3B - Cell Walls and Cytoplasm of Bacteria

Question 1

Gram negative bacteria

Answer 1

complex cell wall (stains pink)
• Gram-negative cell walls are more complicated than gram +ve cell walls
◦ The cell wall is made up of an outer cell membrane, a much thinner peptidoglycan layer and a periplasmic space
◦ Lipopolysaccharides (LPS)- are embedded in the outer membrane and are very antigenic
◦ The outer membrane in gram –ve bacteria has a negative charge and forms a selective barrier similar to the cell membrane in eukaryotic cells
‣ Porins are like transmembrane proteins in eukaryotic cells

Question 2

Gram positive bacteria

Answer 2

simple cell wall (stains purple)
thick peptidoglycan
◦ Lipoteichoic acids (LTA) anchors peptidoglycan to the cytoplasmic membrane

Question 3

Lipoteichoic acids (LTA)

Answer 3

nchors peptidoglycan to the cytoplasmic membrane
◦ LTA’s are important antigens that stimulate the immune system of the host
◦ LTA’s are only found in G+ bacteria

Question 4

Lipopolysaccharides (LPS)

Answer 4

s embedded in the outer membrane of gram –ve bacteria.
‣ The immune response to large amounts of LPS causes a toxic response called endotoxic shock with fever and vascular changes.
‣ Therefore the LPS is also called an ENDOTOXIN
• The endotoxic properties of LPS cause the violent symptoms (diarrhea, vomiting, gas production) of infections with gram –ve organisms such as Salmonella spp and E Coli

Question 5

Complement cascade

Answer 5

‣ LPS is one of the innate activators of the complement cascade
• Activation of the complement cascade → release of cytokines and other inflammatory mediators → attraction of inflammatory cells

Question 6

Myoplasma

Answer 6

a type of pathogenic bacteria that causes disease in humans and animals, do not have cell walls but have sterols in their cell membrane for added strength

Question 7

cytoplasmic membrane of bacteria structure and functions

Answer 7

a Phospholipid bilayer with membrane proteins similar to the cell membrane of eukaryotic cells membrane proteins that act as transport proteins
◦ Functions
‣ Retains cytoplasm
‣ Selectively permeable membrane with

Question 8

Cytoplasm contains

Answer 8

cytosol and organelles(genetic material and protein production)

Question 9

location of genetic material in bacterial cells

Answer 9

Nucleoid ( chromosomal DNA) or Plasmids (genetic materal)

Question 10

functions of chromosomal DNA

Answer 10

◦ Essential cellular function
‣ Housekeeping genes
◦ Protein synthesis
‣ Essential for growth

Question 11

Escherichia coli genome info

Answer 11

◦ Single circular double stranded DNA chromosome with 4.68 million base pairs
◦ Has been completely sequenced and we know it contains about 4300 genes

Question 12

Plasmids

Answer 12

◦ Circular double stranded DNA that replicates separately from the chromosomal DNA
‣ Codes for protective characteristics such as virulence determinants and antibiotic resistance
◦ Transferred from cell to cell by conjugation (Pili) • May be transferred between species of bacteria.
◦ May be incorporated into the chromosome

Question 13

Ribosomes

Answer 13

◦ Thousands of ribosomes in a cell
◦ Consist of protein and RNA
◦ Site of new protein synthesis