Polymers and life

Question 1

What is an amino acid?

Answer 1

Amino acids contain at least one amino (-NH2) group and one carboxylic acid (C=OOH) group.

Question 2

What is the general formula of 2-amino acids?

Answer 2

H2N-CHR-COOH, where R represents a side chain specific to each amino acid.

Question 3

What happens when two amino acids react?

Answer 3

A condensation reaction occurs, releasing water and forming a peptide bond (-CONH-) between the COOH of one amino acid and the NH2 of another.

Question 4

What is a peptide bond?

Answer 4

A -CONH- link formed between amino acids during a condensation reaction.

Question 5

How can proteins be hydrolysed?

Answer 5

Heat with a medium-concentration acid or alkali, or use enzymes as catalysts. This breaks peptide bonds to release amino acids.

Question 6

What are the main steps of paper chromatography?

Answer 6

1. Draw a pencil line near the bottom of the paper. 2. Spot the sample and reference samples onto the line. 3. Suspend the paper in solvent and cover the beaker. 4. Once the solvent reaches the top, remove and dry the paper.

Question 7

What is the primary structure of a protein?

Answer 7

The sequence of amino acids in the protein chain.

Question 8

What is the secondary structure of a protein?

Answer 8

Hydrogen bonds between peptide links form structures such as alpha-helices or beta-pleated sheets.

Question 9

What is the tertiary structure of a protein?

Answer 9

The overall 3D structure formed by additional folding and coiling of the protein, stabilized by ionic, hydrogen, disulfide, and dipole-dipole bonds.

Question 10

What is a disulfide bridge?

Answer 10

A covalent bond between two -SH groups on the Cys amino acid.

Question 11

What are the monomers of DNA?

Answer 11

Nucleotides, which consist of a phosphate group, a sugar (deoxyribose), and a base (A, T, C, or G).

Question 12

How are DNA strands held together?

Answer 12

Hydrogen bonds form between complementary bases: A-T with 2 hydrogen bonds, and C-G with 3 hydrogen bonds.

Question 13

What is RNA

Answer 13

and how is it different from DNA?

Question 14

What is the role of the genetic code?

Answer 14

It determines the sequence of amino acids in proteins using base triplets (codons), where each codon specifies an amino acid.

Question 15

What is a receptor?

Answer 15

A site on a cell where specific molecules can bind due to complementary size, shape, orientation, and bonding groups.

Question 16

What is a pharmacophore?

Answer 16

The part of a drug that interacts with a receptor site, determining its biological activity.

Question 17

What is an enzyme?

Answer 17

A biological catalyst that speeds up reactions by lowering the activation energy. It has a specific active site for its substrate.

Question 18

What happens when an enzyme denatures?

Answer 18

The active site’s shape changes due to non-optimal pH or temperature, preventing substrate binding.

Question 19

What is a competitive inhibitor?

Answer 19

A molecule that binds to an enzyme’s active site without reacting, preventing the substrate from binding.

Question 20

What happens to enzyme activity at high substrate concentrations?

Answer 20

The reaction becomes zero-order because all active sites are occupied, and adding more substrate does not increase the rate.

Question 21

What is a zwitterion?

Answer 21

A molecule with both positively charged (H3N+) and negatively charged (COO−) groups, such as amino acids at neutral pH.

Question 22

How do amino acids behave in acidic solutions?

Answer 22

The COO− group gains an H+ ion, forming COOH, and the molecule becomes positively charged.

Question 23

How do amino acids behave in basic solutions?

Answer 23

The H3N+ group loses an H+ ion, forming NH2, and the molecule becomes negatively charged.

Question 24

What is an amine?

Answer 24

An organic compound derived from ammonia (NH3) with one or more hydrogens replaced by carbon chains.

Question 25

Why are amines basic?

Answer 25

The lone pair on nitrogen can accept a H+ ion, forming a cation and acting as a base.

Question 26

What are the products of acid hydrolysis of an ester?

Answer 26

A carboxylic acid and an alcohol.

Question 27

What are the products of alkali hydrolysis of an ester?

Answer 27

A carboxylate salt and an alcohol.

Question 28

What are the products of acid hydrolysis of an amide?

Answer 28

A carboxylic acid and ammonium chloride (for primary amides) or a salt of a primary amine (for secondary amides).

Question 29

What are the products of alkali hydrolysis of an amide?

Answer 29

A carboxylate salt and ammonia gas (for primary amides) or an amine (for secondary amides).

Question 30

What is the general reaction for an acyl chloride with an alcohol?

Answer 30

Acyl chloride + alcohol → ester + HCl (a nucleophilic substitution reaction).

Question 31

What is condensation polymerisation?

Answer 31

A reaction where two monomers with different functional groups form a polymer and release a small molecule, such as water.

Question 32

What is optical isomerism?

Answer 32

The occurrence of two non-superimposable mirror-image isomers (enantiomers) due to a chiral carbon.

Question 33

What is the role of TMS in NMR spectroscopy?

Answer 33

TMS is used as a reference with a chemical shift of 0 ppm because it has one carbon environment, is volatile, inert, and non-toxic.