Cell Biology (288)

Front 1

The ECM is...

Back 1

various types of connective tissue: bone, cartilage, adipose tissue, basal lamina

Front 2

The ECM consists of...

Back 2

fibres, ground substance and connective tissue.

Front 3

The ECM is necessary for... (6)

Back 3

1) structure and support
2) proliferation
3) migration
4) growth
5) differentiation
6) metabolic activity

Front 4

The basal lamina is...

Back 4

a specialized connective tissue made of dense, irregular connective tissue associated with the epithelial and endothelial layers.

Front 5

Types of fibres: (2)

Back 5

1) collagen (for structure)
2) elastin (for flexibility)

Front 6

Ground substance: (2)

Back 6

1) proteoglycans
2) glycosaminoglycans (GAGs)

Front 7

Adhesive glycoproteins: (2)

Back 7

1) fibronectins
2) laminins

Front 8

Collagens are...

Back 8

a large family of glycoproteins with high tensile strength. They are rich in glycine, proline, lycine, hydroxyproline, and hydroxylycine.

Front 9

Structure of collagens:

Back 9

X-gly-Y
(where X is proline or lycine, and Y is hydroxyproline or hydroxylycine).

Front 10

Two types of collagens (five subtypes):

Back 10

A) Fibrous
-Type I (90% of collagen in the body)
-Type II (cartilage)
-Type III (internal organs)
-Type V (???)
B) Lesser Abundance
-Type IV (epi- and endothelial tissue [basal lamina])

Front 11

How collagen is assembled:

Back 11

1) Assembly of procollagen in lumen of the ER
a) Precursor alpha-chains that form into
b) Triple helix procollagen trimers
2) Procollagen is secreted
3) Outside the cell, procollagen peptidase removes loose ends of the procollagen trimers to form tropocollagen
4) Tropocollagen forms into collagen fibrils
5) Fibrils assemble into fibres

Front 12

Elastin is...

Back 12

a long, hydrophobic protein, rich in glycine and proline, with some hydroxyproline but no hydroxylycine.

Front 13

Elastin is most commonly found in the...

Back 13

skin, arteries, lungs, aorta.

Front 14

A proteoglycan is...

Back 14

a heavily glycosylated protein (up to 95% carbohydrates) whose polysaccharides are long and unbridged. By definition, contains at least one GAG.

Front 15

A glycoprotein is...

Back 15

a glycosylated protein (1-60% carbohydrates) that contains short, bridged oligosaccharide chains attached to polypeptide side-chains.

Front 16

GAGs:

Back 16

Glycosaminoglycans-- long, unbranched polysaccharide chains made of repeating disaccharide units.

Front 17

A proteoglycan complex is...

Back 17

1) a core protein that is
2) covered by GAGs and
3) attached to hyaluronate or hyaluronic acid.
(1 and 2 together form a proteoglycan.)

Front 18

Fibronectin is...

Back 18

a dimeric protein of 2 polypeptide chains joined by 2 disulfide bonds. Each chain has multiple functional modules-- one is RGD, which links together things on cells and in ECM.

Front 19

Laminin is...

Back 19

beta-chain and gamma-chain formed in a helix around a linear alpha-chain to form a 3-stranded coiled coil.

Front 20

4 key molecules in cell-cell recognition and adhesion: (4)

Back 20

1) Selectins
2) Immunoglobulin Super Family members (IgSF)
3) Cadherins
4) Integrins

Front 21

Two types of cell signalling interactions (both inside-out signalling):

Back 21

1) Homotypic: identical molecules interacting (e.g. cadherin interactions)
2) Heterotypic: different molecules interacting (integrins and IgSFs)
IgSFs do both types.

Front 22

Selectins are...

Back 22

a family of single-pass transmembrane glycoproteins that use a Ca2+ binding site to bind to carbohydrate groups on glycolipids and glycoproteins to trigger an inside-out signal.

Front 23

What three kinds of selectins are used in immune system response?

Back 23

P-, L- and E-selectin (placental, leukocyte and endothelial)

Front 24

Three IgSF glycoproteins:

Back 24

N-CAM (neural cell adhesion module), V-CAM (vascular), and I-CAM (intercell).

Front 25

Cadherins are...

Back 25

a family of transmembrane proteins formed of repeating dimers that are dependent on Ca2+ to switch between active and inactive forms.

On the intracellular side, there is a small cytosolic domain that binds to the actin cytoskeleton.

Front 26

A stronger cadherin bond is formed by...

Back 26

more cadherin repeats interacting.

Front 27

Integrins are...

