Chem 471 | Problem Set 10 | Preview

The inner mitochondrial membrane has a phospholipid-to-protein ratio of about 1:1 by weight. What is the molar phospholipid-to-protein ratio? (Assume that the average mitochondrial membrane protein is molecular weight 60,000 g/mol and the average lipid is 750 g/mol.)

1. 1:20
2. 1:1
3. 20:1
4. 80:1
5. 800:1

Membrane proteins:

1. are sometimes covalently attached to lipid moieties.
2. are sometimes covalently attached to carbohydrate moieties.
3. are composed of the same 20 amino acids found in soluble proteins.
4. diffuse laterally in the membrane unless they are anchored
5. have all of the properties listed above.

An integral membrane protein can be extracted from the bilayer with:

1. a buffer of alkaline or acid pH.
2. a chelating agent that removes divalent cations.
3. detergent.
4. a solution of high ionic strength.
5. hot water.

The shortest α-helix segment in a protein that will span a membrane bilayer has about _____ amino acid residues.

1. 5
2. 10
3. 20
4. 50
5. alpha helices typically don't span membrane bilayers

A hydropathy plot is used to:

1. determine the water-solubility of a protein.
2. identify potential membrane-spanning segments in a protein sequence.
3. predict the secondary structure of a membrane protein.
4. determine exposed surfaces of a native protein.
5. estimate the fluidity of a membrane bilayer surrounding a protein.

The fluidity of the lipid side chains in the interior of a bilayer is generally increased by:

1. a decrease in temperature.
2. an increase in fatty acyl chain length.
3. an increase in the number of double bonds in fatty acids.
4. an increase in the percentage of phosphatidyl ethanolamine
5. the binding of water to the fatty acyl side chains.

Membrane fusion leading to neurotransmitter release requires the action of:

1. cadherins.
2. selectins.
3. flipases.
4. tSNARE and vSNARE.
5. none of the above.

Glucose transport into erythrocytes is an example of:

1. active transport.
2. antiport.
3. electrogenic uniport
4. facilitated diffusion.
5. symport.

For the process of solute transport, the constant Kt is:

1. analogous to Ka for ionization of a weak acid.
2. analogous to Km for an enzyme-catalyzed reaction.
3. analogous to Vmax for an enzyme reaction
4. proportional to the number of molecules of glucose transporter per cell.
5. the maximum rate of glucose transport.

Consider the transport of K+ from the blood (where its concentration is about 4 mM) into an erythrocyte that contains 150 mM K+. The transmembrane potential is about 60 mV, inside negative relative to outside. The free-energy change for this transport process is: (These values may be of use to you: R = 8.315 J/mol.K; T = 298 K; 9 (Faraday constant) = 96,480 J/V; N = 6.022 × 10²³/mol.)

1. about 5 J/mol.
2. about 15 J/mol.
3. about 5 kJ/mol.
4. about 15 kJ/mol.
5. impossible to calculate with the information given.