Cell Types, Tissues, and Interactions

Question 1

Epithelial/Epithelial

Answer 1

Tightly joined cells, free surface, function as selective barriers.

Question 2

Simple Epithelium

Answer 2

Simple squamous is flat and spread out, things pass through easily. Lungs have a lot. Simple cuboidal and columnar is regularly spaced out. Single layer.

Question 3

Stratified Epithelium

Answer 3

Stratified squamous and cuboidal. Multiple layers.

Question 4

Pseudo-stratified Epithelium

Answer 4

Pseduostratified columnar. Appears to be stratified but instead consists of a single layer of irregularly shaped and differently sized columnar cells

Question 5

Squamous Epithelium

Answer 5

Large flattened cell with abundant cytoplasm and small round central nucleus

Question 6

Cuboidal Epithelium

Answer 6

Made of cube-shaped cells.

Question 7

Columnar Epithelium

Answer 7

Tall and are arranged like columns.

Question 8

Mesenchyme/Mesenchymal

Answer 8

Loosely organized, mainly mesodermal embryonic tissue which develops into connective and skeletal tissues, including blood and lymph.

Question 9

Connective Tissue

Answer 9

Cells loosely packed, complex extracellular matrix fills space between cells, provides mechanical strength and cushioning.

Question 10

Adherens Junctions

Answer 10

Cell-cell anchoring junctions. Classical cadherins link to actin skeleton. Catenin-family proteins link cadherins at adherents junctions. Actin filaments attach intracellularly. Membrane protrusions initiate cell contact and chagrin and catenin are recruited so that actin and chagrin expands junction. Then, actin remodeling and myosin recruitment expands junction and contraction makes it strong.

Question 11

Desmosomes

Answer 11

Cell-cell anchoring junctions. Non-classical cadherins, like desmoglein and desmocollin, that connect to desmoplakin and plakoglobin (dense plaque of adaptor proteins) linked to intermediate filaments (keratin). Non-classical cadherins: Desmoglein, desmocollin –> Adaptor Plate: Desmoplankin Plankoglobin –> Intermediate Filaments

Question 12

Gap Junctions

Answer 12

Connect cytoplasm. Form connections for small molecule transfer. Anything about 1 kDA can’t get through. Nucleotides, water, ions can get through. Six connections for one connexion. Two connexions form one gap junction. Not all gap junctions have the same permeability.

Question 13

Tight Junctions

Answer 13

Form boundaries for plasma membrane factors and luminal molecules. Form sealing strands that make a permeability barrier. Bring membrane as tight as possible. Lateral binding between claudins(structure) and occludins(permeability) form tight junctions. It seals the apical(top) of cells together.

Question 14

Cadherins

Answer 14

Transmembrane protein capable of binding both outside and inside the cell. Serve as an extracellular connection point between two cells. Mediate Ca2+ dependent, homotypic interactions. Calcium binds to flexible hinge region which reduces flexibility of hinge region so that N-terminal domains can lock-key (like-like) bind.

Question 15

Avidity v. Affinity

Answer 15

Allows cadherins to work like velcro. Avidity (functional affinity) is the accumulated strength of multiple affinities. Important because you want the tissue/cell dynamic strong but not so strong you can’t take them apart.

Question 16

Alpha-catenin

Answer 16

Is initially folded. In presence of tension, the alpha-catenin is extended so that vinculin can bind. This then recruits more actin and more myosin II pulls on actin.

Question 17

Beta-catenin

Answer 17

β-catenin is a dual function protein, involved in regulation and coordination of cell–cell adhesion and gene transcription. Connects alpha-catenin to cytoplamic section of adherin. It is important in Wnt signaling pathway for transcription of Wnt target genes.

Question 18

Mechanosensor

Answer 18

A molecule that responds to mechanical stress by changing its conformation. They are auto-inhibited in solution and in the absence of tension. They have binding sites that become exposed under tension.

Question 19

Mechanotransuction

Answer 19

Mechanisms by which cells convert mechanical stimulus into electrochemical activity

Question 20

Focal adhesion and Hemidesmosome

Answer 20

Cell-matrix anchoring junctions at basal side.

Question 21

Extracellular Matrix

Answer 21

Secreted proteins and carbohydrates found in fibrous network that organizes cells into functional tissues and uses integrin transmembrane receptors. Functions: cell adhesion, migration, strength/shape, barrier, pathogenesis, reservoir for proteins.

Question 22

Apical

Answer 22

Top

Question 23

Basal

Answer 23

Bottom

Question 24

Fibrillar Glycoproteins

Answer 24

Carbs attached to proteins.

Question 25

Glycosaminoglycans (GAGs)

Answer 25

Long chain of repeating disaccharides. Negative charge that attracts sodium and water filling up space and cushioning. Hydrophilic! Come together to form protogycans.

Question 26

Basal Lamina (Basement Membrane)

Answer 26

Same name for basement membrane. Surface for epithelial cells to anchor. Barrier of invasion.

Question 27

Laminin

Answer 27

Part of Basal Body. Primary organizer of basal lamina structure. It has many binding domains that allow it to bind anywhere. It will self assemble into plate of proteins.

Question 28

Collagen IV

Answer 28

Part of Basal Body

Question 29

Perelecan

Answer 29

Part of Basal Body

Question 30

Nidogen

Answer 30

Part of Basal Body

Question 31

Interstitial Matrix

Answer 31

Same name for connective tissue. Provides strength, elasticity, resistance to compression, cell attachment and migration, and signal molecules to bind.

Question 32

Fibrillar Collagens

Answer 32

Provides strength in ECM. Triple stranded helix constructed outside of membrane.

Question 33

Elastin

Answer 33

Provides elasticity in ECM. Surrounded by fibrillin (provides scaffold for elastin to bind).

Question 34

Hyaluronan

Answer 34

Large GAG (Only one not bound to protein). It is BIG and provides cushioning and space. Constructed as it leaves membrane.

Question 35

Fibronectin

Answer 35

Connects cells to interstitial matrix. Have RGD site that binds integrin. Tension causes the fibronectin to form into fibers. Assembles into fibers at surface of cells.

Question 36

Hemidesmosome

Answer 36

Keratin –> BP230 –> Integrin –> collagen –> laminin –> collagen

Question 37

Focal Adhesion

Answer 37

Integrin –> talin –> actin + vinculin