A-Student-Notes-2020-Chemistry-Unit-4-AOS-2-Piper-FINAL - Chemistry Notes - Amino Acids, Proteins, and Carbohydrates

Sep 20, 2026

Uploaded by Levi

Chemistry study notes covering key biomolecule concepts: amino acid structure (functional groups, chirality, R-group types, isoelectric/zwitterion behavior), amphiprotic nature, and how pH shifts dominant ionic forms. Includes protein formation via condensation polymerisation, peptide/amide bonds, di-/polypeptide composition, and bonding patterns underlying primary, secondary (alpha helix, beta pleated sheets), tertiary, and disulphide-stabilized structures. Explains enzyme catalysis, denaturation from heat and pH, and carbohydrate chemistry from monosaccharides and isomers to ring formation, glycosidic bonds, disaccharides, and polysaccharides.

LanguageEnglish

CategoryExam

FormatPDF

Pages21

Reading Time53 min

AccessFree to download

Amino acids and R-group effects

Functional groups, chirality, and isomerism

pH, amphiprotic behavior, and zwitterions

Peptide bonds and protein structure

Condensation polymerisation and peptide links

Primary, secondary, tertiary structure

Denaturation and enzyme activity

Carbohydrates

Monosaccharides and isomers

Ring structures and geometric forms

Disaccharides and glycosidic bonds

Polysaccharides and examples

Lipids

Glycerides and triglycerides

Saturated vs unsaturated fats

Emulsification and hydrolysis

• the monomers that make up proteins (enzymes, hormones, keratin, antibodies) • plants can manufacture all their amino acids, animals obtain these from food • difunctional—contain both a weakly acidic carboxyl group COOH and a weakly basic amino group NH2 • both functional groups are attached to a central alpha carbon *distinguishing difference is the R group • 20 amino acids • some are essential (cannot be synthesised by the body) others are nonessential (can be synthesised) • both functional groups are polar, making amino acids soluble (extensive H bonding with water) • all (except glycine) are chiral • carbons are numbered from right to left (carboxyl group is one) • R-Groups can be: ➢ non-polar (CH3) ➢ polar (CH2COOH) ➢ proton donors (CH2COOH) ➢ proton acceptors (CH2NH2) • amino acids are amphiprotic (can act as acid or base) depending on pH of solution *as an equilibrium reaction, one form will be most dominant • zwitterion (pH 5-7): electrically neutral form of an amino acid which contains both a positive and a negative charge (isoelectric point) • Acid solutions: positive charge when COO-group gains a H+ *acts as a base* • Basic solutions: negative charge when NH3 group loses a proton *acts as an acid* Effect of R Group: some amino acids have basic or acidic R groups due to presence of NH2 or COOH which can influence charges e.g Asn @ pH 3 will have 2+ charge • formed via condensation polymerisation • peptide links AMIDE BONDS-CO-NH-are formed to form a polypeptide (proteins have more than 50 amino acids in the polypeptide chain) • can be dipeptides=two amino acids, trippedide= three amino acids • during digestion, proteins are hydrolysed to produce the individual amino acids (requires water and enzymes) *always two isomers of the dipeptide depending on which way they condense (orientation) ➢ N terminal: NH3 end ➢ C terminal: COOH end • primary structure: the number, type and sequence of the amino acid residuesin the protein—joined by strong covalent bonds *the length is determined by the gene that codes for the protein* • secondary structure: three-dimensional structure, due to Hydrogen bonding between neighbouring amide groups • hydrogen bonding between non-bonding electron pairs on an oxygen atom (C==O) and a hydrogen atom (NH2) from the same amino acid*results in an alpha helix • interchain hydrogen bonding between polypeptides resulting in beta pleated sheets • tertiary structure: bending and folding of the protein overall 3D structure hydrophobic R groups fold inwards (away from water) long and narrow—fibrous proteins responsible for structural functions tightly folded alpha helix chains—globular proteins such as enzymes arise due to bonding between R groups such as ion-ion interactions (NH3+/COO-), hydrogen bonding (C=O/OH), dipole-dipole interactions, dispersion forces disulphide bridges: due to cysteine which bonds to another cysteine to form very strong S-S covalent bonds • denaturation: results in a loss of function due to pH change heat presence of salts involves uncoiling and unfolding of the helices (does not break peptide links) *primary structure left intact* • biological catalysts that speed up the rate of reaction bu providing an alternate reaction pathway with a lower Ea • differ from inorganic catalysts as they are—much more efficient, much more selective, easily denatured • lock and key model: substrate and active site have exact complimentary shapes • enzyme-substrate complex achieved through either dispersion forces, dipoledipole interactions or hydrogen bonds *causes bonds within substrate to weaken and break temperature: as temperature increases, rate of reaction increases due to higher KE of particles and higher proportion of collisions, enzymes will DENATURE past their optimal point as intermolecular bonds break pH: each enzyme has an optimal pH based on acidic or basic nature of R group • most wid

FAQs

How do amino acids differ in charge across acidic and basic solutions?

In acidic solutions, the COO group gains H+ leading to a dominant positive charge and the molecule acts as a base. In basic solutions, the NH3 group loses a proton leading to a dominant negative charge and the molecule acts as an acid.

What determines a protein’s primary structure and how is it formed?

Primary structure is the number, type, and sequence of amino acid residues joined by strong covalent bonds. Proteins form through condensation polymerisation, producing peptide links (amide bonds, CO-NH) along the polypeptide chain.

Why do enzymes denature and what happens to their activity?

Enzymes denature when intermolecular bonds break due to changes such as temperature increase beyond the optimal point or pH change. Denaturation causes loss of function because the overall structure responsible for catalysis is disrupted.

Sep 20, 2026

Uploaded by Levi