1.5 Bacteria - Cell Walls and External Structures

Question 1

Identify the functions associated with the bacterial cell wall.

Answer 1

To protect the cell from harsh conditions outside the cell

Question 2

Describe the structure of peptidoglycan.

Answer 2

only found in bacteria; made up of layers; Each layer is composed of long chains of alternating molecules of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).

Question 3

Identify differences between the structure of peptidoglycan in Gram-positive bacteria and
Gram-negative bacteria.

Answer 3

Gram positive: tetrapeptide chains are linked by pentaglycine cross-bridges.

Gram negative: tetrapeptide chains extending from each NAM unit are directly cross-linked.

Question 4

Describe the effect of lysozyme on peptidoglycan structure.

Answer 4

breaks down and digests the peptidoglycan in their cell walls

Question 5

Describe the structure of a Gram-positive cell wall including the following: peptidoglycan
and teichoic acids.

Answer 5

Teichoic Acid is thought to stabilize peptidoglycan by increasing its rigidity.

Question 6

Describe the structure of a Gram-negative cell wall including the following: peptidoglycan,
periplasm, and outer membrane with lipopolysaccharides (LPS) and porin proteins.

Answer 6

LPS, outer membrane, peptidoglycan layer, plasma membrane

Question 7

Describe the structure of the cell walls of Archaea

Answer 7

archaeal cell walls do not contain peptidoglycan;

Question 8

Describe the location and structure of the glycocalyx

Answer 8

A glycocalyx is a sugar coat; exterior to cell wall

Question 9

Capsule

Answer 9

an organized layer located outside of the cell wall and usually composed of polysaccharides or proteins

Question 10

Slime Layer

Answer 10

a less tightly organized layer that is only loosely attached to the cell wall and can be more easily washed off. Slime layers may be composed of polysaccharides, glycoproteins, or glycolipids.

Question 11

glycocalyses.

Answer 11

allows cells to adhere to surfaces,

Question 12

Pili

Answer 12

longer, less numerous protein appendages that aid in attachment to surfaces

Question 13

fimbriae

Answer 13

short bristle-like proteins projecting from the cell surface by the hundreds. Fimbriae enable a cell to attach to surfaces and to other cells. For

Question 14

Function of F pilus or sex pilus

Answer 14

important in the transfer of DNA between bacterial cells, which occurs between members of the same generation when two cells physically transfer or exchange parts of their respective genomes