Lecture 2 - Plasma membrane Flashcards
Give 4 reasons why bacterial physiology is used
- Explains ubiquity and success = evolution, survival, adaptation
- Explains beneficial and detrimental effects
- Insight into life and evolution ie expression of genome
- Strategic dvlpmt of antibacterials
List the 5 components of the bacterial cell envelope
- Plasma membrane (PM) = all
- Cell wall (CW) = most
- Outer membrane (OM) = some
- Periplasmic space (P) = some
- Flagella, pili, fimbriae, capsules, S layers = some
What are the 7 functions of the cell envelope?
- Rigidity and structure
- Prevent osmotic lysis
- Encloses contents
- Interact with external environ
- Receptors to respond to external environ
- Motility and attachment
- Critical to evolution eg monoderms or diderms 1st unknown
Describe bacterial lipids incl hopanoids and how they differ from eukaryotic lipids
- Differ bc no sterols/cholesterol except mycoplasma
- Hopanoids = sterol-like molecules that stabilise membrane and increase survival under stress
Describe the 2 types of proteins
- Peripheral (20-30%) = loosely connected, easy removal, water soluble
- Integral (70-80%) = not easily removed, insoluble, amphipathic
Define the fluid mosaic model and the current evidence against it
- Proteins float in homogenously distributed lipids, move laterally
- Functional membrane microdomains (FFMs) with unique integral flotillins = assemble protein complexes for specific processes
Describe the function of the PM as a selectively permeable osmotic barrier
Retain contents and prevent leakage
Describe the 2 functions of the PM controlling movement of chemicals
- Passive barrier to polar, charged, large
- Transport systems for uptake, excretion, secretion
List the 7 cellular processes that the PM functions as a site of
- Assembly and synthesis of lipids/proteins
- Assembly and secretion of extracellular proteins
- Enzymes
- Energy generation
- Receptor molecules
- Motility
- Chromosome attachment and separation
Describe passive diffusion - energy requirements, conc grad, types of molecules
- No energy
- Down conc grad, rate depends on size
- Small, neutral, weakly charged
Describe facilitated diffusion - energy requirements, conc grad, 2 transport proteins, conc grad
- No energy
- Channel proteins = pores; carrier proteins/permeases that change conformation
- Down conc grad till equal, depends on size, faster than passive
Describe overall active transport - energy, conc grad, proteins
- ATP or proton motive force energy
- Against conc grad
- Permeases and peripheral substrate binding proteins
Describe primary active transport - transporter, type of transporter, modifications
- ATP binding cassette (ABC) transporters
- Uniporter
- No mods to substance
What is the 3 step process of primary active transport?
- Solute binding protein binds substrate, attaches to transporter
- ATP hydrolysis releases energy at transport complex
- Substrate transported thru pore
Describe secondary active transport - energy source, modifications, type of transporter and subtypes
- Potential energy from ion gradiens
- No mods
- Cotransporters = 2 substances incl ion
What are the 3 types of cotransporters and give an example of each
- Symporters = same direction eg H+ and solute
- Antiporters = opposite directions eg H+ in solute/Na+ out
Describe group translocation active transport - solutes, type of transporter, mods, system used
- Glucose and mannitol
- Uniporter
- Chemically mods = uptake when membrane de-energised
- Sugar phosphotransferase system (PTS) or phosphorelay system
Describe the 4 step process of the sugar phosphotransferase system (PTS)
- Phosphoenolpyruvate (PEP) donates phosphate to enzyme 1
- E1 donates to heat stable protein HPr
- HPR donates to E2a to E2b
- E2b translocates and phosphorylates sugar across using E2c permease
