Summary of Le biomolecole classe 2° liceo

Summary of "Le biomolecole classe 2° liceo"

This lesson introduces biomolecules, transitioning from general chemistry to biochemistry—the chemistry of life. Biomolecules are fundamental substances that make up cells and sustain life. They are often macromolecules or polymers composed of monomers (building blocks). The lesson covers four main types of biomolecules: Carbohydrates, Proteins, Lipids, and Nucleic Acids, explaining their structures, functions, and key characteristics.

Main Ideas and Concepts

Biomolecules Overview
- Biomolecules = macromolecules/polymers made of monomers.
- Monomers link by condensation reactions (eliminating water).
- Polymers break down into monomers by hydrolysis (using water).
- Hydrolysis is essential for digestion (e.g., protein digestion requires water).

1. Carbohydrates (Sugars/Saccharides)

Hydrophilic (water-loving) compounds.
Composed mainly of carbon, hydrogen, and oxygen.
Functions:
- Energy source (e.g., glucose).
- Energy storage (stored as starch in plants, glycogen in animals).
- Structural role (e.g., cellulose in plant cell walls).
Types:
- Monosaccharides: single sugar units (glucose, fructose, galactose, ribose, deoxyribose).
- Disaccharides: two monosaccharides linked by glycosidic bonds (lactose = glucose + galactose, maltose = glucose + glucose, sucrose = glucose + fructose).
- Polysaccharides: long chains of monosaccharides linked by glycosidic bonds.
  - Starch (plant energy storage)
  - Glycogen (animal energy storage)
  - Cellulose (plant structural fiber, indigestible by humans, aids digestion as fiber)

2. Proteins

Polymers of Amino Acids linked by peptide bonds (a type of condensation bond).
Amino Acids share a common structure but differ in their side chain (radical); 20 different Amino Acids exist.
8 Amino Acids are essential (must be obtained from diet).
Protein structure levels:
- Primary: sequence of Amino Acids.
- Secondary: local folding (alpha helix, beta sheets).
- Tertiary: 3D folding combining alpha and beta structures.
- Quaternary: multiple polypeptide chains assembled (e.g., hemoglobin).
Peptide bond forms between carboxyl group of one amino acid and amino group of another.

3. Lipids

Hydrophobic (water-repelling) compounds, mainly carbon and hydrogen.
Functions: energy storage, structural (cell membranes), photosynthetic, waterproofing, hormonal.
Types:
- Triglycerides: glycerol + 3 fatty acid chains, main energy reserve after Carbohydrates.
- Phospholipids: form cell membranes; have a hydrophilic head and two hydrophobic tails, arranged in bilayers to separate watery environments inside and outside cells.

4. Nucleic Acids (DNA and RNA)

Polymers of nucleotides (monomers).
DNA (deoxyribonucleic acid):
- Located in nucleus (eukaryotes) or cytoplasm (prokaryotes).
- Contains genetic information.
- Nucleotides composed of phosphate group, deoxyribose sugar, and nitrogenous bases (adenine, thymine, guanine, cytosine).
- Bases pair complementarily: A-T, G-C.
- DNA is double-stranded, forming a double helix with antiparallel strands.
- Capable of self-replication and transcription to RNA.
RNA (ribonucleic acid):
- Single-stranded (monohelical).
- Nucleotides include phosphate, ribose sugar, and bases (adenine, uracil instead of thymine, guanine, cytosine).
- Transcribes genetic information from DNA for protein synthesis.

Methodologies / Key Processes

Condensation Reaction:
- Monomers join by removing a water molecule.
- Forms bonds like glycosidic (Carbohydrates) or peptide bonds (Proteins).
Hydrolysis Reaction:
- Polymers break down by adding water.
- Essential for digestion and monomer release.
Complementary Base Pairing in DNA:
- Adenine pairs with thymine.
- Guanine pairs with cytosine.
- Enables DNA replication and transcription.
Protein Folding:
- Primary → Secondary (alpha helix, beta sheet) → Tertiary → Quaternary structures.
- Determines protein function.
Phospholipid Bilayer Formation:
- Hydrophilic heads face watery environments; hydrophobic tails face inward.
- Creates a selective barrier for cells.