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University of Waterloo
BIOL 120
Simon Cheung

Lecture 2 Plants are totipotent  Plants cells have the ability to change from one cell type to another and even develop into a whole plant - Totipotency  Plant cells can differentiate into another cell types  Eg. Photosynthetic cells of the leaf have the ability to dedifferentiate into other cell types Chloroplasts:  Contain a pigment called chlorophyll and are the site of photosynthesis  Larger than mitochondria by 5x or more  Cells can have one to several hundred chloroplasts  Have two outer membranes and circular chomosome  Have series of internal membrane-bound sacs called thylakoids Plastids:  Plants organelles that make or store food or pigments  Chloroplast is a type of plastid  Leucoplasts lack pigment giving it a white colour - amyloplasts, elaioplasts, proteinoplasts  Chromoplasts are pigmented and are responsible for the coloration in leaves, flowers, and fruits  Plastids are versatile and can change from one type to another like cells Vacuoles:  90% by volume of a plant is occupied by the central vacuole  Vaccus means empty  Central vacuoles does not have any contents and plays an important role in metabolism  Site for sequestering toxic compounds, break down of large macromolecules  Helps maintain cell shape  Surrounded by a membrane called tonoplast Cytoskeleton:  Gives cell its shape  Helps with organelles anchoring and cargo movement Lecture 2  Network of thread-like proteins found throughout the cytosol (fluid part of the cytoplasm)  Three main components:  Microtubules:  Long hollow tubes that move cell components such as chromosomes, organelles and molecules  Moves cells or multicellular organisms through water  Made up of α and β tubulin proteins  May vary in length from 200-150,00 nm depending on function  Stocked in 13 rows to form an α helix  Form a hollow structure  Are part of appendages involved in cell motility - flagellum and cilium  Flagellum and cilium - axoneme 9+2  Microfilaments:  Made of actin filaments  Organized into helical chains twisted around each others  Mediates cell shape and changes in association with other molecules  Move cell contents around central vacuole - cytoplasmic streamig/cyclosis  Intermediate filaments:  Made up of several types of linear proteins combined  Thinner than microtubules  Role in plant cells not well defined  Hold the nucleus in position and control nuclear shape - nuclear lamins Motor proteins  AKA walking molecules  Associated with microtubules and microfilaments  ATP-dependent movement process  Microtubules and microfilaments provide tracks that guide these molecules/organelles to their destinations Lecture 2  Attach to the structure to be moved (transport vesicles from ER to golgi or two microtubules moving relative to each other)  Many types of movement are dependent upon walking molecules  Legs of these proteins move, release, reattach and move again using ATP Cell membranes  Barrier regulating material that enters and leaves the cell  Phospholipid
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