Properties of Water

1. Molecular Structure

• Water (H₂O): Composed of two hydrogen atoms covalently bonded to one oxygen atom, forming a V-shaped molecule.

2. Polarity

• Polarity: Water is a polar molecule with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. This is due to the difference in electronegativity between oxygen and hydrogen.

3. Hydrogen Bonds

• Role of Hydrogen Bonds: Hydrogen bonds between water molecules contribute to many of water's unique properties, such as cohesion, adhesion, and high specific heat.

4. Cohesion

• Cohesion: Attraction between water molecules due to hydrogen bonding. This property causes water to stick together, resulting in surface tension, which allows small insects to walk on water and causes water to form droplets.

5. Adhesion

• Adhesion: Attraction between water molecules and other surfaces. This helps water cling to plant cell walls, facilitating water transport in plants.

6. Transpiration

• Transpiration: The process where water moves from the roots to the leaves through the xylem. Cohesion keeps water molecules together, while adhesion helps them stick to xylem walls, forming a continuous water column that moves upward against gravity.

7. Capillary Action

• Capillary Action: The ability of water to flow in narrow spaces without external forces, due to the combined effects of cohesion and adhesion. This assists in drawing water up from the roots through plant vessels into the leaves.

8. High Specific Heat

• Specific Heat: Water has a high specific heat, meaning it can absorb or release large amounts of heat with only a slight change in its own temperature. This helps moderate Earth's climate and maintain stable temperatures in organisms.

9. Evaporative Cooling

• Evaporative Cooling: When water evaporates, it takes heat away from the surface, cooling the organism. This process helps regulate temperature in animals and plants through sweating and transpiration.

10. Density of Ice

• Density: Ice is less dense than liquid water due to the crystalline structure of hydrogen bonds, which causes the molecules to be spaced further apart. This results in ice floating on liquid water.

11. Insulation by Ice

• Insulation: The floating ice insulates the water below, creating a stable environment for aquatic life during cold seasons.

12. Universal Solvent

• Universal Solvent: Water is called the "universal solvent" because its polarity allows it to dissolve a wide variety of ionic and polar substances.

13. Solvent vs. Solute

• Solvent: A substance that dissolves other substances.

• Solute: The substance being dissolved in a solvent.

• Solution: A homogeneous mixture of solvent and solute.

14. Dissolving Ionic Compounds

• Importance: Water’s ability to dissolve ionic compounds (e.g., salts) is crucial for transporting nutrients, gases, and waste products in biological organisms.

Carbon's Unique Properties and Importance

1. Tetravalency

• Tetravalency: Carbon has four valence electrons, which allows it to form four covalent bonds with other atoms. This property is key to forming a wide variety of compounds.

2. Types of Carbon Bonds

• Bond Types: Carbon can form single, double, and triple bonds. This ability to create various types of bonds contributes to the diversity of carbon-based molecules.

3. Catenation

• Catenation: Carbon can bond with other carbon atoms to form long chains and rings. This capability is crucial for creating complex organic molecules and structures.

4. Hydrocarbons

• Definition: Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen.

• Bond Types in Hydrocarbons: The bonds (single, double, or triple) and the length of the hydrocarbon chain determine the shape and properties of the molecule.

5. Importance of Hydrocarbons

• Role: Hydrocarbons are fundamental in forming more complex molecules and are major components of lipids and fuels.

6. Carbon in Biological Molecules

• Versatility: Carbon's ability to form a variety of compounds allows it to create essential biological molecules such as carbohydrates, lipids, proteins, and nucleic acids.

7. Carbon and Energy Storage

• Energy Storage: Carbon-based compounds like glucose and fatty acids are vital for storing and providing energy for cellular processes.

8. Structural Roles of Carbon Compounds

• Structure: Carbon compounds are integral to the structural framework of cells and tissues. Examples include cellulose in plants and collagen in animals.

Biological Macromolecules

1. Biological Macromolecules

• Definition: Large, complex molecules essential for life. They are involved in cellular processes and are critical for the structure, function, and regulation of the body’s tissues and organs.

