UNIT 1: Biochemistry
1.4: Carbohydrates and Lipids
pg. 29 – 38
Carbohydrates
Function, primary energy source for the cell, can also be a structural
component of cells and organisms.
Carbohydrates are the most common biological molecules on Earth. Plants,
through the process of photosynthesis, convert sunlight energy, carbon
dioxide and water into a chemical energy called glucose.
All living organisms require carbohydrates to survive. Glucose is required
for a cellular process called cellular respiration.
Carbohydrate - is a molecule that consists of carbon, oxygen, and hydrogen.
Monosaccharides
The simplest form of sugar is the monosaccharide. There are three different
monosaccharides; glucose, galactose, and fructose which contain 6 carbons
and are isomers of each other.
Monosaccharide - is the simplest form of carbohydrate, consisting of a
single sugar unit; a building block for more complex carbohydrates.
Monosaccharide:
triose
3 carbons
glyceraldehydes
pentose
5 carbons
ribose
hexose
6 carbons
glucose
Figure 2: pg 30
The basic formula for a simple sugar molecule is CnH2nOn (C6H12O6), or a
ratio of 1:2:1 for carbon, hydrogen, and oxygen.
Glucose is the most important monosaccharide, and is linked together to
form complex carbohydrates.
Glucose is a linear molecule, but in the presence of water it forms a ringed
molecule as functional groups (hydroxyl and carbonyl) from the molecule
interact.
When glucose forms a ring there are two possible arrangements created
when the -OH group attached to the carbon at position 1:
α - glucose
β- glucose
Isomer – is a molecule that has the same composition as another, but a
different arrangement of atoms.
These two forms, α – glucose, β- glucose: are isomers.
Disaccharides
When two monosaccharides are bond together through a dehydration
reaction, a disaccharide molecule is created. There are three types of
disaccharides; maltose, lactose and sucrose.
Maltose is created when two glucose molecules form a glycosidic bond
between the –OH group on carbon position 1 of one glucose and the
-OH group on carbon position 4 of another glucose molecule.
glucose + glucose
glucose + galactose
glucose + fructose
→ Maltose
→ Lactose
→ Sucrose
α - linkage
β - linkage
α - linkage
Disaccharide - is a carbohydrate molecule that is made from two
monosaccharide units.
Glycosidic bond - is a bond between two monosaccharides
A linkage is determined by the orientation of the –OH group, to the carbon
position 1 (1 – carbon).
α - linkage
Figure 3: pg 31
β- linkage
Complex Carbohydrates: Polysaccharides
Complex carbohydrates are important energy storage and structural
molecules, depending on the number of monosaccharides make up the chain.
Glycogen and starch are examples of energy storage molecules, while chitin
and cellulose are structural molecules.
Complex carbohydrate - is a molecule that is composed of hundreds to
thousands of monosaccharides linked together; an essential part of nutrition
and a valuable energy source.
Macromolecule, such as: a polysaccharide is made up of many
monosaccharide subunits bond together, glycosidic bonds, through a
dehydration reaction.
This is a polymerization reaction, where large molecules are synthesized.
Polysaccharide molecule - is a molecule that contains many linked
monosaccharides.
Polymerization - is a process in which small subunits are linked to form a
large molecule.
The most common polysaccharides are: plant starch, glycogen and cellulose.
Cellulose is a structural molecule found in plants, making up the cell walls.
Starch is an energy storage molecule found in plants, produced through a
process called photosynthesis.
Glycogen is an energy storage molecule found in animals, created after the
digestion of starch.
Monomer - is a small molecule that can bind chemically to other molecules.
Polymer - is a large molecule that is formed when monomers link together
chemically in a chain.
Energy molecule
Structural molecule
Animal
Glycogen
Chitin
Plant
Starch
Cellulose
Lipids
The function of a lipid is a secondary energy source for the cell (2 X more
energy), structural component of cells, hormones, certain vitamins, immune
response, insulation and water proofing.
Lipids are non-polar molecules, composed mostly of carbon and hydrogen
and some oxygen, and are insoluble in water. Lipids are not polymers,
because they are not made up of repeating subunits, although they are
considered to be macromolecules.
Lipid - is a non-polar compound that is made mostly of carbon and hydrogen.
Fatty Acids
Fatty acid - is a molecule that consists of a carboxyl group and a
hydrocarbon chain.
Fatty acids consists of a single hydrocarbon chain with a carboxyl functional
group (-COOH) at one end. It is this carboxyl group allows for the fatty acid
chain to interact with other molecules and gives it its acidic properties.
Fatty acid chains consist of four or more carbons in their hydrocarbon
backbone. The most common forms of fatty acids have an even number of
carbons ranging from 14 to 22.
Saturated chains are chains that are made up of carbons bonded together by
single covalent bonds. An unsaturated chain made have one or more double
covalent bonds between carbons making up the chain. Monounsaturated,
only one double covalent bond present in the chain, polyunsaturated chain
has many double covalent bonds present.
Fats
Fats are made up of two molecules, glycerol and a fatty acid chains. The
fatty acid chains are bonded to a glycerol group, by a dehydration synthesis
reaction, forming an ester linkage. The carboxyl group of the acid reacts
with the hydroxyl group of the glycerol molecule.
Triglyceride - is a fat, three fatty acid chains linked to a glycerol group.
Triglycerides are primarily an energy storage molecule, and produce more
energy (2X) then carbohydrates.
Saturated fat - is a lipid that is composed of saturated fatty acids with single
bonds in their hydrocarbon chain.
Unsaturated fat - is a lipid that is composed of unsaturated fatty acids with
double bonds in their hydrocarbon chain.
Fats obtained from animals, such as; butter or lard contain only saturated
fatty acid chains, while fats from plants (known as oils) contain unsaturated
fatty acid chains, and are liquid at room temperature.
Phospholipids
Phospholipid - is a lipid that consists of two fatty acids and a phosphate
group bounded to a glycerol group.
Phospholipids are the primary lipids of cell membranes. These molecules are
hydrophilic and hydrophobic, containing 1 phosphate group, 1 glycerol
molecule and 2 fatty acid chains. The phosphate portion (head region) is
polar and therefore hydrophilic. The fatty acid chains are non-polar and
therefore hydrophobic to water.
The phospholipid molecules create a bi-layer cell membrane. The bi-layer is
created because of the properties of the molecule. The hydrophobic ends of
two molecules will face each other and avoiding water. The hydrophilic ends
of each molecule face outward or inward towards water environments.
Figure 9: Phospholipid Molecule, pg. 35
Steroids
Steroid - is a lipid that is composed of four carbon rings.
Sterol is the most abundant steroid.
Cholesterol is a steroid that is essential for animal cell membranes and
converts into a number of compounds; such as vitamin D. Cholesterol can
also be harmful. A high concentration of cholesterol in your diet may lead to
atherosclerosis and eventually to heart attacks.
Sex hormones, such as; estrogen, progesterone, and testosterone are
specialized steroids, that control the development of secondary sex
characteristics as adolescents reach puberty.
Anabolic steroids, banned by all major sporting bodies, mimics testosterone
and are used by athletes to increase muscle mass, and are used to gain an
advantage over other competitors. Steroids can very harmful to your body.
Figure 11: Cholesterol and the sex hormones progesterone, estradiol,
and testosterone are members of the sterol family of lipids. Notice their
structural similarity.
Waxes
Wax - is a lipid that is formed when long fatty acid chains are joined to
alcohols or carbon rings.
Waxes are ideal for water proofing in plants and animals.