The Molecules of Life: Structure and Function of Biological Molecules

The Molecules of Life

Biology and Society: Lactose Intolerance

Lactose is a sugar found in milk and dairy products. Some individuals are unable to digest lactose due to a deficiency in the enzyme lactase, leading to lactose intolerance.

• Lactose intolerance is the inability to properly digest lactose.

• It can be managed by avoiding lactose-containing foods or by consuming lactase supplements.

• Lactase is the enzyme responsible for breaking down lactose into simpler sugars.

• Application: Lactose intolerance is common in adults worldwide and is an example of how genetics and enzyme activity affect nutrition.

Organic Compounds

Definition and Importance

Organic compounds are the foundation of cellular structure and function. While cells are mostly water, the majority of their remaining mass consists of carbon-based molecules.

• Organic compounds are molecules containing carbon atoms bonded to other elements, typically hydrogen, oxygen, and nitrogen.

• Carbon's ability to form large, complex, and diverse molecules is essential for life's functions.

• Example: Glucose, proteins, and DNA are all organic compounds.

Carbon Chemistry

Versatility of Carbon

Carbon is unique in its ability to form stable covalent bonds with many elements, allowing for a vast diversity of molecular structures.

• Carbon can share electrons with other atoms, forming covalent bonds.

• Carbon skeletons vary in size, branching, and the presence of double bonds.

• Common elements bonded to carbon include hydrogen, oxygen, and nitrogen.

Variations in Carbon Skeletons

The structure of carbon skeletons determines the properties and functions of organic molecules.

Variation	Description
Length	Carbon chains can be short or long.
Branching	Chains may be unbranched (linear) or branched.
Double Bonds	Presence and location of double bonds affect molecule shape and reactivity.
Rings	Carbon atoms may form ring structures, as in benzene.

Simple Organic Compounds: Methane

Methane is one of the simplest organic molecules, consisting of one carbon atom bonded to four hydrogen atoms.

• Methane (CH4) is a key example of a simple hydrocarbon.

• Larger hydrocarbons, such as those found in gasoline, are important energy sources.

• Structural representations:

  • Structural formula: shows the arrangement of atoms ($CH_4$)

  • Ball-and-stick model: illustrates the 3D geometry

  • Space-filling model: represents the relative sizes of atoms

Additional info:

• Organic chemistry is the study of carbon-containing compounds, which are central to biochemistry and molecular biology.

• Functional groups (not shown in these slides) are specific groups of atoms within molecules that are responsible for characteristic chemical reactions.