lecture 3: Macromolecules

Proteins structure

• formed of one or more polypeptide chains

• overlapping with itself

polypeptides

• made up of chains of amino acids

• has a N-terminus where the protein/polypeptide starts and a C-terminus where it ends

protein functions

• Enzymes: catalyzes reactions

• Structural: support, shape, and cytoskeleton

• Motility: *cellular movement*, movement of organelles within the cell, and organismal movement through muscle contraction

• Regulatory: control of other functions

• Defence: antibodies

• Communication

Polymerization 

• Protein synthesis

• Making polymers from monomers via Ribosomes

• Condensation and dehydration reactions loses H2O to form an amide/peptide bond

Monomer

A subunit

Polymer

The complex of subunits

Monomeric Protein

Formed of just one polypeptide

Multimeric Protein

More than one polypeptide

• homomeric

• heteromeric

Homomeric polypeptide

Has either two alpha helix’s or two beta sheets

Heteromeric

has both an alpha and a beta head

Protein folding

Conformation of protein dependent in amino acids acid sequence

• interactions between amino acids

• covalent (disulfide)

• Ionic

• Hydrogen

• Hydrophobic

• Van der Waals

Intramolecular

Within the same molecule

Intermolecular

Between multiple molecules

Levels of protein structure - Primary

• The sequence of amino acids from N-terminus to C-terminus

• determines protein folding

Levels of protein structure - Secondary

• alpha helix

• beta sheets

Levels of protein structure - Tertiary

• three-dimensional folding

• determined by interactions between amino acid chains

• involves:

  • disulfide bonds

  • ionic bonds

  • hydrogen bonds

  • hydrophobic interactions

Quaternary Structure

• arrangement of multiple polypeptide chains

• e.g. hemoglobin

Amino acids

• twenty different protein-forming sections

• contains:

  • amino group

  • carboxyl group

  • central carbon

  • Side chain (R group)

Nucleic acids

• composed of nucleotides

  • bases

  • nucleosides

  • nucleotides

Three types of RNA

• tRNA

• rRNA

• mRNA

Carbohydrates

• made up of polysaccharides

  • the monomer unit is polysaccharides

  • d-glucose is the most common

  • used for both storage and structural

Lipids

• very hydrophobic, mostly non-polar

• energy, structural, and functional

• has 6 classes

Classes of lipids

1. Fatty acids

2. Triacylglycerols

3. Oleomargarine

4. Phospholipids

5. Glycolipids

6. Steroids

Fatty Acids

• mainly building blocks for other classes

• created by stepwise addition of two-carbon units

• unsaturated fatty acids have bends/kinks

Triacylglycerols

• also known as triglycerides

• storage/insulation

Phospholipids

amphipathic lipid molecules

glycolipids

• lipids with carbohydrate groups

• often involved in signalling/recognition

Steroids

• involved in membrane structures

• signalling