Chapter 4 -Part 1

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Chapter 4 -Part 1

  1. 1. Chapter 4- Physiology of Cells
  2. 2. Passive Transport Processes Diffusion: the tendency of small particles to spread out evenly within any given space. Particles move from an area of high concentration to low concentration. • Down the concentration gradient
  3. 3. Passive Transport Processes Dialysis: is a form of diffusion in which the selectively permeable nature of the membrane causes separation of smaller solute particles from larger solute particles.
  4. 4. Passive Transport Processes Osmosis: the diffusion of water through a selectively permeable membrane.
  5. 5. Passive Transport Processes Facilitated Diffusion: diffusion of particles through a membrane by means of carrier molecules.
  6. 6. Passive Transport Processes Filtration: involves the passing of water and permeable solutes through a membrane by the force of hydrostatic pressure. • Hydrostatic pressure is the force, or weight, of a fluid pushing against a surface. • Filtration is driven by a hydrostatic pressure gradient. • Example: Movement of water and small solutes from the capillaries to the interstitial spaces.
  7. 7. Active Transport Processes Active Transport: refers to a carrier mediated process in which cellular energy is used to move molecules “uphill” through a cell membrane. • “Uphill” refers to going from a low concentration to a high concentration. Or against the concentration gradient. • Examples: Calcium pumps, Sodium Potassium pumps.
  8. 8. Active Transport Processes Endocytosis: the plasma membrane traps some extracellular material and brings it into the cell. •There are two forms of endocytosis: • Phagocytosis: condition of cell eating • Pinocytosis: condition of cell drinking
  9. 9. Active Transport Processes
  10. 10. Active Transport Processes Exocytosis: the process in which large molecules notably proteins, can leave the cell even though they are too large to move out through the plasma membrane.
  11. 11. Enzymes Enzymes: are functional proteins that act as chemical catalysts that allow metabolic reactions to occur. • Structural attribute that is important is the active site. This is the portion of the enzyme that chemically “fits” the substrate molecule. • The action of an enzyme can be described as a lock and key function.
  12. 12. Classification of Naming Enzymes Classified according to the kind of chemical reactions catalyzed. •Redox enzymes: oxidase, hydrogenases, dehydrogenases. •Hydrolyzing enzymes: Digestive enzymes such as lipase, sucrase, maltase.
  13. 13. Classification of Naming Enzymes •Phosphorylating enzymes: add or remove phosphate groups. •Carboxylases or Decarboxylases: add or remove carbon dioxide •Mutases or Isomerases: rearrange atoms within a molecule. •Hydrases: add water to a molecule.
  14. 14. General Functions of Enzymes • Enzymes regulate cell functions by regulating metabolic pathways. • Most enzymes are specific in their actions. • Allosteric effector: an agent that changes the shape of a molecule. • End product inhibition: a chemical product at the end of a metabolic pathway binds to an allosteric site and thus inhibits synthesis of more product.
  15. 15. General Functions of Enzymes • Most enzymes catalyze a chemical reaction in both directions. • Enzymes are continually destroyed and therefore have to be continually synthesized. • Many are synthesized as inactive proenzymes. • Proenzymes are converted or activated by Kinases.

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