Q 01/05

Which nickname, popularized by a 1957 Scientific American article, do mitochondria carry for making most of our ATP?

A) Protein factory of the cell

B) Powerhouse of the cell

C) Control center of the cell

D) Post office of the cell

Answer · why

B) Powerhouse of the cell

Powerhouse of the cell was the title of Philip Siekevitz's article, and the phrase stuck. A single liver cell can hold more than 2,000 mitochondria.

Q 02/05

Which poison jams the last enzyme of the electron transport chain, leaving cells unable to use oxygen?

A) Cyanide

B) Arsenic

C) Strychnine

D) Ricin

Answer · why

A) Cyanide

Cyanide blocks complex IV, so cells suffocate with oxygen all around them. Victims can turn cherry red because their veins still carry the oxygen that...

Q 03/05

Which gas, released as yeast ferments the sugars in dough, makes a loaf of bread rise?

A) Nitrous oxide

B) Carbon monoxide

C) Carbon dioxide

D) Hydrogen sulfide

Answer · why

C) Carbon dioxide

Carbon dioxide bubbles get trapped in the stretchy dough, leaving the air pockets seen in every slice. Bakers use the same yeast species that brews be...

Q 04/05

Which change after death happens because muscle fibers, starved of ATP, can no longer release their grip?

A) Livor mortis

B) Algor mortis

C) Pallor mortis

D) Rigor mortis

Answer · why

D) Rigor mortis

Rigor mortis sets in because muscle needs ATP to relax, not just to contract. It peaks about 13 hours after death and fades as the tissue starts to br...

Q 05/05

Which organ is only about 2% of human body weight yet burns roughly a quarter of the body's glucose?

A) Brain

B) Heart

C) Lungs

D) Stomach

Answer · why

A) Brain

Brain tissue also takes about a fifth of the oxygen the body uses. It runs mostly on glucose, which is why very low blood sugar can cause a blackout.