C2.1 Molecules to Metabolism (continued)

The section concludes with a historical perspective on organic chemistry, discussing Friedrich Wöhler's accidental synthesis of urea. This discovery was pivotal in undermining the concept of vitalism, which held that organic compounds could only be synthesized by living organisms.

Highlight: Wöhler's synthesis of urea from inorganic compounds was a groundbreaking moment in the history of chemistry and biology, demonstrating that organic molecules could be artificially created.

This historical context helps students appreciate the development of our understanding of organic chemistry and its implications for modern biology and biochemistry.

C2.2 Water

This section focuses on the unique properties of water and its crucial role in biological systems. The polarity of water molecules and their ability to form hydrogen bonds are explained in detail.

Vocabulary:

• Hydrophilic: polar molecules that dissolve in water
• Hydrophobic: non-polar molecules that repel water and are insoluble

A required diagram illustrating the structure of a water molecule and its hydrogen bonding is provided, helping students visualize these important concepts.

The properties of water are discussed in depth, including:

1. Cohesion: The ability of water molecules to stick to each other, creating surface tension.
2. Adhesion: Water molecules' ability to stick to other polar compounds.
3. Thermal properties: Water's role as a coolant in regulating temperature.
4. Solvent properties: Water's ability to dissolve polar compounds.

Example: Cohesion allows water to be pulled up from roots through the xylem in plants, demonstrating the importance of water's properties in biological processes.

The section also compares water to methane, highlighting the differences in polarity and latent heat of vaporization. This comparison helps students understand why water's properties are so unique and important for life.

C2.2 Water (continued)

The role of water as a coolant in biological systems is further explored, emphasizing its importance in maintaining stable temperatures for optimal protein function. The section explains how water's high specific heat capacity and latent heat of vaporization contribute to its cooling effects.

Highlight: Water's ability to act as a coolant is crucial for maintaining body temperature in organisms, preventing protein denaturation due to high temperatures.

The properties of blood as a water-based solution are discussed, with a focus on how different substances interact with the aqueous environment. A table is provided that outlines the properties and applications of various substances in blood, including glucose, amino acids, oxygen, cholesterol, and sodium chloride.

Example: Cholesterol, being non-polar, is transported in blood by lipoproteins that have a hydrophobic interior and hydrophilic exterior, allowing for its dissolution in the aqueous blood plasma.

This detailed exploration of water's properties and its role in biological systems is essential for IB Biology HL students to understand the fundamental principles of biochemistry and physiology.

C2.3 Carbohydrates and Lipids

This section provides a comprehensive overview of carbohydrates and lipids, two major classes of biomolecules. The discussion begins with carbohydrates, explaining their classification into monosaccharides, disaccharides, and polysaccharides.

Definition: Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, typically with a 2:1 ratio of hydrogen to oxygen.

The section includes a detailed table listing various carbohydrates, their monomers, and their biological uses. This information is crucial for IB Biology HL students to understand the diversity and functions of carbohydrates in living systems.

Example: Sucrose, a disaccharide composed of glucose and fructose, is used to transport energy from leaves to storage organs in plants.

Polysaccharides are given special attention, with a focus on starch, glycogen, and cellulose. The properties of these complex carbohydrates are discussed, including their compact nature, insolubility, and ease of enzymatic hydrolysis.

Highlight: The structural differences between alpha and beta glucose are crucial for understanding the diverse functions of polysaccharides in nature.

The section begins to touch on the industrial applications of starch, setting the stage for a broader discussion of the practical uses of carbohydrates in various fields.

This detailed exploration of carbohydrates provides IB Biology HL students with a solid foundation for understanding more complex biochemical processes and the role of these molecules in living organisms.

C2.1 Molecules to Metabolism

This section introduces the fundamental concepts of molecular biology, focusing on the structure and properties of key biological molecules. The carbon atom's unique ability to form four covalent bonds is highlighted, explaining its central role in organic compounds.

Definition: Molecular biology is the study of the composition, structure, and interactions of cellular molecules.

The chapter delves into the structures of carbohydrates, lipids, proteins, and nucleic acids, providing required diagrams for ribose, deoxyribose, and glucose molecules. These diagrams are essential for understanding the structural differences between various biomolecules.

Highlight: The section emphasizes the importance of understanding molecular structures, as they directly relate to the functions of these biomolecules in living systems.

Metabolism is introduced as the sum of all reactions in our body, with a focus on anabolism and catabolism. These processes are explained with specific examples, such as the synthesis of maltose from glucose (anabolism) and the breakdown of lactose into glucose and galactose (catabolism).

Example: Anabolism example: glucose + glucose → maltose (glycosidic bond formation) Example: Catabolism example: lactose → glucose + galactose (glycosidic bond hydrolysis)

This comprehensive overview sets the stage for a deeper understanding of biochemical processes in living organisms, crucial for IB Biology HL students.