Atoms and Elements

Unstable Atoms and Isotopes

Atoms are the fundamental building blocks of matter, and their stability is crucial for both environmental and biological systems. Unstable atoms, such as radioactive isotopes, can have significant impacts, as illustrated by the Fukushima Daiichi nuclear power plant incident in 2011, where radioactive isotopes were released into the atmosphere.

• Atoms: The smallest structural units of elements, retaining all chemical properties of the element.

• Element: A pure substance that cannot be broken down into simpler substances by ordinary chemical reactions.

• Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons. For example, carbon has isotopes 12C, 13C, and 14C (with 14C being radioactive).

Additional info: Radioactive isotopes are used in medical imaging and dating fossils, but can also pose health risks due to radiation.

Atomic Structure

Atoms are composed of subatomic particles, each contributing to the atom's properties and behavior.

• Protons: Positively charged particles found in the nucleus.

• Neutrons: Uncharged particles also located in the nucleus.

• Electrons: Negatively charged particles that orbit the nucleus in distinct energy levels (shells).

• Atomic Number: Number of protons in the nucleus, unique to each element.

• Mass Number: Total number of protons and neutrons in the nucleus.

Electrons occupy shells around the nucleus, with the first shell holding up to 2 electrons, the second up to 8, and so on. The arrangement of electrons determines how atoms interact and bond with each other.

The Periodic Table

The periodic table organizes elements by their atomic number and chemical properties.

• Horizontal rows are called periods.

• Vertical columns are called groups or families.

• Elements in the same group have similar chemical properties.

• Metals react with non-metals (e.g., sodium reacts with chlorine).

• Noble gases are chemically inert (e.g., helium, argon).

Biological Molecules

Organic vs. Inorganic Molecules

Biological molecules are essential for life and are classified as organic or inorganic based on their composition.

• Organic molecules: Contain carbon and usually hydrogen and oxygen. Nearly all biological molecules are organic.

• Inorganic molecules: Generally lack carbon atoms and are simpler (e.g., water, salts).

The bonding properties of carbon allow for the complexity and diversity of organic molecules. Carbon can form up to four covalent bonds, enabling the creation of large and varied molecular structures.

Functional Groups in Organic Molecules

Functional groups are specific atoms or groups of atoms that attach to the carbon backbone of organic molecules, influencing their chemical behavior.

Synthesis and Breakdown of Biological Molecules

Large biological molecules are formed by joining small organic molecules (monomers) into chains called polymers. The process of joining monomers is called dehydration synthesis, while breaking them apart is called hydrolysis.

• Dehydration synthesis: Removal of water to join monomers into polymers.

• Hydrolysis: Addition of water to break polymers into monomers.

Dehydration synthesis equation:

$ \text{Monomer}_1 + \text{Monomer}_2 \xrightarrow{\text{Dehydration}} \text{Polymer} + H_2O $

Hydrolysis equation:

$ \text{Polymer} + H_2O \xrightarrow{\text{Hydrolysis}} \text{Monomer}_1 + \text{Monomer}_2 $

These reactions are essential for the formation and breakdown of proteins, nucleic acids, and other biological polymers.

Carbohydrates

Structure and Function

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, typically in a ratio of 1C:2H:1O. They serve as energy sources and structural components in cells.

• Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose).

• Disaccharides: Two monosaccharides joined together (e.g., sucrose).

• Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose).

Monosaccharides typically have a backbone of three to seven carbon atoms. Glucose is a hexose (6 carbons), while ribose is a pentose (5 carbons). The general formula for monosaccharides is:

$ \text{(CH}_2\text{O)}_n $

where n is the number of carbon atoms.

Examples and Applications

• Glucose: The most common monosaccharide and primary energy source for cells.

• Fructose: Stored as energy in some plants.

• Galactose: Secreted by mammals in milk.

Many organisms synthesize monosaccharides with the same chemical formula as glucose but with slightly different structures, leading to diverse functions.

Case Study: Mad Cow Disease and Prions

Prions and Disease Transmission

Mad cow disease (bovine spongiform encephalitis) is a neurodegenerative disease caused by infectious proteins called prions. Prions induce normal proteins in the brain to change shape and become abnormal, leading to disease.

• Derived from a sheep disease called scrapie.

• Transmission occurred through contaminated cattle feed containing body parts from infected sheep.

• Prions are unique infectious agents because they lack nucleic acids.

Additional info: Prion diseases are also known as transmissible spongiform encephalopathies and can affect humans (e.g., Creutzfeldt-Jakob disease).

Summary Table: Types of Biological Molecules

Conclusion

Understanding atoms, elements, and the structure of biological molecules is foundational to the study of biology. The unique properties of carbon enable the diversity of organic molecules essential for life, while the synthesis and breakdown of these molecules underpin biological processes such as metabolism and growth.