Download SAM Teachers Guide Lipids and Carbohydrates - RI

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Page 1:
Introduction
Page 2:
1. Hydrocarbons are referred to as organic
molecules with a "backbone." Take a
snapshot of the hydrocarbon you created
and drag the snapshot into the box below.
Use the arrow tool to point to the carbon
backbone.
1. Why do you think the charge arranges
itself for ketene in this way?
The negatively charged electrons are attracted
to the oxygen atom. Since the oxygen end of the
molecule steals more of the negative charge, the
remainder of the molecule is left partially
positive.
2. Which compound boils first?
(a)
3. How does the presence of the oxygen
atoms in the molecule account for the
difference?
The oxygen atoms make ketene a polar
molecule increasing the attraction between
partial positive and partial negative ends of
molecules. Therefore, it requires more energy, in
the form of heat, to break the molecules apart
and cause the liquid to boil.
Page 4:
1. Which of the following are true? (a) (b) (c)
2. Take a snapshot of a lipid that is fully
dissolved (evenly spread in the solvent).
Sample snapshot: Lipids evenly spread in
the solvent.
Sample Snapshot: Hydrocarbon molecule
created.
2. How many bonds does every carbon atom
have?
Four (4)
Page 3:
3. Hydrophilic means something is attracted
to water and hydrophobic means something
is excluded from water because water is
more attracted to other water molecules than
to it. Are the lipids hydrophobic or
hydrophilic? Explain your answer.
The lipid molecule is hydrophobic. This is
apparent because the lipid molecule is not
dissolving in water. The water molecules are
more attracted to each other than they are to the
fat. This results in the lipid remaining together as
a clump.
Page 5:
1. What can you tell about the properties of
the fatty acid from observing it? Check all
that apply.
(a) (c) (f)
2. Compare the structure and the polarity of
the fatty acid to the hydrocarbon.
The hydrocarbon is non-polar (neutral) while the
fatty acid is polar. The carboxyl head on the fatty
acid has oxygen atoms that will steal negative
charge.
3. Explain why the tails are located in the oil
and the heads in the water.
The tail of the molecule is a long hydrocarbon
chain that is hydrophobic. The head is a polar
carboxyl group that makes it hydrophilic. So
water molecules attract the heads but not the
tails.
Sample Snapshot: Fatty acids in oil.
7. Have you ever observed beads of oil on
the surface of soup? Explain how this model
can help explain the occurrence of those
beads.
The oil forms clusters on the surface of the soup
because they are not soluble in the water-based
soup. The fat molecules are excluded from the
water.
4. Why are fatty acids compared to the twofaced deity Janus?
(c)
Page 6:
5. Take a snapshot of the lipid structure in
water. Drag the snapshot into the box below.
1. Which statement about membrane
phospholipids is NOT true?
(e)
2. Membranes can keep chemicals inside
and outside of the cell. What would happen if
a cell membrane breaks?
If the cell membrane breaks there would be no
regulation of what can enter and leave the cell.
Page 7:
1. How is the lipid molecule different from
the sugar molecule? (Check all that apply.)
(b) (c)
Sample Snapshot: Fatty acids in water.
6. Take a snapshot of the lipid structure in
oil. Drag the snapshot into the box below.
2. An increase in the ratio of oxygen atoms
to hydrogen and carbon... (Check all that are
true.)
(a) (c)
3. Select a snapshot image that shows
benzene molecules do not mix well with
water molecules.
When aligned together the function of these
molecules can be to act as a building material or
protective coating. Link back to Intermolecular
Attractions.
2. Long linear polysaccharides make strong
fibers because:
(d)
Page 9:
1. Branched polysaccharides can be more
easily separated into individual chains then
linear polysaccharides like cellulose. This is
explained by:
(d)
Sample Snapshot: Benzene with Water
Molecules
4. Fill in a snapshot image that shows
glucose molecules mix better with water
molecules.
2. Based on your observations of the
polysaccharides in the models, explain why
starch is edible and wood is not.
Starch, a branched polysaccharide, has many
fewer intermolecular attractions because the
polymers cannot fit together tightly. It breaks
apart as the temperature is increased. Wood's
linear nature makes so many more attractions
between molecules that is it much stronger, and
they do not break apart even at higher
temperatures.
Page 10:
1. Which substance produces more
chemical energy, starch or glycogen, when
enzymes work on it? Why?
Sample Snapshot: Glucose with Water
Molecules
Glycogen produces more chemical energy
according to the bar graph. Because it is more
highly branched, it has more "ends" for the
enzymes to attack.
5. Explain how the presence of six OH
groups affects the solubility and properties
of glucose.
2. Which substance would produce more
chemical energy if enzymes could attack in
the middle of the chain rather then just at the
ends?
The presence of six OH groups makes glucose
a polar molecule. The uneven distribution of
charge increases its solubility in water, which is
also polar.
There would be less of a difference in the
chemical energy released if the enzyme could
attack anywhere in the molecule.
Page 8:
1. How do long chains of parallel cellulose
molecules relate to its ability to do its
function?
Page 11:
1. In the model to the left, three molecules
tagged as "A", "B" and "C" are placed in
water. Click the "" button to run the model
and observe what happens. Based on your
observation, can you tell which molecule is
the most polar?
(a)
2. Compare two hydrocarbon chains: one
that includes oxygen atoms and one without.
How does the presence of oxygen affect the
properties of a hydrocarbon chain?
(a)
3. What makes cellulose so strong?
(a)
4. Describe which lipids are so important to
cellular evolution. Why?
Scientists believe that the first step in cellular
evolution was the emergence of lipids. These
lipids are thought to have become more
complicated. Then, the lipids formed
membranes that created an interior space,
separating it from an outside environment.
5. Table sugar and wood are both made of
glucose. Why can you serve cubes of sugar
with tea, but not cubes of wood (without
offending your guests)?
The amount of branching in polysaccharides will
impact their structure, particularly at different
temperatures. Cubes of sugar will dissolve when
heated by being placed in hot tea while cubes of
wood will maintain their solid structure. This is
due to the increased attraction (hydrogen
bonding) in wood, which is linear as opposed to
sugar, which is branched.
6. Which statement about membrane
phospholipids is NOT true?
(d)
SAM HOMEWORK QUESTIONS:
Lipids and Carbohydrates
Directions: After completing the unit, answer the following questions to review.
1. What is the difference between a polar and non-polar molecule? How does this relate to
the term electronegativity?
2. What properties impact if a molecule is soluble in specific solvents?
3. What will happen if you try to dissolve a lipid in water? If you change the solvent to oil,
instead of water, what will happen to the lipid? Why?
4. Phospholipids form the cell membrane. In the space below, draw how the phospholipids
arrange themselves in the cell membrane. Then, explain why this is the case given what
you know about the hydrophobic and hydrophilic parts of the molecules. Be sure to label
your drawing.
5. Write captions that explain what is happening to the phospholipids in the two pictures
seen below.
Caption:
Caption:
6. How do intermolecular attractions play a role in the behavior of polysaccharides?