Key Concepts in Biology and Chemistry

Radioactive Radiation

  • Radiation can be both harmful and beneficial; harmful when uncontrolled, beneficial in controlled medical uses (nuclear medicine).

  • Controlled radiation is essential for diagnosing and treating diseases (e.g., PET scans, radiation therapy).

Basic Chemistry: Matter and Elements

  • Matter is anything occupying space with mass; exists in solid, liquid, gas.

  • Composed of elements (92 naturally occurring); cannot be broken down by chemical reactions.

  • Key elements in human body: Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N) make up 96% of body mass.

Trace Elements

  • Essential but needed in minute amounts (e.g., Iodine prevents goiter).

  • Iron prevents anemia; too much can cause overload issues.

Compounds and Molecules

  • Compounds consist of two or more elements in a fixed ratio (e.g., NaCl, H2O).

  • Chemical interactions can give compounds different properties than their elements.

Atoms and Subatomic Particles

  • Atoms: smallest unit of matter; consist of protons (+), electrons (-), and neutrons (0).

  • Atomic number = number of protons; mass number = protons + neutrons.

Isotopes and Radioactivity

  • Isotopes: atoms of the same element with different neutrons, e.g., Carbon-12 (stable) vs. Carbon-14 (radioactive).

  • Radioactivity poses health risks but can date fossils (half-life method).

Chemical Bonds

  • Chemical bonds include ionic (electron transfer) and covalent (electron sharing).

  • Hydrogen bonds are a result of polar covalent bonds, affecting water's properties (e.g., cohesion, temperature moderation).

Properties of Water

  1. Cohesion: Attraction among water molecules; essential for plant water transport.

  2. Temperature moderation: Absorbs heat, stabilizes climate.

  3. Ice floating: Ice is less dense; insulates liquid water below.

  4. Versatile solvent: Facilitates biochemical reactions in organisms.

Acids, Bases, and pH

  • Acids release H+; bases accept H+; pH scale indicates H+ concentration (neutral at 7).

  • Buffers maintain pH balance in biological systems; excess CO2 can lead to ocean acidification.

Evolution Connection: Radiometric Dating

  • Radioactive decay in fossils allows estimation of age through ratios of isotopes (e.g., Carbon-14).

  • Supports the fossil record and evolution evidence.