(Biological and Biochemical) Flashcards

Which cell type in the nervous system forms the myelin sheath in the peripheral nervous system?

Answer: Schwann cells

Schwann cells myelinate axons in the peripheral nervous system, while oligodendrocytes perform the same function in the central nervous system.

A substrate analog that binds irreversibly to an enzyme's active site is best described as what kind of inhibitor?

Answer: Suicide (mechanism-based) inhibitor

Suicide inhibitors (mechanism-based inhibitors) bind covalently and irreversibly to the active site, permanently inactivating the enzyme.

Which phase of meiosis is responsible for genetic recombination through crossing over?

Answer: Prophase I

Crossing over between homologous chromosomes occurs during Prophase I of meiosis, at the tetrad stage (synapsis), increasing genetic diversity.

Which hormone stimulates the reabsorption of sodium in the collecting duct of the kidney?

Answer: Aldosterone

Aldosterone, a mineralocorticoid secreted by the adrenal cortex, acts on the collecting duct to increase Na+ reabsorption and K+ secretion.

What is the Michaelis constant (Km) a measure of?

Answer: Substrate affinity for the enzyme

Km is the substrate concentration at which reaction velocity is half of Vmax; a lower Km indicates higher affinity of the enzyme for its substrate.

Which lipid modification is required to anchor a protein to the outer leaflet of the plasma membrane?

Answer: GPI anchor

GPI (glycosylphosphatidylinositol) anchors attach proteins to the extracellular leaflet of the plasma membrane via a lipid-linked glycan bridge.

In a feedback inhibition pathway, the end product of a biosynthetic pathway typically inhibits which enzyme?

Answer: The first (committed) step enzyme

End-product (feedback) inhibition classically targets the first committed step of the pathway, preventing wasteful synthesis when the product is abundant.