Prokaryotic cell structure

Question 1

What is phylogeny?

Answer 1

They study of the evolutionary relationship between organisms.
before RNA sequencing it was based on what the organism looked like.

Question 2

Bacterial shapes

Answer 2

Cocci - Spherical - most common in the mouth
Bacilli - Straight rods
Spirillum - Curved rods
Spirochetes - Spirals

Question 3

What are the differences between gram positive and gram negative bacteria?

Answer 3

Gram negative bacteria have a thin peptidoglycan layer, a cytoplasmic membrane (inner), outer membrane and periplasm. It appears pink in gram staining
Gram positive bacteria have a thick peptidoglycan layer, a cytoplasmic membrane. appears violet in gram-staining.

Question 4

What is endosymbiosis?

Answer 4

Ingestion of a primitive prokaryote by a primitive eukaryote followed by loss of genes from nuclear genome.

Question 5

Bacterial cytoskeleton

Answer 5

Homologues of actin and tubulin.
Actin - cell shape
Tubulin - cell division
Opposite to eukaryotes.

Question 6

Mycoproteins?

Answer 6

Bacteria that do not conform to the simple G+ve/G-ve model. They are considered G+ve because they only have a single membrane. A waxy outer layer makes them highly resistant to host defences.

Question 7

Structure of the cell membranes

Answer 7

They are both phospholipid bilayers. The cytoplasmic membrane contains enzymes fro oxidative phosphorylation. The outer membrane (only G-ve) have porins to allow ions, sugars and AA into the periplasm.

Question 8

What are lipopolysaccharides?

Answer 8

Only found in G-ve (outer membrane). Chains pack together in the outer membrane, forms an impermeable structures. it stops destruction by phagocytes
O-polysaccharides hides the cell from the immune system (each O has different immune response - causes different strains).

Question 9

Describe the cell wall in bacteria?

Answer 9

Peptidoglycan layer (thick in G+ve and thin in G-ve). Contain chains of sugars. provides mechanical strength and impermeability to G+ve cell walls.
Glycan strands have AA side chains, they are held together by peptide cross links. Bacteria cells are encased in a  single peptidoglycan molecule - join together and wrap around the cell. Peptidoglycan is found only in bacteria so antibiotics can target it.