Type: Knowledge | Weight: 10% of Exam
Tests conceptual understanding of biological processes at the molecular level.
Key Topics:
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According to the Central Dogma of molecular biology, which of the following represents the typical flow of genetic information?
DNA → RNA → Protein
The Central Dogma describes the flow of genetic information within a biological system: DNA is transcribed into RNA, which is then translated into Protein (DNA→RNA→Protein).
In the Michaelis-Menten equation, what does the constant Km represent?
The substrate concentration at which the reaction velocity is half of Vmax
Km (Michaelis constant) is defined as the substrate concentration at which the reaction rate is half of the maximum velocity (Vmax/2). It is an inverse measure of the enzyme's affinity for the substrate.
Which level of protein structure is primarily stabilized by hydrogen bonds between the carbonyl oxygen and the amide hydrogen of the peptide backbone?
Secondary structure
Secondary structures, such as α-helices and β-sheets, are stabilized by hydrogen bonds formed between atoms of the polypeptide backbone (specifically the carbonyl group of one residue and the amide group of another).
During DNA replication, which enzyme is responsible for unwinding the DNA double helix at the replication fork?
Helicase
DNA Helicase is the enzyme responsible for breaking the hydrogen bonds between base pairs, thereby unwinding the DNA double helix to create the replication fork.
In hybridoma technology for monoclonal antibody production, which agent is commonly used to fuse B-cells with myeloma cells?
Polyethylene glycol (PEG)
Polyethylene glycol (PEG) is a fusogen used to facilitate the fusion of plasma membranes between B-cells and myeloma cells to form hybridomas.
A mutation changes a Glutamate residue (negatively charged) to a Valine residue (hydrophobic) on the surface of a protein. How is this most likely to affect the protein structure?
It will likely cause aggregation due to the exposure of a hydrophobic patch.
Replacing a charged, hydrophilic residue (Glutamate) with a hydrophobic one (Valine) on the surface exposes a hydrophobic patch to the aqueous environment. This is thermodynamically unfavorable and often leads to protein aggregation (as seen in Sickle Cell Anemia hemoglobin).
An enzyme has a Km of 2 mM for its substrate. If the substrate concentration is 2 mM, what is the reaction velocity (V0)?
0.5 Vmax
By definition, Km is the substrate concentration [S] at which the reaction velocity is half the maximum velocity. Since [S]=Km=2 mM, V0=0.5 Vmax.
Which of the following modifications occurs at the 5' end of eukaryotic mRNA during processing?
Addition of a 7-methylguanosine cap
Eukaryotic mRNA is modified at the 5' end by the addition of a 7-methylguanosine cap (5' cap), which protects the mRNA from degradation and assists in translation initiation.
Why are Okazaki fragments formed during DNA replication?
Because DNA Polymerase can only synthesize DNA in the 5′→3′ direction and the strands are antiparallel
DNA strands are antiparallel, and DNA Polymerase can only synthesize in the 5′→3′ direction. Therefore, on the lagging strand (3′→5′ template), synthesis must occur discontinuously away from the replication fork, creating Okazaki fragments.
What is the specific function of the HAT (Hypoxanthine-Aminopterin-Thymidine) medium in hybridoma selection?
It allows only fused hybridoma cells to survive by blocking the de novo nucleotide synthesis pathway.
Aminopterin in HAT medium blocks the de novo nucleotide synthesis pathway. Myeloma cells lack the salvage pathway enzyme (HGPRT) and die. Unfused B-cells die naturally. Only hybridomas (which have HGPRT from the B-cell) can use Hypoxanthine and Thymidine via the salvage pathway to survive.