2. Main Classes of Biological Macromolecules

• Carbohydrates: Provide energy and structural support.

• Proteins: Function in structure, function, and regulation of tissues and organs.

• Nucleic Acids: Store and transmit genetic information.

• Lipids: Involved in energy storage, membrane structure, and signaling.

3. Monomers

• Definition: Small, basic molecular units that can join together to form polymers.

• Examples:

  • Glucose: Monomer of carbohydrates.

  • Amino Acids: Monomers of proteins.

  • Nucleotides: Monomers of nucleic acids.

  • Fatty Acids: Components of lipids.

4. Polymers

• Definition: Large molecules composed of repeating monomer units.

5. Formation of Polymers

• Dehydration Synthesis: Polymers are formed through dehydration synthesis reactions, where monomers are bonded together by the removal of a water molecule.

6. Dehydration Reaction

• Definition: A chemical reaction where two molecules are covalently bonded with the loss of a water molecule, forming polymers from monomers.

7. Hydrolysis

• Definition: The reverse of dehydration synthesis, where water is added to break the bonds between monomers, breaking down polymers into monomers.

8. General Formula for Carbohydrates

• Formula: Carbohydrates are composed of carbon, hydrogen, and oxygen, usually in a 1:2:1 ratio.

9. Function of Carbohydrates

• Primary Function: Carbohydrates serve as the main source of energy for the body.

Carbohydrates

1. Definition of Carbohydrates

• Carbohydrates: Organic molecules composed of carbon, hydrogen, and oxygen, typically in a 1:2:1 ratio. They function as the body's main source of energy and fuel and also contribute to structural materials.

2. Utilization of Carbohydrates

• Usage: Carbohydrates are broken down into simple sugars, which are absorbed into the bloodstream as glucose (blood sugar). Glucose is used by cells for energy or stored for later use.

3. Classification Based on Size

• Types:

  • Monosaccharides: Single sugar molecules.

  • Disaccharides: Composed of two monosaccharides.

  • Polysaccharides: Long chains of monosaccharide units.

4. Monosaccharides

• Definition: The simplest form of carbohydrates, consisting of single sugar molecules.

• Examples:

  • Glucose

  • Fructose

  • Galactose

5. Disaccharides

• Definition: Carbohydrates formed by the joining of two monosaccharides through a dehydration reaction.

• Examples:

  • Sucrose: Glucose + Fructose

  • Lactose: Glucose + Galactose

  • Maltose: Glucose + Glucose

6. Polysaccharides

• Definition: Long chains of monosaccharide units bonded together.

7. Types of Polysaccharides

• Storage Polysaccharides: Store glucose.

  • Examples:

    • Starch: Found in plants.

    • Glycogen: Found in animals.

• Structural Polysaccharides: Provide structural support.

  • Examples:

    • Cellulose: Found in plant cell walls.

    • Chitin: Found in the exoskeletons of arthropods and the cell walls of fungi.

Proteins

1. Composition of Proteins

• Proteins: Complex molecules made up of amino acids linked by peptide bonds.

2. Amino Acids

• Definition: The building blocks of proteins. There are 20 different amino acids commonly found in proteins.

3. Essential vs. Nonessential Amino Acids

• Essential Amino Acids: Cannot be synthesized by the human body and must be obtained through the diet.

• Nonessential Amino Acids: Can be synthesized by the body.

4. General Structure of an Amino Acid

• Components:

  • Amino Group (NH₂)

  • Carboxyl Group (COOH)

  • Hydrogen Atom

  • R Group (Side Chain): Attached to a central carbon atom.

5. Side Chains (R Groups)

• Effect on Amino Acids:

  • Nonpolar Side Chains: Hydrophobic (water-fearing), typically found in the interior of proteins.

  • Polar Side Chains: Hydrophilic (water-loving), usually found on the exterior of proteins, interacting with water.

  • Charged Side Chains: Can be positively or negatively charged; important for protein interactions.

6. Peptide Bond

• Definition: A bond formed by a dehydration reaction between the amino group of one amino acid and the carboxyl group of another.

