Question

2. You are studying the uptake of nutrients into a bacterium under acidic pH, neutral pH and alkaline pH. The table below shows the transport rate for nutrients under the different pH conditions. (6 points) Table 1. Transport rate for nutrients at different pH environments Alkaline pH sec 3 μM/ sec sec Compound Acidic pH 0.5 uM/ sec 60 uM/ sec sec Neutral pH 0.6 uM/ sec 30 uM/ sec 30 0.5 sec i. From this information, what transport mechanism is involved in the uptake of compound A and why? ii. Compound B and why? iii. Compound C and why?

Answer 1

Lets understand the bacterial nutrient composition :

Nutrients

– obtained from the environment- used for energy and biosynthesis of macromolecules

• Cell solids components (H, O, C, N, P and S)

• Cations (K, Mg, C a, Fe, Mn, C o, Cu, Mo and Zn)

• Anions (Cl)

• Vitamins

Now lets see the basic mechanism of food intake in bacteria: Passive Transport comprise :Passive/simple diffusion and Facilitated diffusion, Active transport,Group translocation, Receptoral intake.

Coming to the question :

Compound A: We can see there is no change in the nutrient uptake by the bacterial cell even at various Ph changes. This is due to the facilitated diffusion intake , wher irrespective of the nutrient present outside the cell the presence of carrier proteins (sometimes called permeases) are embedded within the cell membrane and provide a channel or pore across the membrane barrier, allowing for the passage of larger molecules. If the concentration gradient dissipates, the passage of molecules into the cell stops. Each carrier protein typically exhibits specificity, only transporting in a particular type of molecule or closely related molecules

Compound B: Here there is a acidic Ph in which the bacteria is able intake much nutrient. Only Aciodophilic bacterias can thrive in this Ph. The mechanism is Secondary active transport which utilizes energy from a proton motive force (PMF). A PMF is an ion gradient that develops when the cell transports electrons during energy-conserving processes. Positively charged protons accumulate along the outside of the negatively charged cell, creating a proton gradient between the outside of the cell and the inside. ex: Thiobacillus thiooxidans

Compound c : Neutral Ph is the condition wher there is a maximum nutrient intake. This might be the simple diffusion of nutrients.