Ims: Histo Block 1 Lecture 1

Front 1

What is resolving power?

Back 1

Ability to distinguish 2 very close objects

Front 2

What type of microscopy is best suited for the study of living, unstained organisms?

Back 2

Light microscopy

Front 3

What is the most common form of LM?

Back 3

Bright-field

Front 4

When is phase-contrast microscopy useful?

Back 4

For studying ordered structures, e.g., mitotic spindles, striated muscle

Front 5

What distinguishes Nomarski microscopy from other types of LM?

Back 5

Three-dimensional appearance to cell

Front 6

Describe dark-field microscopy.

Back 6

Cell is illuminated form one side.

Front 7

How does fluorescent microscopy work?

Back 7

a fluorescent molecule is tagged to an antibody to identify a specific molecule. Once it is bound, the amount of fluorescence is increased by using a fluorescent marker bound to secondary antibodies which bind to the primary antibody.

Front 8

When is fluorescence microscopy useful?

Back 8

When studying the location and behavior of molecules in living cells in vitro.

Front 9

What are the advantages and requirements of transmission electron microscopy?

Back 9

High magnification with high resultion; requires dead, dehydrated, ultrathin sections

Front 10

When is transmission electron microscopy useful?

Back 10

Study isolated, small cell components (ribosomes, viruses, large molecules), or ultrathin sections through cells.

Front 11

When is autoradiography useful?

Back 11

Identifying molecules and following movement through a cell

Front 12

What are the functions of cell membranes?

Back 12

Physical boundries
Enable cell-cell recognition
Compartmentalize eukaryotic cells
Attach to cytoskeleton and ECM
Sites for receptor molecules, channels, and pumps
Sites for biological reactions (electron-transport chain in mitochondria for example)

Front 13

What does the fluid mosaic model state?

Back 13

Membranes are a bilayer of lipids (mainly phospholipids) with proteins present on surface (peripheral proteins) or extending into/across bilayer (integral proteins)

Front 14

How was the fluid aspect of the fluid mosaic model demonstrated?

Back 14

Fluid: molecules diffuse laterally

Fusion of a mouse and human cell whose plasma membranes had been stained different colors; lateral movement (in movement of membrane) of lipids and proteins occurred so that plasma membranes were intermingled.

Front 15

How was the mosaic aspect of the fluid mosaic model demonstrated?

Back 15

Mosaic: appearance of transmembrane proteins; arrangement of molecs

Freeze-fractured membrane allowed metal replica of surface of fractured membrane; showed particles (transmembrane prots) and pits (former sites of transmembrane prots which were pulled out)

Front 16

Contrast P face with E face.

Back 16

Post-freeze fracture, P face is cytoplasmic (or protoplasmic) face of fracture; E face is external face

Front 17

Define ampipathic. Give examples of cell structures that are ampipatic.

Back 17

Exhibiting both hydrophilic and hydrophobic components.

Membrane lipids and PROTEINS are ampipathic.

Front 18

Contrast integral proteins with peripheral proteins.

Back 18

Integral proteins normally function as membrane receptors and transport proteins, and attach cells to each other and to ECM. They're firmly attached to the lipid bilayer; detergent must be used to destroy the membrane in order to isolate them. Usually transmembrane segment can be identified by a sequence of 20-30 hphobic AA's.

Peripheral proteins normally regulate ion channels and cell signaling. They are relatively easily removed because they do not extend into lipid bilayer.

Front 19

What are the three main roles of cell junctions?

Back 19

Seal compartments between different regions of multicellular organisms, attach cells to each other or to ECM, enable communications between cells

Front 20

What's another term for tight junctions?

Back 20

Occluding junctions

Front 21

What types of molecules traverse the lipid bilayer via diffusion?

Back 21

Small molecs, oxygen, CO2

Front 22

What is active transport and how is it mediated in cells?

Back 22

Requires energy to move molecules against [ ] gradient; only carriers can drive active transport.

Front 23

What is passive transport and how is it mediated in cells?

Back 23

Passive transport is driven by [ ] gradient; carriers and channels can both mediate passive transport

Front 24

What do carriers in mitochondria import/export?

Back 24

Import pyruvate, export ATP

Front 25

Describe a uniport.

Back 25

Carrier protein that transports just 1 kind of solute.

Front 26

Describe a symport.

Back 26

Carrier proteins that couple transport of 2 different solutes in same direction. Both solutes should be present for effective uptake.

Front 27

Describe an antiport.

Back 27

An antiport carrier protein couples transport of 2 solutes in opposite directions (Na-K pump)

Front 28

What effect do tight junctions have on epithelial cells?

Back 28

Provide a seal between epithelial cells - ensuring nutrient molecules take intracellular route through epithelial cells, rater than passing between them

Front 29

What role do tight junctions play in cell polarity? How?

Back 29

TJ's maintain cell polarity by separating apical and basal domains. The circumferential seals created by tight junctions confine some proteins involved in transport to apical surfaces whereas others are confined to basolateral surfaces; this ensures proteins do not migrate between these surfaces.

Front 30

What transmembrane proteins assist tight junctions?

Back 30

Claudins and occludins seal together adjacent plasma membranes; other proteins attach these to the actin cytoskeleton.

Front 31

What function do adherens junctions and desmosomes serve? How do they differ?

Back 31

They both attach cells together and are anchored to the cystoskeleton.

Adherens junctions join actin bundles in one cell to a similar bundle in a neighboring cell

Desmosomes join the IM fils in one cell to those in a neighbor.

Front 32

How do adherens junctions serve their function?

Back 32

Form a belt around inner surface of epithelial cell near apex and connects to adherens junction of neighboring cell via cadherins which span gap between neighboring plasma membranes.

Front 33

What role do cadherin molecules play in junctions?

Back 33

Cadherin molecules extend through plasma membranes and are joined to actin filaments by linker molecules (catenin). They connect adherens junctions.

Front 34

What are focal contacts?

Back 34

Similar to adherens junctions, but join actin cytoskeleton to ECM via integrin heterodimeric proteins. Are especially important in connective tissue cells where they aid in locomotion.

Front 35

Describe desmosomes.

Back 35

Plaque-like structures that are attached to plasma membrane and bind cells together (esp. where there is much mechanical stress) via cadherins. Cytoplasmic side of plaque is attached to IM fils that anchor desmosomes.

Front 36

Describe hemidesmosomes.

Back 36

Hemidesmosome resembles a half desmosome. Hemidesmosomes attach cells to ECM (basal lamina) via integrins that span plasma membrane and attach to the IM fils (keratin) via hemidesmosome plaque.

Front 37

Describe gap junctions.

Back 37

Create aqueous channels between adjacent cells that are in communication. Gap exists bc of connexons spanning space between adjacent cells. Connexon of one membrane aligned with connexon of another, creating a channel through which molecs up to 1,000 daltons can pass (sugar, water). Increase in intracell Ca++ causes conformational changes which close channel; thus isolating damaged cell from neighboring healthy cell.

Front 38

List cytoskeletal anchor, transmembrane attachment, and what cell is attached to for different junctions.

Back 38

Tight: (blank), claudins/occludins, neighboring cells

Adherens: actin fils, cadherins, neighboring cells

Gap: (blank), connexons, neighboring cells

Desmosomes: IM fils, cadherins, neighboring cells

Hemidesm: IM fil's, integrins, ECM