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Nutrients
To survive, humans require:
1) Carbohydrates
2) Lipids
3) Proteins
4) Nucleic Acids
5) Vitamins
6) Minerals
7) Water
The first four groups are called MACROMOLECULES because they are
large organic molecules that contain dozens of carbon atoms and many
functional groups.
Functional Groups – Are a cluster of atoms that give compounds specific
chemical properties. Many organic molecules contain carbon atoms with
functional groups attached.
1. CARBOHYDRATES
STRUCTURE: - primary building block of carbohydrates is glucose
FUNCTION:
- primarily used as a source of energy by living organisms
The Carbohydrate Family
MONOSACCHARIDES (simple sugars)
DISACCHARIDES (double sugars)
POLYSACCHARIDES (complex
carbohydrates)
Three types of Carbohydrates:
A) Monosaccharides (simple sugars) (mono = “one”, saccharide = “sugar”)
- the simplest carbohydrates
- chemical formula:
- water soluble
- the three key monosaccharides have the same number and type of
atoms but in different arrangements (6 carbons, 12 hydrogens, 6
oxygens)
Glucose (C6H12O6) – primary energy source for living things
Fructose (C6H12O6) – sweetest of sugars, found in fruits and honey
Galactose (C6H12O6) – seldom occurs naturally
B) Disaccharides (double sugars)
- two monosaccharides bonded together (glucose is always included)
through dehydration synthesis
- chemical formula:
- water soluble
SUCROSE = GLUCOSE + FRUCTOSE
- table sugar, fruits, vegetables and grains
MALTOSE = GLUCOSE + GLUCOSE
- produced when starch breaks down (during carbohydrate digestion
and fermentation)
LACTOSE = GLUCOSE + GALACTOSE
- principle carbohydrate of milk
C) Polysaccharides (complex carbohydrates)
- contain tens, hundreds even thousands of monosaccharides strung
together as long chains
- insoluble and very large, therefore when eaten, reactions in the
digestive system break everything down to glucose molecules
- there are three important polysaccharides: glycogen, starches, and
fibres
Glycogen
- animals store glucose as glycogen in muscle and liver cells
- when blood glucose levels drop, certain hormones (e.g. glucagon) are
released which cause stored glycogen to be broken down into glucose
which can then be used by the cells
Starches
- plants store glucose as starch
- a major source of energy
Fibres
Cellulose:
- primary component of plant cell walls
- cannot be broken down by human digestive enzymes
- ruminants (e.g. sheep and cows) have bacteria which release
enzymes that can break down cellulose
Chitin
- a modified form of cellulose
- makes up the exoskeleton of insects and crustaceans
2. LIPIDS
STRUCTURE: - the primary building blocks of most lipids are fatty acids
FUNCTION: - primarily used by animals to store excess energy
- can be used as an energy source (secondary)
- insulate and protect body parts
- required to synthesize hormones
- key components of cell membranes
The Lipid Family
1. TRIGLYCERIDES: FATS, OILS AND WAXES
2. PHOSPHOLIPIDS
3. STEROIDS
1. Triglycerides
- triglyceride molecules are composed of a glycerol backbone with 3
fatty acid chains attached
- the structure of fatty acids determines whether the lipid is considered
SATURATED or UNSATURATED
Saturated, Unsaturated and Trans-Fats
Type
Structure
Properties
Saturated Fats - fatty acid
- solids at room
(Saturated fatty contains the
temperature
acids)
maximum number
of H atoms
- single bonds
between carbon
atoms of fatty acid
Unsaturated
- fatty acid has H
- liquids at room
Fats
atoms missing
temperature
(Unsaturated
- a double bond is - double bonds
fatty acids)
present between
react readily, thus
one or more of the unsaturated fats
carbon atoms
are easily broken
down
Trans – Fats
- hydrogen atoms - unsaturated fats
(Trans – fatty
are added to an
with the
acids)
unsaturated fatty
advantages of
acid
saturated fats
(hydrogenation)
i.e don’t oxidize
(become rancid)
as quickly and
have enhanced
texture (creamy)
and taste
Examples
2. Phospholipids
- composed of a glycerol backbone, two fatty acid chains and one
phosphate group
-
found in the bilayer of the cell membrane
Head: hydrophilic (water loving) points to the outside
Tail: hydrophobic (water hating) points to the inside
Phosphate Group
(polar)
Fatty acid tail
(nonpolar)
3. Steroids
- the structure is a carbon-based, multiple ring structure
Examples: cholesterol, testosterone and estrogen
- Cholesterol is required to make vitamin D and the
sex hormones
- Cholesterol is also an important part of the cell
membrane
- Cholesterol is found solely in animal sources
3. PROTEINS
STRUCTURE: - proteins are composed of carbon, hydrogen, oxygen
and NITROGEN
- proteins are synthesized in the cytoplasm on the
ribosomes
- the building blocks of proteins are amino acids
- a chain of more than 10 amino acids is called a polypeptide
- there are 20 different amino acids which are either ESSENTIAL or
NONESSENTIAL (see table below)
Essential versus Nonessential Amino Acids
Type
Description
Essential Amino
The body cannot synthesize at all
Acids
or not enough to meet its needs.
(9)
These amino acids must be
supplied by the diet.
A shortage can lead to protein
deficiencies and disease.
Nonessential Amino The body can synthesize.
Acids
(11)
FUNCTION:
Examples
- structural component of muscles, tendons and cells
- last resort (after carbohydrates and fats) as a source
of energy
- make up enzymes
What is protein denaturation?
- a process by which the peptide bonds between the amino acids are
reconfigured which causes a loss of the protein’s biological properties
- can be caused by heat, radiation, pH changes or salty environments
- once the physical or chemical factor is removed, the protein may
assume its original shape
Examples:
4. NUCLEIC ACIDS
STRUCTURE: - the building blocks of nucleic acids are nucleotides
FUNCTION: - are not nutrients but are essential to all living things
- organisms use nucleic acids to store and decode
hereditary information
Two Types of Nucleic Acids:
1. DNA (deoxyribonucleic acid)
- stores genetic information
- double helix structure
- made of four nitrogenous bases: guanine, thymine, cytosine,
adenine
- A and T pair and G and C pair
2. RNA (ribonucleic acid)
- “decodes” DNA
- single helix structure
- nitrogenous bases are not paired
- instead of thymine, RNA contains uracil