Bioenergetics Flashcards
At rest how much ATP does the body make a day?
1/2 your body weight. With normal amounts of work your full body weight and with heavy work one tonne.
What does chemiosmosis involve?
One or more energy release reactions. Redox creates a transmembrane gradient used to make ATP and ATP can make an energy gradient.
What are the two main sources for the Proton Motive Force?
Respiration and photosynthesis.
What are the three main uses of PFM?
ATP synthesis.
Motility.
Soulte transport.
What is the central dogma of energy conversion?
‘Release, transfer, trapping.’
Redox… transmembrane gradient…. ATP synthesis.
What step of the central drogma of energy conversion is reversible?
Transmembrane gradient…. ATP synthesis.
What step of the central dogma of energy conversion is not easily reversible?
Redox… transmembrane gradient.
How can a cell membrane resit osmosis?
If work is put in to push in the opposite direction.
What does a ‘leaky membrane’ result in?
The movement of some H+ through the membrane without any useful energy being produced.
Why do the outer membrane in bacteria and mitochondria not use chemiosmosis?
They have holes in them.
Where is the N phase found in regards to a cell?
Outside and inside an organelle.
Where is the P phase found in regards to a cell?
In the cytoplasm.
What two things can cause the breakdown of the cytoplasmic membrane?
Lsyzome and osmotic shock.
What type of bacterium does the P and N phase apply to?
Intact bacteria.
In gram negative bacteria what phase is the periplasm considered as?
P.
In what phase is ATPsynthase normally found?
N.
After osmotic shock and lyzosome activity where is the ATPase found?
Right-side-out of vesicle (N).
After the french press where is the ATPase found?
Outside out (O).
What are Mitchells 4 postulates?
- Respiratory and photosynthetic electron transfer should translocate protons.
- The ATPase should function as a reversible proton translocating ATPase.
- Energy transducing membranes should have a low effective proton conductance.
- Energy transuding membranes should posses specific exchange carriers to permit metabolites to penetrate and osmotic stability to be maintained at a high energy potential.
Why did measuring the driving force allow?
- Quantitative approach allowing calculation away from equilibrium.
- The replacement of the wrong idea about a high energy intermediate.
- Eliminates thermodynamically imposible reactions.
Energy from ATP does not come from the high energy phosphate bond. Where does the energy come form instead?
How far the mass action ratio is equilibrium.
What drives a reaction?
A increase in entropy.
How can you asses the entropy change of a system?
Measuring the flow of heat/ enthalpy across a system.
In photosynthesis what can Gibbs energy quantify?
Light absorption.
In a closed system if A becomes B what is the observed mass action ratio?
[B} obvs/ [A} obvs.
As the mass action ratio is displaced from K what happens to Gibbs free energy?
It increases.
What is Gibbs free energy at equilibrium?
0.
If the mass action ratio is smaller than K what is Gibbs?
Negative.
If the mass action ratio is bigger than K what is Gibbs?
Positive.
What two forces act on an ion gradient?
- Concentration gradient.
2. Electrochemical potential difference.
What is the membrane potential?
The electrochemical potential difference across the membrane.
What charge is inside the mitrochrondria/ bacterial cell and why?
H+ move out.
What is delta P?
The function of the electrochemical proton gradient. It has the units of mv and was defined by Mitchell.
How can TTP be used to measure the membrane potential?
The inside of the cell is negative and TTP has a positive charge (it is a cation). Despite being charged TTP can cross the membrane and sit in the bilayer as it is very hydrophobic. The amount of TTP that travels into the cell will determine the membrane potential. The TTP used is radiolaballed to quantify the data.
What is used to measure the pH of the membrane potential?
A weak acid such as acetate. This dissociates into H+ and A-. The A- will accumulate inside and HA will be at the same concentration on both sides.
What is special about thylakoid membranes and what does this show?
They have a massive pH difference and almost no membrane potential. delta P is the opposite to this. this shows that l is determined by the combination of the two and IF YOU MAKE ONE SMALLER THE OTHER GETS LARGER.
Delta p is a combination of the membrane potential and the pH difference. How was it shown that if you increase one the other will decrease?
K+ was added to reduce the membrane potential the pH difference goes up.
Membrane potential and ph difference are defined as P phase minus N phase. Which is positive and which is negative?
Membrane potential is positive as positive outside and pH diff is negative as acidic outside.
What do classic uncouplers do?
They uncouple electron transfer by carrying H+ across the membrane and not through ATP synthase. Causes energy to be wasted as heat.
FCCP/ CCP and 2-4DNP are classic uncouplers. What else are they?
Catalysts as they never get used up. This means that you only need them in small amounts.
What uncoupler is toxic and can be used as a slimming agent?
2-4 DNP.
Classic uncouplers move H+ across the membrane. What does the other category of uncouplers do to uncouple electron transfer?
They distrupt the ATP synthase so H+ can not be translocated.
What technique can be used to determine the bacterial H+/O ratio?
The oxygen pulse/ proton pulse technique.
What are the four steps of the oxygen pulse/ proton pulse technique?
- Oxidisable substrate is added to the chamber, all oxygen in the chamber is used and the bacteria become anerobic.
- Air saturated with a known oxygen medium. This causes the pumping go H+ ions and a drop in pH.
- Oxygen is exhausted and pH transient decays as the H+ leaks back in. This can be accelerated by the use of FCCP.
- Calibration with anerobic HCL occurs.
What two things does the buffer used in the oxygen pulse/ proton pulse contain and why?
Valinomycin and K+. V moves K+ across the membrane so the charge balance does not change throughout the experiment and the full extend of H+ movement can be measured.
Genes that encode ATPase are all similar in size. True or false?
False, they are all very different and can range between 79-500 amino acids.
What genes products make up the F0 domain of ATPase?
A, C, B
What gene products make up the F1 domain of ATPase?
Delta, alpha, gamma, betta, epsilon.
What did ATP genes used to make called?
unc genes (as discovered through uncoupled mutants.)
Are more genes for ATPase encoded in the mitochondria or the chloroplast?
Chlorplast. Only two genes (8,6) are now encoded in the mitochondria.
What domain of the ATPase is found in the membrane?
F0 (named after the biding drug oligomycin)
What portion of the ATPase is catalytic?
F1.
What subunits of the ATPase make up the F1 domain?
Alpha, beta, gama, delta, eplison.
What subunits of the ATPase make up the F0 domain?
A, C, B.
What subunit of the ATPase can you recover a crystal structure of?
F1.