MIC102 M2

Explain how the properties of phospholipids possibly led to the first cell membranes. (9)

Combined properties of hydrophilic and semi-permeable membranes created a micelle, then trapped RNA inside. (9)

Describe how lipids and proteins are transported through and into various membranes. How is this similar/ different for Gram (+)/ (-)? (9)

Lipids transport is translocated by flippase (flippase=outer, floppase=inner, scramblase=bidirectional)

Protein transport: regulated by signal recognition particles (SRPs)

• carry peptide to secretion machinery

• Sec is Gram (+), BAM is Gram (-)

How does the Sec system work? (9)

• SecA binds to signal sequence

• SecB (chaperone) prevents folding before protein is passed through channel

• Signal peptide is cleaved during transport by LepB (signal peptidase)

• requires ATP

How does BAM work? (9)

• folds proteins and inserts, with SurA, into outer membrane

• If mistake > misfolded proteins are degraded by DegP

Type III Secretion System (9)

• evolved from flagella

• deposits toxins into extracellular space/ cytoplasm

Type VI Secretion System (9)

• bacteriophages inject DNA into host

• needles passing through cell wall

How are the constituents of the cell wall put together? What are the differences between Gram (-) and Gram (+)? (9)

G(+): some species constantly lose murein at outside of cell wall so must be replaced

G(-): lipoproteins connect cell wall to outer membrane

(L14) What is the difference between antibiotic resistance and antimicrobial resistance? 

antibiotic: specifically targets bacteria

antimicrobial: umbrella term that targets across bacterial, virla, fungal, and parasitic

(L14) Describe top 6 pathways targeted by existing antibiotics.

• cell wall synthesis

• protein synthesis

• nucleic acid synthesis

• metabolic pathways

• cell membrane

• RNA transcription

(L14) Define the mechanism of action for B-lactam antibiotics (penicillin).

Penicillin binding proteins (PBPs) inhibit cell wall synthesis of cross-link peptidoglycan chains.

(L14) Explain the 4 mechanisms of acquiring antibiotic resistance.

• activation of drug efflux pumps

• inhibition of drug uptake

• alteration of drug target

• inactivation of drug by enzymes

(L14) Describe how HGT may promote antibiotic resistance.

bacteria can uptake stronger resistant genes to antibiotic drugs.

(L14) Describe how mutations in existing genes may promote antibiotic resistance.

Mutation can alter target genes that antibiotic attacks, diminishing those effects.

(L14) How can existing antibiotics be used effectively?

• no over usage

• take only when prescribed and throughout entire dosage period