Day 2, Lecture 1: Fundamentals of Cell Biology, Part 1 Flashcards Preview

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Flashcards in Day 2, Lecture 1: Fundamentals of Cell Biology, Part 1 Deck (43):
1

Plasma Membrane 

  • Barrier between cytoplasm and extracellular environment
  • Composed of Lipids, proteins and carbohydrates
  • Lipid Bilayer 
    • continuous double layer of lipids approximately 5nm thick. The lipid composition provides an impermeable barrier to the passage of water-soluble molecules 

2

Cytoskeleton

 

  • Network of protein filaments that that extends throughout the cytoplasm of eukaryotic cells and has roles in:
    • Cell movement
    • Support an strength for cell
    • Phagocytosis and cytokinesis 
    • Cell-Cell and Cell-matrix attachment
    • Changes in cell shape
  • Composed of three major types of protein filaments
    • Microfilaments (actin filaments) 
    • Microtubules 
    • Intermediate filaments

3

Cytoplasm

  • Cytosol
    • site of protein synthesis 
  • Cytoskeleton
  • Cytoplasmic organelles suspended in cytosol 

4

membrane proteins

  • Proteins can act as sensors (receptors) of external signals, or can serve as structural links that connect the plasma membrane ot the cytoskeleton or to the extracellular matrix 
  • Carry out specific funcitons of plasma membrane 
  • Integral membrane proteins
    1. Transmembrane proteins
      • hydrophobic portions of the protein pass through the lipid bilayer (while hydrophilic regions are located on either surface of the membrane). These proteins may be covalently anchored to the plasma membrane via insertion of a lipid bilayer 
    2. Membrane surface proteins
      • Proteins are associated only with the internal or external surface of the plasma membrane, and are anchored to the plasma membrane via insertion of a lipid side chain into the lipid bilayer 
  • Peripheral memebrane proteins 
    • are bound by noncovalent interactions with other membrane proteins 

5

Connexon

A hexigonal array of connexins that form a pore with a diameter of 1nm for intercellular-communication 

6

Microtubules 

  • Long, rigid, Hollow cylinders made of the protein tubulin
  • Polymerization and depolymerization of tubulin controls the movement of transport vesicle and other organelles 
  • originate at the centrosome (microtuble organizing center) 
  • outer diameter of 25nm

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Microfilaments (actin filaments) 

 

  • flexible, Double-stranded helical polymers of actin
  • Involved in cell movements , especially near the cell surface
  • Diameter 5-9 nm 

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Tubulin 

is a protein that polymerizes into microtubules 

9

Intermediate filaments

  • Intermediate in size between microfiaments and microtubules 
  • Ropelike fibers that provide structural support and cell attachment sites 
  • Ex
    • keratin
    • vimentin
    • desmin
    • GFAP
    • Nuclear lamins

10

cell junctions

 

  • Specialized proteins that provide
    • cell-to-cell adhesion
    • communication
    •  cell-to-matrix adhesion
    • Cellular polarity
    • Barrier capabilities
  • Juncitonal complex
    • Zonula occludens (tight junction)
    • Zonula adherens (belt desmosome)
    • Macula adherens (desmosomes) 
    • Gap junctions
    • Hemidesmosome

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microvilli

  • non-motile, about 1 micron long
  • comprised of core of actin 
  • Increase absorptive surface area 
  • composed of a core of actin filaments
  • Major Locations:
    • Intestinal Tract and Kidney Tubules 

12

cilia

  • Motile processes on apical surface
  • about 10 microns long
  • Coordinated movement aids luminal transport of materials
  • 9+2 arrangement of microtubules forms core complex of axoneme
    • Radial spokes and connecting structures stabilize the axoneme
  • lines the apical surface fo respiratory and reproductive epithelium 

13

stereocillia

  • Ultrastructurally identical to microvilli
  • Approximately 20-50 microns in length
  • Absorptive function (e.g. Epididymis of male reproductive tract) 

14

gap junction

  • intercellular communication
    • allows the passage of small water-soluble ions and molecules 
    • Results in electrical and metabolic coupling 
    • Cooridinates activities 
      • Ex. 
        • Peristalsis
        • heart contractions
        • cilia movement
  • formed by integral membrane proteins connexins coming together to form a hexagonal array (called connexons). Thes register with pores in the apposing membrane
    • allow rapid flow of small molecules (

