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BCH 4024 Exam 2 > Lecture 16- Biological Membranes > Flashcards

Lecture 16- Biological Membranes Flashcards

1
Q

What are the 2 major components of all membranes?

Which composes a majority of a membrane?

A

Lipids and Proteins

Lipids

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2
Q

Functions of a Biological Membrane:

  1. ​Defines _______ boundaries of a cell
  2. Controls molecular ______ across boundary
  3. Divide cells (_______) into ____________
  4. Organizes ________ sequences
  5. ____-to-____ communication
  6. Matrix for _________, ________, _________ molecules
  7. ________ transduction w/in cell (________, ________)
A

Functions of a Biological Membrane:

  1. ​Defines external boundaries of a cell
  2. Controls molecular traffic across boundary
  3. Divide cells (eukaryotes) into compartments
  4. Organizes reaction sequences
  5. Cell-to-Cell communication
  6. Matrix for transporters, receptors, adhesion molecules
  7. Energy transduction w/in cell (mitochondria, chloroplasts)
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3
Q

Amount of Å a lipid portion of a bilayer is?

2 monolayers of a bilayer?

A

30 Å

Leaflets

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4
Q

1 wedge-shaped fatty acid tail consisting of a fatty acid/lysolipids

A

Micelle

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5
Q

2 cylindrical fatty acid tails (Glyerophospholipids, Sphingolipids)

Combo above that contains an aqueous cavity

A

Bilayer

Vesicles

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6
Q

Concentration of lipid req’d for micelle formation

A

Critical Micelle Formation

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7
Q

What do the formation of micelles depend on? (3)

A

Temp, lipic concentration & lipid composition

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8
Q

What is a vesicle prepared from purified lipid?

A

Liposome

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9
Q

T/F: Lipid composition of all cell membranes is the same.

(Explain)

A

False: Lipid composition of cell membranes is different depending on organelle and function.

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10
Q

LIpid composition of bilayer leaflets is (bisymmetrical/asymmetrical) w/ _______ lipids and/or ________ on the ________ leaflet.

A

LIpid composition of bilayer leaflets is asymmetrical w/ neutral lipids and/or glycolipids on the external leaflet.

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11
Q

What kind of model best describes biological membranes?

This can be described as a non-rigid, complex mixture of _______ & ________ molecules ______ in bilayer

A

Fluid Mosaic Model

This can be described as a non-rigid, complex mixture of lipids & protein molecules floating in bilayer

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12
Q

The interior of a bilogical membrane is consisted of _____ ______ that forms a _____, ___________ region.

A

The interior of a bilogical membrane is consisted of fatty acyl (C-H) that forms a fluid, hydrophobic region.

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13
Q

___________ interactions of ____ side-chains hold membrane proteins together.

A

Hydrophobic interactions of AA side-chains hold membrane proteins together.

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14
Q

What type of membrane proteins are the site of hydrophobic AA interaction and are only reremovable by hydrophobic agents (EX?)

A

Integral Membrane Proteins (Removable by hydrophobic agents: detergents, organic solvents, denaturants)

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15
Q

What type of membrane proteins associate with electrostatic interactions with H-bonding and how are they released?

A

Peripheral (mild detergents/interference w/ charge or H-bonding)

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16
Q

What type of membrane proteins is located in the cytosol that can associate/dissocate thru electrostatic interactions/lipid tails? (EX)

A

Amphitropic Proteins

(Covalent/Noncovalent = Lipidation, phosphorylation, ligan binding)

17
Q

What is the localization of proteins relative to the lipid bilayer and how can it be assessed?

A

Membrane Protein Topology, analysis of AA sequence

18
Q

What are common transmembrane motifs within membrane protein topology?

What do proteins have that is important to distinguish its function?

A

Alpha helices and Beta-strands

“Sidedness”

19
Q

For protein-lipid interactions, how are membrane proteins classified? (4)

A

Sidedness, # of transmembrane (TM) helices, # polypeptides, lipid modifications

20
Q

Type of protein-lipid interaction that has a single TM helix & Amino-terminus on the outside?

