What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

What are macromolecules? Give examples.

Macromolecules are large molecules of the acid-insoluble fraction with high molecular weight, such as proteins, nucleic acids and polysaccharides.

Which is the most abundant chemical in living organisms?

Water is the most abundant chemical, followed by proteins, carbohydrates, lipids and nucleic acids.

How many types of amino acids and nucleotides occur in proteins and nucleic acids?

There are twenty types of amino acids that occur in proteins and five types of nucleotides (with adenine, guanine, cytosine, thymine and uracil bases).

Name the most abundant protein in the animal world and in the whole biosphere.

Collagen is the most abundant protein in the animal world, and RuBisCO is the most abundant protein in the whole biosphere.

Differentiate between primary and secondary metabolites.

Primary metabolites such as amino acids and sugars have identifiable roles in normal physiology, while secondary metabolites such as alkaloids, pigments and antibiotics have no known role in normal physiology but are often useful to humans.

What is an active site of an enzyme?

It is a crevice or pocket formed by the criss-crossing of the polypeptide chain in the tertiary structure, into which the substrate fits and is converted to product.

How do enzymes lower the energy barrier of a reaction?

They bind the substrate at the active site forming an enzyme-substrate complex, stabilise the transition state and thereby reduce the activation energy, greatly speeding the reaction.

What factors affect enzyme activity?

Temperature, pH, substrate concentration and the binding of inhibitors affect enzyme activity, since each enzyme has an optimum temperature and pH and a maximum velocity at substrate saturation.

Name the six classes of enzymes.

Oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases.

Biomolecules

Q: What is meant by the primary, secondary, tertiary and quaternary structure of a protein?

Primary structure is the sequence of amino acids, secondary is the helical folding, tertiary is the overall 3-D folding, and quaternary is the arrangement of more than one polypeptide subunit, as in haemoglobin.

Class 11 Biology · Biology · Chapter 9

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CBSE Class 11 · Biology

19 chapters: every table, cycle and pathway

Marks booster + cheatsheet: key concepts in 2 lines each, common traps
18 marks: Unit V, breathing to hormones
15 marks each: Units I and III
Common traps, corrected
Five kingdoms classification table
Physiological numbers, with page numbers

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CBSE Class 11 · Biology

19 chapters: every table, cycle and pathway

Marks booster + cheatsheet: key concepts in 2 lines each, common traps
18 marks: Unit V, breathing to hormones
15 marks each: Units I and III
Common traps, corrected
Five kingdoms classification table
Physiological numbers, with page numbers

Page 1 free about 8 min read, Full kit about 55 min read

₹159See the full kit

View all 44 amazing Marks Booster kits →

Summary

This chapter analyses the chemical composition of living tissues and the major classes of biomolecules. A chemical analysis shows that all the elements found in earth's crust are also present in living matter, but the relative abundance of carbon and hydrogen is higher in organisms, and water is the most abundant compound in a cell. Grinding a tissue in acid and filtering gives an acid-soluble pool of small molecules (18 to 800 daltons) such as amino acids, sugars, fatty acids, glycerol, nucleosides and nucleotides, and an acid-insoluble fraction of macromolecules. There are twenty types of amino acids and five nitrogen bases. Lipids include fatty acids, glycerides, phospholipids and cholesterol. Primary metabolites have known roles, while secondary metabolites such as alkaloids, pigments and antibiotics are typical of plants and microbes. Only proteins, nucleic acids and polysaccharides are true biomacromolecules; lipids separate with them only because of membranes. Proteins are heteropolymers of amino acids with primary, secondary, tertiary and quaternary structure; collagen and RuBisCO are the most abundant proteins. Polysaccharides like cellulose, starch and glycogen are sugar polymers, and nucleic acids (DNA and RNA) are polynucleotides. Enzymes are proteins (some are ribozymes) that lower activation energy; their activity depends on temperature, pH, substrate concentration and cofactors.

Chemical analysis of living tissuesAmino acids, lipids and nucleotidesPrimary and secondary metabolitesProteins and their structurePolysaccharides and nucleic acidsEnzymes, enzyme action and cofactors

Key terms

Biomacromolecule

A large polymeric molecule of the acid-insoluble fraction: protein, nucleic acid or polysaccharide.

Metabolite

A biomolecule produced in metabolism; primary metabolites have known roles while secondary metabolites are typical of plants, fungi and microbes.

Enzyme

A protein (or rarely a nucleic acid called a ribozyme) that catalyses a biochemical reaction by lowering activation energy.

Active site

The crevice or pocket of an enzyme into which the substrate binds during catalysis.

Activation energy

The energy difference between the substrate and the transition state that must be overcome for a reaction to proceed.

Cofactor

A non-protein constituent (prosthetic group, coenzyme or metal ion) required to make an enzyme catalytically active.

Extra questions & answers

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The most abundant chemical compound in living organisms is:

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