Structure and function of the cell — organelles, membrane transport, and the difference between plant and animal cells. The exam rewards knowing not just what each organelle is called, but what job it actually does. Every question comes with a written explanation of the underlying function.
Mitochondria produce usable energy (ATP) from food in nearly every cell; chloroplasts capture light energy to produce food, and only exist in plant and some protist cells — mixing up which organelle does which job is one of the most common errors on this subtopic.
Osmosis is specifically the diffusion of water across a semipermeable membrane — using it as a catch-all for any substance moving down its concentration gradient misses what makes it distinct.
Red blood cells lack a nucleus, and prokaryotic cells lack membrane-bound organelles entirely — a question describing an unusual cell is testing whether that exception is known, not testing a typo.
Straight from the bank — one per difficulty tier. Reveal the answer to see the explanation you'd get in a real session.
Which organelle is primarily responsible for producing the cell's usable energy?
A — Mitochondria. Mitochondria convert nutrients into ATP, the cell's usable energy currency, through cellular respiration — earning them the nickname "the powerhouse of the cell." Chloroplast (B) captures light energy to produce food in plant cells, a related but distinct process.
A cell is placed in a solution with a much higher solute concentration than the fluid inside the cell. What will most likely happen to the cell?
A — Water will leave the cell, causing it to shrink. Water moves by osmosis from an area of lower solute concentration to higher solute concentration — from inside the cell to the more concentrated solution outside, causing the cell to lose water and shrink. Water will enter the cell, causing it to swell (B) describes the opposite situation, when the outside solution is less concentrated than the inside of the cell.
A cell biologist observes that a particular molecule moves into a cell against its concentration gradient, and the process stops when the cell's ATP supply is depleted. Which transport mechanism is most likely responsible?
A — Active transport. Moving a substance against its concentration gradient — from low to high concentration — requires energy, and the process stopping when ATP runs out confirms it's active transport. Facilitated diffusion (C) also uses membrane proteins, but like simple diffusion it only moves substances down their concentration gradient and doesn't require ATP.
Cell biology questions reward matching structure to function precisely — a lot of wrong answers come from knowing the vocabulary but pairing it with the wrong job.
For each organelle, state its function in a single sentence before moving to the next question. Untimed practice is where those pairings get locked in.
Move to timed sessions once organelle-function pairs are instant recall. These should be some of the faster Biology questions once the vocabulary is solid.
Pair cell biology with genetics in a mock — both build on the same cell-level foundation before scaling up to organisms.
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