Question

Each of the following medical problems involves a malfunction of an organelle or other cell structure. In each case, identify the organelle or structure involved, and indicate whether it is likely to be underactive or overactive.

a. A girl inadvertently consumes cyanide and dies almost immediately because ATP production ceases.
b. A boy is diagnosed with neonatal adrenoleukodystrophy (NALD), which is characterized by an inability of his body to break down very-long-chain fatty acids.
c. A young man learns that he is infertile because his sperm are nonmotile.
d. A young child dies because her cells lack an enzyme that normally breaks down a membrane glycolipid that therefore accumulated in the membranes of her nervous system.
e. A young child is placed on a milk-free diet because the mucosal cells that line his small intestine do not secrete the enzyme necessary to hydrolyze lactose, the disaccharide present in milk.

Answer 1

a. mitochondria, underactive

b. peroxisome, underactive

c. flagella, underactive

d. lysosome, underactive

e. Endoplasmic reticulum/Golgi apparatus/transport vesicles, underactive

Step-by-step explanation:

Cyanide is a toxic compound that inhibits the Cytochrome c Oxidase I (COI) in mitochondria, which is an enzyme known to catalyze the final step in the mitochondrial electron transfer chain. Adrenoleukodystrophy is an X-linked genetic disease caused by a mutation in the ABCD1 gene (ATP-binding cassette, subfamily D, member 1). ABCD1 encodes the adrenoleukodystrophy protein (ALDP), which is involved in the transport of long-chain fatty acids into peroxisomes. Flagella are cellular structures composed of proteins (microtubules) specialized to carry the male's DNA to the egg cell, i.e., they are responsible for sperm motility. Lysosomal storage disorders (LSDs) represent a group of inherited diseases caused by mutations capable of altering lysosome functions. LSDs are especially associated with defective (abnormal) lysosomal enzymes that are unable to degrade macromolecules such as, in this case, a membrane glycolipid. Finally, lactase is an enzyme produced in small intestine cells. Within these cells, the signal sequence of the preprolactase precursor is cleaved in the endoplasmic reticulum (ER). Subsequently, the protein precursor travels to the Golgi complex for processing (i.e., glycosylation), thereby a mature enzyme (lactase) is generated.