Study Questions relating to mechanisms of nutrient uptake by bacteria.
Q1. How are proton gradients created?
Q2. What is the role performed by outer-membrane pores (porins) of gram-negative bacteria?
Q3. Give two examples of facilitated diffusion as a substrate uptake mechanism in bacteria?
Q4. How is facilitated diffusion selective?
Q5. The group translocation process accomplishes transport by chemically modifying the solute, which arrives inside the cell as a different molecule.
Give an example of substrate uptake by group translocation in bacteria, and describe the source of energy used for active uptake.
Your responses in comments please.(They can be anonymous!)
Q2. What is the role performed by outer-membrane pores (porins) of gram-negative bacteria?
Q3. Give two examples of facilitated diffusion as a substrate uptake mechanism in bacteria?
Q4. How is facilitated diffusion selective?
Q5. The group translocation process accomplishes transport by chemically modifying the solute, which arrives inside the cell as a different molecule.
Give an example of substrate uptake by group translocation in bacteria, and describe the source of energy used for active uptake.
Your responses in comments please.(They can be anonymous!)
posted by GMO Pundit at 1:43 pm
18 Comments:
Q1. And where to the electrons finally go Jamesie?.
What are the mann carriers in the membrane?
Q2: Very good answer Mr J
Would the main carrier be the membrane ATP synthase or the F1Fo ATPase. Fo forms a proton channel through the membrane. Passage of 3 to 4 protons form the enviro threw Fo drives F1 to form one ATP molecule from ADP. This is most helpful during respiration.
Also note that hydrogen can act as a proton or an election. It can be transferred to either NAD+ or NADP+ giving reduced forms as NADH or NADPH respectively. The NADH be regulated by the NADH dehyrdogenase I within the electron transport system.
Jamie,
I was thinking of carriers for electrons in the membrane that include cytochromes and unbiquinone.
To continue these questions though: what are the TERMINAL acceptors for the electrons?
Jamie:
PS. Maybe it would be good for you to to dexcribe where the protons for the F1Fo ATPase come from and where they go to?
Q3. Give two examples of facilitated diffusion as a substrate uptake mechanism in bacteria?
First eg: glucose transport--some species of Zymomoans and streptococcus
2nd eg: glycerol transport--E.coli and other enteric bacteria.
Q4. How is facilitated diffusion selective?
Through the presence of channel proteins which form selective channels and thus facilitating passage of specific molecules.
Give an example of substrate uptake by group translocation in bacteria, and describe the source of energy used for active uptake.
One of eg would be the transport of glucose from outside and trasnlocated in become glu-6-P.
One source of energy used is phophoenolpyruvate
Q3. Give two examples of facilitated diffusion as a substrate uptake mechanism in bacteria?
First eg: glucose transport--some species of Zymomonas and streptococcus
2nd eg: glycerol transport--E.coli and other enteric bacteria.
Yes these are right, and also there are ammonia channels in E. coli as I mentioned in the lecture.
Q4. How is facilitated diffusion selective?
Through the presence of channel proteins which form selective channels and thus facilitating passage of specific molecules.
RIGHT ON!!.They can even discriminate between optical isomers (=chiral forms)in the same fashion as enzymes.
Give an example of substrate uptake by group translocation in bacteria, and describe the source of energy used for active uptake.
One of eg would be the transport of glucose from outside and trasnlocated in become glu-6-P.
One source of energy used is phophoenolpyruvate
Yes correct. This is an IMPORTANT example.
FOLLOW UP QUESTION What are the advantages gained by the cell through this process?
FOLLOW UP QUESTION What are the advantages gained by the cell through this process?
This can be regarded as free gift gaining from glycolysis pathway where phosphorylation of glu to glu-6-P have to be made anyway. This facilitates the transport of glucaose.
Thats right anon. The phospate ester on Glu-6 P is recovered as ATP
what is the justification for combining energy and reducing power into a single entity driving force.
is it to do with creating an electrical potential to aquire ATP via the proton motive force.
Re combining reducing power and energy in one concept;
That question was about concepts that we formulate to better ubderstant what happens inside the cell.
So perhaps the question should be altered to say what concepts about cell organisation does combining the two chemical forms, reducing power and phosphate bond energy as "driving force".
The reason for asking the question is to get you to think about processes and howw they are used and organised by cells.
what concepts about cell organisation does combining the two chemical forms, reducing power and phosphate bond energy as "driving force".
It relies on the concept that they are interconvertible such as by using transmembrane ion gradient method
yes thats right fam. Thank you so much for helping me with teaching these last 13 weeks
M. Pundit Ph.D.
;-)
what is the importance of the proton motive force? where do the protons come from and where do they go?
Dear Mr Pundit,
Where do H+ ions accumulate in Gram negative bacteria? In the periplasm?
What about Gram positives? If they accumulated outside the cell, then wouldnt the H+ be swept away by any convection currents?
Microbe Pundit says:
As far as protons being swept away, this does not alter the fact that the cell interior is more negative and alkaline than the outside, so the gradient is still there.
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