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143 Cards in this Set
- Front
- Back
How do cells cling to eachother?
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Through direct cell-cell interactions
Bound by extracellular materials that they secrete |
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What is adhesion?
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The ability of cells to cling or stick to their surroundings
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What is one of the controlling aspects of cellular architecture (shape, strength, and arrangement)?
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The mechanisms of cell adhesion
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What are two building strategies of multicellular structures?
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1) The strength of the extracellular matrix
2) The strength of the cytoskeletal filaments and cell-cell adhesions |
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What type of tissue is an example of the building strategy that relies on the strength of the extracellular matrix?
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Connective Tissue
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What type of tissue is an example of the building strategy that relies on the strength of the cytoskeletal filaments and cell-cell adhesions?
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Epithelial tissue
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What are epithelia?
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Sheets of closely bound cells, found in epithelial tissues
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What is the extracellular matrix of epithelial tissue?
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Basal Lamina
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What is the extra cellular matrix Composed of?
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A network of proteins and polysaccharides
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How thick is the basal lamina?
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40-120nm thick
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What types of cells do the basal lamina Surround?
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epithelial, fat, muscle, Schwann Cells
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Does the basal lamina have more than just structural support?
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yes
In Kidney glomerulus the basal lamina provides a filtering function |
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What are four functions of the basal lamina?
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Structural Support
Filtering Determines cell Polarity Promotes cell survival |
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What is the composition of the basal lamina?
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Laminin, Type IV Collagen, nidogen, perlecan
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What are the two linkers in the basal lamina?
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nidogen & perlecan
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what is the predominant cell type in the extracellular matrix?
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fibroblasts
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What does the Extracellular matrix influence?
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Cell survival
Cell division Cell migration Cell shape Cell function |
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What are fibroblasts found in bone?
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Osteoblasts
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what are fibroblasts found in cartilage?
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Chondroblasts
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What is the main function of GAG's?
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To resist compression and serve as a space filler
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What does Hyaluronan do in the extracellular matrix?
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Acts as a space filler and facilitates cell migration
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What are three glycoproteins found in the extracellular matrix?
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Collagens
Fibronectin Elastin |
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What are physical attachments between cells or between cells and the extracellular matrix?
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Junctions (or Adhesions)
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What are three classes of cell junctions in animal tissues?
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Anchoring Junctions
Occluding Junctions Channel-Forming Junctions (Gap Junctions) |
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What type of junctions are both cell-cell and cell-extracellular matrix adhesions, linked with cytoskeleton and transmit stresses?
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Anchoring Junctions
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What types of junctions seal the gaps between cells in the epithelia, which also make the epithelial sheet impermeable to outside molecules?
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Occluding Junctions
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What types of junctions create passageways that link the cytoplasm of adjacent cells and allow passage of small molecules and ions from cell to cell?
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Channel-forming junctions or Gap Junctions
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What are the two types of anchoring junctions?
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Those linked to the actin cytoskeleton
Those linked to intermediate filaments |
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What are desmosomes?
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Cell to cell adhering junctions associated with intermediate filaments
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What are hemidesmosomes?
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Cell to Matrix junctions associated with intermediate filaments
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What are adherin junctions?
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Cell to cell junctions associated with the actin cytoskeleton
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What links the cytoskeleton to extracellular structures in anchoring junctions?
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Transmembrane adhesion proteins
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What are the proteins that mediate attachment of cell to cell?
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Cadherin
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What are the proteins that mediate attachment of cells to the matrix?
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Integrin
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What do cadherins depend on?
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Calcium Ions
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What happens to cadherins when Ca is removed from the extracellular medium?
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They come adrift
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What is the process whereby cells are joined by cell-cell junctions so that the outer surface of the embryo becomes smoother?
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Compaction
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What type of binding occurs between cadherins?
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Homophillic
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What is homophillic binding between cadherins?
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Specific cadherin molecules of one subtype bind to cadherin molecules of the same subtype on adjacent cells
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How do cells of different types not bind with cadherin proteins?
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Cadherins mediate highly selective recognition
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Where does the interaction between two cadherin molecules occur?
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At the N-terminal tips
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How does calcium regulate the cadherin function?
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Calcium allows the protein to remain rigid. Without calcium ions, the protein would become floppy.
The lack of calcium binding also destabilizes the protein |
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What do attached cadherin proteins function like?
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Velcro
They are strongly joined but also easily peeled apart |
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What does the linkage of cadherin to the cytoskeleton depend on?
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Accessory Anchor Proteins
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What connects actin bundles via cadherins from cell to cell across the epithelium?
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The Adhesion Belt
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What can help an actin network of the adhesion belt to contract?
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Myosin Motor Proteins
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What does the desmosome connect cell-cell?
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Intermediate filaments
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What is the main function of desmosomes?
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To provide mechanical strength
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What do the cadherins of the desmosome bind to in the cell?
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A dense plaque of intracellular anchor proteins
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What proteins are used for linkage in the hemidesmosome?
