MACRONUTRIENTS AT THE MOLECULAR LEVEL
CARBOHYDRATES – High in C, H, and O
 They are the body’s main source of energy
 They are formed in green plants through the
process of photosynthesis
 They include simple sugars, starches, and
fibres
 Glucose (a simple sugar/monosaccharides) is
the basic sugar unit around which all
carbohydrates are formed
 Different types and arrangements of
molecules affect the properties of
carbohydrates
 The body regulates levels of blood glucose,
which is critical to cell functions. Otherwise,
serious health complications such as diabetes
can develop.
LIPIDS
High in C and H (only have O in –COOH group).
 The body needs fat to supply the ‘essential lipids’
 Lipids are a family of chemical compounds that are a
main component in every living cell
 Triglycerides make up the largest category of lipids
and are commonly referred to as fats; they are the
storage form of fat in adipose tissue (fat cells).
Triglycerides perform a number of necessary
functions in the body:
-
insulate the body
-
cushion our organs
-
transports fat-soluble vitamins
-
reserve source of energy (9kcal/g.)
-
source of essential fatty acids
There are three types of Fatty Acids:
 saturated,
 monounsaturated,
 polyunsaturated
Triglycerides are made up of one glycerol
molecule and three fatty acids (usually a mix of
fatty acids).
Where each fatty acid consists of a carbon chain
of varying lengths and a carboxyl group at the
end:
e.g.
or
etc.
The following are examples of different types of fatty
acids in food:
1. Saturated - found in animal sources such as milk, cream, cheese, butter, meat,
poultry. Also in coconut and palm oil. Saturated fats are much more harmful
than cholesterol. Because it can be made from saturated fatty acids,
cholesterol levels in the blood are related to the amount of saturated fat eaten.
Saturated fats raise the LDL and HDL levels of cholesterol in the blood.
2. Polyunsaturated - are better than saturated fats. They are found in vegetable
oils and fish.
Polyunsaturated fats may lower both the LDL and HDL cholesterol levels in
the blood.
3. Monounsaturated - the best type of fat. It is found in both animal and plant
sources. Olive, canola and peanut oils are the most common examples. Most
margarines and hydrogenated vegetable oils are highly monounsaturated. *Most
shortenings (“Crisco” type fats) and margarines are a blend of saturates and
polyunsaturates.
Monounsaturated fats lower LDL and raise HDL levels of cholesterol in the
blood
 Cholesterol – a fatty alcohol made from
glucose or saturated fatty acids; the liver
makes all the cholesterol the body needs. Its
functions include:
-
involvement in Vitamin D and hormone
production
-
integral part of cell membranes
There are two kinds of cholesterol – both are
lipoproteins:
i. HDL -
transport cholesterol from the
bloodstream to the liver for disposal
(“Healthy” cholesterol)
ii. LDL - transport cholesterol from the liver
to the bloodstream (“Lousy” cholesterol)
OTHER LIPIDS
Omega-3 Fatty Acids – make it more difficult
for plaque to form on arteries
Trans Fats – very little found in nature, usually in
animal-based foods but also in store-bought
baked goods;
-
made by adding hydrogen to unsaturated
fats (hydrogenation)
-
increases stability and shelf-life of food
-
raises levels of LDL
- some research has found it to be more
dangerous than saturated fat
PROTEINS – contain C,H,O, and N; because they are
organic acids they also contain –COOH group
o Made up of chains of amino acids joined by
peptide bonds
o There are 20 different amino acids (9 are
essential a.a.s)
-
all contain a –COOH (carboxyl group) and
an –NH2 (amine group)
-
the rest of the amino acid molecule
varies from one amino acid to another
and is usually referred to as the –R
group
o
two or more amino acids form peptide bonds:
o the main function of protein is to build, repair and
maintain body tissue
o because protein is a macronutrient, it can also be
broken down by the body to supply energy when
needed (4 kcal/g)
o protein makes up 18-19% of the body
o protein also has a regulatory function
o 10-15% of daily food intake should come from protein
THERE ARE TWO CATEGORIES OF PROTEIN IN
FOOD:
i. Complete proteins – contain all of the Essential
Amino Acids
ii. Incomplete proteins – lack one or more of the
Essential Amino Acids (EAAs).
FOOD SOURCES OF PROTEIN
The Meats & Alternatives Food Group in the
Canada Food Guide.
o Most animal proteins are complete proteins
(exception is gelatin which is incomplete)
o Most plant proteins are incomplete proteins
(exception is soyabean protein which is
complete)