of ribosome synthesis • Genetic Material DNA • Chromatin contains DNA in thread-like form (cell is not dividing) • Chromosomes contains DNA in short, rod-like structures (cell is reproducing)

  35. Cell Nucleus

  36. Organelles • Specialized structures and portions of the cell with characteristic shapes that assume specific roles: • growth • repair • maintenance • control of cellular functions

  37. Organelles and Structures • Ribosomes • Endoplasmic Reticulum • Golgi Complex • Mitochondria • Lysosomes • Vacuoles • Peroxisomes • Microfilaments • Microtubules

  38. Organelles and Structures, cont • Centrioles • Centrosomes • Flagella • Cilia • Microvilli

  39. Ribosomes • Appear as small, round, granular structures within the cell • Sites of protein synthesis by assembling the amino acids in the correct order. • Made up of special type of RNA called ribosomal RNA (rRNA)

  40. Ribosomes

  41. Endoplasmic Reticulum • Double membranous channels which are continuous with the nuclear membrane • Granular (Rough) Endoplasmic Reticulum • studded with ribosomes • site of protein synthesis • Agranular (Smooth) Endoplasmic Reticulum • free of ribosomes • site of lipid synthesis

  42. Functions of Endoplasmic Reticulum • Mechanical support and distribution of cytoplasm • Surface area for chemical reactions • Intracellular transport system • Storage of synthesized molecules • Protein (RER) and lipid (SER) synthesis • Detoxification of certain molecules • Release of calcium ions in muscles

  43. Endoplasmic Reticulum

  44. Golgi Complex (Bodies) • Flattened membranous sacs (4 - 8) stacked upon one another • Processes, packages, sorts, and delivers proteins to various parts of the cell • Secretion of lipid molecules from the cell

  45. Golgi Complex

  46. Mitochondria • Powerhouse of the cell • Small, spherical or rod-shaped structures • Sites of cellular respiration • conversion of glucose and lipids to ATP • aerobic energy metabolism

  47. Mitochondria

  48. Lysosomes • Nicknamed “suicide packets” • Small membrane enclosed spheres of digestive enzymes • Intracellular digestion • Autophagy is the process by which old worn out organelles are digested • Autolysis is the process by which lysosomes digest themselves

  49. Lysosomes

  50. Vacuoles • Fluid filled organelles enclosed by a membrane • Used to store digested cellular food or water

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