Ch 2: Chemistry of Life pt. 1
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).
- 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.
- 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.
- 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.