(Biological and Biochemical) Flashcards

Which base pairing rule describes complementary DNA strands?

Answer: A pairs with T, G pairs with C

In DNA, adenine (A) pairs with thymine (T) via two hydrogen bonds, and guanine (G) pairs with cytosine (C) via three hydrogen bonds (Chargaff's rules).

Which muscle type has intercalated discs and is under involuntary control?

Answer: Cardiac muscle

Cardiac muscle has intercalated discs containing gap junctions that allow coordinated electrical conduction, and it functions involuntarily.

The lac operon in E. coli is an example of which type of gene regulation?

Answer: Both positive and negative regulation

The lac operon is regulated negatively by the lac repressor (which blocks transcription without lactose) and positively by the CAP-cAMP complex (which enhances transcription when glucose is low).

Which immunoglobulin class is the first to be produced during a primary immune response?

Answer: IgM

IgM is the first antibody produced during a primary immune response due to its pentameric structure and early B cell expression before class switching occurs.

What is the role of helicase during DNA replication?

Answer: Unwinds the double helix by breaking hydrogen bonds

Helicase unwinds the DNA double helix by breaking the hydrogen bonds between complementary base pairs at the replication fork.

Which type of hypersensitivity reaction involves IgE and mast cell degranulation?

Answer: Type I (immediate hypersensitivity)

Type I hypersensitivity involves IgE antibodies bound to mast cells; upon re-exposure to antigen, cross-linking triggers mast cell degranulation and histamine release.

During beta-oxidation of a 16-carbon fatty acid, how many cycles of beta-oxidation occur?

Answer: 7

A 16-carbon fatty acid (e.g., palmitate) undergoes 7 cycles of beta-oxidation to produce 8 acetyl-CoA, because each cycle removes 2 carbons and n/2 - 1 = 7.