Lecture 4: Infectious disease and bacteria.

Question 1

What are prions?

Answer 1

Infectious proteins, very small, different from viruses.

Question 2

True or false? Domains of life are determined base on DNA.

Answer 2

False, they are based on RIBOSOMAL RNA.

Question 3

List 3 main differences between bacteria and eukaryotic cells.

Answer 3

Bacteria lack membrane bound organelles. They have a nucleoid instead of chromosomes. They have peptidoglycan cell walls. They also replicate by binary fission.

Question 4

List 4 key components of bacteria.

Answer 4

They only have ribosomes (not membrane bound) and cell wall. Their cytoplasmic matrix is mostly water, hypertonic. They may carry one or more plasmids, which are circular dsDNA that can replicate independently of the circular DNA. Their nucleoid contains NO introns or exons.

Question 5

How many genes are “core” genes in E. coli?

Answer 5

Approximately 2000 genes. They have 6000, the rest are known as accessory genes.

Question 6

True or false? Bacteria can acquire new genes.

Answer 6

True. They can do so via plasmids, transposons, integrons, bacteriophages etc.

Question 7

Describe some key features of gram positive bacteria.

Answer 7

Thick peptidoglycan wall that cannot be decolourised from alcohol washing. They also contain teichoic acids (polymers of glycerol) and lipoteichoic acids (bound to plasma membrane beneath).

Question 8

Describe some key features of gram negative bacteria.

Answer 8

They have an outer membrane then a periplasmic space in which we find a thin peptidoglycan wall. This outer membrane is easily washed away by alcohol, which is what allows it to be decolourised. Outer membrane is stabilised by a lipopolysaccharide and can also act as an endotoxin.