Download Grade 12 University Biology

Lipids
Ch 1.4
Introduction
 Unlike CHO, lipids are NON-POLAR, hydrophobic and
therefore repel water.
 Lipids provide a slow, long-lasting energy source and
form many steroid hormones in the body such as
cholesterol, testosterone and cortisol
Introduction
You can see how these lipid hormones are much
smaller than the CHO molecules we previously
looked at….
Introduction
 There are 5 main categories of lipids in the human
body:
1) Fatty Acids
2) Fats
3) Phospholipids
4) Steroids
5) Waxes
Fatty Acids
  Consist of a single hydrocarbon chain with a
carboxyl R-Group (-COOH) on the end.
This Carboxyl
group on the
end gives this
molecule it
“acid”
characteristic.
Fatty Acids
 The longer the chain, the less water soluble it
becomes because of  non-polar character.
 Carbons in the fatty acid “tail” try to attach to as
many hydrogen's as they can. – For maximum
“saturation”
Fatty Acids
 Saturated Fatty Acid  a fatty acid with no double bonds
between the individual carbon atoms of the fatty acid chain. That
is, the chain of carbon atoms is fully "saturated" with hydrogen
atoms.
 Unsaturated Fatty Acid  a fatty acid that has one or
more double bonds between carbon atoms which reduces the
hydrogen “saturation” on each carbon in the fatty acid chain.
 Fig 7 Pg. 34 - the double bonds in unsaturated fatty acids cause a
kink in the chain due to the orientation of the H’s within the double
bond.
Fats
  composed of 1-3 fatty acid chains joined by a
glycerol molecule.
Fats ~ Triglycerides
 Triglycerides  contain three fatty acid chains. These
fatty acid chains can all be the same or can be different
but are all linked up to a glycerol head.
Saturated Fat  a lipid that is composed of
saturated fatty acids with single bonds in their
hydrocarbon chain.
Unsaturated Fats a lipid that is made up of
unsaturated fatty acids with double bonds in their
hydrocarbon chain.
Fats ~ Triglycerides
 The tight packing of fatty acids makes saturated fats
SOLID at room temperature.
These saturated fats come from animal products and are found in meat, cheese,
butter and cream.
Fats ~ Triglycerides
 Unsaturated fats come from plant sources such as olive
oil, canola oil, and avocado.
The kinks formed
between the double
bonds of the carbons in
the fatty acid tail do not
allow for tight packing of
molecules which is why
unsaturated fats are
liquid at room
temperature.
Fats~Triglycerides
Three unsaturated fatty acid tails attached to a glycerol
molecule = very loosely packed.
It is beneficial to eat
plant based fats
because living
organisms require
fluidity in their cells and
so too much saturated
fat disrupts the flow of
living cells.
Triglyceride Function
 Number one function = energy storage!
 Each gram of lipid yields over 2X the energy of each
gram of CHO.
Triglycerides
 Unsaturated fats are considered to be the most healthy
kind of fats.
 Studies have shown that consuming unsaturated fats
such as omega-3 can actually lower ones risk for heart
disease among other things.
 -Sources of these unsaturated fats which are
recommended in the diet are avocado, nuts, seeds,
olives, hemp, and grains.
 Diets rich in saturated fats and animal products can
increase the likelihood of developing heart disease and
stroke.
Phospholipids
 Consist of two fatty acids and a phosphate group
bound to glycerol.
 These are the primary lipids in cell membranes
 Glycerol forms the backbone.
 Recall the structure of a triglyceride….
A phosphate Group
Phospholipids
The phosphate group binds to a polar or charged head
group.
The fatty acid tails are hydrophobic and the head group is polar and
hydrophilic.
Phospholipids
 Amphipathic molecules  molecules that contain
both hydrophobic and hydrophilic regions. A
hydrophobic tail and a hydrophilic head group.
Fig 10 Pg. 36  The
structure of a phospholipid;
hydrophilic “head” and two
hydrophobic “tails”
Phospholipid Bi – layer
Steroids
 Steroids lipid molecules composed of four fused
carbon rings. Each molecule differs in the in structure
by the attached side chains.
Sterols
  most abundant type of steroid lipid (ex – cholesterol)
 AKA : steroid alcohols
 have single polar –OH group at one end of the ring
framework
Sterols
 Example  Cholesterol embedded within the cell
membrane helps to maintain the integrity and fluidity of
the membrane.
Phospholipid Membrane
Cholesterol
If a person consumes too much dietary cholesterol they are at risk for developing
atherosclerosis and CVD.
Too much cholesterol circulating in the bloodstream causes plague buildup on arterial
walls.
Sex Hormones
 Sex Hormones control the development of sexual traits
and sex cells that are specific to males and females.
 Ex – Testosterone,
 estrogen,
 progesterone
Cholesterol is the precursor of other steroid sex hormones
Waxes
 Waxes  lipids formed from the linkage of long fatty
acid chains alcohol chains or carbon rings
•Hydrophobic
•extremely non-polar
•soft solids over wide range of
temperatures
•make excellent waterproof
coatings
-
honeybees and hexagons
Proteins Ch 1.5
 Most diverse molecules in living organisms and most important
 Enzymes  Proteins that act as biological catalysts
 Amino Acids  The building blocks that made complex chains of
proteins.
 There are 20 different amino acids in living organisms.
Fig 1 Pg. 39
 Essential Amino Acids  the 8 amino acids that the
body cannot produce and must therefore be taken in
from the diet.
 Non-Essential Amino Acids  the remaining 12 A.A.
which the body can produce.
 Peptide Bonds  The bonds that hold A.A. together.
 formed through a condensation reaction between the
amino end of one amino acid and the carboxyl group
from a second adjacent amino acid.
Fig 4 Pg. 42
Protein Folding
1. Primary structure  is a polypeptide chain of amino
acids.

Sequence is determined by the DNA sequence. During
protein synthesis the amino acids are added to the chain one
at a time. As the chain grows it folds
2. Secondary structure the folds and coils of the
primary sequence.

In certain places hydrogen bonds form, forming the
polypeptide coil into an  helix or a  pleated sheet.
3. Tertiary structure is formed when the polypeptide
chain undergoes complex folding.
4. Quaternary structure forms when two or more
polypeptide chains come together.
Fig 5 Pg. 43
 Chemical and physical factors also help to determine a
proteins particular shape.
 Temperature and pH changes can cause a protein to
unravel (denature).

A denatured protein is unable to carry out its
biological function.