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44 Cards in this Set

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Nuclear Envelope
-double membrane-inner/outer
-lipid bilayer
-encloses nucleus
Nuclear Pores
-openings in the nuclear envelope
-connect inside of nucleus with the cytoplasm and acts as a transport mechanism acros nuclear envelope
-consists of over 50 proteins (delicate)
-forms nuclear pore complex
Nucleus
-largest organelle in cell
-houses chromatin/DNA
-enclosed by nuclear envelope
Nucleolus
-electron dense circular structure within the nucleus
-site of a particular type of RNA synthesis (ribozomal)
-efficient
Nuclear Lamina
-basket of fibrous proteins-form lattice-like sheet
-boundary inside the nuclear envelope
-used for structural support-stiffens the envelope and helps organize the chromosomes
Nuclear Matrix
-Within nucleoplasm
-Skeleton of the entire volume of nucleus
-Made of proteins
Nuclear transport
-passive diffusion-small molecules
-energy-dependent transport- RNA and proteins
-size restriction through nuclear pore
Nuclear localization signal (NLS)
-sequence of amino acids-zip code
-tantigen, nucleoplasmin
-located in tail of protein
-marks them for transport through nuclear pore complex
Importins/Transport
-binds to NLS containing protein
-protein-importin complex enters nucleus and binds to Ran-GTP
-protein dissociates-forced by conformational change
-Importin + Ran-GTP complex moves to cytoplasm
-GTP is hydrolied to GDP; importin dissociates
Exportins
-shuttle proteins
-need nuclear export signal (NES)
-highly regulated and energy demanding
-export of RNA, RNP, ribosomal subunits
Chromatin
-Beads on a string, fibers, chromosomes-different ways chromatin is structured/packaged
-protein scaffold combined w/ DNA loops to form chromatin
-DNA that is tightly complexed with a series of ball-shaped histone proteins
Heterochromatin
-more condensed chromosomal state-has more color
Euchromatin
-not as condensed chromosome
Nucleosome
8 subunits, different types of histones- forms alpha helices
Actin Filaments (Microfilaments)
-long fibrous structures made of a globular protein called actin
-found underneath plasma membrane cortex
-rigid-but cannot withstand force
-distinct polarity- plus/minus ends
-strands in double helix
Functions: maintain cell shape by resisting tension, motility via muscle contraction or cell crawling, cell division in animals, movement of organelles and cytoplasm in plants, fungi, and animals
Intermediate Filaments
-Protein subunits: keratin, vimentin, lamin
-fibers wound into thicker cables
-Functions: maintain cell shape by resisting tension, anchors nucleus and some other organelles
-not polar
-commonly found in the skin
Microtubules
-composed of alpha and beta tubulin arranged in a hollow tube
-Functions: maintain cell shape by resisting compression, motility via flagella or cilia, formation of cell plate during plant cell division, move organelles, growth of plant cell walls
-distinct polarity
-constantly growing and shrinking
Microtubule organizing center (MTOC)
-centrosome made up of 2 centrioles
-on top of nuclear envelope
-centrioles provide template for microtubules-help organze
-controls # of microtubules, assembly, and location in the cell
Motor Proteins
-help move organelles through the cell
-kinesin/dynein mediated transport
-converts chemical energy in ATP into mechanical work
-travels along microtubules
Myosin
-ATP powered interaction with actin filaments
-head attaches to actin and moves, the actin filaments slide
-involved in cell crawling
Axonal Transport
inward/outward transport of organelles-microtubules based
Cilia
-Short filamentous projections found in eukaryotic cells
-ie. cells that line the respiratory tract
Flagella
-Long, hairlike projections from the cell surface that function in movement
-eukaryotic flagella are constructed from microtubules
-i.e. sperm cells
G1 Phase/G2 Phase
-G1= gap between M-phase and S-phase
-G2= gap between S-phase and M-phase
-Cell grows and syntheizes organelles during this time
-G1 phase-cells perform normal functions
S-phase
-DNA Synthesis, chromosme replication
M-phase
Dividing phase
Functions: reproduction, repair, growth, development
Binary Fission
-chromosomes attached to membrane
-Chromosome replicates
-Contractile ring composed of FtsZ (bacterial equivalent of microtubule) fibers form between the two chromosomes
Interphase (Mitosis)
After chromosome replication, each chromosome is composed of two sister chromatids. Centrosomes have replicated
Prophase (Mitosis)
Chromosomes condense, and mitotic spindle (made of microtubules) begins to form
Centrosomes
Microtubule-organizing centers responsible for mitotic spindle formation
-contain centrioles
Prometaphase (Mitosis)
Nuclear envelope breaks down. Spindle fibers contact chromosomes at kinetochore.
Metaphase (Mitosis)
Chromosomes complete migration to the middle of the cell. Chromosomes are lined up on the metaphase plate. Each chromatid is attached to spindle fibers that run from its kinetochore to one of the two poles of the cell
Anaphase (Mitosis)
Sister chromatids separate-ensures that each daughter cell receives the same complement of chromosomes. Chromosomes are pulled to opposite poles of the cell
Telophase (Mitosis)
The nuclear envelope re-forms, and the spindle apparatus disintegrates and chromosomes begin to decondense
Cytokinesis
Cytoplasm is divided-formation of a cleavage furrow- appears bc a ring of actin and myosin filaments forms just inside of the plasma membrane in a plane that bisects the cell
Plant cell division
-No furrow-laying down of new cell wall
-Phragmoplasts-helps create new cell wall-microtubular based-gets membranes from golgi-derived vesicles
-helps cell plate grow- no actin filaments/myosin motor
Early Prophase I (Meiosis)
Chromosomes condense, nuclear envelope breaks up, spindle apparatus forms. Synapsis of homologous chromosomes- forms a tetrad-non sister chromatids, set of proteins b/w chromosomes
Late Prophase I (Meiosis)
Crossing over of non-sister chromatids (often multiple cross-overs between the same chromatids)-forms chiasma-DNA exchange
Metaphase I (Meiosis)
Tetrads migrate to metaphase plate- each tetrad moves to the metaphase plate independently of the other tetrads- alignment of maternal and paternal homologs from each chromosome is random
Anaphase I (Meiosis)
Homologs separate and begin to move to opposite sides of the cell
Telophase I (Meiosis)/Cytokinesis
Homologs finish moving to opposite sides of the cell- then cell divides
Meiosis II
-Begining.. each chromosome still consists of two identical sister chromatids but only one member of each homologous pair is present so the cell is haploid
-Results in a total of 4 daughter cells (haploid)
What makes meiosis unique?
-Independent assortment of maternal and paternal homologs during meiotic division I 2^n possibilities
-Crossing over during meiotic prophase I-genetic recombination
-Fertilization
-Thus- reproductive diversity
Nondisjunction
Meiosis I starts normally, but one set of homologs does not separate
-thus all gametes have an abnormal # of chromosomes-(n+1, n-1)
Chromosome 21-prone to nondisjunction-leads to down syndrome
-many meiotic errors not viable-leads to miscarriages