1. Atoms Ions, and Molecules

Living things consist of atoms and different elements

• atom: the smallest basic unit of matter.

  • everything is made out of atoms.

Atoms and Elements

• Atoms have protons, neutrons, and electrons.

  • Protons and neutrons form the nucleus in the center

  • Electrons circle outside the nucleus.

  • Protons are charged positively, electrons negatively, and neutrons are neutral.

• Element: A type of atom that cannot regularly be broken down into a simpler substance.

  • All atoms of an element have a number of protons that never changes.

  • The number of electrons determines the properties of the element.

Compounds

• Compound: a substance made of atoms of different elements bonded together in a certain ratio.

  • Compounds can be different from the base elements. (Ex. gaseous hydrogen and oxygen make water).

Ions form when atoms gain or lose electrons.

• Ion: an atom that had gained or lost one or more electrons.

  • Certain atoms are more stable when they lose or gain electrons.

  • Ions have an electrical charge, either positive or negative.

• Atoms that lose electrons = positively charged ions

• Atoms that gain electrons = negatively charged ions

• Electrons are usually gained/lost through moving electrons between atoms.

• Ionic Bond: A bond that forms through the electrical force between positively and negatively charged ions.

Atoms share pairs of electrons in covalent bonds

• Some atoms share pairs of electrons between them to be stable.

• Covalent bond: a bond that forms when atoms share a pair of electrons.

• Molecule: two or more atoms held together by covalent bonds.

• Diatomic molecules are molecules that have two of the same type of atom. (Ex. 2 Oxygen as a molecule).

2. Properties of Water

life depends on hydrogen bonds in water.

• water has unique properties like how it expands when frozen.

Water and Hydrogen Bonds

• A polar molecule is a molecule that has a region with a slight positive charge and a region with a slight negative charge.

  • Forms when atoms in a molecule have unequal pulls on shared electrons.

• Water is a polar molecule, with the hydrogen atoms having slight positive charges and the oxygen atom having a slight negative charge.

• A nonpolar molecule is a molecule that does not have charged regions.

• Hydrogen bond: An attraction between a slightly positive hydrogen atom and a slightly negative atom.

Properties related to hydrogen bonds

• Hydrogen bonds give unique properties to water.

  • Water has a high specific heat, which means it takes longer to heat up.

  • Water molecules stick to each other better with cohesion.

  • Water molecules stick to other things better with adhesion.

• Cohesion: The attraction among molecules of a substance.

• Adhesion: The attraction among molecules of different substances.

Many compounds dissolve in water.

• Molecules and ions must dissolve in water to take part in chemical processes in cells.

• Solution: a mixture of substances that is all the same throughout.

  • Called a homogeneous mixture (the same).

  • Requires two parts, the solvent, and the solute.

• Solvent: the substance in a solution that dissolves another substance.

• Solute: a substance in a solution that dissolves in a solvent.

• A solution’s concentration is the amount of solute dissolved in a certain amount of solvent.

• Polar substances dissolve more in water than nonpolar substances.

Some Compounds form acids or bases.

• Acid: a compound that releases a hydrogen ion when it dissolves in water.

• Bases: compounds that remove H ions from a solution.

• pH: A scale that measures the acidity of a solution.

  • Scale usually between 0 to 14.

  • 0 is the most acidic and 14 is the most basic.

• More acid means a higher positive hydrogen ion concentration.

• Most organisms need a specific pH.

  • Buffers help to regulate pH in organisms.

3. Carbon-Based Molecules

Carbon atoms have unique bonding properties.

• Carbon atoms are the basis of most moluecules that make up living things.

  • Carbon’s atomic structure gives it special bonding properties so it can bond with many other atoms.

• Carbon molecules can be straight chains, branched chains, and rings.

• Monomer: a subunit in a complete molecule.

  • A subunit can be a molecule inside a bigger molecule.

• Polymer: a large molecule made of many monomers bonded together

  • Large molecules are called macromolecules.

Four main types of carbon-based molecules are found in living things.

Carbohydrates

• Carbohydrates: molecules made of carbon, hydrogen, and oxygen.

  • Include sugars and starches.

• Simple sugars are the simplest form of carbohydrates.

  • Simple sugars bond to make larger carbohydrates.

Lipids

• Lipids: nonpolar molecules that include fats, oils, and cholesterol.

• Fatty acids: chains of carbon atoms bonded to hydrogen atoms.

  • Lipids contain fatty acids.

• Lipids contain three fatty acids called triglycerides.

• Saturated fats have the most hydrogen atoms while unsaturated fats have the least hydrogen atoms.

• All cell membranes are mostly made of phospholipid, a lipid with a polar head and a nonpolar end.

  • A phospholipid’s polar head contains a phosphate group.

• Cholesterol is a lipid that is needed in the human body.

Proteins

• Proteins: A large molecule (polymer) made out of smaller molecules (monomers) called amino acids.

• Amino acids: molecules that build proteins.

  • Amino acids form covalent bonds called peptide bonds.

  • Through peptide bonds, amino acids form polypeptides.

• One or more polypeptides form a protein.

• The sequence of amino acids effect the structure and function of a protein.

  • Proteins can be bent with certain elements (Sulfur and hydrogen)

Nucleic Acids

• Nucleic Acids: Larger molecules (polymers) that are made out of smaller molecules (monomers) called nucleotides.

  • Nucleic acids store information on how to build proteins.

• A nucleotide is made of a sugar, a phosphate group, and a molecule with nitrogen in it.

• Two types of nucleic acids are DNA and RNA.

  • DNA stores the information to build proteins.

  • RNA helps build the proteins.