Lecture 6

Question 1

The scientific name of an organism consist of two words. What are they?

Answer 1

Genus and species.

Question 2

True or false. The species name is capitalized

Answer 2

False. The genus name is capitalized.

Question 3

True or false. Both the genus and species name should be italicized, but only the genus name can be abbreviated.

Answer 3

True

Question 4

In Escherichia coli, which is the genus and which is the species?

Answer 4

Escerichia is the genus and coli is the species.

Question 5

What three distinct shapes are recognized in bacteria.

Answer 5

1- Sperical or ellipsoidal termed cocci
2-Cylindral or rod-shaped termed bacilli
3-Spiral shaped shaped subdivided into
-Vibros are curved rods resembling commas.
-Spirilla have a corkscrew shape and rigid bodies
-Spirochetes are like spirilla but are flexible

Question 6

Explain the 5 arrangements of the cocci cell.

Answer 6

1-Diplococci-pairs of cocci (Neisseria gonorrhoeae)
2-Streptococci- chains of cocci (Streptococcus pyogenes)
3-Staphylococci-clusters of cocci (Staphylococci aureus)
4-Tetrads- four cocci arranged in a square (Micrococcus luteus)
5-Sarcinae- cubical of eight cocci (Sarcina ventriculi)

Question 7

Explain the 4 arrangements of the bacilli cell.

Answer 7

1-Diplobacilli- pairs of bacilli (Pseudomonas aeruginosa)
2-Streptobacilli- chains of bacilli (Bacillus cereus)
3-Palisade arrangement- bacilli stacked on top of each other (Corynebacterium diphtheriae)
4-Letter arrangement - bacilli forming letters X,Y or Z (Corynebacterium diphtheriae)

Question 8

What does this unit (um) represent in measurable amount? What is it’s name and other known names.

Answer 8

1 um= 10-6 m = 1/25,400 in. um= nanometer

Question 9

What size are most bacteria?

Answer 9

0.2 um - 4 um in width x 0.3 um- 10um in length.

Question 10

What size is E. coli?

Answer 10

1.1 x 2.0 um

Question 11

List the following organism from smallest to largest- bacteria, (fungi, algae, protozoa) and viruses.

Answer 11

Virus, bacteria and (fungi, algae, protozoa).

Question 12

What factors contribute to the size of bacteria?

Answer 12

The age of the culture and medium which it’s isolated from.

Question 13

Name four characteristic of the cell wall.

Answer 13

1. The cell wall is rigid and not flexible.
2. Is responsible for the shape of the cell.
3. Protects the cytoplasm, which is the center of vital activities.
4. Plays a part in cell division.

Question 14

What is the thickness of a cell wall?

Answer 14

10-25 nm

Question 15

From Gram-positive and Gram-negative bacteria, which of them has a thinner cell wall?

Answer 15

Gram-negative.

Question 16

Define a hypotonic medium.

Answer 16

Lower solute medium relative to the cell.

Question 17

What is lysozyme?

Answer 17

An enzyme that degrades the cell wall.

Question 18

Describe osmotic lysis.

Answer 18

When Gram-positive cells are exposed to lysozyme in a hypotonic medium, they undergo rapid lysis referred to lysis osmosis.

Question 19

True or false. If lysozyme treatment is conducted in a isotonic medium, destruction of the cell wall is followed by the formation of protoplast.

Answer 19

True

Question 20

Peptidoglycan is present in the cell wall of which types of cell? What is their function?

Answer 20

Procaryotic. Responsible for the strength and shape of the cell.

Question 21

True or false. Cell wall can account for 15% of the dry weight of bacterium.

Answer 21

False, they account for 20%

Question 22

Peptidoglycan accounts for how much % of the dry wights of the Gram-positive cell?

Answer 22

50-80%

Question 23

Peptidoglycan accounts for how much % of the dry weight of the Gram-negative cells?

Answer 23

1-10%

Question 24

Name the four amino acids that create a polypeptide chain which result in cross linking, chain and lastly a sheet to occur.

Answer 24

1- L-alanine
2-D-glutamate
3-L-lysine
4-D-alanine

Question 25

True or false. A sheet of amino acids can be stacked very high for Gram-negative cells.

Answer 25

False. They can stack only once, E. coli in particular has one sheet stack. Gram-positive cell amino acid can stack several times high.

Question 26

What component makes Gram-negative cells toxic to animals?

Answer 26

LPS (lipopolysaccharides) molecules.

Question 27

What molecule anchor the outer membrane to the peptidoglycan?

Answer 27

Lipoprotein molecules.

Question 28

The binomial system of nomenclature was proposed by whom in what year?

Answer 28

Linnaeus in 1753