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Transcript
A Tour of the Cell, cont… Last Time: The Nucleus and the Endomembrane System Today: Other Organelles and the Cytoskeleton Cells need energy to work Sunlight glucose phot osynthesis Glucose ATP cell respiration ATP ADP + energy hydrol ysi s Figure 6.8 The structure and hydrolysis of ATP Chloroplasts in plant cells convert sunlight into chemical energy that will be used to make ATP ATP is manufactured through cellular respiration that takes place in the mitochondria Peroxisomes H 2 O 2 H2 O2 H 2O 2 H 2 2H 2O The cytoskeleton 3 types of cytoskeletal structures Microfilaments Protein subunits Structure Actin Keratin, others Two intertwined strands 7 nm Actin subunit Functions Intermediate filaments Fibers wound into thick cables 10 nm Keratin subunits a-tubulin and btubulin dimers Hollow tube 25 nm Tubulin dimer • maintain cell shape by resisting compression • motility via flagella/cilia • anchor nucleus • move organelles and some other organelles • move chromosomes during cell division • maintain cell shape by resisting tension • motility via pseudopodia • muscle contraction • cell division in animals Microtubules Motor molecules like kinesin, myosin, and dynein work with the cytoskeleton to produce movement Structure of kinesin Tail Stalk Head Kinesin "walks" along a microtubule track Transport vesicle ATP Kinesin Microtubule ADP+Pi ATP ADP+Pi Microfilaments and Intermediate Filaments Networks of filaments near the plasma membrane help to maintain a cell’s shape Microfilaments aid in motility Centrosome containing a pair of centrioles Microtubules often grow out from the region called the centrosome Cilia and Flagella move the entire cell Cilia Flagella Cilia and Flagella have a “9 +2” arrangement of microtubule doublets TEM of flagella Cell membrane Central pair Outer doublet Dynein Microtu bule doublet Spoke The motor protein Dynein “walks” along the microtubules within the flagella on one side, causing bending Figure 7.23 A comparison of the beating of flagella and cilia Plant cells are surrounded by cell walls made of cellulose Plasmodesmata connect adjacent plant cells Animal cells are connected through Intercellular junctions Review of an animal cell (centrioles) Review of a plant cell