Illustrative demo
medtrainit™
Know why you got it wrong.
Biology · Osmosis
A red blood cell is placed in a hypotonic solution containing a solute that cannot cross the membrane. What happens?
AThe cell shrinks because water leaves the cell
BThe cell swells because water enters by osmosis
CThe cell swells because solute diffuses into the cell
DIt remains unchanged — concentrations equalise
It's okay, Sara — this one catches a lot of people.
You went with water leaving the cell. Let's walk through why it actually does the opposite.
In a hypotonic solution the solute is more dilute outside, so there's more water outside than in. Water naturally moves into the cell by osmosis — and the cell swells.
Remember — hypotonic means dilute outside, so water enters the cell.
We tell you why — not just that you're wrong.
Practice · check the idea
Water moves across the membrane toward…
The lower solute concentration
The higher solute concentration
Still feels odd? Let's try it a different way.
Picture the most extreme version.
Imagine the cell sitting in pure water — no solute at all. Water would obviously rush in. A hypotonic solution does the very same thing, just more gently. So water enters, and the cell swells.
Remember — if you're ever unsure, picture pure water. It always flows in.
hypotonic
The rule to keep
Hypotonic outside → water enters → the cell swells.
Then we fix the thinking — step by step.
Biochemistry · Krebs cycle
Each acetyl-CoA entering the Krebs cycle produces how many GTP?
A1 GTP (per single turn)
B2 GTP
Good instinct, Sara — just the wrong unit.
You knew the number — it was attached to the wrong thing.
2 GTP is right per glucose, because glucose makes two acetyl-CoA and the cycle turns twice. But this question asks per single acetyl-CoA — so it's 1 GTP. The trick is always to check the unit first.
Remember — per acetyl-CoA = 1 GTP. Per glucose = 2 GTP.
Every wrong answer has a reason — across every subject.
Session overview
Your progress
PracticeProgress
Questions answered
2
of 200 target
Correct rate
50%
1 correct · 1 wrong
Mistakes corrected
1
confirmed via practice
Error patterns
1
distinct reasoning error
Milestones
20
50
75
100
200
Error patterns
Biology · Osmosis
1 encountered · 1 corrected via practice
Improving
Every mistake, named and tracked — until it's fixed.
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Know why you got it wrong.
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