SBI4U - Unit One - Biochemistry: Bonding

Bonding

Ionic Bonds

• Formed by the transfer of one or more electrons between atoms with electronegativity greater than 1.7.
• Results in oppositely charged ions: cations (positive) and anions (negative).
• Easily dissociate in water, making them soluble.

Covalent Bonds

• Involve the sharing of electrons between atoms.
• Types include:
  • Polar Covalent Bonds: Unequal sharing of electron pairs (EN 0.41 - 1.7), e.g., water (H₂O).
  • Nonpolar Covalent Bonds: Equal sharing of electrons (EN < 0.4), e.g., diatomic molecules like H₂, O₂, and hydrocarbons.
  • Amphiphilic Molecules: Contain both polar and nonpolar regions, e.g., fatty acids.
• Polar substances dissolve in polar solvents, while nonpolar substances dissolve in nonpolar solvents.

Electronegativity

• Measures the ability of an atom to attract electrons; fluorine is the most electronegative element.
• Affects bond strength and molecule polarity.
• Determines molecular shape, influencing properties and behavior.

Intermolecular Forces

• Hydrogen Bonds: Attraction between partially positively charged hydrogen and partially negative atoms in other molecules, crucial in water.
• Van der Waals Forces: Weak, transient attractions between molecules, including London dispersion and dipole-dipole forces.

Chemical Reactions

Dehydration Reaction

• Combines smaller molecules by removing OH and H forming water (e.g., sugar refining).

Hydrolysis Reaction

• Splits larger molecules by adding water, common in digestion (e.g., lactase activity).

Neutralization Reaction

• Reaction between acids and bases yielding water and salt, such as enzymatic processes in digestion.

Redox Reaction

• Involves electron transfer between atoms (e.g., cellular respiration). Remember LEO (Lose Electrons Oxidation) and GER (Gains Electrons Reduction).

Properties of Water

• Polarity: Oxygen's higher electronegativity causes unequal electron distribution, leading to hydrogen bonding.
• Cohesion and Adhesion: Water molecules attract each other and other polar molecules, essential for capillary action.
• Surface Tension: Increased hydrogen bonding at the surface leads to unique properties in water.
• Lower Density: Ice is less dense than liquid water, allowing it to float, which insulates aquatic life during winter.
• Turnover: Natural mixing in lakes enhances oxygen distribution and gas release.
• High Heat of Vaporization: Evaporation of sweat cools the body by pulling heat away.
• High Heat Capacity: Large heat input required for temperature change, highlighting ocean temperature concerns.
• Universal Solvent: Water dissolves ionic and polar substances efficiently.

Carbon Chemistry of Life

Carbon Chains

• Backbone for complex molecules; capable of forming single, double, and triple bonds.

Functional Groups

• Include amino (NH₂), carboxyl (COOH), carbonyl (CO), hydroxyl (OH), peptide (CHON), and phosphate (PO₄).

Macromolecules

• Types: Carbohydrates, Lipids, Nucleic Acids, Proteins.

Carbohydrates

• Composed of carbon, hydrogen, and oxygen (CHO).
• Types include monosaccharides, disaccharides, and polysaccharides.

Monosaccharides

• Basic unit, represented as CHO 1:2:1; soluble and vital for energy transport, e.g., glucose.

Disaccharides

• Formed by the condensation of two monosaccharides; can be hydrolyzed back to monosaccharides. Example: sucrose.

Polysaccharides

• Include structural forms like cellulose (fiber) and storage forms like glycogen and starch.
• Digestive enzymes differentiate between α and β linkages.

Lipids

• Comprised of carbon, hydrogen, and sometimes phosphorus (CHO(P)).
• Nonpolar and hydrophobic, lacking true monomers.

Types of Lipids

• Triglycerides: Consist of glycerol and fatty acids, serve energy storage and insulation.
• Phospholipids: Form cell membranes, displaying amphiphilic properties with hydrophilic heads and hydrophobic tails.
• Other Fats: Serve as hormones and protect biological tissues.

Nucleic Acids

• Composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus (CHONP).
• Include DNA and RNA, built from nucleotides with covalent and phosphodiester bonds.

Proteins

• Composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur (CHON(S)).
• Built from amino acids (monomers), forming dipeptides and polypeptides.

Protein Functions

• Enzymatic catalysts, antibodies, hormones, oxygen transport (hemoglobin), and structural roles (actin, myosin).

Passive Transport

• Molecules diffuse from high to low concentration across membranes without energy.
• Osmosis: Diffusion of water across membranes.
• Facilitated Diffusion: Involves specific protein channels for large or polar molecules.

Solutions and Tonicity

• Hypotonic: Lower solute concentration than inside cell; can cause bursting in animal cells.
• Hypertonic: Higher solute concentration outside; can cause cell shrinkage.
• Isotonic: Equal solute concentration; maintains cell equilibrium.

Active Transport

• Moves substances against the concentration gradient using ATP, essential for removing toxins or nutrients.

Explore the fundamentals of bonding in biochemistry with this quiz focused on ionic and covalent bonds. Learn about the characteristics of each bond type, including electron transfer and sharing properties. Test your understanding of how these bonds contribute to molecular interactions in biological systems.