Professor Andrews - Bacteria morphology

Question 1

What are the two main cell subgroups?

Answer 1

Eukaryotes and Prokaryotes

Question 2

What two groups are found in Prokaryotes

Answer 2

Archaea & Eubacteria

Question 3

Name 7 key differences between prokaryotes and eukaryotes

Answer 3

• Eukaryotes have nucleus, double membrane bound linear genetic material, prokaryotes have free floating genetic material
• Eukaryotes have membrane bound organelles, prokaryotes don’t
• Eukaryotes undergo mitosis, prokaryotes undergo binary fission
• Eukaryotes have multiple chromosomes, prokaryotes have 1 chromosome
• Prokaryotes can have plasmids, eukaryotes can’t
• Eukaryotes have histones to organise their chromosomes, prokaryotes don’t
• Eukaryotes have cell walls occasionally whereas prokaryotes usually have them

Question 4

Name and briefly explain bacterial organelles

Answer 4

• Gas Vacuoles - Tubes of protein, bacteria regulate the amount of gas in them and the number of tubes. Allows depth control in a column of water
• PHS Storage Granules - Store potential energy sources, metabolise during starvation
• Magnetosome - Crystals used to orientate in magnetic field can regulate location. Made of iron
• Ribosomes - 70s, 30s and 50s subunits. Bacterial 16S ribosomal RNA, 23S ribosomal RNA, and 5S rRNA genes are typically organized as a co-transcribed operon.
• Cell Wall - Can be Gram +ve & -ve made up of peptidoglycan

Question 5

Describe differences in prokaryotic and eukaryotic ribosomes

Answer 5

• Eukaryotic - 80s ribosomes, with 40s and 60s subunits. They have poly a tail, cap RNA which can separate prokaryotes from eukaryotes. Each gene has its own promoter. They generally have many copies of the rRNA genes organized in tandem repeats. The 18S rRNA in most eukaryotes is in the small ribosomal subunit, and the large subunit contains three rRNA species (the 5S, 5.8S and 28S in mammals, 25S in plants, rRNAs).
• Prokaryotic - 70s ribosomes, 30s and 50s subunit. Bacterial 16S ribosomal RNA, 23S ribosomal RNA, and 5S rRNA genes are typically organized as a co-transcribed operon.

Question 6

What is the difference between bacterial, eukaryotic & fungal cell walls?

Answer 6

• Bacterial - peptidoglycan
• Eukaryotic - cellulose & pectin (plants)
• Fungi - Chitin

Question 7

Describe the main differences between gram +ve and gram -ve cell walls (10 properties/features)

Answer 7

1) Chemical composition
\+ = Peptidoglycan, teichoic acid and lipotechoic acid
- = Lipopolysaccharide, lipoproteins and peptidoglycan
2) Outer membrane
\+ = Absent
- = Present
3)  Number of layers
\+ = One
- = Two
4) Thickness
\+ = Thick (20-80nm)
- = Thin (8-10nm)
5) Resistance to molecules
\+ = Less
- = More
6) Lipid
\+ = Less
- = More
7)  Periplasmic space
\+ =  Present in some
- = Present in all
8) Porins proteins
\+ = Absent
- = Present
9) Peptidoglycan
\+ = More
- = Less
10) Permeability of molecules
\+ = More penetrable
- = Less penetrable