Chapter 6: Biomolecules

Solve · page 108: Define amino acid and draw its structure. What are the basic components of lipids? Draw their shictires.

Amino acid (امینو ایسڈ) – an organic molecule that contains both an amino group (‑NH₂) and a carboxyl group (‑COOH) attached to the same carbon atom (the α‑carbon). The α‑carbon also carries a hydrogen atom and a variable side‑chain (R) that determines the identity of the amino acid.

Structure of a generic amino acid

<svg viewBox="0 0 340 240" xmlns="http://www.w3.org/2000/svg"> <defs> <marker id="arrow" markerWidth="6" markerHeight="6" refX="5" refY="3" orient="auto"> <polygon points="0 0,6 3,0 6" fill="currentColor"/> </marker> </defs> <!-- central carbon --> <circle cx="180" cy="120" r="4" fill="currentColor"/> <!-- bonds --> <line x1="180" y1="120" x2="130" y2="80" stroke="currentColor" marker-end="url(#arrow)"/> <line x1="180" y1="120" x2="230" y2="80" stroke="currentColor" marker-end="url(#arrow)"/> <line x1="180" y1="120" x2="180" y2="170" stroke="currentColor" marker-end="url(#arrow)"/> <line x1="180" y1="120" x2="250" y2="120" stroke="currentColor" marker-end="url(#arrow)"/> <!-- labels --> <text x="115" y="75" font-size="13" fill="currentColor">NH₂</text> <text x="235" y="75" font-size="13" fill="currentColor">COOH</text> <text x="185" y="185" font-size="13" fill="currentColor">H</text> <text x="260" y="115" font-size="13" fill="currentColor">R</text> <text x="185" y="125" font-size="13" fill="currentColor">Cα</text> </svg>

Scale: arbitrary; bonds drawn to the same length. Construction: draw a central carbon, then add four single‑bond vectors for NH₂, COOH, H, and R; label each.

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Basic components of lipids (چربیوں کے بنیادی اجزاء)

1. Glycerol (گلیسرول) – a three‑carbon backbone, each carbon bearing a hydroxyl group (‑OH).
2. Fatty acid (چربیاتی تیزاب) – a long hydrocarbon chain ending in a carboxyl group (‑COOH).

Structure of glycerol

<svg viewBox="0 0 340 240" xmlns="http://www.w3.org/2000/svg"> <defs> <marker id="arrow2" markerWidth="6" markerHeight="6" refX="5" refY="3" orient="auto"> <polygon points="0 0,6 3,0 6" fill="currentColor"/> </marker> </defs> <!-- carbon chain --> <circle cx="120" cy="120" r="4" fill="currentColor"/> <circle cx="170" cy="120" r="4" fill="currentColor"/> <circle cx="220" cy="120" r="4" fill="currentColor"/> <line x1="124" y1="120" x2="166" y2="120" stroke="currentColor"/> <line x1="174" y1="120" x2="216" y2="120" stroke="currentColor"/> <!-- OH groups --> <line x1="120" y1="120" x2="120" y2="80" stroke="currentColor" marker-end="url(#arrow2)"/> <line x1="170" y1="120" x2="170" y2="80" stroke="currentColor" marker-end="url(#arrow2)"/> <line x1="220" y1="120" x2="220" y2="80" stroke="currentColor" marker-end="url(#arrow2)"/> <text x="115" y="75" font-size="13" fill="currentColor">OH</text> <text x="165" y="75" font-size="13" fill="currentColor">OH</text> <text x="215" y="75" font-size="13" fill="currentColor">OH</text> <text x="120" y="130" font-size="13" fill="currentColor">C₁</text> <text x="170" y="130" font-size="13" fill="currentColor">C₂</text> <text x="220" y="130" font-size="13" fill="currentColor">C₃</text> </svg>

Structure of a fatty acid (example: a 6‑carbon chain)

<svg viewBox="0 0 340 240" xmlns="http://www.w3.org/2000/svg"> <defs> <marker id="arrow3" markerWidth="6" markerHeight="6" refX="5" refY="3" orient="auto"> <polygon points="0 0,6 3,0 6" fill="currentColor"/> </marker> </defs> <!-- carbon chain --> <circle cx="120" cy="180" r="4" fill="currentColor"/> <circle cx="160" cy="180" r="4" fill="currentColor"/> <circle cx="200" cy="180" r="4" fill="currentColor"/> <circle cx="240" cy="180" r="4" fill="currentColor"/> <circle cx="280" cy="180" r="4" fill="currentColor"/> <line x1="124" y1="180" x2="156" y2="180" stroke="currentColor"/> <line x1="164" y1="180" x2="196" y2="180" stroke="currentColor"/> <line x1="204" y1="180" x2="236" y2="180" stroke="currentColor"/> <line x1="244" y1="180" x2="276" y2="180" stroke="currentColor"/> <!-- carboxyl group at left end --> <line x1="120" y1="180" x2="100" y2="160" stroke="currentColor" marker-end="url(#arrow3)"/> <line x1="100" y1="160" x2="100" y2="140" stroke="currentColor" marker-end="url(#arrow3)"/> <text x="95" y="135" font-size="13" fill="currentColor">O</text> <text x="95" y="155" font-size="13" fill="currentColor">OH</text> <text x="105" y="165" font-size="13" fill="currentColor">C=O</text> <!-- labels --> <text x="115" y="195" font-size="13" fill="currentColor">C₁</text> <text x="155" y="195" font-size="13" fill="currentColor">C₂</text> <text x="195" y="195" font-size="13" fill="currentColor">C₃</text> <text x="235" y="195" font-size="13" fill="currentColor">C₄</text> <text x="275" y="195" font-size="13" fill="currentColor">C₅</text> </svg>

Scale: each C–C bond drawn the same length; COOH group shown at the left end. Construction: draw a straight carbon chain, add a terminal –COOH (C=O and –OH), label each carbon.

Answer Summary

• Amino acid: molecule with –NH₂, –COOH, H and R attached to a central α‑carbon.
• Basic lipid components: glycerol (three‑carbon backbone with three –OH groups) and fatty acids (long hydrocarbon chain ending in –COOH).

Check: Verify that the amino‑acid diagram shows four bonds to the α‑carbon (NH₂, COOH, H, R) and that the lipid diagrams display glycerol’s three –OH groups and a fatty‑acid chain with a terminal –COOH.