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Chapter 2: The Chemistry of Life

Macro-Biomolecules

• Types of Macro-Biomolecules:

  • Carbohydrates

  • Proteins

  • Nucleic Acids

  • Lipids

Section 2.5 - Carbon: The Basis of Life on Earth

Major Classes of Biological Molecules

• All biological molecules are carbon-based, referred to as "organic compounds".

• Types of Major Biological Molecules:

  1. Starch

  2. Sugars

  3. Proteins

  4. Lipids

  5. Nucleic Acids

Carbon's Role

• Carbon's unique atomic structure facilitates diverse organic compounds.

• It forms single, double, or triple covalent bonds.

• Carbon has 6 protons and 6 electrons:

  • 2 electrons in the first orbital

  • 4 electrons in the valence shell

• Capable of forming up to 4 single covalent bonds, providing strong and stable connections, allowing for varied molecular shapes.

Functional Groups

• Definition: Specific arrangements of atoms in a compound that dictate the compound's reactions.

• Common Functional Groups in Biology:

  1. Alcohol (-OH): Products of fermentation.

  2. Carboxyl (-COOH): Present in carboxylic acids, can lose a proton to become reactive.

  3. Amino (-NH2): Present in amino acids, essential for protein synthesis.

  4. Phosphate (-PO4): Key in nucleic acids (DNA, RNA) and ATP.

  5. Sulfhydryl (-SH): Important for protein structure.

  6. Methyl (-CH3): Involved in regulating function of macromolecules.

Biological Macromolecules and Polymers

• Polymers: Composed of many covalently linked units (monomers).

• Types:

  • Synthetic Polymers: Plastics, polyester, etc.

  • Natural Polymers: DNA, proteins, starches,

  • Examples: DNA/RNA – nucleotides, Proteins – amino acids (20+).

Building and Breaking Polymers

• Dehydration Synthesis:

  • Reaction where two monomers bond, releasing a water molecule.

  • Enables bonding and requires cellular energy.

  • Example: Sucrose production in plants.

• Hydrolysis Reaction:

  • Process of breaking polymers into monomers using water.

  • Involves specific enzymes catalyzing the reaction.

Learning Outcomes for Section 2.5

• Explain carbon's properties that make it essential for life.

• Describe various functional groups of organic compounds.

• Diagram dehydration synthesis and hydrolysis reactions.

Section 2.5 - Carbohydrates

Overview of Carbohydrates

• Carbohydrates are vital for energy and structural support.

• Definition: A saccharide, often referred to as sugar.

  • Biological polymer; monomer units are monosaccharides.

  • Common examples: glucose, fructose, sucrose, lactose, maltose.

• Atomic Ratio: 1 Carbon : 2 Hydrogen : 1 Oxygen

• Functions:

  • Immediate energy source

  • Energy storage (starch)

  • Structural molecules (fiber)

Classification of Carbohydrates

• Based on the number of monomer units:

  1. Monosaccharides: One unit (e.g., glucose).

  2. Disaccharides: Two monomers linked (e.g., sucrose).

  3. Oligosaccharides: 3 to 10 monomers.

  4. Polysaccharides: Over 11 monomers (e.g., starch, cellulose).

Formation and Breakdown of Disaccharides and Polysaccharides

• Dehydration Synthesis: Forms glycosidic bonds.

• Hydrolysis: Breaks bonds utilizing water.

Types of Starch and Fiber

• Amylose: Energy-storage polysaccharide, digestible by humans due to the enzyme amylase.

• Cellulose: Structural component in plants, indigestible by humans; no cellulase enzyme available.

Animal Energy Storage

• Glycogen: Storage form of glucose in muscle and liver; can be hydrolyzed for energy during starvation (glycogenolysis).

Learning Outcomes for Carbohydrates

• Distinguish between various carbohydrate types: monosaccharides, disaccharides, polysaccharides.

• Relate the structure of plant and animal polysaccharides to their functions.

Section 2.5 – Proteins

Overview of Proteins

• Proteins are diverse macromolecules made from amino acids.

• Amino acids are joined by covalent peptide bonds to form polypeptides.

• Common Components of Amino Acids:

  • Central carbon

  • A single hydrogen

  • Amino group (-NH2)

  • Carboxyl group (-COOH)

  • Variable R group affecting structure and function.

Protein Structure and Function

• Determines protein function through folding driven by R group interactions.

• Levels of Protein Structure:

  1. Primary Structure: Linear sequence of amino acids.

  2. Secondary Structure: Interaction leading to helices and sheets.

  3. Tertiary Structure: 3D shape from interactions within a single polypeptide.

  4. Quaternary Structure: Multiple polypeptides forming a complex.

Protein Stability and Denaturation

• Denaturation disrupts protein 3D structure due to pH, temperature, or salt concentration.

• Can result in loss of function.

Proteins Functionality

• Proteins perform most biological functions, including:

  • Enzymatic reactions (e.g., sucrase).

  • Structural functions (e.g., actin, myosin).

  • Transport mechanisms (hemoglobin carrying oxygen).

Learning Outcomes for Proteins

• Diagram amino acid structure.

• Explain functions of various proteins.

• Describe the four levels of protein structure.

• Outline factors impacting protein shape and function.

Section 2.5 – Nucleic Acids

Overview of Nucleic Acids

• Nucleic acids (DNA and RNA) are critical for genetic information storage and transfer.

• Structure: Composed of nucleotides, which consist of:

  • Nitrogenous base

  • Pentose sugar

  • Phosphate group.

• Types:

  1. DNA (Deoxyribonucleic acid): Double-stranded polymer; stores genetic information.

  2. RNA (Ribonucleic acid): Single-stranded polymer; involved in protein synthesis (transcription and translation).

DNA and RNA Composition

• Base Pairing Rules:

  • A pairs with T (2 H-bonds)

  • G pairs with C (3 H-bonds).

Learning Outcomes for Nucleic Acids

• Diagram nucleotide structure.

• Distinguish between DNA and RNA.

• Explain base pairing and the central dogma of biology.

Section 2.5 – Lipids

Overview of Lipids

• Lipids are non-polar molecules with diverse functions in organisms:

  • Barrier formation (cell membranes)

  • Insulation

  • Energy storage.

• Not considered polymers but formed through dehydration synthesis.

Types of Lipids

• Types Include:

  • Fatty acids

  • Triglycerides

  • Phospholipids

  • Steroids

  • Waxes.

Fatty Acids: Saturated vs. Unsaturated

• Saturated Fats: Only single bonds between carbons, maximum hydrogen.

• Unsaturated Fats: At least one double bond between carbons, leading to kinks and differing properties at room temperature.

Phospholipids and Cell Membranes

• Structure: Composed of hydrophilic heads and hydrophobic tails, forming bilayers.

• Function: Essential for cell membrane structure and function.

Learning Outcomes for Lipids

• List various classes of lipids.

• Diagram triglyceride structure and its properties related to fatty acids.

• Explain bilayer formation of phospholipids in water.

Exam Preparation

1. Review chapter 2 thoroughly.

2. Cover all learning outcomes listed.

3. Schedule study time efficiently.

4. Utilize Connect post-lecture questions to reinforce learning.