3. The Structure and Function of Large Biological Molecules

IF it has C-H it is an organic componenent

Structure & Function of Large Biological Molecules

• Lipids, Carbohydrates, Proteins, and Nucleic Acids are organic components.

• Macromolecules: Large molecules with many connections.

• Polymers: Made of monomers (building block molecules). These need to be built from the same substance.

• Condensation Reaction/Dehydration Synthesis: Monomers build bonds through the loss of a water molecule $(n-1)$.

• Enzymes: Macromolecules that speed up the dehydration synthesis process.

• Hydrolysis: The reverse of dehydration, breaking polymers into monomers.

5.2: Carbohydrates - Fuel & Building Material

• Monosaccharides/Disaccharides: Single sugar blocks.

• Carbonyl group present (either aldose or ketose).

• $CHO$ with a $1:2:1$ ratio (all sugars).

• Disaccharides: Dehydration joins two monosaccharides.

  • All contain glucose (examples: maltose, sucrose, fructose).

  • Covalent bond formed is called a glycosidic linkage.

• Polysaccharides: Composed of many sugar building blocks.

  • Serve in storage and structural roles, defined by sugar monomers and glycosidic linkage positions.

  • Starch:

    • Made of amylose (20%) and amylopectin (80%).

    • Plants store glucose as starch in chloroplasts.

  • Glycogen:

    • Animals store excess sugar as glycogen in the liver and muscle cells.

    • Highly branched polymer.

• Structural Polysaccharides: Cellulose & chitin.

  • Alpha vs. Beta configurations affect structure.

  • Hydrogen bonds hold shape, providing strength.

    $OH$

    $\downarrow$

    $OHT$

• Carbohydrate Summary:

  1. Made of $CHO$ in a $1:2:1$ ratio.

  2. Monosaccharides, disaccharides, and polysaccharides exist.

  3. Bonds are glycosidic linkages.

5.3: Lipids - Diverse Group of Hydrophobic Molecules

• Examples: triglycerides, fatty acids, phospholipids, steroids.

• Consist of $CHO$; ratio is not $1:2:1$, lipids have a much lower proportion of oxygen relative to carbon and hydrogen.

• Fats: Made of glycerol and fatty acids joined by dehydration.

  • Ester Linkage: The bond present in all lipids.

• Saturated Fatty Acids: Maximum number of hydrogen atoms; no double bonds (typically solid at room temperature).

• Unsaturated Fatty Acids: One or more double bonds (typically liquid at room temperature).

  • Hydrogenation: Converting unsaturated fats to saturated fats by adding hydrogen.

• Major Function: Energy storage.

• Also function in vitamin storage, cushioning vital organs, and transport.

• Phospholipids: Amphipathic (both hydrophilic and hydrophobic).

  • Head faces water (hydrophilic).

  • Hydrophobic tail inside.

• Steroids:

  • Four fused carbon rings (e.g., cholesterol).

  • Hormones often made from steroids.

5.4: Proteins - Diverse Structures & Functions

• Protein structure determines function (conformation).

• Polypeptides shaped into unique forms.

• Make up more than 50% of the dry mass of most cells.

• Consist of $CHONS$.

• Enzymes: Proteins that speed up chemical reactions.

• Polypeptides: Polymers built from a set of 20 amino acids.

• Proteins consist of one or more polypeptides.

• Amino Acids: Consist of a carboxyl group + an amino group.

  $H$

  $|$

  $amino$

  $group$

  $|$

  $H-C-COOH$

  $|$

  $R$

  $carboxyl$

• Linked by peptide bonds.

  $H$ $O$

  $|$ $|$

  $C-N$ = peptide bond

  $|$

  $R$ group: Provides unique function/different compositions.

• Denaturation: Loss of a protein's native structure.

• Chaperonins: Protein molecules that assist in folding other proteins.

• Levels of Protein Structure:

  1. Primary: Determined by genetic inheritance.

  2. Secondary: Hydrogen bonds hold shape (e.g., helix).

  3. Tertiary: Polypeptide folded together.

  4. Quaternary: Combination of two or more polypeptide chains.

5.5: Nucleic Acids - Store & Transmit Hereditary Information

• Consist of $CHONP$.

• Polymers called polynucleotides, made of nucleotides.

• Nucleotide: Nitrogenous base, pentose sugar, phosphate group.

• Nitrogenous Bases:

  • Pyrimidines: Cytosine, thymine (DNA), uracil (RNA) - single ring structure.

  • Purines: Adenine, guanine - double ring structure.

  • $A=T(or U)$

• DNA (Deoxyribose): Carbon #2 has no oxygen.

  $O$$\|$$N$

• Double helix & anti-parallel structure.

  $G \equiv C$

• RNA (Ribose): Carbon #2 has oxygen.

• Phosphodiester Bond: Bond between nucleotide polymers.

• Central Dogma:

  $DNA \rightarrow RNA \rightarrow Protein$

  $transcription$

  $translation$

• DNA vs. RNA:

  • DNA: Deoxyribose sugar, long & stable, located in the nucleus, stores genetic information.

  • RNA: Ribose sugar, short & less stable, can be in the cytoplasm, functions in making protein.

• Transcription: Process of making RNA from DNA.

• Memorize the 4 macromolecules and