Bmed 3600 - Test 1 - Membranes

Front 1

State 3 characteristics of the Plasma Membrane.

Back 1

1) Encloses the cell, 2) defines it boundaries, and 3) maintains the separation between the cytosol and the extracellular environment.

Front 2

What maintains the differences between the contents of the organelles and the cytosol in eukaryotic cells?

Back 2

The membranes of the ER, Golgi apparatus, and mitochondria.

Front 3

State 2 characteristics of the Ion gradients across membranes.

Back 3

1) Drive the transmembrane movement of selected solutes or 2) produce and transmit electrical signals.

Front 4

The plasma membrane contains receptors. Define them.

Back 4

Proteins that act as sensors of external signals which transfer information across the membrane.

Front 5

What is the general structure of a membrane?

Back 5

Very thin film of lipid and protein molecules held together by non covalent interactions

Front 6

How this is lipid arranged as a double layer?

Back 6

5-10nm

Front 7

What is a relatively impermeable barrier to most water-soluble molecules?

Back 7

Lipid Bilayer

Front 8

2 characteristics of transmembrane proteins.

Back 8

1) Span the lipid bilayer and mediate nearly all of the other functions of the membrane. 2) Serve as structural links that connect the cytoskeleton through the lipid bilayer to either the extracellular matrix, other cells.

Front 9

What percentage of all encoded proteins are membrane proteins?

Back 9

30%

Front 10

What is the basic structure of all cell membranes?

Back 10

Lipid Bilayer

Front 11

Lipid molecules constitute what percentage of the mass of most animal cell membranes, the rest being protein.

Back 11

50%

Front 12

All Lipids are amphiphilic. Define amphiphilic.

Back 12

They have a "water loving" or hydrophilic or polar end and a hydrophobic or non polar end.

Front 13

What type of lipids are the most abundant membrane lipids?

Back 13

Phospholipids

Front 14

Name two characteristics of phospholipids in terms of structure.

Back 14

They have a polar head group and two hydrophobic hydrocarbon tails. The tails are usually fatty acids.

Front 15

What are phosphoglycerides (in terms of structure)?

Back 15

Have a three carbon glycerol backbone and two long-chain fatty acids are linked via ester bonds to adjacent carbon atoms of the glycerol and the third carbon is attached to a phosphate group, which is linked to a number of different head groups.

Note: By combining different fatty acids and head groups cells make different phosphoglycerides, such as phosphatidylethanolamine, phosphatidylserine, and phosphotidylcholine.

Front 16

Important phospholipid that is not built from glycerol (the standard) and often seen in nerve cell membranes, specifically along the axon.

Back 16

Sphingomyelin

Front 17

Hydrophilic molecules dissolve readily in water because (2 reasons)

Back 17

1) they contain charged groups or 2) uncharged polar groups that form either favorable electrostatic interactions or hydrogen bonds with water.

Front 18

Lipid molecules spontaneously aggregate to bury their hydrophobic hydrocarbon tails in the interior and expose their hydrophilic heads to water. They can do this two ways...

Back 18

 Form spherical micelles, with the tails inward (single layer)
 Form double-layered sheets or bilayers with the hydrophobic tails sandwiched between the hydrophilic head groups.

Front 19

In what year was it realized individual lipid molecules can
diffuse freely within lipid bilayers.

Back 19

1970

Front 20

Phospholipid molecules are manufactured in only one monolayer of a membrane, where?

Back 20

In the cytosolic membrane of the ER.

Front 21

Fluidity of a lipid bilayer depends on _____ and _____.

Back 21

composition, temperature

Front 22

Describe the synthetic bilayer?

Back 22

They're composed of single type of phospholipid, changes
from liquid to a rigid crystalline structure at a specific freezing point. This is called the phase transition. This occurs at a lower temperature if
the hydrocarbon chains have short or double bonds.

Front 23

Double bonds produce____ that make it difficult to pack and remain fluid at lower temperature

Back 23

Kinks

Front 24

________ enhances permeability-barrier properties.

Back 24

Cholesterol

Front 25

What are Lipid Rafts?

Back 25

Small Region of the plasma membrane enriched in sphingolipids and cholesterol.

Front 26

What are caveolae?

Back 26

small surface invaginations or indentations (think gold ball) seen in many cell types.

