Question

Question 5. (10 marks each)

1. Give an overview of MALDI-TOF MS for bacterial identification.
2. What is the maximum theoretic ATP yield from aerobic respiration? Give a breakdown of where in aerobic respiration this ATP comes from.      
3. What are the metabolic alternatives to pyruvate metabolism in the absence of oxygen?
   

Answer 1

A) Ans=

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is a method for accurate and quick identification of bacterial species by analyzing the mass spectrum from whole bacterial cells. Bacterial mass is either derived from ribosomal or from other abundant bacterial proteins which could be used as biomarkers for subspecies discrimination. This technique is based on the generation of mass spectra from whole cells and their comparison to reference spectra.

Principle-. MALDI-TOF MS needs a stage where sample crystallization in a matrix on inert support can be made. The irradiation on the crystalline mixture with a brief laser pulse, desorbs and ionizes characteristic ions (MALDI). The ionized molecules are then accelerated in an electric field and separated, as a function of molecular weight, in a vacuum tube. The time-of-flight (TOF) of each ion is measure of the time taken by the ion to reach the detector. The ions reach the detector, more or less rapidly, according to their m/z ratio. The electrical signal is processed by the computer and converted into a mass spectrum. From analyzing the spectrum the bacterial species can be identified.

B) Ans= The Maximum theoretical yield of ATP from aerobic respiration is 38 ATPs.

Glycolysis	2 ATP
Krebs Cycle	2 ATP
Electron Transport Chain	34 ATP
TOTAL	38 ATP

C) Ans= The metabolic alternative to pyruvate metabolism in absence of oxygen is

• Lactose Fermentation.
• Alcoholic Fermentation.

(Both yield 2 ATPs)