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Biology I
Shere/Harrison
Unit 2 Study Guide: The Chemistry of Life
Good Luck and Happy Studying!
The Nature of Matter
1. The three particles that make up atoms are protons, neutrons, and electrons.
2. Protons have a positive charge, while electrons have a negative charge. Do neutrons have a
charge? No
3. The number of protons is equal to the number of electrons, if the atom is uncharged.
4. The number of protons is the atomic number of an element.
5. The total number of protons and neutrons determines the atomic mass of an element.
6. To find the number of neutrons in an atom, you subtract the atomic number from the atomic
mass.
7. Covalent bonds form when atoms share electrons, which are stronger than ionic bonds when
electrons are transferred from one atom to another.
8. Atoms from the same element that have a different number of neutrons are called isotopes and
are sometimes radioactive. Do these atoms have a charge? No
9. Atoms from the same element that have a different number of electrons are called ions.
These atoms can have either a negative charge (if they have extra electrons), or a positive charge
(if they have lost electrons).
Properties of Water
10. The two atoms that make up a water molecule are hydrogen and oxygen. They are connected to
each other by covalent bonds within the molecule.
11. Draw three water molecules below.
Label the atoms, the partial charges, the hydrogen bonds between the molecules.
12. What causes water molecules to be attracted to one another?
Water molecules are polar, with a slightly negative end (the oxygen) and a slightly positive end
(the hydrogens). The partially positive hydrogens in one water molecule are attracted to the
partially negative oxygen in another water molecule, like two magnets.
13. Describe the key properties of water listed below. Give an example of that property.
a. Cohesion- Water molecules stick to one another
Example: Surface tension allows Water Strider bugs to stand/walk on water
b. Adhesion- Water molecules stick to other substances
Example: Water “climbs” up a paper towel
c. High Specific Heat and High Heat of Vaporization (Temperature Stability)- Water
requires a lot of energy to heat up, and removes a lot of energy/heat when it evaporates
Example: Cooler temperatures near lakes (specific heat); sweating (high heat of
vaporization)
d. Universal Solvent- Water is able to dissolve many different compounds
Example: Water can dissolve salt
e. Low Density as a Solid- Water is less dense as a solid (ice) than as a liquid
Example: Ice floats
pH
14. pH is a measure of the concentration of H+ ions in a solution.
15. Circle the correct answers: Acids have a pH of more than or less than 7 and have a higher or
lower concentration of H+ ions than OH- ions.
16. Circle the correct answers: Bases have a pH of more than or less than 7 and have a higher or
lower concentration of H+ ions than OH- ions.
Organic Molecules
17. Organic (in biochemical terms) means: Contains carbon
18. Another word for large molecules is macromolecules
19. The removal of H2O to form macromolecules, such as complex carbohydrates, is called
Dehydration synthesis
20. Complete the table below about the four biological polymers (macromolecules).
Macromolecule
Carbohydrates
Elements
Monomer
Function(s)
Examples
Carbon,
Hydrogen,
Oxygen
Monosaccharide
Provide quick
energy
Glucose, Lactose
General Chemical
Formula is CH2O
Enzymes,
Hemoglobin
Bonds between
monomers are called
peptide bonds.
Don’t mix with water
(are hydrophobic)
Proteins
C, H, O, N
Amino Acids
Structure,
Transportation,
Aid chemical
reactions
Lipids
C, H, O
Fatty Acids,
Glycerol
Store Energy
Triglycerides,
Fats, Oils
Nucleic Acids
C, H, O, N
Nucelotides
Store Genetic
Information
DNA, RNA
Other Important Info
Study the chemical structures below. You should be able to recognize them if asked to identify:
Monosaccharide
Triglyceride
Amino Acid
Also know saturated fatty acid structure
Nucleotide
Important Lab Information
21. The chemical indicator for starch (polysaccharides) is Iodine
Color of a positive reaction? Blue-Black
22. The chemical indicator for protein is Biuret test
Color of a positive reaction? Violet
23. The chemical indicator for sugar (monosaccharides) is Benedict’s test
Color of a positive reaction? Red
24. The chemical indicator for lipids is Sudan III
Color of a positive reaction? Orange-red
Disaccharide
Chemical Reactions and Enzymes
25. What type of macromolecule is an enzyme? Protein
26. Describe how an enzyme speeds up the rate of a chemical reaction. Enzymes speed up chemical
reactions by lowering the activation energy needed by the reaction.
27. Label the indicated portions of the diagram below involved in an enzyme-catalyzed reaction.
Substrate
Products
Active
Site
28. List 4 ways to control an enzymatic reaction
a. Inhibitors
b. Activators
c. Change in pH
d. Change in temperature
29. What has happened if an enzyme is denatured? Why will it no longer work?
If an enzyme is denatured, it loses its shape. This causes the active site to no longer be the correct
shape for binding with the enzymes’ substrate. Because the enzyme and substrate cannot bind, the
enzyme can no longer act on the substrate—the enzyme loses its function (ability to do its job).