7. Polypeptide

• Definition: A long chain of amino acids; proteins are composed of one or more polypeptides.

8. Protein Structures

• Primary Structure: The sequence of amino acids in a polypeptide chain.

• Secondary Structure: Local folding into alpha-helices and beta-sheets, stabilized by hydrogen bonds.

• Tertiary Structure: The overall 3D shape of a polypeptide, determined by interactions between R groups.

• Quaternary Structure: The arrangement of multiple polypeptide chains into a functional protein.

9. Functions of Proteins

• Antibodies: Defense against pathogens.

• Enzymes: Catalysts that speed up chemical reactions.

• Messengers: Hormones that regulate physiological processes.

• Structural Components: e.g., Collagen in connective tissues.

• Transporters: e.g., Hemoglobin, which carries oxygen in the blood.

Nucleic Acids

1. Definition of Nucleic Acids

• Nucleic Acids: Macromolecules that store and transmit genetic information.

2. Types of Nucleic Acids

• DNA (Deoxyribonucleic Acid): Stores genetic information for all living things; has a double-stranded helix structure.

• RNA (Ribonucleic Acid): Transmits genetic information and helps in protein synthesis; is single-stranded.

3. Monomers of Nucleic Acids

• Nucleotides: The building blocks of nucleic acids.

4. Structure of Nucleotides

• Components:

  • Sugar:

    • Deoxyribose in DNA.

    • Ribose in RNA.

  • Phosphate Group.

  • Nitrogenous Base.

5. Nitrogenous Bases

• In DNA:

  • Adenine (A)

  • Thymine (T)

  • Cytosine (C)

  • Guanine (G)

• In RNA:

  • Adenine (A)

  • Uracil (U)

  • Cytosine (C)

  • Guanine (G)

6. Pyrimidines vs. Purines

• Pyrimidines: Single-ring nitrogenous bases.

  • Cytosine (C)

  • Thymine (T) (DNA only)

  • Uracil (U) (RNA only)

• Purines: Double-ring nitrogenous bases.

  • Adenine (A)

  • Guanine (G)

7. Phosphodiester Linkage

• Definition: A bond between the phosphate group of one nucleotide and the sugar of another, forming the backbone of nucleic acid strands.

8. Directionality

• Importance: Nucleic acids have a 5' to 3' direction, which is crucial for processes such as replication and transcription.

9. Genetic Information

• Sequence of Nucleotides: The order of nucleotides in a nucleic acid determines the genetic information and instructions for protein synthesis.

Lipids

1. Definition of Lipids

• Lipids: Hydrophobic molecules involved in energy storage, membrane structure, and signaling.

2. Main Components of Lipids

• Glycerol: A three-carbon alcohol.

• Fatty Acids: Long hydrocarbon chains with a carboxyl group.

3. Structure of Fats (Triglycerides)

• Composition: One glycerol molecule linked to three fatty acids by ester bonds.

4. Saturated Fats

• Characteristics: No double bonds between carbon atoms, solid at room temperature.

• Sources: Found in foods like butter and coconut oil.

5. Unsaturated Fats

• Characteristics: One or more double bonds in the fatty acid chains, liquid at room temperature.

• Sources: Found in foods like olive oil, avocado, and nuts/seeds.

6. "Good" Fats

• Monounsaturated Fats: Found in olive oil, avocados, and nuts; help reduce bad cholesterol.

• Polyunsaturated Fats: Includes omega-3 fatty acids; beneficial for heart health and reducing inflammation.

7. "Bad" Fats

• Saturated Fats: Found in animal products and some plant oils; can raise bad cholesterol levels.

• Trans Fats: Created by hydrogenating oils; found in processed and fried foods; raise bad cholesterol and lower good cholesterol.

8. Phospholipids

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

• Function: Form cell membranes with hydrophilic heads facing the exterior and hydrophobic tails facing the interior.

9. Steroids

• Structure: Four fused carbon rings.

• Function: Include hormones like testosterone, and cholesterol, which is a component of cell membranes. Steroids can diffuse through cell membranes, bind to DNA, and regulate gene expression.