Ch 5 Pearson Study guide from Lecture Outline

The Versatile Carbon Atom (Properties of Carbon)

Introduction

Carbon is a unique element that forms the backbone of all organic molecules. Its versatility allows it to form stable covalent bonds with many elements, making it essential for the complexity of life.

• Tetravalency: Carbon has four valence electrons, allowing it to form four covalent bonds with other atoms.

• Bonding Diversity: Carbon can form single, double, and triple bonds, as well as chains, branched molecules, and rings.

• Stability: Carbon-carbon bonds are stable, enabling the formation of large and complex molecules.

• Compatibility: Carbon readily bonds with hydrogen, oxygen, nitrogen, sulfur, and phosphorus, which are key elements in biological molecules.

Organic Molecules and Photosynthesis

Organic vs. Inorganic Molecules

Organic molecules contain carbon atoms bonded to hydrogen and often other elements. Inorganic molecules may contain carbon but lack C-H bonds.

• Photosynthesis Equation:

• Organic: C6H12O6 (glucose)

• Inorganic: CO2, H2O, O2

Macromolecules and Biomolecules

Definitions

• Macromolecule: A large molecule composed of thousands of atoms, typically formed by polymerization of smaller subunits.

• Biomolecule: Any molecule produced by living organisms, including carbohydrates, lipids, proteins, and nucleic acids.

The Four Major Classes of Biomolecules

1. Carbohydrates

2. Lipids

3. Proteins

4. Nucleic Acids

Polymers and Monomers

• Polymer: A large molecule made up of repeating subunits (monomers) joined by covalent bonds.

• Monomer: The basic building block or subunit of a polymer.

Polymerization Reactions

Dehydration Synthesis

Dehydration synthesis (condensation reaction) is the process by which monomers are joined to form polymers, releasing a molecule of water for each bond formed.

• Example: Formation of a peptide bond between two amino acids.

Hydrolysis

Hydrolysis is the process by which polymers are broken down into monomers by the addition of water.

• Example: Digestion of starch into glucose monomers.

Carbohydrates

Main Functions of Carbohydrates

• Energy source (e.g., glucose)

• Energy storage (e.g., starch, glycogen)

• Structural support (e.g., cellulose in plants, chitin in fungi and arthropods)

• Cell recognition and signaling (e.g., oligosaccharides on cell surfaces)

Elements in Carbohydrates

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

Functional Groups in Carbohydrates

• Hydroxyl group (-OH)

• Carbonyl group (C=O)

Monosaccharides

Simple sugars with the general formula (e.g., glucose, fructose, galactose).

• Examples: Glucose, Fructose, Galactose, Ribose (in RNA), Deoxyribose (in DNA)

Disaccharides

Formed by joining two monosaccharides via a glycosidic linkage.

• Examples: Sucrose (glucose + fructose), Lactose (glucose + galactose), Maltose (glucose + glucose)

Oligosaccharides

Short chains of 3–10 monosaccharide units, often involved in cell recognition.

Polysaccharides

Long chains of monosaccharides; serve as energy storage or structural molecules.

Good vs. Bad Carbohydrates

• Good carbs: Complex carbohydrates (whole grains, vegetables) provide fiber and nutrients.

• Bad carbs: Simple sugars (refined sugars) can cause rapid spikes in blood glucose and lack nutrients.

Lipids

Main Functions of Lipids

• Long-term energy storage

• Structural components of cell membranes

• Insulation and protection

• Signaling molecules (hormones)

Elements in Lipids

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Additional info: Some lipids may contain phosphorus (e.g., phospholipids)

Fatty Acids

• Saturated fatty acids: No double bonds between carbon atoms; solid at room temperature.

• Unsaturated fatty acids: One or more double bonds; liquid at room temperature.

• Trans fatty acids: Unsaturated fats with trans double bonds; associated with negative health effects.

Triglycerides

• Composed of one glycerol and three fatty acids.

• Formed by ester linkages through dehydration synthesis.

Functions of Fats and Oils

• Energy storage

• Insulation

• Protection of organs

Phospholipids

• Composed of a glycerol backbone, two fatty acids, and a phosphate group.

• Amphipathic: hydrophilic (phosphate head) and hydrophobic (fatty acid tails) regions.

• Major component of cell membranes, forming the phospholipid bilayer.

Function of Phospholipids

• Form biological membranes

• Regulate membrane fluidity

Steroids

• Structure: Four fused carbon rings.

• Functions: Cholesterol (membrane fluidity), hormones (e.g., estrogen, testosterone).

Waxes

• Long-chain fatty acids esterified to long-chain alcohols.

• Function: Waterproofing and protection (e.g., plant cuticle, earwax).

Proteins

Main Functions of Proteins

• Enzymatic catalysis (enzymes)

• Structural support (keratin, collagen)

• Transport (hemoglobin, membrane channels)

• Immune defense (antibodies)

• Regulation (hormones)

• Motion (muscle fibers, microtubules)

• Storage (casein, ovalbumin)

• Receptors (cell signaling)

Elements in Proteins

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

• Sulfur (S) (in some amino acids)

Functional Groups in Proteins

• Amino group (-NH2)

• Carboxyl group (-COOH)

Amino Acids

• Monomers of proteins, each with a central (α) carbon, amino group, carboxyl group, hydrogen atom, and R group (side chain).

Peptide Bonds and Polypeptides

• Amino acids are joined by peptide bonds (covalent bonds between amino and carboxyl groups).

• Polypeptide: A chain of amino acids linked by peptide bonds.

Protein Structure

• Primary: Sequence of amino acids.

• Secondary: Local folding (α-helix, β-sheet).

• Tertiary: 3D shape of a single polypeptide.

• Quaternary: Association of multiple polypeptides.

Protein Folding

• Folding determines function; misfolding can cause diseases.

Mutation and Denaturation

• Mutation: Change in amino acid sequence, potentially altering function.

• Denaturation: Loss of structure and function due to environmental changes (e.g., heat, pH).

Complete vs. Incomplete Protein Sources

• Complete: Contain all essential amino acids (e.g., animal proteins).

• Incomplete: Lack one or more essential amino acids (e.g., most plant proteins).

Nucleic Acids

Types of Nucleic Acids

• DNA (deoxyribonucleic acid)

• RNA (ribonucleic acid)

Elements in Nucleic Acids

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

• Phosphorus (P)

Functional Groups in Nucleic Acids

• Phosphate group

• Hydroxyl group

Nucleotides

• Monomers of nucleic acids, each consisting of a phosphate group, a five-carbon sugar (ribose or deoxyribose), and a nitrogenous base.

Phosphodiester Linkage

• Covalent bond joining the phosphate group of one nucleotide to the sugar of another.

Polynucleotides

• Long chains of nucleotides forming DNA or RNA.

• Backbone alternates between sugar and phosphate groups.

DNA vs. RNA

ATP (Adenosine Triphosphate)

• Main energy currency of the cell.

• Structure: Adenine base, ribose sugar, three phosphate groups.

• Energy is released by hydrolysis of the terminal phosphate bond:

• Function: Provides energy for cellular processes such as muscle contraction, active transport, and biosynthesis.