Biomacromolecules and the Acid Insoluble Fraction
When living tissue is ground and treated with acid, it separates into two revealing fractions: a soluble pool of small molecules and an insoluble fraction of large structures. This quiz tests your grasp of that chemical boundary.
- Micromolecules: compounds with molecular weights from about 18 to around 800 Da.
- Macromolecules: proteins, nucleic acids, polysaccharides and lipids — the four organic classes of the acid-insoluble fraction.
- The lipid puzzle: why small lipids still travel with the macromolecular fraction.
- Abundance: which chemical dominates the composition of living organisms.
Work carefully through each question — the reasoning behind the lipid anomaly is the heart of this lesson.
Q1. The compounds found in the acid-soluble pool have molecular weights approximately in which range?
All compounds of the acid-soluble pool share molecular weights ranging from 18 to around 800 daltons.
Q2. Which of the following is NOT one of the four types of organic compounds found in the acid-insoluble fraction?
The acid-insoluble fraction contains only proteins, nucleic acids, polysaccharides and lipids. Alkaloids are secondary metabolites, not part of this fraction.
Q3. With the exception of lipids, the molecular weights of the compounds of the acid-insoluble fraction lie in which range?
The acid-insoluble classes, except lipids, have molecular weights in the range of ten thousand daltons and above.
Q4. Biomolecules with molecular weights less than one thousand daltons are usually referred to as:
Compounds with molecular weights less than one thousand daltons are called micromolecules or simply biomolecules, while those in the acid-insoluble fraction are macromolecules.
Q5. Which statement about the molecules of the insoluble fraction is correct?
The molecules of the insoluble fraction, with the exception of lipids, are polymeric substances.
Q6. Lipids have molecular weights that do not exceed:
Lipids are small molecular weight compounds whose molecular weights do not exceed 800 Da, yet they appear in the macromolecular fraction.
Q7. Why do lipids separate along with the acid-insoluble fraction when a tissue is ground?
Grinding disrupts the cell, and membranes break into pieces forming vesicles that are not water soluble; these separate with the acid-insoluble pool.
Q8. Which statement best describes the status of lipids in the macromolecular fraction?
The lesson states explicitly that lipids are not strictly macromolecules, even though they are recovered in the macromolecular fraction.
Q9. The acid-soluble pool represents roughly:
The acid-soluble pool represents roughly the cytoplasmic composition, while macromolecules from cytoplasm and organelles form the acid-insoluble fraction.
Q10. Which chemical is the most abundant in living organisms?
When the chemical composition of living tissue is arranged from the abundance point of view, water is the most abundant chemical.
Q11. According to the average composition of cells, water accounts for approximately what percentage of total cellular mass?
Water makes up 70-90% of the total cellular mass, far more than any other component.
Q12. In the average composition of cells, which component accounts for 10-15% of total cellular mass?
Proteins account for 10-15% of total cellular mass, the second most abundant component after water.
Q13. The lower boundary of the molecular weight range of the acid-soluble pool, 18 Da, corresponds to which molecule?
The lower boundary of 18 daltons corresponds to water, the smallest and most abundant molecule in living systems.
Q14. Together, the acid-soluble pool and the acid-insoluble fraction represent:
The acid-soluble pool represents roughly the cytoplasmic composition and the macromolecules form the acid-insoluble fraction; together they represent the entire chemical composition of living tissues.
Q15. A compound with a molecular weight of about 500 Da is best classified as:
Any compound falling within the 18 to around 800 Da window is classified as a micromolecule.