Front 27

What are some cell types that have plasma membranes with numerous caveolae?

Back 27

Adipocytes, endothelial cells, and smooth muscle cells.

Front 28

there is a class of abundant molecules on the extracellular surface of the cells called glycolipids. Describe them.

Back 28

Lipids that contain sugars attached to them and tend to self associate on the membrane surface.These sugar groups are specifically added while in the lumen of
the Golgi.

Front 29

Glycolipids compose about what percentage of the lipid molecules

Back 29

5%

Front 30

What is the most complex glycolipid?

Back 30

gangliosides, which contain
oligosaccharides with one or more sialic acid residues making
them negatively charged.

Front 31

Name two ways glycolipids are beneficial to the membrane.

Back 31

Glycolipids help protect the membrane against harsh conditions
and charged glycolipids may be important for electrical affects,
such as altering membrane charge and ion concentrations.

Front 32

Lipid bilayer provides the structure – _____ provide the function.

Back 32

Proteins. Proteins constitute 25-75% of the membrane composition by mass.

Front 33

What is the function of Glycosylphophatidylinositol Anchor (GPI)?

Back 33

anchors the protein to the
non-cytosolic side of the membrane and is made in the ER.

Front 34

What are 4 characteristics of transmembrane proteins?

Back 34

1)Only membrane proteins that function on both sides of the membrane
2)Can transport molecules across it
3)Can transport information; bind signal molecules on extracellular side
and generate intracellular signals on the cytosolic side.
4) They have a unique orientation in the membrane; inserted in an
asymmetric way in the ER during biogenesis. Most form alpha helices
formed from hydrogen bonding with themselves.

Front 35

What do single-pass transmembrane proteins do?

Back 35

Cross the membrane only once.

Front 36

What do Multi-pass transmembrane proteins do?

Back 36

Cross multiple times.

- one type is the Beta-barrel formation, where beta sheets are rolled up into a barrel, example porin proteins.
-Others utilize mulitple alpha helices

Front 37

Typically transmembrane segments
contain (about how many amino acids) with high degree of
hydrophobicity and can span as alpha
helix.

Back 37

20-30 aa

Front 38

Single pass transmembrane proteins (in terms of structure).

Back 38

their alpha helix does not contribute to
folding on either side of bilayer and
often form homodimers.

Front 39

Multi pass transmembrane proteins (in terms of structure).

Back 39

alpha helices occupy specific positions in folded protein structure determined by helix-helix
interactions.

Front 40

Describe 3 characteristics of Beta barrels.

Back 40

-abundant in outer membrane of the
mitochondria;
-often are pore forming proteins
creating water filled channels for
small hydrophilic molecule transport.
-Not all Beta barrels are transporters;some serve as enzymes or receptors.

Front 41

Where are transmembrane proteins glycosylated?

Back 41

in ER andGolgi, and therefore on the noncytosolic side of the membrane.

-Reason for this is that the cytosol is reducing environment, therefore
reduces disulfide bonds which are
important to the folding of many
proteins.
-ER and Golgi are not reducing
environments.

Front 42

What is the importance of Glycolipids and glycoproteins.

Back 42

impt in cell-cell adhesion, sperm-egg interaction, blood clotting, etc

Front 43

What is Glycolax?

Back 43

-describes carbohydrate rich zone of cell surface.
-protects cell from mechanical and chemical damage.

Front 44

What is photobleaching?

Back 44

incident light can cause formation of O atoms that react with fluorophore to create a nonfluorescent form of the molecule, effectively turning it off
or preventing it from exhibiting fluorescence.

Front 45

What is Fick's Law?

Back 45

given enough time, virtually any molecule will diffuse across a protein-free membrane down its
concentration gradient (Fick’s Law) – the rate varies a lot!

Front 46

How much transport do large polar molecules experience?

Back 46

little to no transport.

Front 47

How much transport do small non-polar molecules experience?

Back 47

diffuse readily (O2 or CO2)

Front 48

How much transport do Charged molecules experience?

Back 48

no–go even though very small. The charge and high degree of hydration prevent them from entering the hydrophobic core.

Front 49

How much transport do Small hydrophobic molecules experience?

Back 49

can make it across the membrane– or a least we think so.