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Cell Structure

Explore the components of the cell's cytoplasm, including the role of cytosol, organelles like ribosomes, endoplasmic reticulum, Golgi complex, lysosomes, and mitochondria. Learn their structures and functions.

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Cell Structure

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  1. Cell Structure

  2. Cytoplasm • All of the cellular contents between the plasma membrane and the nucleus

  3. Cytosol • Fluid portion of the cytoplasm • ~55% of the cell’s volume • 75%-90% water • Contains dissolved/suspended solutes: • Ions, glucose, ATP, lipids, proteins, amino acids, waste • Site of most of the chemical reactions in the cell

  4. Organelles • Specialized structures inside cells that have characteristic shapes and specific functions

  5. Cytoskeleton • Network of protein filaments: • Microfilaments, intermediate filaments, microtubules

  6. Microfilaments • Thinnest • On the periphery of the cell • Contribute to shape and strength • Help generate movement • Support microvilli

  7. Intermediate Filaments • Thicker than microfilaments, thinner than microtubules • Found in cells subject to tension • Help to hold organelles in place

  8. Microtubules • Largest • Help determine shape • Function in movement of organelles • Function in movement of cilia and flagella

  9. Centrosome • Near the nucleus • Pair of centrioles • Cylindrical structures composed of clusters of microtubules arranged in a circular pattern • Pericentriolar Material • Tubulins – organizing center for the growth of mitotic spindles

  10. Cilia and Flagella • Motile projections on the cell surface • Cilia – numerous short hair-like projections on the cell surface. • Propel fluids across the surface of the cell • Flagella – longer than cilia, propel the entire cell. • Only example in the human is sperm cell

  11. Ribosomes • Site of protein synthesis • High content of RNA • 2 sub-units • Large and small • Made in the nucleolus and assembled in the cytosol • Attached to ER or free in cytosol

  12. Endoplasmic Reticulum • Network of folded membranes that extends through the cytoplasm • Rough ER: extends from nuclear envelope; has ribosomes attached; processes and sorts proteins that will be incorporated into the membranes • Smooth ER: extends from rough ER; no ribosomes attached; fatty acids and steroids are synthesized.

  13. Golgi Complex (Body; Apparatus) • Packages and transports materials • Cisterns – flattened membranous sacs with bulging edges that make up the Golgi Body

  14. Transport of Proteins by the Golgi Body • Protein is surrounded by ER membrane and buds of to form a transport vesicle • Transport vesicle moves toward Golgi Body • Vesicle fuses with Golgi Body and proteins enter • Proteins move from one cistern to another by transfer vesicles • In last cistern proteins are sorted and packaged • Proteins leave Golgi Body in secretory vesicles, other membrane vesicles or transport vesicles

  15. Lysosomes • Membrane enclosed vesicles that contain digestive enzymes • Help to recycle cellular components • Autophagy – worn out organelles are digested • Autolysis – enzymes destroy its own cell

  16. Tay-Sachs Disease • An inherited condition in which one lysosomal enzyme is absent. • Normally breaks down a membrane glycolipid found in nerve cells. It is not broken down, it accumulates which makes the nerve cell function less efficiently • Seizure, muscle rigidity, blindness, dementia, uncooridated. Usually die before age 5

  17. Peroxisomes • Similar to lysosomes but smaller • Contain oxides • Enzymes that can oxidize various organic substances • Abundant in liver where there are a lot of toxic substances • Contain catalase

  18. Proteasomes • Contain enzyme called protease • Continuously destroys unneeded, damaged or faulty proteins • Recycles amino acids

  19. Mitochondria • Site of cellular respiration (makes ATP) • Active cells have a larger number • Double Membrane • Outer – smooth • Inner –folded • Cristae – folds • Enzymes that catalyze a series of reactions are found in the matrix

  20. Check Point Questions • What is the difference between cytoplasm and cytosol? • What is an organelle? • Describe the structure of a ribosome, the Golgi Body and a mitochondrion.

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