15

desmosomes (macula adherens)

  • Intercellular adhesion via "spot" attachements) 
  • Plaque-like adhesions of 500nm diameter, restricted to epithelial cells and a few others
  • Apposed membranes separated by gap of 20-35 nm
  • Dense cytoplasmic plaque beneath plasma membrane associated with cytoplasmic keratin intermediate filaments (tonofilaments) and various cadherin proteins) 
    • Complementary cadherin proteins attach to each other extracellularly, and to protein plaques intracellularly 

16

tight junction (zonula occludens)

  • Widely distribulted in all tissues but especially abundant in epithelium
  • located just basolateral to the apical membrane
  • Provides paracellular barrier 
    • forms a tight, circumferential seal between lateral membranes of epithelial cells occluding the passage of macromolecules and electrolytes between cells 
    • prevents vectorial movement of membrane proteins and lipids from apical to lateral membranes 
  • complementary transmembrane proteins (e.g. occludin and claudins) attach to each other extracellularly 

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zonula adherens (belt desomosome) 

  • Mechanical attachment between neighboring cells 
  • provides mechanical adhesion between cells 
  • widely distributed in all cells but generally found as part of the junctional complex of polarized epithelial cells 
  • located basolateral relative to the tight junction
  • Transmembrane Cadherin proteins attach to each other extracellularly 
    • Attach to cytoplasmic proteins anchored to filamentous actin 

18

hemidesmosome

  • Anchors intermediate filaments in a cell to the basal lamina
  • (note Bullous pemphigoid , a blistering skin disease is due to production of autoantibodies to protein in plaque of hemidesmosomes

19

nucleus

  • Site of DNA and RNA synthesis 

20

nucleolus

  • Site of ribosomal RNA synthesis and initial pre-ribosomal assembly 
  • Contains multiple loops of DNA encoding rRNA genes 

21

nuclear envelope

  • Encloses the Nucleus
  • Composed of two phospholipid bilayers
  • Outer membrane continous with ER
  • Inner and outer nuclear membrane with perinuclear space between membranes
  • Nuclear lamina of intermediate filaments underlying inner membrane
  • Phosphorylation and de-phosphorylation of nuclear lamins regulate disassembly of nuclear envelope during cell division 

22

nuclear pores

  • Bi-directional transport of proteins and RNA occurs via gated transport through nuclear pores 
  • outer and inner nuclear membranes fuse in places to form nuclear pores 
  • Cytosolic nuclear import receptors bind to prospective nuclear protein
    • Requires nuclear localization signal (7a.a)

23

mitochondria

  • Generates ATP for energy

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rough endoplasmic retiulum

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smooth endoplasmic reticulum 

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lysosome

  • Formed by vesicle fusion of endosomes and transport vesicles from the Golgi Apparatus 
  • function:
    • controlled degradation of intracellular macromolecules
  • Unique phospholipids and glycosylation of membrane proteins protect membrane from enzymatic degradation 

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endosome

  • Protein and membrane trafficking

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peroxisome 

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Golgi apparatus

  • Transport vesicles bud off from one compartment and fuse with another
  • Intramembranous and soluble (cytosolic) proteins and the lipid portions of membranes are transported from the RER to the Golgi apparatus by vesicular transport 
  • Post-Translational modifications occur in the lumen of the Golgi Apparatus
    • Note that specific modifications occur in specific subcompartments, because localization of modifying enzyme is tightly controlled
    • More than 200 different proteins participate 

30

endocytosis 

31

exocytosis 

32

The centrosome is composed of 

  • Paired centrioles located near center of the cell
  • Nucleates polymerization of tubulin into microtubles 
  • duplicates once every cell cycle

 

33

what is the site of origin of basal bodies of cilia

Centrosome

34

____ anchors cilia microtubules 

Basal bodies (note that basal bodies have a triplet formation while cilia have a doublet) 

35

what regulates the disassembly and reassembly of nuclear envelope during cell division?

Phosphorylation and de-phosphorylation of nuclear lamins 

36

A lightly stained nucleus is an indication of what

Cancer cells: large, light nuclei 

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Secretory Granules

contents released by exocytosis upon hormonal or neuronal stimulation

41

Macrophages contain numerous____ for the controlled intracellular degradation of phagocytized macromolecules

Lysosomes

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