Review Biology Test #1
Chapter 3: Water and life
• Polar covalent bonds in water result in Hydrogen bonding between the molecules. These bonds give water its special properties
• In presence of water, ionic bonds are weak and covalent bonds are strong. Without water, ionic bonds are stronger.
• Each water molecule can make 4 hydrogen bonds.
• Water properties:
2. Surface tension
6. High specific heat
7. Heat bank
8. Heat of vaporization allows evaporation cooling.
9. Abundant and versatile solvent
10. Solid is less dense than liquid
11. It is a reactant and a product in many biological reactions (Photosynthesis, dehydration ...view middle of the document...
• pH lower than 7 à acidic, pH higher than 7à basic
• Each pH unit represents a tenth fold difference in the concentration of the ions. (Ex: a solution of pH 3 is not twice as acidic as one of pH 6, it is a thousand times (10·10·10) more acidic)
• The internal pH of cells is close to 7. Changes in pH can be fatal because chemical processes are very sensitive to them.
• Buffers: Substances that minimize changes in the concentrations of H+ and OH-. Most buffers contain weak bases and acids which combine reversibly (Ex: carbonic acid)
Chapter 4: Carbon and the molecular diversity
I. Organic chemistry: study of carbon compounds
• Carbon enters the biosphere through the action of photosynthetic organisms.
• Organic compounds: Compounds containing carbon
• Inorganic compounds include salts, H2O, CO2…
• Friedrich Wohler: German chemist that accidentally made urea in the laboratory by trying to mix ammonium ions and cyanate ions.
• Stanley Miller: In 1953, he set up a closed system to imitate the conditions of the early Earth and concluded that complex organic molecules can arise spontaneously under certain conditions à A theory about the origin of life on Earth.
• The experiments of these chemists invalided the concept of vitalism by demonstrating that organic molecules can be produced using inorganic materials.
• Carbon atoms can form diverse molecules by bonding to four other atoms.
• Electron configuration – key to chemical properties.
• Carbon has 6 electrons total; it has four valence electrons; it can make up to four bonds.
• The four major atomic components of organic molecules are carbon, nitrogen, oxygen and hydrogen. Sulfur and Phosphate are also very common.
• Hydrocarbons: Organic molecules consisting only of carbon and hydrogen. Nonpolar, they can release a lot of energy.
• Isomers: Variations in the architecture of organic molecules that have the same number of the same atoms. These variations give different properties.
1. Structural isomers: Differ in covalent arrangements of the atoms or locations of double bonds.
2. Cis-trans isomers: Covalent bonds to same atoms but arranged spatially different due to the inflexibility of double bonds. (cis: same on one side, trans: same on opposite sides)
3. Enantiomers: Isomers that are mirror images of each other and that differ in shape due to an asymmetric carbon.
II. A few chemical groups are key to chemical function
• The properties of organic molecules depend on the atom arrangement and on chemical groups called functional groups which interact in chemical reactions and give each molecule a specific shape and function.
• Most important functional groups:
-Polar, Forms H-bonds, They are known as Alcohols, Hydrophilic, Ex: Ethanol, Propanol…
Polar, It may be within the molecule (ketone) or in the end (aldehyde), Hydrophilic, Ex: Acetone, Propanal…
Acts as an acid (donates H), Ionized form (-COO-), It can...