2 Microbial Physiology Module 2: Cytoplasmic Membrane and Cytopl

Which statement is not true about the assembly of cell membrane proteins?

• SecA binds to unfolded preprotein

• Proteins pass through across the plasma membrane using the translocase.

• Cell membrane proteins are produced by cytosolic ribosomes.

• A signal peptide is required at the amino terminus.

Answer explanation

Option 1: Correct! (SecB binds to unfolded preprotein. All other choices are true).

Reference:

Madigan, M. T., Bender, K. S., Buckley, D. H., Sattley, W. M., & Stahl, D. A. (2018). Brock biology of microorganisms. Pearson Higher Education.

What is the function of the intracytoplasmic membrane in Rhodopseudomonas palustris?

• It is involved in cell wall formation

• It is involved in septum formation

• It stores ions

• It increases the surface area for energy transduction

Answer explanation

Option 4: Correct! (Intracytoplasmic membranes are stacks of extra membrane that are continuous with the inner membrane. They are known to increase the surface area for energy transduction).

Reference:

Jensen, C. M. O. a. G. J. (n.d.). 4.3 Intracytoplasmic membrane | Atlas of bacterial and archaeal cell structure. https://www.cellstructureatlas.org/4-3-intracytoplasmic-membrane.html

Madigan, M. T., Bender, K. S., Buckley, D. H., Sattley, W. M., & Stahl, D. A. (2018). Brock biology of microorganisms. Pearson Higher Education.

All statements are true regarding fatty acid biosynthesis during membrane synthesis except:

• Acetyl-CoA must be converted to Malonyl-CoA to initiate fatty acid synthesis

• ATP is required in the process.

• Bactoprenol plays a key role in fatty acid biosynthesis

• Biotin carboxylase and carboxyl transferase are required for the reaction to proceed.

   

Answer explanation

Option 3: Correct! (Bactoprenol is involved in peptidoglycan synthesis. Biotin Carboxyl Carrier Protein (BCCP) is the one involved for catalyzing the conversion of acetyl-CoA to malonyl-CoA in a committed step during the de novo biosynthesis of fatty acids).

 

Reference:

Madigan, M. T., Bender, K. S., Buckley, D. H., Sattley, W. M., & Stahl, D. A. (2018). Brock biology of microorganisms. Pearson Higher Education.

 

White, D., Drummond, J., Drummond, J. T., & Fuqua, C. (2012). The physiology and biochemistry of prokaryotes. Oxford University Press, USA.

Which statement is not true regarding the composition of phospholipids in the cell membrane?

• The phosphatidylglycerol component is formed from equimolar ratios of glycerol 3-P and fatty acids

• The fatty acid composition depends on species and environmental conditions.

• Lipids associated with the cell membrane are structurally symmetric

• All statements are true.

Answer explanation

Option 3: Correct! (Membrane-associated lipids are structurally asymmetric. Options 1 and 2 are true).

 

Reference:

Madigan, M. T., Bender, K. S., Buckley, D. H., Sattley, W. M., & Stahl, D. A. (2018). Brock biology of microorganisms. Pearson Higher Education.

 Which statement is not true regarding the bacterial cell membrane?

• The glycerol backbone of the phospholipid is connected to a phosphate group via a covalent bond.

• The hydrophobic side chain is connected to glycerol by ether linkages.

• The non-polar fatty acid regions interact with each other via hydrogen bonding.

• The polar region interacts with cations and water via ionic interactions.

Answer explanation

Option 2: Correct! (In lipids of bacteria and eukarya, ester linkages bond fatty acids to glycerol).

 

Reference:

Madigan, M. T., Bender, K. S., Buckley, D. H., Sattley, W. M., & Stahl, D. A. (2018). Brock biology of microorganisms. Pearson Higher Education.