A review of initial concepts for AP Biology

1. AP Biology Unit 0: Review of Chemistry
• Key Topics:
1. Periodic Table
2. Electronegativity
3. Cations and Anions
4. Polar vs Nonpolar Covalent
5. Hydrogen Bonds
6. Functional Groups
7. Molarity and Solutions
AP BIOLOGY UNIT 0 @WilsonHerndon 1

2. AP BIOLOGY UNIT 0 @WilsonHerndon 2
This Photo by Unknown Author is licensed under CC BY-SA
Atomic Number =
# protons
Cation = (+) ion
more p+ than e-
Ca+2 K+1
Anion = ( - ) ion
more e- than p+
O-2 N-3 PO4
-3

3. AP BIOLOGY UNIT 0 @WilsonHerndon 3
Valence electrons –
create bonds, outer
most electrons,
What element is this?
Na
Label the Table
with Valence electrons.
H
1
ve-
Be
2
ve-
B
3
ve-
C
4
ve-
N
5
ve-
O
6
ve-
F
7
ve-
He
8
ve-
Valence Electrons

4. AP BIOLOGY UNIT 0 @WilsonHerndon 4
How many valence e- ?
1
Which element is this?
K or potassium
What is the common ionic form?
K+1
How many valence e- ?
4
Which element is this?
C or carbon
What are the common charges?
C+4 or C-4
Valence Electrons

5. AP BIOLOGY UNIT 0 @WilsonHerndon
Lewis Dot
1. Count valence e- total
2. Draw dots around each element
3. Put most EN elements on outer side of
molecule
4. Join 2 e- to make a single bond
5. Join 4 e- to make a double bond
6. Every element wants an octet except
for H, Be, and He
7. H can only make 1 bond
8. C can make 4 bonds
9. Include unshared electrons
HCl total of 8 valence e-
H• Cl •
Cl is most EN
H Cl
Does Cl have an octet? Yes, 2 shared & 6 unshared e-

6. AP BIOLOGY UNIT 0 @WilsonHerndon 6
CH3OH CO2H2 C2H2 C4H8 CH3NH2
Draw Lewis Dot Structures

7. Look at the model of HCl. The bonding electrons
are not evenly shared between the two atoms.
AP BIOLOGY UNIT 0 @WilsonHerndon 7
Electronegativity -
measure of how atoms in a
covalent bond share e-
more EN atom will pull on
electrons making the atom
partially negative or 𝛿 −
The following elements are
found in all living beings:
C H O P N
List in order of increasing EN:
H and P, C, N, O
𝛿 −
𝛿 +
Electronegativity Pauling Values
This Photo by Unknown Author is licensed under CC BY-SA-NC
Element EN value 𝛿 + Or 𝛿-
H 2.1 𝛿 +
Cl 3.0 𝛿 −

8. AP BIOLOGY UNIT 0 @WilsonHerndon 8
Ionic
Bond
Transfer of
electrons
Usually
between
metal and
nonmetal
∆ EN > 1.7
Ca3(PO4)2
Ca+2 PO4
-3
Ions are important in biological systems:
Ion # protons # electrons Charge
H+ 1 0 +1
Na+1 11 10 +1
Ca+2 20 18 +2
Cl-1 17 18 -1
PO4
-3
47 50 -3
This Photo by Unknown Author is
licensed under CC BY-SA
This Photo by Unknown Author is licensed under CC BY

9. AP BIOLOGY UNIT 0 @WilsonHerndon 9
Polar
Covalent Bond
Uneven
sharing of
electrons
Usually
between two
nonmetals
∆ EN from
0.5 to 1.7
C-O
3.5 – 2.5 = 1
Molecule Name Formula Lewis Dot
Electron
Distribution
Isopropyl Alcohol (CH3)2CHOH
Methanol CH3OH
Hydrogen Sulfide H2S
Ammonia NH3

