bioo

• Compounds are formed by atoms joined by bonds
• Protons determine an atom's identity
• Electron distribution determines an atom's ability to form bonds
• Compound properties depend on its atoms and how they are bonded together
• Matter is anything that takes up space and has mass
• An element is a substance that cannot be broken down to other substances by chemical reactions
• Essential elements needed for a healthy life and reproduction:

  • Humans require 25 elements
  • Plants require 17 elements
• 96% of living matter consists of:

  • Oxygen (65.0% in air and H2O)
  • Carbon (18.5% in organic molecules)
  • Hydrogen (9.5% in H2O)
  • Nitrogen (3.3%)
• The remaining 4% of living matter includes elements like Ca, P, K, S, and a few others, which are crucial despite being present in smaller amounts
• Trace elements are required by organisms in only minute quantities
• Iron (Fe) is needed by all forms of life
• Iodine is an essential ingredient for vertebrates, particularly for the hormone produced by the thyroid glands
• A deficiency of iodine can lead to goiter, where the thyroid glands grow to an abnormal size
• Arsenic, naturally occurring, has been linked to numerous diseases and can be lethal; it can make its way into groundwater
• A case study of arsenic in Southern Asia shows unintentional exposure of millions through arsenic in wells
• Serpentine is a jade-like mineral containing chromium, nickel, and cobalt
• Natural selection and evolutionary adaptations have led to some plants surviving in soil forming serpentine rocks, while most cannot
• Wood ants defend themselves by ejecting formic acid from venom glands towards predators
• Organisms can harness the power of chemicals both within and outside the body, such as in medications
• Atoms are the smallest unit of matter that still retains the properties of an element
• Subatomic particles include neutrons, protons, and electrons
• The atomic nucleus contains protons and neutrons packed tightly in a dense core, with electrons forming a cloud of negative charge around it
• Attraction between opposite charges keeps electrons in the vicinity of the nucleus
• The unit for atomic mass is the Dalton (amu), where the sum of protons and neutrons equals 1 Dalton, and electrons are 1/2000 Daltons
• Isotopes have slight differences in mass but behave identically in chemical reactions, with different physical properties; unstable isotopes can affect behavior
• Radioactive isotopes decay spontaneously, giving off particles and energy, leading to a change in the number of protons
• Decaying radioactive isotopes are not affected by temperature, pressure, or any other environmental factors
• Radioactive isotopes change the number of protons by transferring the atom to an atom of another element, releasing energy in the process
• Radioactive isotopes are used as diagnostic tools in medicine, where cells use both non-radioactive and radioactive atoms
• Tracers are incorporated into biologically active molecules to label or tag atoms during metabolism, relying on naturally occurring isotopes
• In cancer cells, tracers like glucose can be used to monitor growth and metabolism in the body
• Radiation from decaying isotopes can damage cellular molecules, with severity based on type, amount, and absorption, potentially damaging DNA
• Radiometric dating uses the ratio of different isotopes to calculate how many half-lives have passed since fossilization, with more instability leading to a faster rate of decay
• Short-lived isotopes like P32 have half-lives of seconds or days, while long-lived isotopes like Uranium-238 have half-lives of 4.5 billion years
• Carbon-14 has a half-life of 5730 years and is used in carbon dating fossils
• Fossils provide evidence of evolution, showing differences between past and present organisms
• Fossil beds establish that deeper fossils are older than shallow ones, but the age of a fossil cannot be determined by position alone
• Energy is the capacity to cause change by doing work
• Potential energy is the energy that matter possesses due to its location or structure
• Water in a reservoir on a hill has potential energy due to its altitude