Bio200 POGIL Cell Biology Activity 1 – Biological Molecules
What are the properties of biological molecules?
Schivell
MODEL 1:
Relative electronegativities:
A
O>N>C~H
B
D
C
QUESTIONS:
1. On the model, draw in the pairs of electrons shared between atoms. Draw the electrons
closer to the more electronegative atom, or in the middle of the bond if the atoms are equally
electronegative. (Make sure to put the correct number of electrons!)
2. For each ATOM, determine if it has any electrons that are shared unequally. If so, write a
partial charge next to that atom. (+ or -)
3. Label all polar bonds with an asterisk.
4. Can a molecule have polar bonds and yet be a non-polar molecule (overall)? Explain
briefly, and give an example.
5. Which of the following molecules is the most polar?
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Bio200 POGIL Cell Biology Activity 1 – Biological Molecules
Schivell
MODEL 2: Life takes place in water
Methanol (
) and ethane (
) are mixed with water (
):
= Oxygen
= Carbon
= Hydrogen
6. Which molecule(s) are polar? _____________________
7. Which molecule(s) are non-polar? _____________________
8. Which molecule is "water-fearing" or "hydrophobic"? ________________
9. Which molecule is "water-loving" or "hydrophilic"? _________________
10. What is the relationship between polarity and hydrophobicity (in general)?
11. By looking at the bonds in each of the following important biological molecules, indicate
whether the molecule is primarily hydrophobic or hydrophilic.
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Bio200 POGIL Cell Biology Activity 1 – Biological Molecules
Schivell
MODEL 3: Molecular interactions
Hydrogen Bond
12. Draw in the shared electrons for bonds that are shown in bold (as you did for Model 1).
13. Draw the partial charges on the atoms involved in the bonds that are bold.
14. Why is an attraction possible between the H and O involved in the Hydrogen Bond?
15. Draw an alternative hydrogen bond between different atoms of these two molecules in the
space below:
16. Go back to Model 2 and draw in some of the possible hydrogen bonds in both mixtures.
17. For the following pairs of molecules, draw their structures and at least one hydrogen bond
connecting them. If no hydrogen bond is possible between these two molecules, indicate that.
a. Water and CH3NH2
b. Methanol and CH3NH2
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Bio200 POGIL Cell Biology Activity 1 – Biological Molecules
Schivell
18. Hydrogen bonds are a crucial component of biomolecular structure and biomolecular
interactions. In the following drawings, draw in any hydrogen bonds that are possible
between atoms within the same molecule or between different molecules:
A: Protein structure
B: DNA base pairing
C: Plant cell wall (cellulose)
Oxygen
(dark gray)
Carbon
(light gray)
Hydrogen
(white)
On your own:
Biomolecules like DNA, proteins, and carbohydrates depend on hydrogen bonds to maintain
their overall structure. However, each individual hydrogen bond is very weak. Using
cellulose from the question above as an example, explain how to resolve the apparent
contradiction between these two statements.
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