sa group 4 to teh

Which of the following factors does NOT influence the separation of molecules during electrophoresis?

• The type of gel or liquid medium used

• The size of the molecule

• The temperature of the molecules being separated

• The charge of the molecule

Answer explanation

The temperature of the molecules does not affect their separation during electrophoresis. Factors like size, charge, and the medium used determine how molecules migrate in an electric field.

How does the combination of gas chromatography (GC) and mass spectrometry (MS) enhance the identification and quantification of compounds in complex mixtures, and why is this technique particularly suited for volatile compounds?

• GC separates compounds based on volatility, while MS provides structural information through ionization, making it ideal for volatile compounds.

• GC separates compounds based on their volatility using a gas phase, while MS identifies non-volatile compounds by utilizing ionization and interaction with the stationary phase.

• The technique eliminates the need for sample preparation and directly analyzes solid compounds.

• The technique eliminates the need for sample preparation and directly analyze liquid compounds

Answer explanation

Gas chromatography (GC) separates compounds based on their volatility, while mass spectrometry (MS) identifies the separated compounds by analyzing their mass-to-charge ratio through ionization. This combination allows for precise analysis of volatile compounds and detailed structural information.

You were tasked with determining the protein content of a newly manufactured milk sample in a laboratory. Due to the complexity of the protein mixtures, you had some difficulty separating the protein molecules. Which method do you intend to utilize instead?

• LiquidChromatography-Mass Spectrometry

• Capillary Isoelectric Focusing

• Tandem Mass Spectrometry

• Two-dimensional Electrophoresis

Answer explanation

Two-dimensional gel electrophoresis (2DGel) is a successful method used for the detection and analysis of proteins. It has been designed as a combination of the 2DGel, IEF and SDS-PAGE methods, and is used in the analysis of complex protein mixtures

The following are NOT a function of Capillary Gel Electrophoresis, EXCEPT:

• It separates only non-volatile protein molecules.

• It separates proteins by size and determines molecular mass using the sieving phenomenon.

• It separates proteins primarily by their mass-to-charge ratio.

• It separates proteins through a gel in a direction that depends on the sign of their charge, and at a rate that depends on the magnitude of the charge, and the friction to their movement.

Answer explanation

Capillary gel electrophoresis (CGE) is a powerful method for analysis of biopolymers such as DNA, RNA, and proteins by sieving phenomena, according to size (molecular weight).

What is the primary advantage of using capillary electrophoresis (CE) in the detection of gluten in food products labeled as gluten-free?

• It can separate gluten proteins based on their size and charge, allowing for accurate quantification.

• It can detect gluten at very high concentrations, but not at low concentrations

• It can only detect gluten in certain types of food products, such as bread and pasta.

• It is a more expensive and time-consuming method compared to other detection techniques.

Answer explanation

CE is effective for detecting gluten and can accurately quantify its presence by separating the gluten proteins based on their physical properties, making it suitable for ensuring compliance with gluten-free labeling standards.

Mass spectrometry involves several critical components, each serving a unique function. Which of the following is NOT a primary function of the ion source in a mass spectrometer?

• To convert sample molecules into charged particles (ions)

• To amplify the ion signal for detection

• To maintain a vacuum environment within the instrument 

• To separate ions based on their mass-to-charge ratios

Answer explanation

The ion source is responsible for ionizing the sample, not for separating ions based on their mass-to-charge ratios, which is the function of the mass analyzer.

Which of the following best describes the principle of mass spectrometry?

• The mass spectrometer measures the weight of a molecule by detecting light absorption.

• The mass spectrometer generates multiple ions from the sample under investigation, sorts and separates them according to their mass-to-charge ratio, and records their relative abundance.

• The mass spectrometer sorts molecules by their chemical bonding and size alone.

• The mass spectrometer identifies compounds based on their boiling points and melting points.

Answer explanation

Mass spectrometry is based on sorting ions by their mass-to-charge ratio (m/z) and determining their abundance to identify compounds or molecular structures.

Liquid Chromatography-Mass Spectrometry (LC-MS) is used for the following purposes EXCEPT:

• To separate compounds in liquid samples based on polarity

• To analyze non-volatile, polar molecules using advanced ionization methods

• To chemically transform non-volatile compounds in liquid samples

• To identify chemicals in complex liquid mixtures

Answer explanation

LC-MS is an analytical tool designed to identify and analyze compounds by separating them based on polarity. It does not perform chemical transformations; this is a feature of chemical synthesis.

At a pH higher than the isoelectric point (pI) of a protein, the protein will have a _____________

• Negative net charge

• Positive net charge

• Neutral charge

• Constant charge regardless of pH

Answer explanation

Proteins become negatively charged at pH values above their isoelectric point due to deprotonation of amino acid side chains.

A food safety laboratory receives a batch of chicken suspected to be contaminated with Salmonella. The team extracts bacterial DNA from the samples and amplifies it using PCR. They then load the amplified DNA onto a gel for analysis.

What is the primary purpose of using gel electrophoresis in this situation?

• To measure the protein concentration in the chicken samples

• To destroy the Salmonella DNA and eliminate contamination

• To identify the presence of Salmonella by analyzing the DNA bands formed on the gel

• To isolate Salmonella cells from the chicken for further growth in culture

Answer explanation

Gel electrophoresis is used to separate and visualize DNA fragments. In this case, it helps confirm the presence of Salmonella by identifying specific DNA patterns.