Biomolecules: Lipids, Proteins, Nucleic Acids and Coenzymes

Lipids: Phospholipids and Fatty Acids

Biomolecule OP: a) Phospholipids are lipids made up of one glycerol molecule, whose two OH groups are esterified with fatty acids, while the third is bound to orthophosphoric acid. In general, the fatty acid esterified at carbon no. 1 is saturated, and the one at no. 2 is unsaturated. The figure represents the simplest of all phospholipids, phosphatidic acid, which carries stearic and oleic acid as fatty acids, the first esterified at C no. 1 and the second at no. 2. b) The figure symbolizes the two fatty acids, stearic acid and oleic acid. Each segment represents one C-C bond, with the carbon atoms located at the end of each segment. c) Phospholipids are found in the plasma membrane of all cells and in the membranes of cell organelles. Their function is to constitute the basic structure of membranes. d) In an aqueous medium, due to their amphipathic character, they orient themselves forming a double layer or forming micelles.

Fatty acids: Organic monocarboxylic acids with a long carbon chain and an even number of C atoms.

Saturated: palmitic and stearic acid.

Unsaturated: oleic, linoleic and linolenic acid. b) Carotenoids are insaponifiable lipids formed by tetraterpene groups made of 8 isoprene molecules. They are vegetable pigments of orange color that form part of the antenna complex of photosystems.

Macromolecules: Proteins

Macromolecule (protein): A protein is a polymer whose essential components are amino acids linked by peptide bonds between the amino group of one amino acid and the carboxyl group of another amino acid, with loss of one molecule of water. The peptide bond has some of the characteristics of double bonds, which prevents free rotation; it is a more stable covalent bond than most bonds between C and N. b) It is a secondary structure of the alpha-helix type. This structure arises when the polypeptide chain winds into a spiral around itself due to rotations around the alpha carbon. This structure is kept stable thanks to intrachain hydrogen bonds formed between the NH group of one peptide bond and the C=O group of the 4th amino acid that follows. All these groups are oriented in the same direction, and the NH groups are oriented in the opposite direction.

Protein Structure References

Reference to proteins: a) Definition: Tertiary structure is the arrangement that a protein adopts when it folds in space. This structure is possible thanks to the bonds produced between amino acid radicals. Quaternary structure is the special structure adopted by those proteins formed by more than one polypeptide chain, which may be equal or different. b) Denaturation: Definition. Only the primary structure is maintained. c) Hormones, insulin, prothrombin, hemoglobin, reserve proteins, ovalbumin. Definition: immunoglobulins.

Proteins and Polysaccharides

Protein: a) Cellulose is a polysaccharide with a structural function that forms part of the cell wall of plant cells. b) The beta sheet is a type of secondary structure adopted by some proteins. c) Glycine and serine are two amino acids that bind through a peptide bond. d) The union of amino acids through peptide bonds with the consequent formation of a protein takes place in ribosomes.

Dinucleotide and Nucleic Acids

Dinucleotide drawing: This is NAD (nicotinamide adenine dinucleotide), which is a coenzyme of dehydrogenases, enzymes that catalyze oxidation-reduction reactions of cellular metabolism. It acts as a carrier of H from one substrate to another.

Nucleic acids: a) Nucleotide components. b) Purines: A, G; pyrimidines: T, C, U. c) RNA: A, G, C, U. DNA: A, G, C, T. d) In DNA, the bonds are phosphodiester, which link the nucleotides together, and H bonds, which join the two nucleotide strands. In RNA, phosphodiester bonds form between the ribonucleotides that make up the molecule, and in those RNAs that present a helix-shaped structure somewhere in their molecule, there will be H bonds.