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44 Cards in this Set
- Front
- Back
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Nuclear Envelope
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-double membrane-inner/outer
-lipid bilayer -encloses nucleus |
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Nuclear Pores
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-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 |
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Nucleus
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-largest organelle in cell
-houses chromatin/DNA -enclosed by nuclear envelope |
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Nucleolus
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-electron dense circular structure within the nucleus
-site of a particular type of RNA synthesis (ribozomal) -efficient |
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Nuclear Lamina
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-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 |
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Nuclear Matrix
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-Within nucleoplasm
-Skeleton of the entire volume of nucleus -Made of proteins |
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Nuclear transport
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-passive diffusion-small molecules
-energy-dependent transport- RNA and proteins -size restriction through nuclear pore |
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Nuclear localization signal (NLS)
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-sequence of amino acids-zip code
-tantigen, nucleoplasmin -located in tail of protein -marks them for transport through nuclear pore complex |
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Importins/Transport
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-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 |
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Exportins
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-shuttle proteins
-need nuclear export signal (NES) -highly regulated and energy demanding -export of RNA, RNP, ribosomal subunits |
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Chromatin
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-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 |
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Heterochromatin
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-more condensed chromosomal state-has more color
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Euchromatin
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-not as condensed chromosome
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Nucleosome
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8 subunits, different types of histones- forms alpha helices
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Actin Filaments (Microfilaments)
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-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 |
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Intermediate Filaments
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-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 |
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Microtubules
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-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 |
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Microtubule organizing center (MTOC)
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-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 |
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Motor Proteins
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-help move organelles through the cell
-kinesin/dynein mediated transport -converts chemical energy in ATP into mechanical work -travels along microtubules |
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Myosin
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-ATP powered interaction with actin filaments
-head attaches to actin and moves, the actin filaments slide -involved in cell crawling |
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Axonal Transport
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inward/outward transport of organelles-microtubules based
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Cilia
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-Short filamentous projections found in eukaryotic cells
-ie. cells that line the respiratory tract |
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Flagella
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-Long, hairlike projections from the cell surface that function in movement
-eukaryotic flagella are constructed from microtubules -i.e. sperm cells |
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G1 Phase/G2 Phase
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-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 |
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S-phase
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-DNA Synthesis, chromosme replication
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M-phase
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Dividing phase
Functions: reproduction, repair, growth, development |
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Binary Fission
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-chromosomes attached to membrane
-Chromosome replicates -Contractile ring composed of FtsZ (bacterial equivalent of microtubule) fibers form between the two chromosomes |
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Interphase (Mitosis)
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After chromosome replication, each chromosome is composed of two sister chromatids. Centrosomes have replicated
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Prophase (Mitosis)
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Chromosomes condense, and mitotic spindle (made of microtubules) begins to form
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Centrosomes
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Microtubule-organizing centers responsible for mitotic spindle formation
-contain centrioles |
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Prometaphase (Mitosis)
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Nuclear envelope breaks down. Spindle fibers contact chromosomes at kinetochore.
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Metaphase (Mitosis)
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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
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Anaphase (Mitosis)
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Sister chromatids separate-ensures that each daughter cell receives the same complement of chromosomes. Chromosomes are pulled to opposite poles of the cell
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Telophase (Mitosis)
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The nuclear envelope re-forms, and the spindle apparatus disintegrates and chromosomes begin to decondense
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Cytokinesis
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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
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Plant cell division
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-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 |
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Early Prophase I (Meiosis)
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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
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Late Prophase I (Meiosis)
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Crossing over of non-sister chromatids (often multiple cross-overs between the same chromatids)-forms chiasma-DNA exchange
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Metaphase I (Meiosis)
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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
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Anaphase I (Meiosis)
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Homologs separate and begin to move to opposite sides of the cell
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Telophase I (Meiosis)/Cytokinesis
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Homologs finish moving to opposite sides of the cell- then cell divides
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Meiosis II
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-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) |
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What makes meiosis unique?
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-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 |
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Nondisjunction
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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 |
