Chemistry of Life is one of 9 topics in the Grade 10 Life Sciences CAPS syllabus, covered across 3 lessons on Study Vault. Below are real practice questions from this topic with full worked answers.
Sample practice questions
Easy
1. Approximately what percentage of a living cell's mass is water?
60-70%
5-10%
95-99%
Less than 1%
Answer: 60-70% — Water typically makes up around 60-70% of a living cell's mass, making it the most abundant molecule in cells.
Easy
2. Why is a water molecule described as polar?
The oxygen end carries a slightly negative charge and the hydrogen ends carry a slightly positive charge
It has no charge anywhere on the molecule
It is made only of hydrogen atoms
It carries a full negative charge overall
Answer: The oxygen end carries a slightly negative charge and the hydrogen ends carry a slightly positive charge — Oxygen attracts the shared electrons more strongly than hydrogen, giving the oxygen end a slight negative charge and the hydrogen ends a slight positive charge -- this uneven charge distribution is what makes water polar.
Medium
3. Why is water such an effective solvent for biochemical reactions in cells?
Its polar nature allows it to surround and dissolve other polar or ionic substances
It is a non-polar molecule that repels charged particles
It cannot form hydrogen bonds with other substances
It has a very low specific heat capacity
Answer: Its polar nature allows it to surround and dissolve other polar or ionic substances — Because water is polar, it can surround and separate polar or ionic substances such as salts and sugars, dissolving them and allowing biochemical reactions to occur in aqueous solution.
