Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Cell structure

114 views

Published on

cell structure

Published in: Health & Medicine
  • Be the first to comment

Cell structure

  1. 1. Cell Structure and Genetic Control Human physiology
  2. 2. Cell • Basic unit of structure and function of the body. ▫ Highly organized molecular factory. • Great diversity of function. ▫ Organ physiology derived from complex functions of the cell. • 3 principal parts: ▫ Plasma membrane. ▫ Cytoplasm and organelles. ▫ Nucleus.
  3. 3. Plasma Membrane • Is selectively permeable. • Composition: ▫ Double layer of phospholipids due to hydrophobic/hydrophilic parts.  Restrict passage of H20 and H20 soluble ions. ▫ Proteins span or partially span the membrane.  Provide structural support, transport molecules, serve as receptors. ▫ Negatively charged carbohydrates attach to the outer surface.  Involved with regulatory molecules.
  4. 4. Plasma Membrane (continued)
  5. 5. Cytoplasm, Organelles, Nucleoli • Cytoplasm: ▫ Aqueous content of the cell. • Organelles: ▫ Sub-cellular structures within the cytoplasm. • Nucleus: ▫ Is a large spheroid body. ▫ Largest of the organelles. ▫ Contains the genetic material (DNA). ▫ Nucleoli:  Centers for production of ribosomes.
  6. 6. Cytoplasm, Organelles, Nucleoli (continued)
  7. 7. Bulk Transport • Phagocytosis: ▫ Phagocytic cells use pseudopods to surround and engulf particles. ▫ Pseudopods join, fuse, and surround ingested particle (food vacuole).  Lysosomes digest food vacuole. ▫ Protects from invading organisms. ▫ Removes debris. • Endocytosis: ▫ Pinocytosis:  Nonspecific process.  Plasma membrane invaginates, fuses, vesicle containing ECF pinches off, and vesicle enters cell.
  8. 8. Bulk Transport (continued) • Receptor-mediated endocytosis: ▫ Interaction of molecules in ECF with specific membrane receptor proteins. ▫ Membrane invaginates, fuses, pinches off and forms vesicle. ▫ Vesicle enters cell. • Exocytosis: ▫ Process by which cellular products are secreted into extracellular environment. ▫ Proteins and other molecules to be secreted are packaged in vesicles by Golgi complex. ▫ Vesicles fuse with plasma membrane and release contents into extracellular environment.
  9. 9. Cilia, Flagella, Microvilli • Cilia: ▫ Tiny hair-like structures that project from the surface of the cell.  Stroke in unison.  Respiratory tract, uterine tube. • Flagella: ▫ Simple whip-like structure that propels sperm through its environment. • Microvilli: ▫ Numerous folds (finger-like projections) increase surface area.  Aid absorption.
  10. 10. Cytoplasm and Cytoskeleton • Cytoplasm: ▫ Jelly-like matrix within the cell. ▫ Includes organelles and cytosol. ▫ Highly organized structure with microtubules and microfilaments that function as cytoskeleton. • Cytoskeleton: ▫ Actin and myosin (microfilaments). ▫ Spindle apparatus (microtubules).
  11. 11. Lysosomes ▫ Primary:  Contain only digestive enzymes. ▫ Secondary:  Primary lysosome fuses with food vacuole or organelle.  Contain partially digested remnants of other organelles and organic material. ▫ Residual body:  Contain undigested wastes. ▫ Autophagy:  Process that destroys worn-out organelles, so that they can be continuously replaced. ▫ Apoptosis (programmed cell death):  Lysosomes release digestive enzymes into the cell.
  12. 12. Peroxisomes • Membrane-enclosed organelles. ▫ Contain specific enzymes that promote oxidative reactions. ▫ Oxidize molecules and form H202. • Catalase: converts H202 H20 + 02. • Oxidation of toxic molecules by peroxisomes is an important function of liver and kidney cells.
  13. 13. Mitochondria • Sites for energy production of all cells; but mature RBCs. • Contain own DNA, can reproduce themselves. • Structure: ▫ Outer membrane: smooth. ▫ Inner membrane: cristae. ▫ Cristae and matrix compartmentalize mitochondrion space.  Have different roles in energy generation.
  14. 14. Ribosomes • Protein factories: ▫ Proteins produced according to genetic information contained in mRNA. ▫ Located in cytoplasm and on the surface of endoplasmic reticulum. • rRNA molecules serve as enzymes (ribozymes) required for protein synthesis. ▫ Contains 2 subunits composed of rRNA and proteins.
  15. 15. Endoplasmic Reticulum (ER) • Granular (rough) ER: ▫ Bears ribosomes on surface, in cells active in protein synthesis.  Proteins enter cisternae are modified for secretion. • Agranular (smooth) ER: ▫ Provides site for enzyme reactions in steroid hormone production and inactivation. ▫ Storage of Ca2+ in striated muscle cells.
  16. 16. Golgi Complex • Stacks of hollow, flattened sacks with cisternae. ▫ One side of sack faces site for entry of vesicles from ER that contain cellular products. ▫ Other site faces towards plasma membrane and releases vesicles of chemically modified products. • Modifies proteins, separates according to destination, and packages into vesicles.
  17. 17. Cell Nucleus Most cells have single nucleus. Enclosed by inner and outer membrane (nuclear envelope). ◦ Outer membrane is continuous with ER. Nuclear pore complexes fuse inner and outer membranes together. ◦ Selective active transport of proteins and RNA.  Regulation of gene expression.  Transport of mRNA out of nucleus to ribosomes. Nucleoli: ◦ DNA contains the genes that code for the production of mRNA.
  18. 18. Cell Death • Pathologically: ▫ Cells deprived of blood supply swell, the membrane ruptures, and the cell bursts (necrosis). • Apoptosis: ▫ Cells shrink, membranes become bubbled, nuclei condense. • Capsases (“executioner enzymes”): ▫ Mitochondria membranes become permeable to proteins and other products. • Programmed cell death: ▫ Physiological process responsible for remodeling of tissues during embryonic development and tissue turnover in the adult.

×