Biomolecules: questions with answers

Liquid passing through the filter is the acid-soluble filtrate, while material retained on the filter is the acid-insoluble retentate. Each is one complementary part of the tissue's chemical composition.

Drying removes water and leaves dry matter. Complete burning then oxidises carbon compounds to gases and leaves inorganic ash; neither mass step identifies individual biomolecules.

A left-to-right amino-acid sequence represents primary structure. A local helical portion of a protein chain represents secondary structure.

Primary structure records the N-to-C amino-acid sequence, while secondary structure includes local helices and other folds. Tertiary structure is the three-dimensional folding of one chain, and quaternary structure is the arrangement of multiple folded subunits; therefore, not every protein has quaternary structure.

Each alpha-amino acid has amino, carboxyl and hydrogen groups attached to the alpha carbon. The fourth attachment is the variable R group; it is H in glycine, CH3 in alanine and CH2OH in serine.

Saturation is decided by carbon-carbon bond pattern, not hydrocarbon-chain length. A fatty acid with no carbon-carbon double bond is saturated; one with a C=C bond is unsaturated.

The primary-secondary distinction is not a simple abundant-rare split. Primary metabolites have identifiable normal physiological roles, while secondary metabolites can have ecological importance or value for human welfare even when all host functions are not understood.

Grinding disrupts membranes into insoluble fragments and vesicles that carry lipids into the retained fraction. Individual lipid molecules are small and non-polymeric. Acid-insoluble material can come from both the cytoplasm and organelles.

Glycogen has branches and multiple chain ends. Starch forms helices that can hold iodine and produce a blue colour, whereas cellulose lacks such complex helices and cannot hold iodine in the same way.

A nitrogenous base joined to a sugar, without phosphate, is a nucleoside. Adding phosphate esterified to the sugar would make it a nucleotide.

Nucleic acids (DNA and RNA) are the genetic material. They carry hereditary information and are passed from parents to progeny.

The lower peak represents the enzyme-catalysed path because the enzyme lowers the activation-energy barrier. Both paths begin at the same substrate level and end at the same product level, so the substrate-product energy difference is unchanged. Each peak represents an unstable transition state rather than a stable product.

The action sequence is E + S → ES → EP → E + P. ES is formed obligatorily when substrate binds at the active site, EP follows bond breaking or formation, and product release recovers the unchanged enzyme.

The pH curve has one optimum and declines on either side. The substrate-concentration curve approaches a maximum after enzyme molecules become saturated, so further substrate addition does not raise velocity indefinitely.

An enzyme shows highest activity at a particular optimum pH. Activity declines on both sides of that optimum rather than remaining maximal across a broad range.