Transcript Lipids - AHSbogna

Four Groups of Macromolecules:
Recently the FDA gave its approval to Proctor and Gamble to use a controversial fat replacement
in snack foods. What makes olestra unique is that it is not just a fat substitute, but it is a fat. It has
all of the same properties of fat when it is used in cooking, but the body can not absorb it so it has
no calories. At first glance, olestra sounds like the answer to the prayers of many dieters'.
However, there are some serious pro's and con's that go with this story.
Proctor and Gamble began developing and studying olestra 25 years ago. To date the
company has spent a reported $200 million testing the product. Originally, the intent was to have
olestra approved for use in many products, but the scope had to be narrowed to quicken the
approval process. The company plans to use olestra in Pringles chips. It is estimated that the
approval of olestra will generate an annual market of one billion dollars
within the next ten years.
The Pro's:
•products taste very similar to the real thing
•zero calories
•no fat absorbed by the body
•non- toxic
The Con's:
The arguments against olestra are strong as well. One less than pleasant
side effect is diarrhea and in some individuals, something called "anal leakage". The Diarrhea is
caused by the chemical structure of olestra. It is a large molecule with fatty acids packed very
close together. The body's enzymes can not break down the fat and the molecule passes through
the intestine unabsorbed.
http://www.cheshire-med.com/services/dietary/nutrinew/olest.html
Second Macromolecule Group:
The Fats of Life: LIPIDS
• Fats, oils, cholesterol, hormones
• Composed of C,H,O but not water soluble
• Store the most energy: these are energy
storing molecules!
Three types of fats
1. Triglycerides
2. Phospholipids
3. Sterols
1. TRIGLYCERIDES
• Most common fat in plants and animals,
used in storage
• A molecule of 3 fatty acids attached to a
glycerol backbone:
fatty acid
fatty acid
fatty acid
There are two types of
triglycerides:
1) Saturated triglycerides
-have single bonds, solid at
room temperature
-have straight chains
2) Unsaturated triglycerides
-have double bonds, liquid
at room temperature
-have bent chains
2. PHOSPHOLIPIDS
-structural components of cell membrane
hydrophilic
phosphate head
hydrophobic tail
Some cool things you can do with lipids…
3. STEROLS
• Cholesterol is a natural component of cell
membranes
• used by cells to make steroid hormones, vitamin
D, bile salt
• if there is too much, cholesterol
can close arteries, depriving tissue
of nutrients and leading to stroke
good cholesterol vs. bad cholesterol
Cholesterol and blood do not mix well. So, for cholesterol
to travel through your blood, it is coated with a layer of
protein to make lipoprotein
• You want to have low LDL (low density
lipoprotein) and high HDL (high density
lipoprotein
cholesterol
testosterone
progesterone
Third Group of Macromolecules:
PROTEINS
• The functional molecules
– Help chemical reactions take place (ex.
enzymes)
– Repair and maintain the cell
– Transport materials around the body
– Ex. enzymes, hemoglobin, hair
• Proteins are "unbranched polymers of
amino acids"
• Amino acids: small molecules containing a
central C atom and a side chain
– There are 20 amino acids in human food
– 8 of those are essential: we do not produce
them and therefore must EAT them
• Amino acids link together during protein
synthesis through peptide bonds to form a
POLYPEPTIDE
– Most functional proteins will contain hunderds
and thousands of amino acids linked together
• As the polypeptide lengthens it can fold into
sheets (b-sheets) or wrap into coils (a-coils)
• Protein function depends on its 3-dimensional
shape
Primary: specific amino
acids join together using
peptide bonds to form a
polypeptide
Secondary: the
polypeptide forms ahelices or b-sheets
Tertiary: polypeptides
form and fold in a specific
way, making extra bonds
between parts of the
protein
Quarternary: two or more
polypeptides assemble to
form a larger protein
Figure 3.9 Life 8e: Quaternary Structure of a Protein Hemoglobin consists of
four folded polypeptide subunits that assemble themselves into the quaternary
structure shown here. In these two graphic representations, each type of subunit
is a different color. The heme groups contain iron and are the oxygen-carrying
sites.
• Both shape and chemistry allow a protein to
behave in a specific way
• Denaturation:
– a change in the three-dimensional shape of a
protein caused by high temperatures or harsh
chemical conditions (ex. acids, bases, salts)
• A denatured protein cannot carry out its
original function
positives
negatives
- fever: can
denature bacteria
- straightening/
curling hair
- cooking meat
- fever: can cause
damage
- if peptide bonds
are broken protein
will be destroyed
Homework
1. Describe some groups of lipids that are not triglycerides.
2. What are the structural components of triglycerides?
3. How do saturated fats differ from unsaturated fats?
4. How can only 20 amino acids account for the many
different proteins?
5. Define protein denaturation. Why is it important?