10. AP BIOLOGY UNIT 0 @WilsonHerndon 10
Nonpolar
Covalent Bond
Even
sharing of
electrons
Usually between two of
the same nonmetals or
nonmetals next to each
other on Periodic Table
∆ EN < .4
Note: C-H is considered
nonpolar
C-C
2.5 – 2.5 = 0
Molecular Name Formula Structure
Electron
Distribution
Methane CH4
Benzene C6H6
Ethene C2H4
Carbon Dioxide CO2

11. AP BIOLOGY UNIT 0 @WilsonHerndon 11
Ionic
Bond
Transfer of
electrons
Usually
between
metal and
nonmetal
∆ EN > 1.7
Ca+2 PO4
-3
Polar
Covalent Bond
Uneven
sharing of
electrons
Usually
between two
nonmetals
∆ EN from
0.4 to 1.7
C-O
3.5 – 2.5 = 1
Nonpolar
Covalent Bond
Even
sharing of
electrons
Usually between two of the
same nonmetals or
nonmetals next to each other
on Periodic Table
∆ EN < .4
C-C
2.5 – 2.5 = 0

12. AP BIOLOGY UNIT 0 @WilsonHerndon 12
Common bounds found in biomolecules
C-C C-N C-H C-O C-S O-H N-H P-O S-H
∆ EN
2.5-2.5
=
0
3.0-2.5
=
.5
2.5-2.1
=
.4
3.5-2.5
=
1.0
2.5-2.5
=
0
3.5 -2.1
=
1.4
3.0-2.1
=
.9
3.5-2.1
=
1.4
2.5-2.1
=
.4
Bond
Type
Nonpolar
Polar
Nonpolar
Polar
Nonpolar
Polar
Polar
Polar
Nonpolar

13. AP BIOLOGY UNIT 0 @WilsonHerndon 13
Ionic
Compounds
Cations are
positive charged
Anions are
negative
NaNO3
Na+1
NO3
-1
Polar
Molecules
Uneven charge
distribution in the
molecule
𝛿 + and 𝛿-
CH3OH
C-OH is polar
Nonpolar
Molecules
may have
induced
dipole : dipole
interaction
C2H6
C-H and C-C bonds are all
nonpolar, short lived
dipoles
𝛿 –
𝛿 +

14. AP BIOLOGY UNIT 0 @WilsonHerndon 14
Apply and Practice: Molecular Models
COLOR
ELEMENT
REPRESENTED
BLACK Carbon
WHITE Hydrogen
RED Oxygen
Green
Chlorine
(halogen)
Yellow Sulfur
BLUE Sodium
Name Formula Model
Polar vs
Nonpolar?
Pentane C5H12
Nonpolar
Lots of C-H and
C-C bonds
Fructose C6H12O6
Polar
Lots of C-O
bonds
Ethylene C2H4
Nonpolar
Lots of C-H and
C-C bonds

15. AP BIOLOGY UNIT 0 @WilsonHerndon 15
Ion:
Dipole
Cations attracted
to 𝛿 -
Anions attracted
to 𝛿 +
NaCl dissolves in
H2O
Na+ attracted to
𝛿 – of water
Dipole:
Dipole
𝛿 – of molecule A
is attracted to 𝛿 +
of molecule B
CH3OH
Nonpolar:
Nonpolar
may have
induced
dipole : dipole
interaction
C2H6
C2H6
CH
3
OH
𝛿 –
𝛿 +
𝛿 +
𝛿 –

16. AP BIOLOGY UNIT 0 @WilsonHerndon 16
1. Which side is more concentrated?
the left side
2. Solvent
most plentiful substance in a solution,
dissolves the solute
Water is the universal solvent
3. Solute
Substance that gets dissolved;
CaCl2 is dissolved by water forming Ca+2 + 2 Cl-1
Left Side Right Side
4. Solution
mixture of solvent + solute

17. Concentration
If you have 2 packets of sweet n low
in a half of cup
of coffee, what is the concentration?
AP BIOLOGY UNIT 0 @WilsonHerndon 17
2 packets / .5 cup
= 4 packets per cup
amount of solute
L of solution

