Characteristics of Living Things

• Living things contain nucleic acids, proteins, carbohydrates, and lipids
• Living things are composed of cells
• Living things grow and reproduce
• Living things use energy and raw materials
• Living things respond to their environment
• Living things maintain homeostasis
• Populations of living things evolve and have adaptive traits
• 3 domains of biological world

  bacteria, eukarya , and archaea
• Eukarya is the domain containing all other cells with nuclei (including plants, animals, fungi, protists).
• Bacteria are prokaryotes that lack membrane-bound organelles.
• Archaea are prokaryotic microorganisms that live in extreme environments such as hot springs or deep sea vents.
• Biological hierarchy of the world

  atoms to molecules to organelles to cell to tissue to organ to organ systems to individual to population to community to ecosystem to biosphere
• atoms

  units of matter cannot be broken down further
• All atoms have a nucleus in the center and surrounding “cloud:” - the cloud is made up of protons and neutrons but electrons are always moving around the atoms
• Shell closest to the nucleus can hold up to 2 electrons
• Next shell can hold 8 electrons
• Atoms with more than 10 electrons have additional shells - electrons with the most energy are farthest from the nucleus
• The number of electrons in the outermost layer determines an atom's chemical properties
• Neutrons are neutral and protons are positively charged
• Atomic number: the number of protons in the atom's nucleus
• Atomic mass: protons and neutrons are one unit each, while electrons are too tiny to count
• Isotopes: atoms with the same number of protons but different number of neutrons
• Radioisotopes: unstable isotopes emitting radiation, can be harmful or useful in imaging and medicine
• Compound: formed by two or more elements, held together by chemical bonds
• Covalent Bonds: formed when atoms share electrons in their outer shells
• Single covalent bond: one electron shared

  Double or triple covalent bond: more than one electron shared
• Molecule: a chemical structure held together by covalent bonds
• Ionic Bond: formed by the mutual attraction of oppositely charged ions
• Polarity: distribution of electrical charge over atoms joined by a bond
• Hydrogen bonds: attraction between slightly positively charged hydrogen atom and a slightly negatively charged atom nearby
• Buffers: substances that keep pH value from changing dramatically
• Acids: release hydrogen ions in water; Bases: release hydroxide ions in water
• Macromolecules: large molecules made up of many small repeating molecular subunits called polymers
• Carbohydrates: compounds made of carbon, hydrogen, and oxygen, used to fuel the body
• Monosaccharides: simple sugars with 3-7 carbon atoms

  Oligosaccharides: chains of a few monosaccharides

  Disaccharides: formed by joining two monosaccharides

  Polysaccharides: complex carbs formed by long chains of monosaccharides
• Lipids: compounds that do not dissolve in water
• Triglycerides: compounds made of one glycerol molecule and 3 fatty acids

  Phospholipids: glycerol bonded to two fatty acids and a phosphate group

  Steroid: lipid made of four carbon rings
• Proteins: polymers made of one or more chains of amino acids
• Amino Acids: building blocks of proteins

  Peptides: chains with a few amino acids

  Polypeptides: chains with 10 or more amino acids
• Protein Structure:

  <|>Primary structure: sequence of amino acids

  Secondary structure: patterns like helices and pleated sheets

  Tertiary structure: overall three-dimensional shape

  Denaturation: changes in environment causing protein to lose its shape