suspended by electrical charges – small organic molecules (simple sugars) & ions • dissolved – inclusions (large aggregates of one material) • lipid droplets • glycogen granules • Site of many important chemical reactions – production of ATP, synthesis of building blocks
3-39 Cell Organelles • Nonmembranous organelles lack membranes & are indirect contact with cytoplasm • Membranous organelles surrounded by one or two lipid bilayer membranes
3-40 Cytoskeleton • Network of protein filaments throughout the cytosol • Functions – cell support and shape – organization of chemical reactions – cell & organelle movement • Continually reorganized
3-41 The Cytoskeletonal Filaments • Microfilaments – thinnest filaments (actin) – locomotion & division – support microvilli • Intermediate filaments – several different proteins – anchor organelles • Microtubules – large cylindrical structures (composed of tubulin) – flagella, cilia & centrosomes
3-42 Centrosome • Found near nucleus • Pericentriolar area – formation site for mitotic spindle and microtubules • Centrosome – 2 centrioles(90 degrees to each other) – 9 clusters of 3 microtubules (9+0 array) – role in formation of cilia & flagella
3-43 Cilia and Flagella • Structure – pairs of microtubules (9+2 array) – covered by cell membrane – basal body is centriole responsible for initiating its assembly • Differences – cilia • short and multiple – flagella • longer and single
3-44 Movement of Cilia and Flagella • Cilia – stiff during power stroke but flexible during recovery – many coordinated together – airways & uterine tube • Flagella – single flagella wiggles in a wavelike pattern – propels sperm forward
3-45 Ribosomes • Packages of Ribosomal RNA & protein • Free ribosomes are loose in cytosol – synthesize proteins found inside the cell • Membrane-bound ribosomes – attached to endoplasmic reticulum or nuclear membrane – synthesize proteins needed for plasma membrane or for export – 10 to 20 together form a polyribosome • Inside mitochondria, synthesize mitochondrial proteins
3-46 Ribosomal Subunits • Large + small subunits – made in the nucleolus – assembled in the cytoplasm
3-47 Endoplasmic Reticulum • Network of membranes forming flattened sacs or tubules called cisterns – half of membranous surfaces within cytoplasm • Rough ER – continuous with nuclear envelope & covered with attached ribosomes – synthesizes, processes & packages proteins for export – free ribosomes synthesize proteins for local use • Smooth ER -- no attached ribosomes – synthesizes phospholipids, steroids and fats – detoxifies harmful substances (alcohol)
3-48 Smooth & Rough Endoplasmic Reticulum Rough ER is covered with fixed ribosomes.
3-49 Golgi Complex • 3-20 flattened, curved membranous sacs called cisterns • Convex side faces ER & concave side faces cell membrane • Processes & packages proteins produced by rough ER
3-50 Packaging by Golgi Complex • Proteins pass from rough ER to golgi complex in transport vesicles • Processed proteins pass from entry cistern to medial cistern to exit cistern in transfer vesicle • Finished proteins exit golgi as secretory, membrane or storage vesicle (lysosome)
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