18. AP BIOLOGY UNIT 0 @WilsonHerndon 18
How many
grams of NaCl is
needed to make
200.0 mL of a 0.3
M NaCl solution?
Find moles of NaCl
using molar mass.
0.200 L x 0.30 mol x 58.44 g =
1 L 1mol
This Photo by Unknown Author is licensed
under CC BY-NC-ND
Mass Na 22.99
+ Mass Cl 35.45
Molar Mass 58.44 g/mol
3.51 g of
NaCl is
needed
Molarity – measurement for concentration
M = moles of solute
L of solution

19. Draw the electron distribution
between a bonding carbon and
oxygen atom.
𝛿+ 𝛿-
C O
The formula for sucrose is C12H22O11
What is the molar mass?
342.3 g/mol
What is the most EN element in sucrose?
Oxygen
What is the least EN element in sucrose?
Hydrogen AP BIOLOGY UNIT 0 @WilsonHerndon 19
This Photo by Unknown Author is licensed under CC BY
Apply and Practice: Sucrose (aka sugar)

20. 20
AP BIOLOGY UNIT 0 @WilsonHerndon 20
Apply and Practice: Sucrose
Gather materials to make a sucrose solution.
Step One: Weigh approximately 10 g of sugar.
Record weight.
Step Two: Transfer to a beaker or cup. Dilute to
100.0 mL with water.
Step Three: Calculate the molarity.
Step Four: Repeat procedure using a different amount
of sugar. Record weight. Calculate the molarity.
Solution
Weight of
sucrose
Molarity
of
solution
A
B

21. AP BIOLOGY UNIT 0 @WilsonHerndon 21
Apply and Practice: Sucrose
Calculate M
Solution
Weight of
sucrose
Molarity
of
solution
A
B
9.90 g .289 M

22. AP BIOLOGY UNIT 0 @WilsonHerndon 22
Apply and Practice: Sucrose
COLOR
ELEMENT
REPRESENTED
BLACK Carbon
WHITE Hydrogen
RED Oxygen
Green Chlorine
Yellow Sulfur
BLUE Sodium
Step Five: Stir each solution. Observe
what happens to the sucrose and water.
Step Six: Use the model of Sucrose,
C12H22O11 (on left) to help explain what is
happening to the sugar.
Use CLAIM, EVIDENCE, REASON (CER)
to explain what happened to the sugar.
This Photo by Unknown Author is licensed under CC BY-SA

23. AP BIOLOGY UNIT 0 @WilsonHerndon 23
Apply and Practice: Sugar and CER
CLAIM: Sugar is dissolved when added to water.
EVIDENCE:
The sugar was no longer visible once added to water. The
white crystals dissipated in the water and became a
homogenous mixture.
REASON:
Electrostatic attraction occurs between positive and negative
charged particles. The water molecules solvated the sucrose
molecules, dissolving the sucrose, while creating H Bonds.
The (𝛿+). Hydrogen on the sucrose molecule is attracted to
the (𝛿−) Oxygen atom on the water.
The (𝛿−) Oxygen on the sucrose molecule is attracted to
the (𝛿+) Hydrogen atoms on the water molecule.

24. AP BIOLOGY UNIT 0 @WilsonHerndon 24
Hydrogen
Bonds
Lone pair of e- on donor atom (O, N, F)
attracted to H on an –OH, -NH, or -FH
Weak interaction (around 2.1
kJ/mol) but when multiplied by
many molecules becomes strong
This Photo by Unknown Author is licensed under CC BY-NC-ND

25. AP BIOLOGY UNIT 0 @WilsonHerndon 25
Molecule Name
Circle the Hydrogens that can
H Bond
Number of H that cannot H
Bond
Glucose
7
Glycerol 5
Saturated Fatty Acid 27
This Photo by Unknown Author is licensed under CC BY-SA

26. AP BIOLOGY UNIT 0 @WilsonHerndon 26
Molecules Structure / Draw H Bond H Bonds?
NH3 & CH3OH
1 H bond between N and HO-
1 H bond between O and HN-
NH3 & CH4
None; the second molecule has only
–CH bonds which are nonpolar, the
H is not 𝛿 +
Cytosine &
Guanine
Flip Guanine and rotate;
3 H bonds will form.
This Photo by Unknown Author is licensed under CC BY-SA

