Cytoplasmic Membrane Flashcards
Explain the composition of the cytoplasmic membrane!
It contains lipids and proteins
lipids lack sterols (steroid alcohols)
there are both peripheral and integral proteins
Explain the functions of the cytoplasmic mebrane
- controls what enters and exits the cell
- keeps cytoplasm in
- part of chemotaxis system
- part of photosynthesis system
- Energy generation
What are the two steps of ATP generation?
1) substrate level phosphorylation
ADP is phosphorylated to ATP
2) electron transport
Where is electron transport located?
plasma mebrane
Explain the electron transport chain
- A series of proteins that transfer electrons inside the PM
- Each member must be able to reduce the protein that follows it and oxidize the member that precedes it
What is the final electron acceptor in aerobes? What about in anaerobic respiration?
Aerobes - usually oxygen
Anaerobes - Nitrate or sulfate
What is Glycolysis?
Glycolysis breaks down glucose into pyruvate and small amounts of ATP
Where do the electrons come from for the electron transport chain? (4 steps)
- Glycolysis breaks glucose into pyruvate and small amounts of ATP
- Pyruvate converts to CO2 which enters the citric acid cycle aka TCA cycle
- this produces NADH and FADH2
- these provide the electrons for the ETC.
What is the chemiosmotic theory?
As electrons pass down the ETC the energy released upon each redox reaction is used to pump H+ across the PM. (proton motive force much like the one that drives flagella)
What is the result of Chemiosmosis?
the pumping of protons OUT of the cell the cell creates a pH and charge gradient that drives a proton motive force.
Explain start to end the ETC and the proton motive force
- primary electron donors NADH and FADH2 reduce the carrier one protein
- this transports the electrons until oxygen is reached
- each transfer pumps H+ out creating gradients
- ATP synthase brings the H+ back which converts ADP to ATP simultaneously.
Is the PM permeable to H+?
No, needs to be pumped in via ATPase
What is oxidative phosphorylation?
simply the process of produces ATP via the ETC with NADH and FADH2 coming from the break down of glucose -> pyruvate -> CO2
How do bacteria obtain nutrient sources from macromolecules that are too large to pass through the PM? what are the macromolecules?
- Macromolecules such as Starch and Cellulose are too large
- bacteria release digestive enzymes out of the plasma mebrane such as amylase and cellulase which break down the large molecules
- smaller transportable units come into the cell
Explain simple diffusion. Provide an example of molecules that use this method of transport
- requires no ATP
- high concentration to low concentration flow
- Oxygen and water by osmosis are only molecules to diffuse
Explain Facilitated diffusion. Provide an example of molecules that use this method of transport
- requires no ATP
- molecule still goes down concentration gradient
- uses a carrier protein called permeases to aid transport of a molecule
- specific due to binding sites
- glycerol
Explain Active transport: Binding protein DEPENDENT transport. (3 steps)
- substrate enters the OM
- periplasm binding proteins bind to the substrate
- combination goes to a transport protein inside the PM which permits passage using ATP as a energy source
in Binding protein DEPENDENT transport if a substrate binds to a transport protein in the PM what will occur?
Nothing!! its binding dependent. The substrate needs to be bound to a periplasm protein
what are some molecules that use Binding protein DEPENDENT transport
- maltose
- histidine
- arabinose
What occurs if you perform an osmotic shock (place cultured microbes into 4 degree distilled water) on microbes that use Binding protein DEPENDENT transport
Osmotic shock will disrupt the OM in most gram negative bacteria
as a result the periplasm proteins will diffuse away
now histidine, arabinose and maltose cant be taken up by the cell
Briefly explain how histidine enters the cell? (3 points)
1) HisJ is a periplasm protein that binds histidine
2) It brings it to HisM and HisQ which form a channel for the histidine to pass through
3) HisP uses up ATP to allow passage
does the protein in the periplasm pass through the transport protein too?
No!
Explain Binding protein INDEPENDENT transport (3 points)
- the solute can interact directly with the PM transport protein
- Energy used is a proton gradient, NOT ATP
- symport of H+ and solute gets solute in the cell
What molecules pass via Binding protein INDEPENDENT transport
- malate
- lactose
Can a sodium gradient be used to up take malate and lactose?
Yes, Sodium and H+ are coupled in an anti porter system. This creates a higher concentration of Na outside the cell which symports malate and lactose back into the cell
What is another common way to get sugars into the cell?
Group Translocation
modification of sugar during transport
what does the PTS System do, what is its energy source?
- Translocation system
- PTS stands for Phosphotransferase system by which when a sugar enters the cell it gets phosphorylated
- The energy used for this is PEP
does Group translocation set up a concentration gradient?
No, this is because the molecule inside the cell has been modified and therefore is not the same as the exterior molecules.
Explain the steps of the PTS system (4 points)
1) A phosphate bond is transferred from PEP to E1
2) E1 gives phosphate group to HPr
3) HPr gives it to E2
4) E2 is the actual transporter which gets the sugar across the membrane and phosphorylates it
Explain E1, HPr, and E2 in the PTS system
E1 and HPr are common to all PTS sugars. These are very conserved. E2 is specific to each sugar.
What would occur if a mutant arose in E1 or HPr
no sugars could use the PTS system to transport across PM
what would occur if a mutant arose in E2
only the specific sugar for that E2 would no longer cross the PM
