Question

1. O Polysaccharides are :

A. found on all bacteria

B. not part of the LPS found in Gram-positive cells

C. used to identify certain bacteria

D. found only on gram-positive cells

E. found in the plasma membrane of all bacteria

2. A barrier to water is achieved in the interior of the plasma membrane by orienting the ___ of phospholipid layers toward each other

A. hydrophobic tails

B. hydrophobic heads

C. hydrophilic tails

D. hydrophilic heads

E. integral proteins

3. a consequence of raising the temperature above the maximum growth temperature when culturing bacteria produces a marked.

A. destabilization of hydrogen bonds in proteins

B. increase in the oxygen concentration

C. a decrease in pH causing acidification

D. increase osmotic pressure

E. decrease in osmotic pressure

4. bacteria will typically grow faster in ___ medium :

A. complex

B. selective

C. differential

D. chemically defined

E. anerobic

Answer 1

1. B - O Polysaccharide a repretitive glycan polysaccharide contained within a lipopolysaccharide. The O- antigen is attached to the core oligosaccharide and comprises the outer most domain of the LPS molecule and is found in the outer membrane of gram negative bacteria.

2. A - The plasma membrane is composed mainly of phospholipids, which consist of fatty acids and alcohol.The phospholipids in the plasma membrane are arranged in two layers, called a phospholipid bilayer.Each phosholipid molecule has a head and two tails. The head loves water (hydrophillic) and the tail hates water (hydrophobic).The water hating tails are on the interior of the membrane , where as the water loving heads point outwards towards either the cytoplasm or the fluid that surrounds the cell.Molecules that are hydrophobic can easily pass through the plasma membrane, if they are small enough, because they are water hating like the interior of the membrane.Molecules that are hrdrophillic, on the other hand, cannot pass through the plasma membrane .

3. A - An increase in temperature will increase increase the enzyme activity. But if temperature gets too high, enzyme activity will diminish and the protein will denature.

4 A - complex media usually provides the full range of growth factors that may be required by an organism so that they may be more handily used to cultivate unknown bacteria or bacteria whose nutritional requirements are complex.