27. AP BIOLOGY UNIT 0 @WilsonHerndon 27
Molecules that are NONPOLAR are called
HYDROPHOBIC. They do not like water.
Molecules that are POLAR are called
HYDROPHILIC. They LOVE water.
Different FUNCTIONAL GROUPS can be attached
to a Carbon atom, resulting in a variety of
molecules.
FUNCTIONAL GROUPS that are POLAR make
Carbon based molecules HYDROPHILIC.
Functional
Group
Lewis Structure
Hydrophilic OR
Hydrophobic?
Hydroxyl Hydrophilic
Carboxyl Hydrophilic
Amino Hydrophilic
Sulfhydryl
In between
Disulfide Bond
Phosphate
Hydrophilic
Methyl
Hydrophobic

28. AP BIOLOGY UNIT 0 @WilsonHerndon 28
Apply and Practice: Salt & CER
COLOR ELEMENT
REPRESENTED
BLACK Carbon
WHITE Hydrogen
RED Oxygen
GREEN Chlorine (halogen)
YELLOW Sulfur
BLUE Sodium
Step 1: Add ⍨10.0 g of salt and add it to a cup of
water. Stir. Observe. What happens to the salt?
Step 2: Use the model (below – left) to help
explain what is happening to the NaCl. Use
CLAIM, EVIDENCE, REASON to explain what
happened to the salt.

29. AP BIOLOGY UNIT 0 @WilsonHerndon 29
Apply and Practice: Salt and CER
CLAIM: Salt is dissolved when added to water.
EVIDENCE:
The salt was no longer visible once added to water. The
white crystals dissipated in the water and became a
homogenous mixture.
REASON:
Electrostatic attraction occurs between positive and
negative charged particles. The water molecules
solvated the ions.
Na+1 is a cation and is attracted to the (𝛿−) Oxygen atom
in the water molecule.
Cl-1 is an anion and is attracted to the (𝛿+) Hydrogen
atoms in the water molecule.

30. AP BIOLOGY UNIT 0 @WilsonHerndon 30
Apply and Practice: Oil and Water
This Photo by Unknown Author is licensed under CC BY-SA
Oil
Oil is a long molecule with a Polar Head
and a Nonpolar tail.
Circle the Polar Head in RED
How many H Bonds can this molecule
form?
1 with OH and 1 with =O
Water
Water is a Polar molecule.
How many total H Bonds can water have?
4
Can water H Bond with the Nonpolar tail on
oil?
NO

31. AP BIOLOGY UNIT 0 @WilsonHerndon 31
Apply and Practice: Oil, Water, and Isopropyl Alcohol
This Photo by Unknown Author is licensed under CC BY-SA
Water
Oil
Step 1: Place drops of oil, water, and isopropyl alcohol on
separate corners of a plate. Observe how quickly the drops
“spread apart.”
Step 2: Use CLAIM, EVIDENCE, REASON (CER) to explain
what happened to each drop of liquid.
Isopropyl Alcohol

32. AP BIOLOGY UNIT 0 @WilsonHerndon 32
Apply and Practice: Oil, Water, Isopropyl Alcohol
This Photo by Unknown Author is licensed under CC BY-SA
Water
Oil CLAIM: Molecules with more H Bonds will stick together and
maintain the shape of their droplet.
EVIDENCE:
The water drop maintained its shape, the oil drop moved apart
creating a greater surface area, the isopropyl alcohol rapidly spread
out, creating the greatest surface area.
REASON:
Water is a polar molecule with the ability to make 4 H bonds, Oil has
the ability to make 2 H bonds, and Isopropyl alcohol molecules can
make 1 H Bond. Molecules with a greater number of H Bonds are
held in place by the additive strength of the H Bonds (around 2.1
kJ/mol per H bond).
Isopropyl Alcohol