CLEP Biology Cell Organelle Structure/Function 4

Question 1

A researcher discovers a protein with a signal sequence targeting it to the mitochondrial matrix. Through which structure(s) must this protein pass after synthesis on cytoplasmic ribosomes?

Accepted Answer

Both the outer and inner mitochondrial membranes via translocases

Answer

Cytoplasmic proteins destined for the mitochondrial matrix must cross both the outer membrane (via TOM complex) and the inner membrane (via TIM23 complex) using translocase complexes.

Question 2

Plasmodesmata in plant cells are functionally analogous to which structure in animal cells?

Accepted Answer

Gap junctions

Answer

Both plasmodesmata and gap junctions allow direct cytoplasmic communication between adjacent cells, enabling the passage of small molecules and ions.

Question 3

Which organelle would be most abundant in a cell that secretes large amounts of digestive enzymes, such as a pancreatic acinar cell?

Accepted Answer

Rough ER and Golgi apparatus

Answer

Secretory proteins like digestive enzymes are synthesized on rough ER ribosomes, then processed and packaged in the Golgi for exocytosis.

Question 4

The mitochondrial matrix contains all enzymes needed for which metabolic pathway?

Accepted Answer

The citric acid (Krebs) cycle

Answer

The enzymes of the citric acid cycle are located in the mitochondrial matrix, where they oxidize acetyl-CoA and generate NADH, FADH2, and CO2.

Question 5

Which of the following is a key difference between prokaryotic and eukaryotic ribosomes?

Accepted Answer

Prokaryotes have 70S ribosomes; eukaryotes have 80S ribosomes

Answer

Prokaryotic ribosomes are 70S (50S + 30S subunits) while eukaryotic cytoplasmic ribosomes are 80S (60S + 40S subunits); this difference is exploited by many antibiotics.

CLEP Practice Test

CLEP Practice Test

CLEP Biology Cell Organelle Structure/Function 4