Back 27

heterodimeric transmembrane receptors with alpha and beta subunits; large extracellular head and small intracellular component.

Abundant, but with low binding affinity to their ligand: easy catch and release. Very important in cell-ECM interaction.

Front 28

3 key types of integrin interactions:

Back 28

1) Cell-ECM adhesion
2) Signal transduction
3) Cell-cell adhesion

Front 29

What happens when there is inflammation at the site of an injury? (5)

Back 29

1) Inflammation causes upregulation of endothelial P-selectins and E-selectins.
2) Selectins slow leukocyte rolling in the artery by binding to leuk. glycolipids/proteins.
3) Leukocyte signals endothelial cells to activate integrins.
4) Integrins bind to I-CAM to lock the leukocyte down to the endothelial cells.
5) Leukocyte undergoes extravasation into the injured tissue.

Front 30

Three types of cellular junctions (7 subtypes):

Back 30

1) Anchoring/adhesive
a) Adherens (cell-cell via an adhesion belt of cytosolic actin filaments)
b) Focal adhesions (anchor cells to basal lamina via actin microfilaments)
c) Desmosomes (plaque as specific site of cell-cell adhesion)
d) Hemidesmosomes (plaque as specific site of cell-ECM adhesion)
2) Occludens
a) Sealing junctions/zonula occludens/tight junctions
3) Communication
a) Gap (large, open communication between two cells, w/ cytosolic exchange)
b) Chemical synapses

Front 31

5 types of cell signalling:

Back 31

1) Autocrine
2) Paracrine
3) Juxtacrine
4) Endocrine
5) Synaptic/electric

Front 32

3 types of signalling where site of secretion dictates site of action:

Back 32

1) Autocrine: signalling molecule travels short distances through the ECM to its target (which is the cell that released the signal)
2) Paracrine: same as above, but target is a different nearby cell
3) Juxtacrine: two cells are in intimate contact (e.g. gap junction or interaction between two transmembrane proteins)

Front 33

2 types of signalling where site of receptors dictates site of action:

Back 33

1) Endocrine: signalling molecules travel significant distances via the circulatory system
2) Synaptic/electric: like a specialized paracrine signal

Front 34

5 types of signalling molecules:

Back 34

1) Amines: amino acid derivatives including neurotransmitters, endocrine hormones, and molecules acting as both
2) Gases: nitric oxide and carbon monoxide
3) Steroids: derivatives of cholesterol
4) Eicosanoids: fatty acid derivatives (immune and inflammatory)
5) Peptide/polypeptide/protein hormones/paracrine factors (e.g. insulin, glucagon, FSH, endorphins, oxytocin)

Front 35

Signal transduction via steroids:

Back 35

Steroids signal via nuclear receptors, with ligand-dependent activation. In the nucleus, they bind to the hormone response element (HRE) in the promoter of a gene and regulate transcription.

Interaction with co-activators-->upregulation--> mRNA--> protein--> cellular response.

Front 36

Repression by unliganded receptors (positive regulation):

Back 36

An unliganded receptor bound to the gene promoter turns off the gene because the unliganded receptors interact with co-repressors. Ligand binding re-activates the gene by releasing the co-repressors and recruiting co-activators.

Front 37

Repression by liganded receptors (negative regulation):

Back 37

A liganded receptor bound to the gene promoter turns off the gene because the liganded receptors interact with co-repressors.

Front 38

Signal transduction via cell-surface receptors:

Back 38

The ligand (soluble or membrane-bound molecule) does not enter the cell, but interacts with a surface receptor to transduce its signal.

Front 39

Signal amplification:

Back 39

exponential signal growth that is necessary for signal transduction.

Front 40

Signal transduction via G protein-coupled receptors (GPCRs): (7)

Back 40

1) Ligand binds to GPCR (a transmembrane protein)
2) GCPR cytosolic tail changes conformation
3) G protein activates when G-alpha releases GDP and binds to GTP
4) G-alpha and G-beta/gamma separate
5) Separated subunits activate other proteins
6) G-alpha hydrolyzes GTP to GDP and becomes inactive
7) Inactive subunits recombine to form inactive G protein trimer

Front 41

What is the universal signalling molecule? What is the most important hormone in the body and why?

Back 41

Ca2+ is universal signalling molecule. Parathyroid hormone is most important because it regulates Ca2+ concentrations.

Front 42

Turning off a GPCR: (3)

Back 42

1) Ligand degradation and/or re-uptake
2) Reabsorption of receptor (endocytosis)
3) GTPase activity (hydrolysis of GTP on G-alpha)