biokjemi kap 12

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

16 or 18

How many molecules thick are membranes?

2

True about membranes

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

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 membranes would be the most fluid?

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

What substance inhibits prostaglandin H2 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

Helps regulate membrane fluidity in animals

cholesterol

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

cholesterol

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

clathrin

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

Membrane-bound organelles thought to have evolved from bacteria by endosymbosis?

mitochondria

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

palmitoyl groups attached via Cys residues. glycolipid structures attached to the carboxy terminus. farnesyl groups attached via Cys residues

Carbohydrate residues attached to the membrane lipids are almost always

positioned on the extracellular side of the membrane.

What important property is conferred on membranes by transport systems?

selective permeability

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

The most common motif found in membrane spanning proteins is

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