Wet Weight, Dry Weight, Ash and Inorganic Constituents
How do biologists prove that living tissues contain inorganic elements? The answer lies in a deliberately destructive experiment: a small piece of tissue — a leaf or a piece of liver — is weighed, dried, and finally burnt.
- Wet weight — the mass of the living tissue, water included.
- Dry weight — what remains after all the water evaporates.
- Ash — the grey residue left after the carbon compounds are oxidised to gases such as ##\ce{CO2}## and water vapour.
This quiz tests your grasp of each stage of that procedure, the inorganic ions and salts listed in Table 9.2, and the crucial distinction between elemental analysis and compound analysis. Work carefully — the logic of the method is one of subtraction.
Q1. A small amount of living tissue, such as a leaf or a piece of liver, is weighed as it stands. This initial measurement is called:
The lesson states that one weighs a small amount of living tissue (say a leaf or liver) and this is called wet weight. It includes all the water present in the tissue.
Q2. When the weighed living tissue is dried, what happens to the water it contains?
On drying, all the water evaporates. The material that remains after this loss of water gives the dry weight of the tissue.
Q3. The material remaining after a living tissue has been dried and all its water has evaporated is called:
The lesson states clearly that the remaining material after drying gives dry weight. Ash is obtained only after the dried tissue is fully burnt.
Q4. When the dried tissue is fully burnt, the carbon compounds are oxidised to gaseous form. Which products are named in the lesson?
The lesson states that on full burning all the carbon compounds are oxidised to gaseous form (##\ce{CO2}##, water vapour) and are removed.
Q5. The grey residue that remains after a tissue is fully burnt is called:
What remains after the tissue is fully burnt is called ash. It contains the inorganic elements that could not be oxidised away as gases.
Q6. According to the lesson, the ash obtained after burning a tissue contains:
The lesson states that ash contains inorganic elements like calcium, magnesium etc. Carbon compounds are oxidised to gases and removed.
Q7. Inorganic compounds such as sulphate and phosphate are said to be seen in which fraction?
The lesson notes that inorganic compounds like sulphate, phosphate, etc., are also seen in the acid-soluble fraction.
Q8. Elemental analysis of living tissues gives the elemental composition in the form of which of the following?
The lesson states that elemental analysis gives elemental composition of living tissues in the form of hydrogen, oxygen, chlorine, carbon etc.
Q9. Analysis for compounds in a living tissue gives an idea of:
The lesson states that analysis for compounds gives an idea of the kind of organic and inorganic constituents present in living tissues.
Q10. Which of the following is listed in Table 9.2 as a representative inorganic constituent of living tissues?
Table 9.2 lists sodium as ##\ce{Na+}##, along with ##\ce{K+}##, ##\ce{Ca^2+}##, ##\ce{Mg^2+}##, water, and compounds such as ##\ce{NaCl}## and ##\ce{CaCO3}##.
Q11. Table 9.2 lists which of the following as an inorganic compound found in living tissues?
Table 9.2 lists compounds such as ##\ce{NaCl}## and ##\ce{CaCO3}##, together with the ions ##\ce{SO4^2-}## and ##\ce{PO4^3-}##.
Q12. In Table 9.2, the ions ##\ce{SO4^2-}## and ##\ce{PO4^3-}## are listed as:
Table 9.2, which lists representative inorganic constituents of living tissues, includes the compounds ##\ce{NaCl}##, ##\ce{CaCO3}##, ##\ce{SO4^2-}## and ##\ce{PO4^3-}##.
Q13. Why is the experiment used to detect inorganic constituents described as destructive?
The experiment is destructive because the sample is dried and fully burnt, converting its carbon compounds to gases. Only the incombustible residue survives.
Q14. Which statement best distinguishes elemental analysis from compound analysis, as described in the lesson?
The lesson states that elemental analysis gives the elemental composition of living tissues (hydrogen, oxygen, chlorine, carbon etc.), while analysis for compounds gives an idea of the kind of organic and inorganic constituents present.
Q15. All the carbon compounds that we get from living tissues can be called:
The lesson states that all the carbon compounds that we get from living tissues can be called biomolecules. Living organisms also contain inorganic elements and compounds.