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Integrin Proteins
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What is another term for occluding junctions?
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Tight Junctions
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What are two functions of occluding junctions (tight junctions)
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To seal the gaps between the cells
Act as fences to separate domains within the plasma membrane of each cell which maintains polarity of individual cells. |
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What junctions play a role in the transport of glucose in epithelial cells?
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Tight Junctions
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How do tight junctions help regulate the transfer of glucose in epithelial cells?
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They confine glucose transport proteins to their appropriate membrane domains
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What are the proteins that form the tight junction?
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Claudins and Occludins
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What protein complexes are associated with gap junctions?
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Connexons
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What are connexins?
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Four-pass transmembrane proteins, a group of six forms a hemichannel or connexon.
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What are two functions of gap junctions?
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Allows action potentials to spread rapidly from cell to cell
Allows neighboring cells to share signaling information and act in a coordinated way. |
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How are gap-junction channels similar to ion channels?
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They do not remain continuously open, but flip between open and closed states by extracellular signals
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How thick are actin microfilaments?
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7nm in diameter
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What is the basic subunity of actin microfilaments?
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Globular actin (G-Actin)
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Where can actin filaments generally be found?
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Microvilli
Stress Fibers Lamellipodia, Filopodia Contractile Ring |
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How are actin filaments polymerized?
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Actin with bound ATP joins to the strand at one end
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How is actin filament's behavior modified?
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Through Actin Binding Proteins
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What proteins influence nucleation of the actin filament?
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Actin-Related Proteins (Arp complex)
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On what end is the actin filament nucleated by the Arp complex?
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The negative end
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What protein influences bundling of actin filaments?
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Myosin II
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What are the proteins that influence non-contractile bundling and sheets?
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Arp 2/3 Complex (lamellipodia)
Villin (microvilli) |
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What protein influences actin molecular motors?
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Myosin I
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What are the functions of Myosin I?
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Membrane Trafficking
Cell Motility Cytokinesis Organelle Transport |
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Where is Myosin II generally located?
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Skeletal Muscle
Smooth Muscle Nonmuscle |
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What is tensegrity?
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Tensional integrity by a self-stabilizing architectural system.
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What is a structure with the highest ratio of enclosed area to external surface area and in which all structural members are equal contributors to the whole?
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Geodesic Dome
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How do the viscoelastic materials help a cell?
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It absorbs stress energy in the bonds of polymeric molecules and deformation occurs according to the viscosity. Removal of stress produces a slow return to original shape.
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What are the results of a mechanical force on a viscoelastic substance?
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An initial resistance
Slow deformation Slow return to original form after removal of force |
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Start @ L-21
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Page 7
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What are the three subphases of interphase?
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G1
S G2 |
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What is an essential prerequisite for cell division?
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DNA replication
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What occurs during G1?
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Cell Growth
Gene Transcription Protein Synthesis DNA Repair Monitors/Responds to External Stimuli Organelles Divide |
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What phase is the extended resting state?
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G0 Phase
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What cells remain permanently in G0 state?
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Nerve Cells, Skeletal Muscle Cells, etc
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What occurs during the S Phase?
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DNA replication
Centrosome Replication |
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What occurs during the G2 phase?
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Cell Growth Similar to G1
Preparations for M Phase (Checkpoints) |
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What are the five subphases of M phase?
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Prophase
Prometaphase Metaphase Anaphase Telophase |
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What is the term for the cytoplasm dividing in two?
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Cytokinesis
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What occurs in prophase?
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Replicated chromosomes condense
Sister Chromatids are joined together by cohesin Mitotic Spindle starts to assemble Centrosomes separate Kinetochores form on Centromere Region |
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What protein aids the condensing of DNA in prophase?
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Condensin
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How does condensin aid in condensing DNA chromatids?
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Condensin forms ring like structures to help coil the mitotic chromatids into smaller more compact structures
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What holds the sister chromatids together?
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Cohesin
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When do cohesins assemble on the sister chromatid?
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In the S Phase
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What stabilizes the microtubules?
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The interaction of the microtubules from one centrosome to the microtubules of the other centrosome
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What are the two centrosomes called after forming the mitotic spindle?
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Spindle Poles
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What do the kinetochores attach the chromosomes to?
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The Mitotic Spindle
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When do kinetochore microtubules attach to the kinetochore?
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Prometaphase
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What occurs at prometaphase?
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Breakdown of the nuclear envelope
Attachment of spindle microtubules through their kinetochores |
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What aids in the disassembly of lamina for the breakdown of the nuclear envelope?
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The phosphorylation by mitosis promoting factor
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What occurs during Metaphase?
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Kinetochore microtubules attach to opposite poles of the spindle.
Chromosomes align at the equator of the spindle, the metaphase plate |
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What are the three populations of spindle microtubules?
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Kinetochore, Interpolar, and Astral
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What do the interpolar microtubules attach to?
