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Whitney - Biochem Test 2 > Lecture 16 - Membrane Lipids 1 > Flashcards

Lecture 16 - Membrane Lipids 1 Flashcards

1
Q

Biological membranes form ________ (covalent/non-covalent) assemblies.

A

Non-covalents

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2
Q

Name the common features of biological membranes

A

Asymmetric
Fluid Structure
Electrically Polarized
Hydrophilic and Hydrophobic units

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3
Q

What does it mean for a lipid to be amphipathic?

A

The lipid contains both hydrophilic and hydrophobic units

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4
Q

Describe how oil forms a monomolecular layer on the surface of water

A

Polar heads are in contact with water

Nonpolar hydrophobic lipid tails project into the air

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5
Q

What is responsible for membrane formation?

A

The amphipathic nature of membrane lipids

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6
Q

What are the two possible arrangements of lipids?

A

Micelle or Lipid Bilayer

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7
Q

When is a micelle formed?

A

Formed when a variety of molecules including soaps and detergents are added to water
Temporary and Fragile
Examples: SI bile detergents and partially digested fats

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8
Q

Why is a bimolecular sheet more favorable than a micelle?

A

Two fatty acyl chains of a phospholipid or a glycolipid are too bulky to fit into the interior of a micelle

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9
Q

Why are phospholipids and related molecules important membrane constituents?

A

They readily form extensive bilayers

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10
Q

Formation of lipid bilayers is a _________ (self or group- assembly) process

A

Self-assembly

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11
Q

What are the major driving forces for the assembly of lipid bilayers?

A

Hydrophobic interactions
Van der Waals attractive forces between hydrocarbon tails
Electrostatic and hydrogen-bonding attractions between polar head groups and water molecules

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12
Q

What are the three significant consequences of the hydrophobic interactions between lipids?

A

Bilayers have an inherent tendency to be extensive
Bilayers will tend to close on themselves so that there are no edges with exposed hydrocarbon chains, and so they form compartments
Bilayers are self-sealing

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13
Q

Why are bilayers self-sealing?

A

The bilayer wants to be thermodynamically stable. A hole in the bilayer is energetically unfavorable

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14
Q

Why is water able to traverse the membrane easily?

A

B/c of its small size, high concentration, and lack of complete charge

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15
Q

The lipid bilayer has a low permeability for what?

A

ions and most polar molecules

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16
Q

What are the two classifications of membrane proteins and what determines this classification?

A

Integral membrane proteins
Peripheral membrane proteins
Classified according to the difference in dissociability

17
Q

What do integral membrane proteins interact with?

A

Extensively with the hydrocarbon chains of membrane lipids

18
Q

How do you release integral membrane proteins?

A

Can be released by agents that compete for the nonpolar interactions, such as organic solvents and detergents

19
Q

What is responsible for most of the dynamic processes carried out by membranes?

A

Membrane proteins

20
Q

How can one visualize the protein components of a membrane?

A

SDS-polyacrylamide gel electrophoresis

21
Q

How are peripheral membrane proteins bound to the membrane?

A

By electrostatic and hydrogen-bond interactions with the head groups of lipids

22
Q

How do you remove peripheral proteins from the membrane?

A

Salt or pH changes

23
Q

Peripheral membrane proteins are bound to the surfaces of integral proteins either on:

A

the cytosolic or extracellular side of membrane or anchored to the lipid bilayer by a covalently attached hydrophobic chain, such as a fatty acid

24
Q

What is the most common structure motif in membrane proteins?

A

Membrane-spanning alpha-helices

25
Q

Bacteriorhodopsin (BR)

A

Membrane protein
light-driven proton pump - converts energy of light into transmembrane proton gradient that is used to synthesize ATP
Made mostly of alpha-helices arranged perpendicular to the bilayer plane

26
Q

Cyclooxygenase (COX) 1 or Prostaglandin H2 synthase (PGHS) 1

A

Integral protein
Binds to the luminal leaflet of the ER
Primarily alpha-helices

27
Q

Lipids are ______ associated to the proteins

A

Covalently

28
Q

________ anchor their attached proteins to membrane and mediate protein-protein interactions

A

Lipids

29
Q

Three kinds of lipid-linked protein modification

A

Palmitoylation of cysteine residues by a thioester bond
Farnesylation of cysteine residues at the C-terminus
Glycosylphosphatidylinositol-link to the carboxyl terminus

30
Q

Farnesylation at the C-terminus

A

Covalent attachment of farnesyl unit to C-term. tetrapeptide CAAX in which Cys is followed by 2 aliphatic residues
After thioether linkage w/ Cys residues, AAX tripeptide is hydrolytically cleaved away

31
Q

Glycosyl phosphatidylinositol (GPI) anchor

A

Anchors protein to outer leaflet of the plasma membrane

Many Cell-surface hydrolytic enzyme and adhesions are tethered to cells by a GPI unit

32
Q

Describe the structure of a mitochondrion

A

Two membrane systems: outer membrane and inner membrane

Two compartments: intermembrane space and matrix

33
Q

Where are the internal ridges, or cristae, located?

A

Inner membrane

34
Q

Where does oxidative phosphorylation take place?

A

Intermembrane space

35
Q

Where does most of the TCA cycle and fatty acid oxidation take place?

A

Matrix

36
Q

What is the outer membrane permeable to?

A

Most small molecules and ions

37
Q

What is the inner membrane permeable to?

A

Impermeable to nearly all ions and polar molecules

38
Q

What is the mitochondrial porin?

A

30-35 kDa pore-forming proteins known as Voltage-dependent anion channel on the outer membrane

39
Q

What type of metabolites are transported across the inner membrane?

A

Metabolites such as ATP, pyruvate, and citrate

Whitney - Biochem Test 2 (6 decks)

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