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Organelles

Organelles. Types of Organelles. Nonmembranous organelles: no membrane direct contact with cytosol (cytoplasm) Membranous organelles: covered with plasma membrane isolated from cytosol (cytoplasm). 6 types of nonmembranous organelles: cytoskeleton microvilli centrioles.

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Organelles

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  1. Organelles

  2. Types of Organelles • Nonmembranous organelles: • no membrane • direct contact with cytosol (cytoplasm) • Membranous organelles: • covered with plasma membrane • isolated from cytosol (cytoplasm) • 6 types of nonmembranous organelles: • cytoskeleton • microvilli • centrioles • -cilia • ribosomes • proteasomes

  3. How does the nucleus control the cell? • Nucleus: • largest organelle • Nuclear envelope: • double membrane around the nucleus • Perinuclear space: • between 2 layers of nuclear envelope • Nuclear pores: • communication passages • Is the cell’s control center

  4. Within the Nucleus • DNA: • all information to build and run organisms • Nucleoplasm: • fluid containing ions, enzymes, nucleotides, and some RNA • Nuclear matrix: • support filaments Nucleoli in Nucleus • Are related to protein production • Are made of RNA, enzymes, and histones • Synthesize rRNA and ribosomal subunits

  5. Ribosomes SEM of rough ER (ribosomes attached to membranes)

  6. Ribosomes • Two types: • free ribosomes in cytoplasm: • proteins for cell • fixed ribosomes attached to ER: • proteins for secretion • Translate the genetic code into proteins. • Build polypeptides in protein synthesis • 60% RNA and 40% protein. Proteasomes (found in the nucleus and the cytoplasm) • Contain enzymes (proteases) • Disassemble damaged proteins for recycling

  7. Endoplasmic reticulum TEM of rough ER (ribosomes attached to membranes)

  8. Endoplasmic Reticulum (ER) • endo = within, plasm = cytoplasm, reticulum = network • Little net • Network of interconnected closed membrane vesicles • Single membrane • Divides cell into compartments • Place of protein and phospholipids synthesis • Connected with the nuclear envelope • Cisternae are storage chambers within membranes

  9. Functions of ER • Synthesis of proteins, carbohydrates, and lipids • Storage of synthesized molecules and materials • Transport of materials within the ER • Detoxification of drugs or toxins • It is of 2 types: 1. Rough ER 2. Smooth ER

  10. Rough Endoplasmic Reticulum • Network of continuous sacs, studded with ribosomes. • Manufactures, pro-cesses, and transports proteins for export from cell. • Continuous with nuclear envelope. • Surface covered with ribosomes: • active in protein and glycoprotein synthesis (late r inserted in the cell membrane and secreted from the cell) • folds polypeptides protein structures • encloses products in transport vesicles

  11. Smooth Endoplasmic Reticulum • Similar in appearance to rough ER, but without the ribosomes. • Involved in the production of lipids, carbohydrate metabolism, and detoxification of drugs and poisons. • Ca (2+) storage • Synthesizes lipids and carbohydrates: • phospholipids and cholesterol (membranes) • steroid hormones (reproductive system) • glycerides (storage in liver and fat cells) • glycogen (storage in muscles)

  12. Golgi complex TEM of Golgi complex

  13. ER and Golgi complex The ER and Golgi complex work together to secrete substances from the cell (via exocytosis)

  14. Golgi Bodies • Contains several hundred flattened compartments and vesicles • Secretory vesicles: • modify and package products for exocytosis • Membrane renewal vesicles: • add or remove membrane components • Transport vesicles: • Carry materials to and from Golgi apparatus

  15. Golgi Bodies

  16. Lysosomes SEM of two lysosomes containing undigested material Cell death caused by lysosomes removes webbing

  17. Lysosome Functions • Powerful enzyme-containing vesicles: • lyso = dissolve, soma = body • Clean up inside cells: • break down large molecules • attack bacteria • recycle damaged organelles • ejects wastes by exocytosis • Primary lysosome: • formed by Golgi and inactive enzymes • Secondary lysosome: • lysosome fused with damaged organelle • digestive enzymes activated • toxic chemicals isolated

  18. Chloroplasts TEM of chloroplasts

  19. Photosynthetic plant cells also contain chloroplasts (a plastid) that capture energy from sunlight. They produce and store carbohydrates like miniature gardens and warehouses. LOCATION inside photosynthetic cells only, suspended in the cytosol DESCRIPTION  green, disk shaped  contains chlorophyll and the enzymes required for photosynthesis FUNCTION absorb sunlight energy photosynthesis occurs here: glucose is synthesized from Carbon Dioxide and water Chloroplasts

  20. PRESENT IN: PROKARYOTIC CELLS? NO PLANT CELLS? YES ANIMAL CELLS? NO VISIBLE WITH: LIGHT MICROCOPE? YES ELECTRON MICROSCOPE? YES Chloroplast

  21. Mitochondria TEM SEM Notice the many folds

  22. Mitochondria Tubular susage shaped Double membrane Own DNA and ribosomes Have smooth outer membrane and folded inner membrane (cristae) Matrix: • fluid around cristae

  23. Mitochondrial Function • Mitochondrion takes chemical energy from food (glucose): • produces energy molecule ATP Figure 3–9b

  24. Animal and plant cells Animal cell Plant cell

  25. Cell skeleton Three structures that make up the cytoskeleton of a cell

  26. The Cytoskeleton(Structural proteins for shape and strength) • Microfilaments • Solid rods of globular proteins. • Important component of cytoskeleton which offers support to cell structure. Thin filaments composed of the protein actin: • provide additional mechanical strength • durable (collagen) • strengthen cell and maintain shape • stabilize organelles • stabilize cell position

  27. Microtubules • Large, hollow tubes of tubulinprotein: • attach to centrosome • strengthen cell and anchor organelles • change cell shape • form spindle apparatus • Microvilli • Increase surface area for absorption • Attach to cytoskeleton

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