Wednesday, April 26, 2006

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!)

20 Comments:

Blogger Jamsie said...

Q1. How are proton gradients created in bacteria?

Protons are removed from the cytosol by reduction of a hydrogen carrier on the inside of the membrane and are released outside the cell by reduction of an electron carrier on the outside of the membrane.

April 27, 2006 8:51 pm  
Blogger Jamsie said...

Q2. What is the role performed by outer-membrane pores (porins) of gram-negative bacteria?

Gram -ve bacteria have a hydrophobic outer membrane thus water and dissolved ions would not readily diffuse across the membrane. Therefore gram -ve bacteria have pores(porein) which can fix this problem by transporting water molecules and other hydrophillic solutes into the periplasm as long as they are no longer than 600 to 700 daltons.

April 27, 2006 9:02 pm  
Anonymous microbialgenes said...

Q1. And where to the electrons finally go Jamesie?.

What are the mann carriers in the membrane?

Q2: Very good answer Mr J

April 28, 2006 9:51 am  
Anonymous Jamsie said...

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.

April 28, 2006 4:34 pm  
Blogger Microbe Pundit said...

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?

April 28, 2006 8:09 pm  
Blogger Microbe Pundit said...

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?

April 28, 2006 8:11 pm  
Anonymous Anonymous said...

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.

April 28, 2006 11:14 pm  
Anonymous Anonymous said...

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

April 28, 2006 11:18 pm  
Blogger Microbe Pundit said...

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.

May 01, 2006 9:39 am  
Blogger Microbe Pundit said...

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?

May 01, 2006 9:41 am  
Anonymous Anonymous said...

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.

May 04, 2006 7:58 pm  
Anonymous microbialcells said...

Thats right anon. The phospate ester on Glu-6 P is recovered as ATP

May 05, 2006 8:07 pm  
Anonymous Anonymous said...

what is the justification for combining energy and reducing power into a single entity driving force.

May 23, 2006 6:19 pm  
Anonymous Anonymous said...

is it to do with creating an electrical potential to aquire ATP via the proton motive force.

May 23, 2006 6:21 pm  
Anonymous microbialcells said...

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.

June 03, 2006 9:22 am  
Anonymous fam said...

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

June 07, 2006 11:07 pm  
Blogger Microbe Pundit said...

yes thats right fam. Thank you so much for helping me with teaching these last 13 weeks

M. Pundit Ph.D.
;-)

June 09, 2006 3:29 pm  
Anonymous Anonymous said...

what is the importance of the proton motive force? where do the protons come from and where do they go?

June 14, 2006 4:06 pm  
Anonymous Anonymous said...

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?

June 14, 2006 6:31 pm  
Anonymous Anonymous said...

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.

April 26, 2007 10:27 am  

Post a Comment

Links to this post:

Create a Link

<< Home