Nature of Infection

Question 1

What are the 4 major groups of human pathogens?

Answer 1

1. Protozoa- Eukaryotes
2. Fungi- eukaryotes
3. Bacteria- prokaryotes
4. Viruses- non living.

Question 2

What are the differences between prokaryotes and eukaryotes?

Answer 2

1. prokaryotes-
   - small size
   - simple cells.
   - Single celled
   - Single circular chromosome
   - Gene strucutre
   - Rigid cell wall.
   - Rapid cell cycle.
2. Eukaryotes:
   - bigger
   - more complex
   - multiple cells
   - linear chromosomes+ histones
   - no fexible cell wall
   - mitosis.

Question 3

What are some common structures found in both cell types?

Answer 3

Prokaryotes:

• plasma membrane
• cell wall
• ribsosomes
• capsule
• flagellum
• pilli
• cytoplasm
• nucleoid

Eukaryotes:

• cell membrane
• nucleus
• ribosomes
• mitochondria
• vacuoles
• ER
• secretory vesicles/lysosomes
• centrosome
• golgi
• cytosol
• cytoskeleton.

Question 4

Describe a nucleoid

Answer 4

Contains DNA
No nuclear membrane
Chromosomes are single circular molecules.
Primitive DNA.

Question 5

What is Gram +/-?

Answer 5

Two types of cell wall varying in organisms:
Gram + = Thich PG multi-layer. Stains Gram test Purple.
Gram - = Thin PG layer. Stains Gram test Pink.

Question 6

What is the Gram test for Lipopolysaccharides and its function?

Answer 6

Gram -
Functions- Antigen + bacterial toxin.
structural role.

Question 7

What is the function of flagella and fimbriae?

Answer 7

Adherence and sex

can be Gram +/-

Question 8

Are all bacterial pilli the same?

Answer 8

No: length, number, shape, arrangement vary.

Question 9

What are the stages of protein synthesis in prokaryotes?

Answer 9

Gene–> Transcription: mRNA–> Ribosomes–> Translation: protein–> 2nd, 3rd, 4th structure–> assembly, processing, export.
These stages can be targeted by antibiotics.

Question 10

What factors affect prokaryotic growth?

Answer 10

• Food
• Temperature
• Osmotic protection
• Oxygen
• Hydrogen ion concentration.

Question 11

What are the sources of food for prokaryotes?

Answer 11

C source organinc- protein
O,H
N source- inorganic salts (Mg, K,

Question 12

What temperature do prokaryotes thrive in?

Answer 12

Mesophiles- body temperature.

Question 13

What is the ideal H concentration for prokaryotes?

Answer 13

Human commensals- pH 6.8-7.2

Question 14

What is the extent of osmotic protection needed for them?

Answer 14

0.85 % NaCl (human commensal)

Question 15

What are the stages of the bacterial growth curve?

Answer 15

1. Log phase
2. Exponential phase
3. Stationary phase
4. Decline phase

Question 16

What is the form of bacterial growth beyond planktonic growth?

Answer 16

Can form complex colonies eg biofilms