Biochem Ch. 12

The rate of diffusion is such that a phospholipid molecule can travel from one end of a bacterium to the other in _______________ of time.

1 second

What is the number of carbons found in the most commonly observed fatty acids?

16 or 18

What substance inhibits prostaglandin H 2 synthase-1 by blocking the channel through which the substrate, arachidonate, travels?

acetylsalicylic acid

What term describes molecules that have both hydrophilic and hydrophobic moieties?

amphipathic

Ionized fatty acids readily form ______________ in aqueous solutions.

micelles

Which of the following membrane-bound organelles is thought to have evolved from bacteria by endosymbiosis?

mitochondria

Carbohydrate residues attached to the membrane lipids are almost always

positioned on the extracellular side of the membrane.

__________________ contain a double bond three carbons from the distal end of the fatty acid.

ω-3 Fatty acids

Hydrophobic molecules can be covalently attached to proteins to increase membrane association. Type(s) of group(s) include

All of the answers are correct.

________________ is a membrane lipid composed of sphingosine, fatty acid, and a simple sugar like glucose or galactose.

Cerebroside

Which of the following is NOT correct concerning the structure given?

It is a sphingolipid.

___________________ are aqueous compartments enclosed by a lipid bilayer which can be created in a laboratory.

Lipid vesicles, or liposomes,

Which of the following is true?

Membranes are lipid bilayers. Membrane lipids have both hydrophobic and hydrophilic properties. Many membranes are electrically polarized.

___________________ membrane proteins are bound to membranes primarily by electrostatic and hydrogen bond interactions with the head groups of lipids.

Peripheral

The temperature at which a phospholipid membrane transitions from a rigid to a fluid state is referred to as _______________.

T m , or melting temperature

How do the membranes of archaea differ from bacteria and eukaryotes?

The lipids do not contain a carboxylic acid ester, but instead have an ether link to the glycerol. The alkyl chains are branched. The stereochemistry of the central carbon of glycerol is inverted.

Which of the following statements is consistent with the structure of biological membranes?

The membrane lipids self-assemble to form the lipid bilayer.

Which of the following membranes would be the most fluid?

a bilayer made of lipids with polyunsaturated 16 carbon-fatty acids

The most common motif found in membrane spanning proteins is

a helices of nonpolar amino acids that pass through the membrane.

In animals, ________________ is the key regulator of membrane fluidity.

cholesterol

Which of the following helps regulate membrane fluidity in animals?

cholesterol

What protein polymerizes into a lattice network around a budding membrane?

clathrin

In phosphoglycerides, the fatty acids are linked to the glycerol backbone by ______________ linkages.

ester

What membrane components contain carbohydrates?

glycolipids

What property is used to determine the probability that a segment of a protein will be found embedded in a membrane?

hydropathy

What is the most common process by which lipids and proteins move in the membrane bilayer?

lateral diffusion

What complex is observed between cholesterol and membrane phospholipids?

lipid raft

Membranes are primarily comprised of

lipids and proteins

The low incidence of protein or lipid flip-flop in a membrane preserves

membrane asymmetry.

Some proteins are anchored to the membrane by being covalently attached to a _______________ group by a thioester linkage to a specific (non-C-terminal) cysteine residue.

palmitoyl

What important property is conferred on membranes by transport systems?

selective permeability

In addition to phospholipids and glycolipids, which of the following is a major type of membrane lipid?

triacylglycerol

How many molecules thick are membranes?

two

The degree of membrane fluidity in bacteria depends mainly on the percentage of

unsaturated fatty acids.

What force(s) stabilize(s) the lipid bilayers?

van der Waals interactions and electrostatic and hydrogen bonding between the polar heads and surrounding water