Fundamental Chemistry of Life

Fundamental Chemistry of Life

• Matter comprises everything in the universe, including living organisms.
• Element: A pure substance that cannot be broken down.
• Atom: The smallest particle of an element.
• Atoms combine in ratios to create molecules and compounds.

Organic Compounds

• Organic compounds are primarily made of carbon (C), hydrogen (H), oxygen (O), and sometimes nitrogen (N).
• Organic compounds make up 96% of the weight of a living organism.
• Other elements like calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), and magnesium (Mg) account for the remaining 4%.

Differences between Living and Non-living Things

• Similar elements are present in various living and non-living organisms but in different ratios.
• Living organisms have significantly higher proportions of oxygen, carbon, hydrogen, and nitrogen compared to non-living examples like seawater, pumpkins or the earth's crust.

Atomic Structure

• Atoms consist of protons, neutrons, and electrons.
• Protons define an atom's identity.
• Atomic mass equals the sum of protons and neutrons.

Subatomic Particle Summary

• Protons: Positively charged, located in the nucleus, and equal to the atomic number.
• Neutrons: Neutral charge, located in the nucleus, and calculated by subtracting the atomic number from the atomic mass.
• Electrons: Negatively charged, found in outer orbitals, and equal to the atomic number.

Isotopes and Radioisotopes

• Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons.
• Radioisotopes: Unstable isotopes that decay and emit particles, detectable as radioactivity.
• Isotopes of the same element behave identically in chemical reactions.

Radioisotopes

• Radioisotopes decay, transforming into a more stable atom of a different element.
• The decay process produces detectable radioactive signals.

In Beta Decay

• A neutron in an unstable isotope turns into a proton.
• This results in a new element forming.

Carbon-14 Dating

• The ratio of Carbon-14 to Carbon-12 is constant in living things (1:1x10¹²).
• In fossils, the Carbon-14 ratio decreases over time, allowing scientists to determine the age of the organism since death.
• The half-life of Carbon-14 is 5730 years.

Electron Arrangements in Orbitals

• Electrons are equal to protons (neutral atoms).
• Electrons occupy orbitals (shells).
• Shells are numbered (1, 2, 3...).
• The first shell holds 2 electrons, the second 8, and the third 18.
• Shells use s, p, d, f orbitals.

Electron Shells

• The first shell (1s) is spherical and holds two electrons.
• The second shell (2s) is spherical and larger than the first and holds two electrons.
• The second shell also contains three 2p orbitals, each holding two electrons for a total of six.

Valence Electrons

• Valence electrons are the outermost shell electrons.
• Atoms with unfilled outer shells are reactive.
• Valence electrons are used in Lewis dot diagrams to illustrate bonding.

Giving, Taking, and Sharing

• Atoms with few outer electrons tend to lose them, becoming positive ions (cations).
• Atoms with many outer electrons tend to gain more to become negative ions (anions).
• Atoms share electrons to complete outer shells, forming covalent bonds.

Chemical Bonds in Biological Molecules

• Ionic bonds form due to attraction between oppositely charged ions.
• Covalent bonds form when atoms share pairs of valence electrons, forming molecules with a distinct structure.
• Electronegativity measures an atom's attraction for electrons, influencing covalent bond strength and polarity.

Chemical Bonds in Biological Molecules (continued)

• Covalent bonds determine the structure of molecules.
• An example, carbon (C) forms four covalent bonds, making complex molecules possible.

Polar Molecules

• Polarity is a property of molecules.
• Electronegativity influences polarity, with higher electronegativity values attracting electrons more strongly.
• Unequal sharing of electrons between atoms creates partial charges in molecules.
• Polarity affects solubility and interactions with other molecules.

Determining Polarity

• Bonds between different atoms are often polar.
• The difference in electronegativity between two atoms measures its polarity, with large differences indicating more ionic bonds and smaller indicating covalent bonds.
• Nonpolar molecules have no net charge.

Properties of Polar Molecules

• Polar molecules tend to dissolve in other polar substances but not in non-polar ones.
• Water is a powerful polar solvent.

Intermolecular Forces

• Intermolecular forces are attractions between different molecules.
• Van der Waals, hydrogen bonds, and dipole-dipole interactions affect interactions between molecules.

Intermolecular Forces (continued)

• Van der Waals forces are weaker than covalent bonds.
• Hydrogen bonds, a special type of dipole-dipole interaction, are particularly strong from the positive hydrogen and negative oxygen attraction and are prevalent in biological molecules.

Hydrogen Bonds and Biological Significance

• Hydrogen bonds are relatively weak, but significant in large numbers.
• Hydrogen bonding stabilizes the complex shapes of biological molecules like proteins.

Chemical Reactions

• Dehydration synthesis: Removing water to link subunits.
• Hydrolysis: Adding water to break down molecules.

Neutralization Reactions

• A reaction between an acid and a base that produces a salt and water.

Redox Reactions

• Oxidation: Loss of electrons.
• Reduction: Gain of electrons.

Homework

• Use radioisotope decay for diagnosing thyroid issues using radioactive iodine-131.

Explore the basics of chemistry that underlie all living organisms. This quiz covers key concepts such as matter, organic compounds, and the distinctions between living and non-living things. Test your understanding of atomic structure and the elements essential to life.