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Other interpolar microtubules of the other centrosome
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What do the Astral microtubules attach to?
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Nothing
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What occurs during anaphase?
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Sister chromatids separate toward the spindle poles
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What triggers the separation of sister chromatids by promoting the destruction of cohesins?
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Anaphase Promoting Complex (APC)
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How does APC promote the destruction of cohesin?
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It catalyzes the destruction of securin, which inhibits separase. With the destruction of securin, separase is free to cleave the cohesin complexes.
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What are the two types of movement during Anaphase?
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Anaphase A
Anaphase B |
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What type of movement is characteristic of the movement of chromosomes toward poles by depolymerization of kinetochore microtubules and action of motors?
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Anaphase A
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What does Anaphase B move?
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Moves the poles apart by the elongation of interpolar microtubules and the action of motors on interpolar and astral microtubules
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What occurs during telophase?
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Kinetochore microtubules depolymerize
Interpolar microtubules elongate further and continue to push Nuclear envelope reforms Condensed chromatin expands Contractile ring forms, identifying the plane of division |
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How is does the nuclear envelope reform during telophase?
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The nuclear pore proteins and nuclear lamins are dephosphorylated
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What occurs during Cytokinesis?
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Cytoplasm is divided in two by contractile ring
Tightening of ring produces cleavage furrow. Reformation of interphase cytoplasmic microtubules M phase ends --> Cell Enters G1 Phase |
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What triggers the major processes of the cell cycle?
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The Cell Cycle Control System
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What determines whether or not the cell proceeds to the next phase of the cycle?
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Checkpoints
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What does the G1 checkpoint check for before entering the S Phase?
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A favorable environment
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What does the G2 checkpoint check for before entering Mitosis?
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DNA is replicated
All DNA damage repaired |
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What does the Mitosis checkpoint check for before pulling the duplicated chromosomes apart?
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The chromosomes are properly attached to the mitotic spindle
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What are the two key families of proteins that control the cell cycle?
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Cyclins
Cyclin-Dependent Protein Kinases (CDKs) |
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What are cyclins?
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Regulatory subunits of the cyclin-dependent protein kinases
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What are cyclin-dependent protein kinases?
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Kinases involved in the initiating and sustaining events of the cell cycle
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What activates a Cdk?
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Cyclin
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Is cyclin or Cdk variable in the cell?
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Cyclin levels rise and fall with the states of the cell cycle
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When is Cdk activity low?
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Interphase
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What are the four major types of cyclin-cdk complexes?
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G1
G1/S S M |
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What must occur for a Cdk complex to be active?
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It must first be phosphorylated by protein kinases, then two of those inhibitory phosphates must be removed by the activating protein phosphatase.
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What is the G1-Cdk activation induced by?
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Growth Factors, Hormones, Oncogenes (Ras)
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What does the G1-Cdk complex help with?
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Helps to drive the cell through G1 toward S
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What does the G1/S-Cdk trigger?
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Triggers entry into S phase
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What does S-Cdk activate?
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The origins of replication leading to DNA replication
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How does S-Cdk begin the replication process and only allow it to be replicated once?
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It causes pre-replicative complex to bind to the origin of replication
S-Cdk triggers the degredation of phosphorylated Cdc6 |
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What does damaged DNA activate?
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p53 protein
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What does p53 protein bound to DNA stimulate?
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Transcription of Cdk inhibitor protein p21
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How can DNA damage arrest the cell in the cell cycle?
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By the creation of the p21 inhibitor protein that binds to G1/S-Cdk and S-Cdk to inactivate them.
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What is cell death?
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Apoptosis
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What phosphorylates the M-cyclin-Cdk complex at one site?
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Cdk-Activating kinase
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What phosphorylates M-Cdk complex at two sites to inhibit its activity?
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Wee1
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What activates the M-Cdk complex after all of the phosphorylation events?
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Cdk-activating phosphatase
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What causes an explosive increase in M-Cdk activity?
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Activated M-Cdk indirectly activates more M-Cdk in a positive feedback loop
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What regulates the abundance of cyclins?
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Protein Degredation by Proteasomes through Ubiquitin Marking
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The removal of webbing between fingers and toes during development is due to what cellular process?
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Apoptosis
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What are the steps of apoptosis?
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Cell Shrinks and Chromatin Condenses
Cytoskeleton collapses Nuclear envelope and other organelle membrane disassemble DNA breaks up into fragments Alteration in cell surface and cell fragmenting Phagocytic cells (macrophages) clean up before cell lysis - avoids cell necrosis |
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What is the machinery responsible for apoptosis?
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Caspase Family of Proteases
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What are procaspases?
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Inactive precursors of caspase proteases
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How are procaspases activated?
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Proteolytic cleavage in response to extracellular and intracellular signals
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What do most apoptotic pathways target?
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Mitochondria
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What molecule from the mitochondria binds to an adaptor and ATP to cleave procaspase?
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Cytochrome C
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