BIO 110 1st Edition Lecture 16Plastids and Pigments - Plastids- general class of plant specific organelles o Most important- chloroplast- capture light energy - Sunlight are polychromatic Chloroplast structure - Outer membrane covers entire organelle - Inner membrane also covers organelle - Thylakoid membrane- greatly folded and shaped into disks o Single disk: thylakoid discs o Stack: granum - Soluble material inside inner membrane and outside grana = stroma - Formerly free-living, then endosymbionts Chloroplast function - Site of photosynthesis - Convert light energy to chemical energy o Used to reduce CO2 to make reduced carbon compounds Have lots of H’s, few O’s – plant carbs, protons o We eat and reoxidize them - CO2 is reduced using electrons from water - When water is oxidized, oxygen is released Cytoskeleton - Eukaryotic cells are relatively large, need internal supporting cytoskeleton to maintain shape andmechanisms for changing shape and moving o Less important in plants- use cell wall/osmotic pressure - Multiple types of fibers make cytoskeleton o Microtubules o Microfilaments o Intermediate filaments Microtubules - Structure: thickest fiber o Hollow tubes made of tubulin protein subunits Noncovalently associated o Have opposite ends where they assemble and disassemble - Functions- provide structural support o Moves material around cello Form spindle o Cell movement Microfilaments - (actin fiber) structure: o Thinnest of 3 fibers o Long, thin fivers of actin protein subunits o 2 helical strands of actin wraped around each other - Function: structural support, form stress fibers at points of attachment, cell movement and shape changes, muscle contraction in specialized muscle cells Intermediate filaments - Intermediate in thickness - Made of several different kinds of fibers protein subunits (keratin lamin) are arranged into a cylinder - Function: shape/ structural support, forms nuclear lamina, no role in movement/motion Cytoskeleton: shape - Changes in cytoskeleton allow changes in shape/mvmt o Actin filaments more agaginst each other o Microtubules can lengthen and shorten o Microtubules completely rearrange themselves for cell division Function: - Some cells move using external cilia and flagella - Kinetoplastidtylanosome- single long flagella Movement: - Other cells move using microfilaments to change shape o Ex) amoeba o Actin filaments create amoeboid movements, sending pseudopods out and hence- crawlo No cells use intermediate filaments to move ** o Movement and shape changes use motor proteins to convert chemical energy to mechanical motion - Myosin interacts with actin microfilaments o Creates amoeboid motion o Actin-myosin basis of contraction in muscle cells Extracellular matrix - In metazoans cells often are divided into tissues - EC matrix holds cells into tissues o ECM consists of proteins/complex carbs, made inside cell then secreted by exocytosis o When relatively few cells, forms “connective tissue” - Special ECM organized into thin sheets form basal lamina- BC separate epithelial cell from rest of the body o Secreted from basal surface o Determines the orientation of new epithelial cells making them polar Plasma Membrane - Outer membrane covers the cell - Acts as a carrier/door that is selection - Barrier separates external/internal compartments - Regulates cell contents o Semipermeable barrier - Structure: thin covering over entire cell surface o Less than 10mm thick - Flexible covering - Monolayer area= 2x red blood cell surface area membrane in cell is a bilayer Phospholipids - Part polar, part nonpolar - Hydrophilic: phosphate - Hydrophobic: fatty acid chains - The central hydrophobic [art of bilayer forms the major barrier between
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