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CELL STRUCTURE AND FUNCTION PART 2: Cytoplasm and Organelles

CELL STRUCTURE AND FUNCTION PART 2: Cytoplasm and Organelles. Cytoplasm : between PM and Nucleus. Cytoplasm = cytosol + organelles + inclusions Cytosol Liquid/syrupy gel Water + dissolved molecules & ions Organelles specialized structures performing specific functions

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CELL STRUCTURE AND FUNCTION PART 2: Cytoplasm and Organelles

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  1. CELL STRUCTURE AND FUNCTION PART 2:Cytoplasm and Organelles

  2. Cytoplasm :between PM and Nucleus Cytoplasm = cytosol + organelles + inclusions • Cytosol • Liquid/syrupy gel • Water + dissolved molecules & ions • Organelles • specialized structures performing specific functions • Division of labor and compartmentalization • Inclusions: • Masses/aggregations of molecules (e.g., lipids, carbs, or pigments) not surrounded by membranes

  3. Non-membrane Bound ribosomes Centrioles/centrosomes Cytoskeleton proteosomes Cilia—discussed later Microvilli—discussed later Membrane Bound nucleus Endoplasmic Reticulum Golgi Apparatus vessicles lysosomes peroxisomes mitochondria Organelles: There are two categories of organelles:

  4. Organelles the build/synthesize Proteins for use in cytosol (cytoplasm) • Free Ribosomes • sER • rER w/ fixed ribosomes • mitochondria • Golgi apparatus Lipids, e.g. phospholipids (and possibly carbs) • Proteins for use in a membrane or release from cell • Creates peroxisomes ATP & CO2 • Alters/modifies products of ER • Makes lysosomes

  5. Organelles the break things down • Waste, ingested macromolecules, & pathogens • many proteins, polysaccharides, lipids, nucleic acids • 30+ enzymes • lysosomes • Peroxisomes • Proteosomes • mitochondria • lipids & toxins/harmful substances • Different enzymes than lysosomes Proteins Nutrients & O2

  6. Mitochondria: • produces ATP for cellular energy by breaking down nutrients and O2 • Nutrients + Oxygen  ATP + CO2 + H20 + Heat • 2 lipid bilayers (two compartments for two different sets of reactions) • Has its own DNA semi-autonomous and self replicating. • Mitochondrial disorder: mitochondrial myopathy, optic neuropathy

  7. Organelles the support/connect and transport • Transport within cell. Transport to and from the PM • “Delivery packages” • Vesicles • Cytoskeleton (microtubules, microfilaments, intermediate filaments) • Cell shape • Cell movement • Attachement point for organelles • Transport routes

  8. Nucleus

  9. Nucleus • Contains and protects DNA • Instructions on how and when to build proteins • Information for growth, development, normal function, repair. • Assembles ribosome parts • Surrounded by nuclear membrane (envelope) • Protects DNA • Double membrane (double phospholipid bilayer) • Controls entry and exit of molecules w/ nuclear pores • continuous with endoplasmic reticulum

  10. Protein Flow through the Golgi Apparatus

  11. Endomembrane System and Membrane Flow: Protein production, modification, and use

  12. Endomembrane System and Membrane Flow: Organelles and internalized vessicles

  13. Cell Differentiation • Our description of cells was/has been of a ‘generic’ cell. • Most cells have most of the components discussed • Specialized cells have a combination of cell features unique to their function. • The specialized (differentiated) cells of our body are different in their: • The DNA they use and proteins they make (and/or use) • Shape • Organelle composition

  14. Differentiated Cells: • Note the shape differences between these cells: • Long thin neurons • Flat sheet of epithelial cells • Tightly packed muscle cells

  15. More detailed descriptions of organelles For your reference out of class Also see the summary/description posted on the website

  16. Non-membrane bound organelles

  17. Ribosomes • The organelle where all proteins are made (synthesized) • Free: floating w/ in cytosol • Synthesize proteins for cell’s use within cytosol of cell • Fixed: attached to endoplasmic reticulum • Synthesizes proteins for export/release from cell or incorporation into membranes ribosome + RNA + amino acids  proteins Ribosome (The non-purple parts are the protein being made from an RNA molecule).

  18. Cytoskeleton = microfilaments + intermediate filaments + microtubules Made of proteins (filaments or tubes) Functions: • Shape of cell and support • holds organelles in place • Cell movement (e.g., contraction) • Movement of internal parts/materials

  19. Cytoskeleton

  20. Centrosome and Centrioles • Centriole – a cluster of microtubules • organizing microtubules (part of cytoskeleton) • Move chromosomes/DNA during cell division • Centrosome – a pair of centrioles

  21. Membrane-Bound Organelles • Surrounded by a membrane • Phospholipidbilay with proteins • Same functions as PM: Isolates contents, selectively permeable, receptors, enzymes/reactions, transport proteins, etc…. • Membrane isolates contents and activity of organelle from cytoplasm • Examples are: • Endoplasmic reticulum • Golgi apparatus • Lysosomes • Peroxisomes • Mitochondria

  22. Endoplasmic Reticulum (ER) • interconnected/continuous with each other (and the nuclear membrane) • Smooth ER: no ribosomes attached. • Rough ER: Ribosomes attached to ER membrane ER can be related to formation of drug tolerances

  23. ER Function Smooth ER: • Synthesis, transport and storage of lipids • Metabolism of carbohydrates • Detoxification of drugs, alcohol and poisons Rough ER: synthesize, transport and store proteins for: • Secretion/release by the cell • The plasma membrane • lysosomes

  24. Transport Vesicles: • sacs, or bubbles, made of lipid bilayers • transport materials to and from the PM and between organelles

  25. Golgi Apparatus • Series of flattened sacs • Receive vesicles from and create vesicles for PM or lysosomes • Modify, sort, and package proteins and lipids from the RoughER • For release from cell • Incorporation into PM • Create lysosomes

  26. Lysosomes • Created by Golgi apparatus • digest (breaks down) waste, pathogens, excess molecules, old/damaged cell parts (organelles) with enzymes If a person lacks a lysosomal enzyme they can develop a lysosomal storage disorder (e.g., tay-sachs, pompay’s/glycogen storage disorder)

  27. Peroxisomes: • contains enzymes that break down lipids, amino acids, and some toxins (inc. hydrogen peroxide, a metabolic waste). • Function is similar to lysosome, but it metabolizes/breaks down a different set of molecules then lysosomes. • smaller then lysosomes • Peroxisomal based disorders can arise if • peroxisomes lack proper enzymes • Originate from ER and can make more of themselves by dividing

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