Meera grinds a piece of liver in trichloroacetic acid and strains the slurry through cotton…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Meera grinds a piece of liver in trichloroacetic acid and strains the slurry through cotton.
- What is the liquid that passes through called?
- Name two kinds of molecule found in it.
- What stays on the cotton?
- Lipids are small molecules, yet they stay on the cotton. Why?
Need a reminder? The key ideaShow
Grinding a tissue in trichloroacetic acid and straining it gives the filtrate (the acid-soluble pool of small molecules) and the retentate (the acid-insoluble fraction of large molecules). Lipids are small but come down with the large ones inside membrane vesicles. Drying removes water; burning dry matter leaves ash, the inorganic elements. A cell is 70 to 90 per cent water. Primary metabolites have known roles; secondary metabolites include alkaloids, rubber, drugs, pigments and gums.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The liquid is the filtrate, the acid-soluble pool.
Step 2. (b) It holds small molecules such as amino acids, sugars, nucleotides and ions.
Step 3. (c) The retentate, the acid-insoluble fraction, stays on the cotton. It holds proteins, nucleic acids and polysaccharides.
Step 4. (d) Grinding breaks the cell membranes into pieces, which curl into vesicles. The vesicles do not dissolve in water, so the lipids settle with the large molecules.
Answer: (a) the filtrate; (b) for example amino acids and sugars; (c) the acid-insoluble fraction; (d) the lipids are inside membrane vesicles.
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