lecture 6

Question 1

Periplasmic space

Answer 1

region between the plasma membrane and the cell wall. This area is loaded with enzymes

Question 2

Enzymes

Answer 2

are present for catabolizing growth media into smaller sub-units. In addition, there are enzymes called restriction exonucleases. These are enzymes that will destroy foreign DNA.

Question 3

penicillinase

Answer 3

Another enzyme, penicillinase may be found. Penicillinase hydrolyzes and thereby inactivates the antibiotic penicillin

Question 4

Plasma membrane (cell membrane)

Answer 4

phospholipid bilayer with non-stationary proteins.

Described as the fluid mosaic model. The membrane serves as a site for selective permeability

Question 5

Selective permeability of molecules moving through the plasma membrane is a function of the
following:

Answer 5

a. size and molecular weight
b. electric charge or polarity
c. lipid solubility
d. presence or lack of presence of enzymes called permeases

Question 6

In prokaryotes, ATP production

Answer 6

sites are located on the plasma membrane

Question 7

mesosomes

Answer 7

Electron micrographs depicted membranous intrusions of the bacterial plasma membrane. These were called mesosomes. Original theories considered these mesosomes to be structures associated with cell division or concentration of metabolic activity. Now they are considered to be artifacts of electron microscope preparation.

Question 8

Cytoplasmic contents

Answer 8

The nucleoid region
Plasmids
Ribosomes 
RNA
Inclusions
Endospores

Question 9

The nucleoid region

Answer 9

contains a single, looped, circular ( no free ends) chromosome. This area comprises approximately 10% of the cell volume. It is free within the cell as it is not membrane bound. The DNA on the chromosome is organized into 2000 to 3000 genes

Question 10

Plasmids

Answer 10

Plasmids are extrachomosomal loops of DNA that replicate independently of the chromosome

Question 11

Ribosomes

Answer 11

Ribosomes are sites for protein synthesis. Thousands are present in a bacterial cell. They are made up of rRNA (ribosomal RNA) and protein.

Question 12

RNA

Answer 12

Bacterial cells have the full complement of RNA. This includes m(messenger)RNA, t(transfer)RNA and r(ribosomal)RNA

Question 13

Inclusions

Answer 13

There are several kinds of inclusions or reserve deposits in prokaryote cells. These include:
volutin (metachromatic) granules
polysaccharide granules
lipid inclusions
sulfur granules

Question 14

volutin (metachromatic) granules

Answer 14

concentrations of polymetaphosphates. These are reserves of excess inorganic phosphates often times seen in older cells

Question 15

polysaccharide granules

Answer 15

-consist of glycogen and starch

Question 16

lipid inclusions

Answer 16

PHB (polyhydroxybutarate) is a common lipid storage material

Question 17

Endospores

Answer 17

Members of the genera Bacillus and Clostridium can form resistant, dormant, non-metabolizing forms of these cells called spores, during adverse conditions. This process is
called sporogenesis

Question 18

Spores

Answer 18

These spores are for protection and not reproduction. These structures are formed internally as endospores. Upon liberation, they are called free spores or just spores.
Spores as endospores or as free spores resist staining and display refractility. They contain low amounts of water and high amounts of calcium. They also contain high amounts of a substance known as dipicolinic acid (DPA) not to be confused with DAP, which is found in
peptidoglycan

Question 19

germination

Answer 19

Favorable conditions will restore theses cells to their vegetative forms. This process is called germination.

Question 20

spore shapes

Answer 20

Spores have different shapes and different locations in varying species. When observing the endospore in Clostridium tetani, the endospore is swollen and terminally located.
This can help in identification. Sporulation has been used as one of the biological models to study the process of differentiation

Question 21

Cell wall synthesis

Answer 21

When Gram positive cells divide, the new cell wall material is laid down at the septum, or area of cross wall formation. When Gram negative cells divide, the new cell wall growth is spread out in what is described as an intercalated pattern.

Question 22

Growth of Bacterial populations in liquid media

Answer 22

A. Lag Phase
B. Log Phase
C. Stationary Phase
D. Death ( Decline) Phase

Question 23

Lag Phase

Answer 23

1. This is a time of cellular adaptation. The bacterial cell is in its “physiologic youth.”
2. Cells are not dividing, yet they are extremely active. We observe the induction of
   enzymes and the synthesis of precursor units.
3. Increases in cell metabolism and mass occur without cell division. Cell size increases

Question 24

Log Phase

Answer 24

1. Observed is exponential or geometric growth.
2. Division occurs at a constant and maximal rate.
3. These young cells are smaller in size and give the most consistent Gram stain. The best
   time to Gram stain is therefore in the Log Phase.
4. The division is not synchronous. The population however, is dividing so often, the cells
   are uniformly small in size.
5. Nutrients are still in excess and the cells are maximizing the utilization of the nutrients.
6. Natality is greater than mortality

Question 25

Stationary Phase

Answer 25

1. Natality is now equal to mortality.
2. The medium is now supporting the maximum concentration of cells.
3. Nutrients become limiting and are no longer in excess.
4. We see the appearance of granules, the accumulation of toxic wastes and the initiation
   of sporogenesis during this phase.
5. Cell walls may start to weaken. Old Gram positive cells may now revert to Gram
   negative.
6. Carbon dioxide levels may increase, and pH will decrease. Oxygen levels decline

Question 26

Death or Decline Phase

Answer 26

1. Mortality rates now exceed natality rates.
2. Death occurs at a constant and maximal rate. This geometric or exponential decline is
   the reverse of the Log Phase.
3. We see the maximal activity of autolytic enzymes if present.

Question 27

When examining a colony, the cells at the

periphery are those that are

Answer 27

in the Lag Phase
These are cells that are reaching out to new and unused
media.

Question 28

The layer of cells just interior to these cells would be in

Answer 28

the Log Phase

Question 29

Moving interiorly, we find the cells in the

Answer 29

Stationary Phase

Question 30

Those cells at the very middle of the colony would be in the

Answer 30

Death or Decline Phase