A

Type 1

21
Q

Type of protein-lipid interaction that contains a single, TM helix & carboxy-terminus on the outside?

A

Type 2

22
Q

Type of protein-lipid interaction that contains multiple TM helices?

A

Type 3

23
Q

Type of protein-lipid interaction that contains multiple, polypeptides that assemble to form protein complexes?

A

Type 4

24
Q

Type of protein-lipid interaction that is attached to the bilayer primarily by lipid modification?

A

Type 5

25
Q

Type of protein-lipid interaction that contains BOTH terminal helices and lipid anchors?

A

Type 6

26
Q

____________: Type 3 Integral Membrane Protein

  • Salt-loving bacteria similar to light-driven molecule in ___ that absorbs protons
  • __ TM helices connected by the inner non-helical loops & outer face membrane
  • Anchored by hydrophobic ____ _____ interactions with _______
A

Bacteriohodopsin: Type 3 Integral Membrane Protein

  • Salt-loving bacteria similar to light-driven molecule in eye that absorbs protons
  • 7 TM helices connected by the inner non-helical loops & outer face membrane
  • Anchored by hydrophobic side chain interactions with lipids
27
Q

Predicting Secondary Structure of Membrane Spanning Portions of Integral Membrane Protein:

  • Alpha-helix: ___ Å rise/residue
  • 30 Å hydrophobic interior req’s __ AA
  • TM helices ~__ turns long
A

Predicting Secondary Structure of Membrane Spanning Portions of Integral Membrane Protein:

  • Alpha-helix: 1.5 Å rise/residue
  • 30 Å hydrophobic interior req’s 20 AA
  • TM helices ~6-7 turns long
28
Q

What is the amount of energy it takes to move an R group from the hydrophobic to hydrophilic area? (Delta G)

A

Hydropathy Index

29
Q

For a hydropathy index, a (+)Delta G requires energy, which indicates a __________ group.

A

hydrophobic

30
Q

Type of graph?

Label the axes.

A

A Hydropathy plot contains successive windows of sequence with the calculated hydropathy index and then its residue number plotted against it.

31
Q

What are aromatic residues found @ the interface of water and lipids?

Name 2 that are also found bw exterior & interior, and @ border.

A

Membrane Interface Anchors

Tyrosine (Y) & Tryptophan (W)

32
Q

Positive-Inside Rule for Membrane Proteins:

  • (-) charged lipids are usually on the ______ leaflet (phosphotidylserine/phosphotidylinositol)
  • Favors (+) charged AA (___, ____, ____) on the inside
  • Look for charge in ___________ regions to determine orientation
A

Positive-Inside Rule for Membrane Proteins:

  • (-) charged lipids are usually on the inner leaflet (phosphotidylserine/phosphotidylinositol)
  • Favors (+) charged AA (Lys (K), Arg (R), His (H)) on the inside
  • Look for charge in non-transmembrane regions to determine orientation
33
Q

__-________: another structure found in integral proteins

  • ___________ inside barrel
  • ___________ outside barrel (touching ______)
  • Important for _______ transport, but hard to determine
  • _______: proteins that allow select polar solutes to cross membranes
A

B-Strands–> B-Barrel: another structure found in integral proteins

  • Hydrophilic inside barrel
  • Hydrophobic outside barrel (touching lipids)
  • Important for passive transport, but hard to determine
  • Porins: proteins that allow select polar solutes to cross membranes
34
Q

_____________ membrane proteins can associate w/ membranes by covalently attached lipids

  • Not integral/peripheral, but how are they attached? (aka?)
  • What is the strongest? (2x16C’s)
  • _______ = Strength!
A

Amphitrophic membrane proteins can associate w/ membranes by covalently attached lipids

  • Not integral/peripheral, but attached by anchors of lipid molecules to target proteins (posttranslational modification)
  • Glycosylphosphatidlyinositol, GPI is the strongest (2x16C’s)
  • Length = Strength!

BCH 4024 Exam 2 (15 decks)

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